A Patient-Derived, Pan-Cancer EMT Signature Identifies ...signature based on a set of 54 lung...

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Cancer Therapy: Preclinical A Patient-Derived, Pan-Cancer EMT Signature Identies Global Molecular Alterations and Immune Target Enrichment Following Epithelial-to-Mesenchymal Transition Milena P. Mak 1,2 , Pan Tong 3 , Lixia Diao 3 , Robert J. Cardnell 1 , Don L. Gibbons 1,4 , William N. William 1 , Ferdinandos Skoulidis 1 , Edwin R. Parra 5 , Jaime Rodriguez-Canales 5 , Ignacio I.Wistuba 5 , John V. Heymach 1 , John N.Weinstein 3 , Kevin R. Coombes 6 , Jing Wang 3 , and Lauren Averett Byers 1 Abstract Purpose: We previously demonstrated the association between epithelial-to-mesenchymal transition (EMT) and drug response in lung cancer using an EMT signature derived in cancer cell lines. Given the contribution of tumor microenvironments to EMT, we extended our investigation of EMT to patient tumors from 11 cancer types to develop a pan-cancer EMT signature. Experimental Design: Using the pan-cancer EMT signature, we conducted an integrated, global analysis of genomic and prote- omic proles associated with EMT across 1,934 tumors including breast, lung, colon, ovarian, and bladder cancers. Differences in outcome and in vitro drug response corresponding to expression of the pan-cancer EMT signature were also investigated. Results: Compared with the lung cancer EMT signature, the patient-derived, pan-cancer EMT signature encompasses a set of core EMT genes that correlate even more strongly with known EMT markers across diverse tumor types and identies differences in drug sensitivity and global molecular alterations at the DNA, RNA, and protein levels. Among those changes associated with EMT, pathway analysis revealed a strong correlation between EMT and immune activation. Further supervised analysis demonstrat- ed high expression of immune checkpoints and other druggable immune targets, such as PD1, PD-L1, CTLA4, OX40L, and PD-L2, in tumors with the most mesenchymal EMT scores. Elevated PD-L1 protein expression in mesenchymal tumors was conrmed by IHC in an independent lung cancer cohort. Conclusions: This new signature provides a novel, patient- based, histology-independent tool for the investigation of EMT and offers insights into potential novel therapeutic targets for mesenchymal tumors, independent of cancer type, including immune checkpoints. Clin Cancer Res; 22(3); 60920. Ó2015 AACR. Introduction Over the past decade, multiple lines of evidence have suggested that epithelial cancers can transform into a more mesenchymal phenotype, a process known as "epithelial-to-mesenchymal tran- sition" (EMT). Studies have shown that EMT plays an important biologic role in cancer progression, metastasis, and drug resistance (13). Tools that facilitate the study of EMT, therefore, will provide new insights into molecular regulation and evolution during oncogenesis and may help to improve treatments for mesenchymal cancers. The development of EMT signatures or other molecular markers to identify whether a cancer has under- gone EMT is an area of active research. Most studies in this area, however, have focused on a single tumor type and/or on preclin- ical models (37). We previously developed a robust, platform-independent EMT signature based on a set of 54 lung cancer cell lines (hereafter called the lung cancer EMT signature). In vitro, this lung cancer EMT signature predicted resistance to EGFR and PI3K/Akt inhi- bitors and identied AXL as a potential therapeutic target for overcoming resistance to EGFR inhibitors [a common treatment for nonsmall cell lung cancer (NSCLC)]. We and others observed signicantly greater resistance to EGFR inhibitors in lung cancers that had undergone EMT, as determined by either their baseline EMT signature (3) or the expression of specic EMT markers after the development of acquired EGFR inhibitor resistance (8). Although it is appealing to apply the lung cancer EMT signature to diverse tumor types, this approach may be limited by tumor type-specic differences in EMT or discrepancies between cell line 1 Department of Thoracic/Head and Neck Medical Oncology,The Uni- versity of Texas MDAnderson Cancer Center, Houston,Texas. 2 Medical Oncology, Instituto do Cancer do Estado de Sao Paulo, Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil. 3 Depart- ment of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston,Texas. 4 Department of Molecular and Cellular Oncology,The University of Texas MDAnderson Cancer Center, Houston, Texas. 5 Department of Translational and Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston,Texas. 6 Department of Biomedical Informatics, Ohio State University, Columbus, Ohio. Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/). M.P. Mak and P. Tong share rst authorship. Corresponding Authors: Lauren Averett Byers, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Unit 0432, Houston, TX 77030. Phone: 713-792-6363; Fax: 713-792-1220; E-mail: [email protected]; and Jing Wang, Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, TX. Phone: 713- 794-4190; Fax: 713-563-4242; E-mail: [email protected] doi: 10.1158/1078-0432.CCR-15-0876 Ó2015 American Association for Cancer Research. Clinical Cancer Research www.aacrjournals.org 609 on March 7, 2021. © 2016 American Association for Cancer Research. clincancerres.aacrjournals.org Downloaded from Published OnlineFirst September 29, 2015; DOI: 10.1158/1078-0432.CCR-15-0876

Transcript of A Patient-Derived, Pan-Cancer EMT Signature Identifies ...signature based on a set of 54 lung...

Page 1: A Patient-Derived, Pan-Cancer EMT Signature Identifies ...signature based on a set of 54 lung cancer cell lines (hereafter called the lung cancer EMT signature). In vitro, this lung

Cancer Therapy: Preclinical

A Patient-Derived, Pan-Cancer EMT SignatureIdentifies Global Molecular Alterations andImmune Target Enrichment FollowingEpithelial-to-Mesenchymal TransitionMilena P. Mak1,2, Pan Tong3, Lixia Diao3, Robert J. Cardnell1, Don L. Gibbons1,4,William N.William1, Ferdinandos Skoulidis1, Edwin R. Parra5, Jaime Rodriguez-Canales5,Ignacio I.Wistuba5, JohnV.Heymach1, JohnN.Weinstein3,KevinR.Coombes6, JingWang3,and Lauren Averett Byers1

Abstract

Purpose:Wepreviously demonstrated the association betweenepithelial-to-mesenchymal transition (EMT) anddrug response inlung cancer using an EMT signature derived in cancer cell lines.Given the contribution of tumor microenvironments to EMT, weextended our investigation of EMT to patient tumors from 11cancer types to develop a pan-cancer EMT signature.

Experimental Design:Using the pan-cancer EMT signature, weconducted an integrated, global analysis of genomic and prote-omic profiles associated with EMT across 1,934 tumors includingbreast, lung, colon, ovarian, and bladder cancers. Differences inoutcome and in vitro drug response corresponding to expressionof the pan-cancer EMT signature were also investigated.

Results: Compared with the lung cancer EMT signature, thepatient-derived, pan-cancer EMT signature encompasses a set ofcore EMT genes that correlate even more strongly with known

EMTmarkers across diverse tumor types and identifies differencesin drug sensitivity and global molecular alterations at the DNA,RNA, and protein levels. Among those changes associated withEMT, pathway analysis revealed a strong correlation between EMTand immune activation. Further supervised analysis demonstrat-ed high expression of immune checkpoints and other druggableimmune targets, such as PD1, PD-L1, CTLA4, OX40L, and PD-L2,in tumors with the most mesenchymal EMT scores. ElevatedPD-L1 protein expression inmesenchymal tumors was confirmedby IHC in an independent lung cancer cohort.

Conclusions: This new signature provides a novel, patient-based, histology-independent tool for the investigation of EMTand offers insights into potential novel therapeutic targets formesenchymal tumors, independent of cancer type, includingimmune checkpoints. Clin Cancer Res; 22(3); 609–20. �2015 AACR.

IntroductionOver the past decade,multiple lines of evidence have suggested

that epithelial cancers can transform into a more mesenchymal

phenotype, a process known as "epithelial-to-mesenchymal tran-sition" (EMT). Studies have shown that EMT plays an importantbiologic role in cancer progression,metastasis, anddrug resistance(1–3). Tools that facilitate the study of EMT, therefore, willprovide new insights into molecular regulation and evolutionduring oncogenesis and may help to improve treatments formesenchymal cancers. The development of EMT signatures orother molecular markers to identify whether a cancer has under-gone EMT is an area of active research. Most studies in this area,however, have focused on a single tumor type and/or on preclin-ical models (3–7).

We previously developed a robust, platform-independent EMTsignature based on a set of 54 lung cancer cell lines (hereaftercalled the lung cancer EMT signature). In vitro, this lung cancerEMT signature predicted resistance to EGFR and PI3K/Akt inhi-bitors and identified AXL as a potential therapeutic target forovercoming resistance to EGFR inhibitors [a common treatmentfor non–small cell lung cancer (NSCLC)].We andothers observedsignificantly greater resistance to EGFR inhibitors in lung cancersthat had undergone EMT, as determined by either their baselineEMT signature (3) or the expression of specific EMTmarkers afterthe development of acquired EGFR inhibitor resistance (8).

Although it is appealing to apply the lung cancer EMT signatureto diverse tumor types, this approach may be limited by tumortype-specific differences in EMT or discrepancies between cell line

1Department of Thoracic/Head and Neck Medical Oncology, The Uni-versity of TexasMDAndersonCancerCenter, Houston,Texas. 2MedicalOncology, Instituto do Cancer do Estado de Sao Paulo, Faculdade deMedicina da Universidade de Sao Paulo, Sao Paulo, Brazil. 3Depart-ment of Bioinformatics and Computational Biology, The University ofTexas MD Anderson Cancer Center, Houston, Texas. 4Department ofMolecularandCellularOncology,TheUniversityofTexasMDAndersonCancer Center, Houston, Texas. 5Department of Translational andMolecular Pathology, The University of Texas MD Anderson CancerCenter, Houston,Texas. 6Department of Biomedical Informatics, OhioState University, Columbus, Ohio.

Note: Supplementary data for this article are available at Clinical CancerResearch Online (http://clincancerres.aacrjournals.org/).

M.P. Mak and P. Tong share first authorship.

Corresponding Authors: Lauren Averett Byers, The University of Texas MDAnderson Cancer Center, 1515 Holcombe Blvd, Unit 0432, Houston, TX 77030.Phone: 713-792-6363; Fax: 713-792-1220; E-mail: [email protected]; andJing Wang, Department of Bioinformatics and Computational Biology, TheUniversity of Texas MD Anderson Cancer Center, Houston, TX. Phone: 713-794-4190; Fax: 713-563-4242; E-mail: [email protected]

doi: 10.1158/1078-0432.CCR-15-0876

�2015 American Association for Cancer Research.

ClinicalCancerResearch

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models [the starting point of the lung cancer EMT signature (3)]and clinical patient samples—especially in regard to the interplaybetween EMT, tumor microenvironments, and immune responseat different disease sites (9). Therefore, we built uponour previousapproach to derive a pan-cancer EMT signature by leveragingmolecular datasets from 11 tumor types (n ¼ 1,934 tumorsoverall; see Supplementary Table S1) using clinical patient sam-ples from The Cancer Genome Atlas (TCGA). The datasets wereobtained from primarily epithelial malignancies, such as breast,colorectal, and endometrial cancer, and two cohorts of lungcancer (adenocarcinoma and squamous cell carcinoma).

We tested the performance of the pan-cancer EMT signature bycomparing its association with established, but independent,EMT markers at the proteomic, microRNA (miRNA), and mRNAlevel and then applied the signature as a tool for exploring cross-platform molecular and clinical features associated with EMTacross multiple cancer types. Given the previously describedassociation of EMT with drug response (both sensitivity andresistance), we then further evaluated the therapeutic relevanceof the pan-cancer EMT signature in preclinical models using twopublicly available drug sensitivity databases: the Cancer Cell LineEncyclopedia (CCLE; ref. 10) and the Genomics of Drug Sensi-tivity in Cancer (GDSC; ref. 11).

Materials and MethodsDatasets

We downloaded cell line drug sensitivity databases from theCCLE (10) and GDSC (11). This included gene expression data(Affymetrix U133 Plus 2 array from CCLE and Affymetrix HT HGU133A array fromGDSC) and drug sensitivity data (IC50 values).The CCLE data included 1,035 cell lines and the GDSC dataincluded 654 cell lines. In total, 425 cell lines were present in bothdrug sensitivity databases. Twenty-four targeted drugs were pro-filed in CCLE and 138 drugs (both targeted and cytotoxic) wereprofiled in GDSC with a cell viability assay. The GDSC confirmedidentity of cell lines by short tandem repeat (STR) analysis and the

CCLE by SNP fingerprinting at multiple steps, profiles werecompared with existing profiles (10, 11). We used level-3 TCGApan-cancer data (12, 13), including RNAseqV2, reverse phaseprotein array (RPPA), miR, copy number, mutation, and clinicaldata. A summary of the TCGA data can be found in Supplemen-tary Table S1. The Profiling of Resistance Patterns and OncogenicSignaling Pathways in Evaluation of Cancers of the Thorax andTherapeutic Target Identification (PROSPECT) dataset of surgi-cally resected NSCLC has been previously described (9). Array-based expression profiling of PROSPECT tumors was performedusing the Illumina Human WG-6 v3 BeadChip according to themanufacturer's protocol and gene expression data have beenpreviously deposited in the GEO repository (GSE42127).

Developing the pan-cancer EMT signatureWe adopted an approach similar to that used by Byers and

colleagues (3) to derive the pan-cancer EMT signature. We usedfour established EMTmarkers, namely, CDH1 (epithelial marker,E type),CDH2 (mesenchymalmarker,M type),VIM (M type), andFN1 (M type) as seeds to derive the pan-cancer EMT signature onthe basis of TCGA pan-cancer RNAseq data. In particular, wecomputed correlations (Pearson correlation, r) between allmRNAs in the RNAseq data and each of the established EMTmarkers for each individual tumor type.

Identification of EMT-associated genomic featuresWe computed Pearson correlation between the EMT score and

individual genomic features because these features are normallydistributed. The genomic features per gene included the mRNAexpression, RPPA expression (either total protein or phosphory-lated protein), and miRNA expression levels (5p and 3p maturestrands).

Association between EMT score and other covariatesWe applied the log-rank test to assess the association between

the dichotomized EMT score (with a cutoff of 0) and overallsurvival. We used the ANOVA test to assess the associationbetween EMT score and tumor grade.

Pathway analysisWe performed a functional annotation of the pan-cancer EMT

signature as well as pathway enrichment analysis usingQIAGEN'sIngenuity Pathway Analysis (14).

Quantitative IHCTissue sections (4 mM thick) were cut from formalin-fixed,

paraffin-embedded blocks containing representative tumor andprocessed for IHC, using an automated staining system (LeicaBond Max, Leica Microsystems). For assessment of PD-L1 expres-sion, the PD-L1 (E1L3N) XP rabbit monoclonal antibody (CellSignaling Technology) was applied at 1:100 dilution followed bydetection using the Leica BondPolymer Refine detection kit (LeicaMicrosystems), DAB staining, and hematoxylin counterstaining.For quantification, stained slides were digitally scanned using theAperio ScanScope Turbo slide scanner (Leica Microsystems).Captured images (200� magnification) were visualized usingImageScope software (Leica Microsystems,) and analyzed usingAperio Image Toolbox (Aperio, Leica Microsystems). For PD-L1analysis in tumor and nontumor cells, five randomly selectedsquare regions (1mm2) in the core of each tumor were evaluated.

Translational Relevance

Epithelial-to-mesenchymal transition (EMT) is associatedwith resistance to many approved drugs and with tumorprogression. Here, we sought to characterize the commonbiology of EMT across multiple tumor types and identifypotential therapeutic vulnerabilities in mesenchymal tumors.A patient-derived, pan-cancer EMT signature was developedusing 11 distinct tumor types from The Cancer Genome Atlas.Mesenchymal tumors had similar patterns of gene, protein,and miRNA expression independent of cancer type. Tumorswith mesenchymal EMT scores not only had a higher expres-sion of the receptor tyrosine kinase Axl (previously implicatedwith EMT and associated with response to Axl inhibitors), butalso expressed high levels of multiple immune checkpointsincluding PD-L1, PD1, CTLA4, OX40L, and PD-L2. This novelfinding, which was validated in an independent patientcohort, highlights the possibility of utilizing EMT status—independent of cancer type—as an additional selection tool toselect patients who may benefit from immune checkpointblockade.

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Analysis of PD-L1 expression specifically in tumor cells was basedon assessment of the whole section. The cell membrane stainingalgorithm was used to obtain the PD-L1 Histo-score (H-score;0–300), which is computed on the basis of both extent andintensity of PD-L1 staining.

Association with drug sensitivity dataFor each drug sensitivity database, we calculated the EMT scores

for the cell lines and associated them with IC50 values using theSpearman rank correlation. Cell lines were obtained from com-mercial vendors and authentication was confirmed by STR anal-

ysis matched to existing STR profiles, as reported previously(10, 11).

Additionalmore detailedmethods are included in Supplemen-tary Materials and Methods.

ResultsDevelopment and evaluation of the pan-cancer EMT signature

We derived the pan-cancer EMT signature using an approachsimilar to that for the lung cancer EMT signature, as shownin Fig. 1A (3). We selected candidate genes from the mRNAs that

A BMesenchymal

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Pan-cancer TCGA analysis of EMT-associated markers

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Figure 1.Development and application of the pan-cancer EMT signature. A, schematic flow of how the pan-cancer EMT score was derived from known EMT markers (CDH1,VIM, FN1, and CDH2) using patient tumor-derived samples from TCGA and subsequently utilized to identify molecular markers and potential therapeutictargets. B, genes in the pan-cancer EMT signature preserved strong correlation with known EMT markers across different tumors. "Type:" indicates whether thesignature gene was epithelial-like (E) or mesenchymal-like (M) and "Origin:" indicates which seed gene was used to identify the signature gene. E markers (red)had positive correlation with CDH1 (Pearson correlation mean ¼ 0.44, median ¼ 0.43); M markers (blue) had positive correlation with VIM, FN1, or CDH2(Pearson correlationmean¼0.67,median¼0.71). OVCA, ovarian cancer (n¼ 123); BLCA, bladder urothelial carcinoma (n¼ 88); HNSC, head and neck squamous cellcarcinoma (n ¼ 203); COAD, colon adenocarcinoma (n ¼ 89); UCEC, uterine corpus endometrial carcinoma (n ¼ 189); BRCA, breast invasive carcinoma(n¼ 503); LUSC, lung squamous cell carcinoma (n¼ 104); Basal, basal-like breast cancer (n¼ 103); LUAD, lung adenocarcinoma (n¼ 131). C, TCGApan-cancer tumortypes exhibit a range of epithelial (score < 0) and mesenchymal (score > 0) samples. D, comparison of lung cancer and pan-cancer EMT signatures. The EMT scoresfrom each signature were highly concordant, except for KIRC. Using TWIST1/TWIST2 mRNA, miR-200a/b, and E-cadherin/fibronectin RPPA data as externalvalidation, the pan-cancer EMT signature performed significantly better (P < 0.01) for fibronectin and TWIST1/2 and similarly well for miR-200a/b and E-cadherin.

Pan-Cancer EMT Molecular and Immune Alterations

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best correlated with four established EMT markers "the seed,"E-cadherin (CDH1), vimentin (VIM), fibronectin (FN1), andN-cadherin (CDH2), across nine distinct tumors types (see Fig.1; Supplementary Table S1 for TCGA tumor types and samplesizes). For this initial process, we excluded kidney renal clear cellcarcinoma (KIRC) and rectal adenocarcinoma (READ) tumorsbecause they contained predominantly mesenchymal (KIRC) orepithelial (READ) tumors (i.e., low dynamic range of EMT; seeMaterials and Methods). Using this approach, we identified a setof 77 unique genes as the pan-cancer EMT signature (seeMaterialsand Methods and Supplementary Table S2). Figure 1B shows thecorrelation between these 77 signature genes and the seed com-ponent (one of the four establishedmarkers) that identified them.We observed strong and consistent correlations with the seedacross different tumor types. This suggests that the pan-cancerEMT signature encompasses core EMT markers that functionacross different tumors.

We observed a wide dynamic range of EMT scores calculatedfrom the pan-cancer EMT signature across the 1,934 tumors thatrepresent 11 distinct tumor types (Fig. 1C). As expected, EMTscores (calculated from the resulting pan-cancer EMT signature)successfully identified KIRC asmostlymesenchymal and READ asmostly epithelial. With the exception of KIRC (90.1%mesenchy-mal), READ (87.2% epithelial), and colon adenocarcinoma(COAD; 94.4% epithelial), each tumor type included a significantnumber of both epithelial (EMT score <0) and mesenchymal(EMT score >0) samples.

Fourteen genes overlapped between the original lung cancerEMT signature and the new pan-cancer EMT signature (Supple-mentary Fig. S1A). EMT scores computed from the pan-cancerEMT signature were highly correlated with scores calculated fromthe lung cancer EMT signature for individual tumor types (r ¼0.76–0.95; overall r ¼ 0.82; Fig. 1D). The most notable outlierwhen comparing the two signatures was KIRC, which had thelowest correlation (r¼ 0.759), possibly due to a relatively narrowrange of EMT scores due to its mesenchymal tissue of origin.

To investigate whether the pan-cancer EMT signature per-formed better than the original lung cancer EMT signature, wecorrelated the EMT scores computed from each signature with sixputative EMT markers. The markers included two proteins(E-cadherin and fibronectin) quantified by RPPA, two miRNAs[miR-200a,miR-200b; well established as regulators of EMT (15)]as measured by RNAseq, and two EMT-associated transcriptionfactors (TWIST1 and TWIST2) represented by mRNA expressionlevels (Fig. 1D). These six putative markers were selected onthe basis of their established roles in EMT (1, 2, 16). They servedas an independent validation set because they (1) include datafrom different (nonsignature) platforms (e.g., protein, miRNA)and/or (2) were not components of either mRNA-based EMTsignature. Figure 1D shows that correlations with the three puta-tive mesenchymal markers, fibronectin, TWIST1, and TWIST2(positive correlation with EMT scores), were significantly strongerfor the pan-cancer EMT signature (one-sided t test, P < 0.01);whereas correlationswith the three epithelialmarkers, E-cadherin,miR-200a, and miR-200b, were similar for both signatures (one-sided t test, P > 0.05; see also Supplementary Fig. S1B).

We then performed a pathway analysis to investigate thebiologic function of the genes identified in the new pan-cancerEMT signature (Fig. 2A). Genes in the pan-cancer EMT signaturewere significantly associated with several molecular functions,such as cellular movement, morphology, growth, and prolifera-

tion, cell-to-cell signaling, and cellular assembly and organiza-tion. Another enriched canonical pathway was leukocyte extrav-asation signaling, suggesting immune activation.

An integrated molecular analysis of EMT across tumor types:gene expression and potential therapeutic targets

Using thepan-cancer EMTsignature,we evaluated the impact ofEMT on the mutational landscape, copy number alterations(CNA), mRNA, miRNA, and protein expression to identify eventsassociated with EMT in patient tumors. To assess how EMTimpacts the overall transcriptome, we correlated EMT scores withmRNA expression data for each tumor type (see SupplementaryFile S1). Genes expressed at higher levels in mesenchymal tumorswere highly conserved across multiple tumor types, indicatinggreater post-EMT biologic homogeneity; whereas those expressedat higher levels in epithelial tumors tended to be more specific toindividual tumor types (Supplementary Fig. S2A–S2C).

Given our previously reported association of EMT with drugresistance (3, 4), individual genes or pathways overexpressed inmesenchymal tumors may have clinical utility as therapeutictargets. For example, we previously showed that the receptortyrosine kinase AXL is highly expressed in lung cancers that haveundergone EMT and, therefore, is a top candidate drug target inmesenchymal lung cancers (3). In the pan-cancer EMT signaturederived here, AXL was again identified as a signature gene basedon its strong correlation with established EMT markers. AXL,therefore, represent a hallmark gene that is positively correlatedwith EMT scores across all tumor types (r¼ 0.53–0.95, median¼0.674; Supplementary Fig. S2D). Other potential therapeutictargets thatwerehighly expressed inmesenchymal tumors includethe a-type platelet-derived growth factor receptor (PDGFRa;r¼ 0.22–0.78, median¼ 0.65), PDGFRb (r¼ 0.59–0.92, median¼ 0.81), and discoidin domain-containing receptor-2 (DDR2; r¼0.29–0.84, median ¼ 0.63), inhibitors of which are in clinicalstudies or have been approved for cancer treatment (17–20).

Immune checkpoint expression in mesenchymal tumorsTo better understand pathways globally dysregulated in the

setting of EMT, we next performed a pathway analysis of genesthat correlated with the pan-cancer EMT signature in all 11tumor datasets, using a cutoff of an absolute r > 0.3. In additionto functions related to EMT regulation (e.g., cellular movement,cell–cell signaling), the top activated pathways were related toimmune cell signaling (Fig. 2B). Given recently published datafrom our group that suggests a role of EMT in regulatingimmune escape in lung cancer (9) and the strong therapeuticpotential of emerging immunotherapies, we performed a morefocused analysis to investigate the association between EMTand key genes involved in the immune response across the 11cancer types.

The expression of 20potentially targetable immune checkpointgenes [based on current drug inhibitors that are in preclinicaldevelopment, clinical trials, or which have been approved by theFDA for specific cancer types (Table 1)] were correlated with theEMT scores for each cancer type. We observed a consistent andstrong positive correlation between EMT score and the expressionlevels of the immune checkpoint genes across all cancer types,with more mesenchymal tumors expressing higher levels of theseimmune targets (Fig. 2C). Notably, high expression of pro-grammed cell death 1 (PD1), cytotoxic T-lymphocyte-associatedprotein 4 (CTLA4), and TNF receptor superfamily, member 4

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(OX40L, also known as CD134) were associated with high EMTscore regardless of tumor type (PD1median r¼ 0.33, median P¼2.1�10�4; CTLA4median r ¼ 0.36, median P ¼ 1.3�10�5; OX40Lmedian r¼ 0.65,median P¼ 2.4�10�13). It has been reported thatOX40L regulates T-cell response, which has led to the study ofOX40L inhibition in conjunction with other checkpoint block-ades (21, 22).

Looking at individual tumor types, samples with higher EMTscores expressed the immune checkpoint genes in a coordinatedway, even in predominantly epithelial tumors, such as READ(Fig. 3A). This enrichment of immune target expression in tumorswith more mesenchymal characteristics corroborated our recentfindings in lung cancer, namely, that lung adenocarcinomas withhigher lung cancer EMT signature scores expressed higher levels ofPD-L1, which is a target of miR-200 (a suppressor of EMT andmetastasis; ref. 9). Clinically, our findings are consistent withresults of immunotherapy trials that have shown the greatestactivity of immune checkpoint inhibitors in cancer types withthe strongest mesenchymal phenotypes, such as melanoma(23–25).

Finally, we validated the association between the mesenchy-mal phenotype and elevated expression of PD-L1 immunohis-tochemically in chemotherapy-na€�ve lung adenocarcinomasand squamous lung cancers that were surgically resected at theUniversity of Texas MD Anderson Cancer Center (PROSPECTdataset). For this analysis, we compared tumors in the top andbottom tertiles for EMT score, using a PD-L1 H-score rangingfrom 0 to 300. In agreement with their gene expression profilesthat confirmed enrichment for immune-related genes (Fig. 3Band C, top panels), mesenchymal adenocarcinomas fromPROSPECT exhibited higher PD-L1 H-score than epithelialtumors (P ¼ 0.003, Mann–Whitney U test; Fig. 3B, bottomleft). Significantly, this finding was upheld when the analysiswas limited to tumor cells (P ¼ 0.002, Mann–WhitneyU test; Fig. 3B, bottom right). We further confirmed the signif-icant, positive correlation between the EMT score and PD-L1H-score in the entire cohort of adenocarcinomas from PROS-PECT, using Spearman rank correlation coefficient (P ¼ 0.002for tumor and nontumor cells and P ¼ 0.011 when the analysiswas limited to tumor cells).

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0.65

0.36

0.53

0.45

0.48

0.47

-0.13

0.24

0.31

0.23

0.22

0.35

0.39

0.25

0.55

0.50

0.43

0.55

0.51

0.49

0.72

0.34

0.48

0.44

0.54

0.49

0.23

0.23

0.40

0.29

0.36

0.49

0.47

0.24

0.36

0.47

0.74

0.53

0.54

0.65

0.68

0.45

0.51

0.49

0.56

0.64

-0.03

0.45

0.18

0.40

0.34

0.41

0.31

0.43

0.27

0.43

0.64

0.41

0.42

0.50

0.58

0.27

0.34

0.44

0.45

0.51

0.28

0.28

0.12

0.14

0.23

0.26

0.24

0.30

0.41

0.34

0.47

0.44

0.49

0.52

0.71

0.35

0.39

0.54

0.47

0.56

0.37

0.41

0.14

0.35

0.33

0.36

0.37

0.47

0.43

0.45

0.32

0.63

0.63

0.72

0.65

0.54

0.71

0.60

0.57

0.66

0.13

0.38

0.28

0.59

0.59

0.56

0.57

0.67

0.41

0.57

0.87

0.55

0.72

0.65

0.67

0.68

0.52

0.79

0.74

0.65

0.03

0.11

0.44

0.21

0.32

0.20

0.27

0.39

0.49

0.41

0.66

0.03

-0.03

-0.13

0.35

0.16

0.27

0.41

0.29

0.26

0.18

-0.16

-0.01

0.16

0.14

0.15

0.11

0.56

0.66

0.53

0.42

0.40

0.47

0.41

0.62

0.34

0.58

0.42

0.39

0.47

0.08

0.17

-0.12

0.23

0.33

0.38

0.35

0.42

0.12

0.20

0.67

0.28

0.24

0.37

0.59

0.27

0.32

0.33

0.34

0.30

-0.02

0.12

0.05

0.09

0.12

0.25

0.20

0.16

0.23

0.17

0.58

0.12

0.31

0.20

0.46

0.42

0.32

0.47

0.20

0.35

-0.01

0.02

-0.06

0.37

0.43

0.39

0.24

0.09

0.07

0.42

HN

SC

LUS

C

CO

AD

BR

CA

LUA

D

BLC

A

RE

AD

KIR

C

OV

CA

Bas

al

UC

EC

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL2IL1APDL1ICOSLGLAG3PD1CTLA4ICOSIL6B7-H3CXCR4

Inhi

bitio

n of

mat

rix m

etal

lopr

otea

ses

Intri

nsic

pro

thro

mbi

n ac

tivat

ion

path

way

Agr

anul

ocyt

e ad

hesi

on a

nd d

iape

desi

s

Leuk

ocyt

e ex

trava

satio

n si

gnal

ing

Reg

ulat

ion

of th

e E

MT

Bla

dder

can

cer s

igna

ling

Gra

nulo

cyte

adh

esio

n an

d di

aped

esis

HIF

1α s

igna

ling

Cav

eola

r-m

edia

ted

endo

cyto

sis

sign

alin

g

Glio

ma

inva

sive

ness

sig

nalin

g

Com

plem

ent s

yste

m

Eic

osan

oid

sign

alin

gIL

K s

igna

ling

Col

orec

tal c

ance

r met

asta

sis

sign

alin

g

Den

driti

c ce

ll m

atur

atio

n

Pho

spho

lipas

e si

gnal

ing

Phe

nyle

thyl

amin

e de

grad

atio

n

Pearson correlation

−0.16 0.0 0.2 0.4 0.6 0.8

Figure 2.The pan-cancer EMT signature is enriched with different molecular functions and pathways. A, functional annotation of the pan-cancer EMT signature usingQIAGEN's Ingenuity Pathway Analysis (14) found five molecular functions (cyan) and six pathways (purple) that were significantly enriched in the pan-cancer EMTsignature. Signature gene names are shown in red (genes associated with mesenchymal phenotype) and blue (genes associated with epithelial phenotype)circles, where text size represents average correlation to EMT signature score across tumors. B, enriched pathway for genes (usingRNAseqdata) strongly correlatingwith EMT score (Ingenuity Pathway Analysis). Immune pathways ranked top among the enriched pathways derived from commonly expressed genes acrossdifferent mesenchymal tumor types (red arrows). C, correlation between immune checkpoint genes and EMT score across different tumor types.

Pan-Cancer EMT Molecular and Immune Alterations

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Table

1.Clinical

dev

elopmen

tofen

riched

immun

etargetsin

mesen

chym

altumors

Basa

lBLCA

BRCA

COAD

HNSC

KIR

CLUAD

LUSC

OVCA

READ

UCEC

Clinical

Targ

et

rP

rP

rP

rP

rP

rP

rP

rP

rP

rP

rP

Dru

gs

development

ADORA2A

0.27

0.006

0.54

<0.001

0.27

<0.001

0.45

<0.001

0.36

<0.001

0.16

0.002

0.35

<0.001

0.34

0.001

0.34

<0.001

0.68

<0.001

0.42

<0.001

ZM

241385

Preclin

ical

CCL2

0.24

0.016

0.63

<0.001

0.42

<0.001

0.54

<0.001

0.48

<0.001

�0.03

0.625

0.49

<0.001

0.51

<0.001

0.47

<0.001

0.72

<0.001

0.31

<0.001

Carlumab

Phase

II

(pro

state)

CD274

(PD-L

1)0.12

0.228

0.38

<0.001

0.28

<0.001

0.45

<0.001

0.24

0.001

�0.16

0.002

0.41

<0.001

0.23

0.017

0.17

0.066

0.11

0.480

0.02

0.762

Pembro

lizumaba

(MK3475)a,

MPDL3280A,

MDX-110

5,

BMS-9

36559,

MSB0010

718C

Phase

III

CD276(B

7-H

3)

0.23

0.021

0.41

<0.001

0.41

<0.001

0.27

0.010

0.55

<0.001

0.66

<0.001

0.43

<0.001

0.36

<0.001

0.12

0.173

0.49

<0.001

0.07

0.340

MGA-271,8H9

Phase

I

CD4

0.34

<0.001

0.57

<0.001

0.45

<0.001

0.56

<0.001

0.48

<0.001

0.29

<0.001

0.47

<0.001

0.54

<0.001

0.39

<0.001

0.74

<0.001

0.20

0.005

Zanolim

umab

Phase

II

CXCR4

0.17

0.083

0.57

<0.001

0.34

<0.001

0.43

<0.001

0.50

<0.001

0.53

<0.001

0.45

<0.001

0.47

<0.001

0.20

0.028

0.41

0.005

0.42

<0.001

BMS-9

36564,

MSX-122

Phase

I

CTLA4

0.25

0.010

0.56

<0.001

0.26

<0.001

0.41

<0.001

0.35

<0.001

0.15

0.005

0.36

<0.001

0.49

<0.001

0.38

<0.001

0.20

0.175

0.39

<0.001

Ipilimumaba,

Tremelim

umab

Phase

III

HAVCR2(T

IM3)

0.37

<0.001

0.72

<0.001

0.50

<0.001

0.65

<0.001

0.52

<0.001

�0.13

0.014

0.52

<0.001

0.49

<0.001

0.41

<0.001

0.65

<0.001

0.20

0.005

MoAb

Preclin

ical

ICOS

0.20

0.048

0.57

<0.001

0.24

<0.001

0.31

0.003

0.39

<0.001

0.11

0.038

0.37

<0.001

0.47

<0.001

0.35

<0.001

0.27

0.065

0.24

0.001

MoAbb

Preclin

ical

ICOSLG

0.05

0.609

0.28

0.008

0.12

0.006

0.18

0.094

0.31

<0.001

�0.01

0.912

0.14

0.103

0.40

<0.001

�0.12

0.172

0.44

0.002

�0.06

0.402

MoAb

Preclin

ical

IL1A

�0.02

0.834

0.13

0.236

0.28

<0.001

�0.03

0.756

�0.13

0.063

0.18

0.001

0.37

<0.001

0.23

0.021

0.08

0.374

0.03

0.844

�0.01

0.888

Anakinra

Phase

I

IL6

0.16

0.097

0.67

<0.001

0.30

<0.001

0.43

<0.001

0.00

<0.001

0.56

<0.001

0.47

<0.001

0.24

0.016

0.42

<0.001

0.39

0.007

0.09

0.204

Tocilizumaba

Phase

I/II

(ovarian

cancer)

IL10

0.32

0.001

0.71

<0.001

0.34

<0.001

0.51

<0.001

0.53

<0.001

0.27

<0.001

0.39

<0.001

0.48

<0.001

0.58

<0.001

0.52

<0.001

0.32

<0.001

MoAb

Preclin

ical

LAG3

0.09

0.380

0.59

<0.001

0.14

0.001

0.40

<0.001

0.23

0.001

0.16

0.003

0.35

<0.001

0.29

0.003

0.23

0.011

0.21

0.152

0.37

<0.001

IMP321,BMS-

986016,MoAb

Phase

III

(breast),

Phase

I

PDCD1(P

D1)

0.12

0.226

0.59

<0.001

0.23

<0.001

0.34

0.001

0.22

0.002

0.14

0.008

0.33

<0.001

0.36

<0.001

0.33

<0.001

0.32

0.028

0.43

<0.001

Nivolumaba,C

T011,

AMP224

Phase

III

PDCD1LG2(P

D-L

2)

0.30

0.002

0.66

<0.001

0.51

<0.001

0.64

<0.001

0.47

<0.001

0.26

<0.001

0.56

<0.001

0.49

<0.001

0.47

<0.001

0.65

<0.001

0.35

<0.001

Nivolumaba,b,

Pembro

lizumaba

(MK3475),CT011,

AMP224

Phase

III

TGFB1

0.67

<0.001

0.32

0.002

0.64

<0.001

0.74

<0.001

0.20

0.005

0.66

<0.001

0.47

<0.001

0.43

<0.001

0.42

<0.001

0.87

<0.001

0.58

<0.001

SB-4

31542,G

C10

08

Phase

I

TNFRSF4(O

X40)

0.33

0.001

0.60

<0.001

0.44

<0.001

0.49

<0.001

0.45

<0.001

0.41

<0.001

0.54

<0.001

0.44

<0.001

0.42

<0.001

0.79

<0.001

0.47

<0.001

Anti-O

X40

MoAb

Phase

I

TNFSF4(O

X40L)

0.59

<0.001

0.65

<0.001

0.58

<0.001

0.68

<0.001

0.65

<0.001

0.35

<0.001

0.71

<0.001

0.72

<0.001

0.62

<0.001

0.67

<0.001

0.46

<0.001

Anti-O

X40

MoAbb

Phase

I

TNFRSF9(C

D137)

0.28

0.004

0.63

<0.001

0.41

<0.001

0.53

<0.001

0.49

<0.001

0.03

0.564

0.44

<0.001

0.55

<0.001

0.40

<0.001

0.55

<0.001

0.12

0.102

Anti-C

D137MoAb,

BMS-6

63513

(Urelumab)

Phase

I,II

(NSCLC

CRT)

Abbreviations:MoAb,m

ono

clona

lan

tibody;

r,Pea

rsonco

rrelation.

aApprove

dbytheFDA.

bIndirecttargeting.

Mak et al.

Clin Cancer Res; 22(3) February 1, 2016 Clinical Cancer Research614

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EMT scoreE M

Expression (mRNA)

Lung adenocarcinoma

B C

Lung squamous

PD-L

1 H

-Sco

re(tu

mor

+ n

on-tu

mor

) P = 0.003 P = 0.002

PD-L

1 H

-Sco

re(tu

mor

cel

ls)

P = 0.019

PD-L

1 H

-Sco

re(tu

mor

+ n

on-tu

mor

)

PD-L

1 H

-Sco

re(tu

mor

cel

ls)

P = 0.110

A

HNSC

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

LUSC

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

OVCA

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

COAD

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

READ

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

LUAD

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

BRCA

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

UCEC

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

Basal

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

KIRC

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

BLCA

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

TGFB1CD137CCL2TIM3OX40LADORA2AIL10OX40CD4PDL-2IL1APDL-1ICOSLGLAG3PD1CTL4AICOSIL6B7-H3CXCR4

200

150

100

50

0

150

100

50

0

E M

200

250

150

100

50

0E ME M

150

100

50

0

E M

Figure 3.Immune target enrichment inmesenchymal tumors. A, expression of immune checkpoint geneswas found in the pan-caner tumor types. Tumor samples within eachcancer type are ordered by EMT score. Mesenchymal tumors have higher expression than epithelial tumors of immune checkpoint genes. B and C, heatmaprepresentation of mRNA expression levels of selected immune checkpoint genes in 151 lung adenocarcinomas (B) and 57 lung squamous carcinomas (C)from the PROSPECT study, rank ordered on the basis of their EMT score (top). Comparison of PD-L1 H-score in epithelial (E) andmesenchymal (M) tumors that wereincluded in the PROSPECT tumor microarray. Automated quantification of extent and intensity of PD-L1 staining was performed in tumor and nontumorcells or limited to tumor cells (B and C, bottom). Lung adenocarcinomas and squamous carcinomas with EMT score in the top/bottom tertile were includedin this analysis. Statistical comparisons are based on the Mann–Whitney U test. � , P � 0.05; �� , P � 0.01.

Pan-Cancer EMT Molecular and Immune Alterations

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Similar results were noted in squamous lung cancers, withhigher PD-L1 H-score recorded in mesenchymal tumors (P ¼0.019, Mann–Whitney U test; Fig. 3C, bottom left) and asignificant, positive correlation noted between the EMT andPD-L1 H-score (P¼ 0.011). Comparison of tumor cell PD-L1 H-score in tumors with EMT scores in the top versus bottom tertilesdid not reach statistical significance in squamous tumors (P ¼0.110, Mann–Whitney U test, Fig. 3C, bottom right), likely dueto a limited number of tumors included in this analysis. How-ever, the correlation between the EMT score and PD-L1 H-score(using all squamous tumors) remained significant (P ¼ 0.028).

miRNA expression patterns in mesenchymal tumorsTo better understand potential factors contributing to the EMT

phenotype, we then investigated changes in other data types(miRNA, protein, mutation, and copy number) that corre-sponded with differences in EMT score across the pan-cancer set.Because severalmiRNAs are known to regulate EMT, we identifiedmiRNAs that were significantly correlated with EMT scores, eitherpositively or negatively, across the pan-cancer sets. Figure 4A andB show the miRNAs that strongly correlate with the EMT score(absolute r > 0.3 in four or more tumor types). As expected, highexpression ofmiR-200 familymembers (miR-200a/b/c,miR-141,

A

B

C

D

−0.8

−0.4

0.0

0.4

Basal BLCA BRCA COAD HNSC KIRC LUAD LUSC OVCA READ UCEC

Cor

rela

tion

with

EM

T sc

ore

hsa-mir-199ahsa-mir-199bhsa-mir-379hsa-mir-127hsa-mir-382hsa-mir-134hsa-mir-214hsa-mir-409

hsa-mir-381hsa-mir-411hsa-mir-758hsa-mir-485hsa-mir-654hsa-mir-369hsa-mir-487bhsa-mir-370

hsa-mir-337hsa-mir-299hsa-mir-889hsa-mir-493hsa-mir-410hsa-mir-154hsa-mir-100hsa-mir-432

hsa-mir-145hsa-mir-495hsa-mir-143hsa-mir-152hsa-mir-655hsa-mir-376chsa-mir-378hsa-mir-429

hsa-mir-141hsa-mir-200chsa-mir-200ahsa-mir-200b

121086420

Frequency associated with mesenchymal phenotype

Freq

uenc

y as

soci

ated

with

epi

thel

ial p

heno

type

ACCPS79

BCL2

BETACATENIN

CAVEOLIN1

CLAUDIN7

ECADHERIN

FIBRONECTIN

GATA3

HER2

HER3

LCKPEA15

PKCALPHAPS657

YB1PAI1

BRAF

FASN

P21

P90RSKRAB25

TAZ

121086420

Frequency associated with mesenchymal phenotype

Freq

uenc

y as

soci

ated

with

epi

thel

ial p

heno

type

miR-431 miR-655

miR-1266

miR-432miR-496 miR-299

miR-370

miR-487b

miR-214

miR-411

miR-335

miR-485

miR-493

miR-494miR-495

miR-323miR-133amiR-154 miR-369

miR-96

miR-758

miR-539miR-410

miR-218

miR-195miR-889

miR-376c

miR-409

miR-577

miR-337miR-136

miR-381

miR-194

miR-654miR-382

miR-708

miR-34c

miR-192

miR-99amiR-132

miR-200b

miR-429miR-148b

miR-224

miR-378

miR-200a

miR-125b

miR-127

miR-375

miR-134

let-7c

miR-152miR-379

miR-141

miR-145

miR-199a

miR-100

miR-199bmiR-30d

miR-182

miR-200c

miR-143

miR-22

miR-21

121086420

Frequency associated with mesenchymal phenotype

Freq

uenc

y as

soci

ated

with

epi

thel

ial p

heno

type

MDM2

CDH11NOS3

GHR

GALNTL2 EPHA3

KLF5

LMO2

CYP27A1

DKK2

CD4SOX17

CCL7

TMEM41B

LILRB4GYPE

GATA3

TRPC6 SPARCNRK

CDK6

CLINT1

MMP9 CD68

AP2M1

BOC

MMP16

QKI VCANRUNX2

NCAM1

ZEB1

LOX

GPD2

SNAI1MSR1

PECAM1

CCR4IBSP

SH3D19

SLC12A4

FOXP1

ITGB1

TOB1

C5AR1

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Figure 4.miRNA expression is highly correlated with EMT status. A, axes show the number of tumor types for which a miRNA was correlated with EMT score (x-axis:miRNA expressed at higher levels in mesenchymal tumors (red); y-axis: miRNA higher in epithelial tumors (blue) at a cutoff of P � 0.3). miR-200 family(200c/b/c and 141) is anticorrelated with EMT (blue), whereas numerous miRNAs are positively correlated with EMT (red). B, correlation between miRNAand EMT score for each cancer type. C, targets of EMT-associated miRNAs (A and B) were identified by miRWalk. Among these, we observed astatistically significant enrichment of targets whose expression correlated with EMT score (Kolmogorov–Smirnov test, P ¼ 1.8 � 10�28). Top miRNA targetsassociated with EMT score are shown based on an absolute correlation >0.3 in at least four tumors (full list of targets and their correlation with EMT score foreach cancer type is provided in Supplementary File S2). D, proteins correlated with EMT score. Similar to the finding at gene expression level, epithelialstatus correlates with expression of HER3 protein, among others. Proteins with an absolute correlation coefficient higher than 0.25 in more than fourtumor types are shown (blue, epithelial; red, mesenchymal).

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and miR-429), which are known to suppress ZEB1 and therebymaintain E-cadherin expression and other hallmarks of an epi-thelial phenotype, was observed among tumors with the lowest(most epithelial) EMT scores (Fig. 4A and B). We observed apositive correlation between the EMT score and numerous othermiRNAs, with the miR-199 family (miR-199a/b) having thegreatest expression in mesenchymal tumors (SupplementaryFig. S3A). ThemiR-199 family has been shown to regulate skeletaldevelopment and to play a role in melanoma invasion andmetastasis, but has been rarely studied in EMT (26, 27). Despitethe tumor-specific association observed between the expressionof somemiRNAs and the EMT score, positively correlatedmiRNAs(i.e., those expressed at higher levels in mesenchymal tumors)were more frequent and homogenous in this analysis than neg-atively correlated miRNAs (those higher in epithelial tumors; Fig.4A and B; Supplementary Fig. S3A), suggesting that miRNAexpression may play an important role in regulating EMT.

To investigate the functional roles of miRNAs identified bythis analysis, we next investigated whether expression of EMT-associated miRNA target genes also correlated with EMT scores.For the EMT-associated miRNAs in Fig. 4A and B, we down-loaded their experimentally validated targets using miRWalk(28) and observed a significant overall association betweentarget expression levels and EMT scores (P < 0.001; Fig. 4C).Taking the miR-200 family as an example, Supplementary Fig.S3B shows the strong associations between the miRNA targetsand the EMT score. Collectively, these findings support anintricate regulation of EMT that is conserved across multipletumor types by miRNAs beyond the miR-200 family and whichmerit further investigation.

Protein expression and EMTNext, we evaluated the correlation between the EMT score and

protein expression using RPPA data. RPPA is a highly quantitativeplatform for the measurement of key total and phosphorylatedproteins. In this analysis, we included 181 proteins for which datawere available across all 11 tumor types. Notably, some proteinsrelevant to EMT, such as AXL, are excluded from the analysisbecause they were evaluated in only a subset of the TCGA pan-cancer tumor types included here.

We found higher levels of several protein markers such as E-cadherin, claudin-7, and Her-3 in epithelial tumors across mosttumor types (�8); with higher levels of PAI1 and p21 in mesen-chymal tumors (Fig. 4D). Fibronectin-1 was the onlymarker withconsistently higher expression in all 11 cancer types, possibly dueto the use of fibronectin (FN1) mRNA levels in deriving the pan-cancer signature (one of the seed genes). In contrast, otherproteins such as protein kinase C-a (PKCa) were associated withEMT in a subset of tumor types (4 of 11), reflecting tumor-specificEMT differences.

Mutational landscape and CNAsTo determine the mutational landscape of mesenchymal

tumors, we investigated whether a mutation was associated withthe EMT score independent of tumor origin. Despite a significantassociation, the results can still be primarily attributed to muta-tions specific to certain tumor types (Supplementary Fig. S4A).For example, a VHL mutation primarily observed in KIRC, wasstrongly associated with higher EMT score. Therefore, after adjust-ing for tumor type and multiple testing, we performed anotheranalysis (see Materials and Methods), and found no significant

association between mutation and EMT score (SupplementaryFig. S4A). We also explored whether mesenchymal status wouldinfluence tumor mutation and CNA burden by quantifying themutation rate and percentage of CNAs in each sample per tumortype, as described by Ciriello and colleagues (29). Using thisapproach, we found no correlation between CNAs versus muta-tion distribution and EMT score (Supplementary Fig. S4C), indi-cating that enrichment of CNAs or mutations is also primarilydriven by the tumor tissue of origin.

EMT score and clinical outcomesIn some cancers, EMT may be associated with worse clinical

outcomes. Therefore, we assessed whether pan-cancer EMT scoreswere associated with clinical covariates such as overall survivaland tumor grade. We did not observe a significant associationbetween EMT score and overall survival, although we found atrend toward shorter survival times in patients withmesenchymalovarian carcinomas [HR, 1.32; 95% confidence interval (CI),0.96–1.81; P¼ 0.08] and uterine corpus endometrial carcinomas(HR, 2.07; 95% CI, 0.93–4.63; P ¼ 0.09). We also found higherEMT scores in KIRC and head and neck squamous cell carcinomaswith higher tumor grade (P < 0.0001 and P ¼ 0.01, respectively;Supplementary Fig. S5).

Drug sensitivity in mesenchymal tumorsFinally, we tested the ability of the pan-cancer EMT signature to

identify associations between EMT and patterns of drug responseacross 1,689 preclinical models, representing 18 tumor types(Supplementary Table S3). We curated gene expression data fromtwo publicly available databases [CCLE (10) and GDSC (11)] tocompute an EMT score for each cell line, which we subsequentlycorrelated with drug sensitivity (based on IC50 values). Among1,035 cell lines in CCLE and 654 cell lines in GDSC with geneexpression data, 425 cell lines were common to both sets, allow-ing us to compare the concordance of EMT scores derived fromindependently generated expression datasets. Despite the geneexpression data having been generated from different versions ofthe Affymetrix array platforms, EMT scores calculated for indi-vidual cell lines were highly concordant, suggesting a robustperformance of our approach across platforms (Fig. 5A). Further-more, the distribution of EMT scores for the cell line models ofeach disease type closely mirrored those observed across patienttumors (Figs. 1B and 5B). For example (and as expected), bonesarcoma, glioblastomamultiforme, andmelanomawere predom-inantly mesenchymal (Fig. 5B). To determine patterns of drugsensitivity in mesenchymal tumors, we correlated the EMT scorefrom each cell line and IC50 values for targeted drugs tested in theCCLE (24 drugs) and GDSC (138 drugs) databases. As previouslydemonstrated with the lung cancer EMT signature (3), we foundincreased resistance to EGFR inhibitors (e.g., erlotinib). Mesen-chymal models also demonstrated greater resistance to otherdrugs that target the ErbB family, including the dual EGFR/VEGFinhibitor vandetanib (ZD-6474) and the EGFR/Her2 inhibitorlapatinib (Fig. 5C and D). In contrast to ErbB inhibitors, butconsistent with higher expression of FGFR1 and PDGFR in mes-enchymal cancers, we observed increased sensitivity to the FGFR1and PDGFRmultikinase inhibitor dovitinib (TKI258) in cell lineswith higher EMT scores (Fig. 5C). To evaluate potential therapeu-tic targets in the GDSC dataset, we performed an exploratoryanalysis of the in vitro effect of drugs against the same targets. Fromthis target analysis (Fig. 5D; Supplementary Fig. S6), we observed

Pan-Cancer EMT Molecular and Immune Alterations

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greater sensitivity to PDGFR inhibitors in mesenchymal tumors.Another interesting finding was increased sensitivity in the mes-enchymal cell lines to the inhibition of the serine/threonineprotein kinases GSK3 and TBK1 (30).

DiscussionEMT has long been recognized as playing a major role in

cancer progression and metastasis (1, 2). Despite extensiveresearch in the field, the best way to characterize this phenom-enon, especially in the clinical setting, is still under debate (2).Here, through the use of a gene expression signature developedfrom multiple tumor types, we were able to evaluate globalmolecular alterations associated with EMT, as well as potentialtherapeutic targets. Comparing our original lung cancer EMTsignature with the pan-cancer EMT signature, we observed a

better correlation of the pan-cancer EMT signature with knownmarkers of EMT across all tumor types evaluated, verifying thestrength of this approach. Interestingly, commonly expressedgenes correlated with the pan-cancer EMT signature in all 11tumor types included a number of potential therapeutic targets,such as the receptor tyrosine kinase AXL, which was also animportant target in mesenchymal lung cancers identified in ourlung cancer EMT signature (3). With AXL inhibitors enteringclinical trials, the finding of high AXL expression across mul-tiple cancer types in the setting of EMT has important clinicalimplications (31). Another major finding of this analysiswas the significant enrichment of multiple immune targets incancers that have undergone EMT, which has potentially impor-tant implications for identifying patients with cancer whomay benefit from immunotherapies. Specifically, we found ahigh correlation of expression of 20 druggable immune targets

A

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Figure 5.Potential therapeutic targets inmesenchymal cell lines. A, EMT scores computed from different datasets are highly concordant. Although gene expression dataweregenerated from different laboratories utilizing distinct platforms, high concordance (Pearson correlation ¼ 0.97, concordance correlation coefficient ¼ 0.96)of the EMT score is found in shared cell lines from both datasets (GDSC, y-axis; CCLE, x-axis), reinforcing the robustness of the signature. B, spectra of EMTscores across different tumor types in CCLE and GDSC. Similar to results from patient-derived tumor samples, cell lines from different tumor types exhibiteddifferent spectra of EMT scores. C, correlation between IC50 and EMT score in CCLE. Dot size is proportional to the P value of correlation; color indicatesmagnitude ofcorrelation. D, correlation between IC50 and EMT score in GDSC. Drugs associated with resistance (red) include EGFR and ERBB2 inhibitors; whereas PDGFRinhibitors have lower IC50's in mesenchymal samples (green).

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and mesenchymal status, as defined by the pan-cancer EMTsignature and were able to validate these findings by mRNAexpression analysis and IHC in an independent lung cancercohort.

Several reports have shown the importance of miRNA regula-tion in EMT (2, 15, 32). As expected, the miR-200 family washighly expressed in epithelial tumors. However, a number ofnovelmiRNAswere found to behighly expressed inmesenchymaltumors, regardless of cancer type, including the miR-199 family.Previously implicated in skeletal development and fibrosis(27, 33), miR-199a seems to have a dual role in cancer, both asa tumor suppressor and a promoter, depending on the tissue oforigin (27). Although its role in EMT is still unknown, thecorrelation we found betweenmiR-199 and EMTwarrants furtherinvestigation.

Although mesenchymal tumors had similar patterns of geneand miRNA expression, the overall mutational landscape andalterations in copy number seem to be mostly determined bytumor type. In contrast, protein expression and drug sensitivitypatterns appear to be driven by both tumor type and EMT status.From this analysis, we identified several drugs as potentially moreactive in the mesenchymal subgroup of each tumor type. How-ever, some limitations of this study include different numbers ofcell lines for each drug testedwithin each tumor type andmultipletargets (both inhibitory and promoter) for many of the drugsincluded in the analysis. Nevertheless, we identified drugs thatmay be more active in mesenchymal cancers, which are oftenhighly resistant to established targeted therapies (e.g., ErbB2family inhibitors used in breast, head andneck, and lung cancers).Further validation is necessary to determine the clinical relevanceof these drugs in the context of EMT.

In summary, the new pan-cancer EMT signature introducedhere identifies global molecular alterations across multiplecancer types that are associated with EMT. Furthermore, theidentification of the association between pan-cancer EMT sig-nature scores and expression of candidate drug targets suggeststhat EMT may be a clinically useful marker for selecting patientsmost likely to respond to specific cancer-targeting approaches.The finding that mesenchymal tumors express higher levels ofimmune checkpoint targets is of particular clinical relevance,given the significant clinical activity of immunotherapies, suchas PD1 and PD-L1 inhibitors in lung cancer (34, 35) and othermalignancies, which currently lack validated biomarkers toselect patients most likely to benefit from these targeted immu-notherapies. The results described here suggest a possible rolefor using a tumor's EMT phenotype to identify cancers that maybe more sensitive to immune targeting strategies.

Except for one previous report (4), other existing EMT signa-tures were developed from a single tumor type (3, 5–7), which islikely to limit their application across diverse cancer types. Fur-thermore, many of these were developed in cell line models,which do not reflect the contribution of the tumor microenvi-ronment and immune response, which play important roles in

therapeutic response, especially with the emergence of the field ofimmunotherapy. By deriving the pan-cancer EMT signature frompatients' tumors, we overcame some of these limitations.

Disclosure of Potential Conflicts of InterestJ.V. Heymach reports receiving commercial research support from AstraZe-

neca, Bayer, and GlaxoSmithKline; and is a consultant/advisory board memberfor AstraZeneca, Boerhinger Ingelheim, Exelixis, Genentech, GlaxoSmithKline,Lilly, Novartis, and Synta. Nopotential conflicts of interest were disclosed by theother authors.

Authors' ContributionsConception and design: M.P. Mak, J.V. Heymach, J. Wang, L.A. ByersDevelopment of methodology: P. Tong, J. Rodriguez-Canales, I.I. Wistuba,J.V. Heymach, K.R. Coombes, J. Wang, L.A. ByersAcquisition of data (provided animals, acquired and managed patients,provided facilities, etc.): P. Tong, E.R. Parra, J. Rodriguez-Canales, I.I. Wistuba,L.A. ByersAnalysis and interpretation of data (e.g., statistical analysis, biostatistics,computational analysis): P. Tong, L. Diao, D.L. Gibbons, W.N. William,F. Skoulidis, J.V. Heymach, K.R. Coombes, J. Wang, L.A. ByersWriting, review, and/or revision of the manuscript: M.P. Mak, P. Tong,R.J. Cardnell, D.L. Gibbons, W.N. William, F. Skoulidis, E.R. Parra, I.I. Wistuba,J.N. Weinstein, K.R. Coombes, J. Wang, L.A. ByersStudy supervision: W.N. William, J. Wang, L.A. Byers

Grant SupportThis project was partially supported by the NIH through the TCGA (5-U24-

CA143883-05), the Lung SPORE (P50 CA070907), DoD PROSPECT grantW81XWH-07-1-0306, and the Cancer Center Support Grant (CCSG-CA016672), by the Mary K. Chapman Foundation, and through generousphilanthropic contributions to The University of Texas MD Anderson LungCancer Moon Shot Program. D.L. Gibbons was supported by Rexanna's Foun-dation for Fighting Lung Cancer, The Stading Lung Cancer Research Fund, theNational Institutes of Health (K08-CA151651), and the Cancer Prevention &Research Institute of Texas (RP150405); W.N. William was supported by aConquer Cancer Foundation Career Development Award (4546); I.I. Wistubawas supported by MD Anderson's Institutional Tissue Bank (ITB), AwardNumber 2P30CA016672 from theNIHNationalCancer Institute. J.V.Heymachwas supported by NIH/NCI (1 R01 CA168484-04) the LUNGevity foundation,TheVFoundation forCancer Research, theDavidBruton, Jr. EndowedChair andthe Rexana Foundation for Fighting Lung Cancer; J.N. Weinstein was supportedby NIH/NCI (5, 2P50 CA100632-11, 2 UL1RR00037106-A1, and 2 P30CA016672 38), the Cancer Prevention & Research Institute of Texas(RP130397), and The Michael and Susan Dell Foundation; L.A. Byers wassupported by an NCI Cancer Clinical Investigator Team leadership Award (P30CA016672), The Sidney Kimmel Foundation for Cancer Research, and theSheikh Khalifa Bin Zayed Al Nahyan Institute for the Personalized CancerTherapy's (IPCT's) Center for Professional Education and Training; D.L. Gib-bons and L.A. Byers are supported by MD Anderson Cancer Center PhysicianScientist Awards, R. Lee Clark Fellowships of The University of Texas MDAnderson Cancer Center, supported by the Jeane F. Shelby Scholarship Fund,and the LUNGvevity Foundation.

The costs of publication of this articlewere defrayed inpart by the payment ofpage charges. This article must therefore be hereby marked advertisement inaccordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received April 13, 2015; revised August 11, 2015; accepted August 28, 2015;published OnlineFirst September 29, 2015.

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