The tumor microenvironment:problems and opportunities

for therapy

Nic Denko PhD MDRadiobiology 2013

The tumor microenvironment

• Unique architectural, physiologic and cellular environment

• Poor perfusion leads to decreased oxygen (hypoxia), decreased nutrients (hypoglycemia), and increased waste products (acidosis

• All these stresses have compensatory adaptive cellular responses

OER can be up to 3

Tannock and Hill BSO 1998

Oxygen is a dose modifying factor

Adaptive Biologic Responses

• Hypoxia: HIF-1 (HIF1a and HIF2a), UPR, SREBP-1, ATF-3, NF-KB

• Hypoglycemia: HIF-1, Mondo, UPR • Acidosis: Sp1 (renal tubule cells), mRNA

stability• Increased IFP: ???

HIF-dependent Gene Induction

HRE

Transactivation

Hypoxia

?

PI3K/PTEN/akt

?

Other targets?

HIFb constitutive

Hif1aInducible

Prolyl hydroxylase

ElonginsVHL

P564-OHP402-OH

Proteasome

Ubi

VHL connects hypoxic gene induction to human tumor formation

• VHL is a classic “two hit” tumor suppressor• Loss of VHL leads to constitutive HIF-1 activity• Model tumors suggest that this regulation of

HIF is a major activity for tumor suppression

VHL-resistant HIF is tumorigenic in Renal Cell Cancers

Kaelin CC 2002

Unfolded proteins generate a complex, three prong response

Kaufman JCB 2012

Disulfide bond formation requires molecular oxygen

Feldman and Koong Mol Can Res 2005

Protein Glycosylation requires glucose

How to overcome hypoxia?

• More oxygen delivery – RBC Mass (transfusion, Epo)– Inhaled oxygen (100% F1 02)– Vasorelaxants (hydralazine)

• Oxygen mimetics (Misonitozole, etanidozole, nimorazole)

• Hypoxic cytotoxins (MMC, TPZ, AQ4N, Pr104)• Less oxygen utilization ?

Misonidozole sensitizes hypoxic cells to XRT

Miso sensitizes model tumors to single dose XRT treatment

1000 mg/kgMiso pre XRT

Development of oxygen mimetics

Nimorazole shown to be beneficial in patients with HNC treated with XRT

Hypoxic Cytotoxins

Tirapazamine

Drug is only Toxic in hypoxia

TPZ + XRT in vivo

TPZ hasLow activity as a single agent

Oxygen tension is a function of Supply and demand

Systemic Circulation

Tumor Circulation

Supply Demand

Can we modify hypoxia from the demand side?

TumorVasculature

0h 2h 4h 6h 24h

0.E+00

2.E+07

4.E+07

6.E+07

-10 0 10 20 30

Cha

nge

in

luci

fera

se a

ctiv

ity

(pho

tons

/s)

Time (hr)

RKORKOshHIF

d

Increased oxygen consumption

Causes Increased hypoxia

post DCA

RKO RKOShHIF

Hours post DCA

Metabolic (PDHK) inhibitors can enhance TPZ activity in vivo

DCA has to be given before TPZ

Can we decrease oxygen consumptionand decrease hypoxia?

• Use drugs that decrease mitochondrial function and reduce overall tumor oxygen consumption

• Measure changes in oxygenation• Measure radiosensitization

Oxylite A549 tumor MTF response

-10 15 40 65 90 115 140-1

4

9

14

19

24

29

34

39

44

49IV high 7a

IV 3.5b

IV 4.5

IV 3.5g

IV 3.5i

IV 3.5j

time (drug injected at t=0)

mm

Hg

Tumor Microenvironment

• No microenvironment modifying agents have yet been successful in improving XRT (nimorazole in Europe).

• HIF1 may be a marginal target, XBP1 may have some efficacy, Hgb increases always make the patient feel better.

Which of the following agents has NOT been found to be useful for measuring human tumor hypoxia?

A. [18F]- 2-fluoro-2-deoxy-D-glucose (FDG),B. pimonidazoleC. [18F]Azomycin Arabinoside (FAZA)D. [64Cu]- Copper dithiosemicarbazone (ATSM)E. [18F]Fluoromisonidazole (FMISO)

Pre-treatment correction of anemia with either blood transfusion or epo may be considered in cancer patients. This is based, in part, on which one of the following observations?A. In a German/Swiss, multicenter, randomized, clinical trial, advanced head and neck cancer patients receiving epoetin alfa achieved higher hemoglobin concentrations and longer progression-free survival than placebo.B. Anemia correction has been shown to improve quality of life by reducing fatigue.C. In the Breast Cancer Erythropoietin Survival Trial (BEST), patients with metastatic breast cancer demonstrated improved overall survival when treated with epoetin alpha compared to placebo.D. The activation of hypoxic signaling pathways, including HIF-1α, is associated with resistance to therapy and depends critically on hemoglobin levels

Which statement describing tumor vasculature is correct?

A. Tumor blood vessels are hyper-permeable, tortuous, and feature haphazard patterns of interconnection, resulting in spatial and temporal heterogeneity of tumor blood flow.B. Tumor blood vessels are hypopermeable, irregular, and densely invested with pericytes resulting in poor diffusion of chemotherapeutics into tumor parenchyma.C. Tumor blood vessels are indistinguishable from normal blood vessels ultrastructurally, however compression caused by proliferating tumor cells leads to vessel collapse and compromised blood flow.D. Tumor blood vessels are dilated, tortuous and have uniformly thick basement membranes, resulting in limited accessibility of chemotherapy agents.E. Tumor blood vessel organization resembles that of normal vessels, however tumor vessels differ ultrastructurally, resulting in poor function and heterogeneous blood flow.

The regulation of hypoxia-inducible factor-1α (HIF-1α) by oxygen concentration is best described by which of the following statements?

A. Under hypoxic conditions, HIF-1α transcription and translation are upregulated, causing the protein to translocate from the cytosol to the nucleus.B. Under aerobic conditions, the HIF-1α heme moiety becomes oxygenated. This drives a conformational change in the protein limiting DNA binding preventing up-regulation of target genes.C. Under hypoxic conditions, HIF-1α is activated by bioreduction, thereby promoting the up-regulation of target genes.D. Under hypoxic conditions, the HIF-1α heme moiety becomesdeoxygenated. This causes a conformational change in the protein,enhancing DNA binding promoting up-regulation of target genes.E. Under aerobic conditions, HIF-1α is hydroxylated by HIF prolylhydroxylases. This targets the protein for ubiquitination and subsequent proteosomal degradation, thereby preventing the up-regulation of target genes.

Methods currently under investigation to monitor the effectiveness of antiangiogenictherapy include all of the following, EXCEPT:

A. dynamic MRI/CT and PET imagingB. serial tumor biopsiesC. plasma levels of bevacizumabD. VEGF concentration in the urineE. presence of vascular endothelial cells in the peripheral blood