Yuri E. Nikiforov Department of Pathology University of Cincinnati Genetic Alterations Involved in...
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Yuri E. NikiforovDepartment of PathologyUniversity of Cincinnati
Genetic Alterations Involved in the Transition from Well Differentiated to Poorly Differentiated and Anaplastic
Thyroid Carcinomas
Endocrine Pathology Companion Meeting
Outline Genetic events in thyroid WDC, PDC,
and AC
Molecular evidence for progression• BRAF and RAS mutations• RET/PTC and PAX8-PPAR
rearrangements • p53 and β-catenin mutations Evidence from LOH studies Molecular pathways in progression of
thyroid CA: Summary
Thyroid follicular
cell
Papillary Carcinoma
AC PDC
PAX8-PPARγ
BRAFRET/PTCRAS
P53β-catenin
RAS
Molecular Alterations in Thyroid Tumors
Hurthle Cell Carcinoma
Follicular Carcinoma
BRAF
SOS
B-RAF
RASGRB2
MEK
ERK
SOS
c-Jun, Fos,c-Myc, Elk-1
Signaling Pathways Activated by BRAF in Thyroid Tumors
Y1015
Y1062PLCγ
Enigma
SHC
FRS2Y1096
P
P
P
RET
P
P
P
RBD C Kinase domain
Spectrum of BRAF Point Mutations in Various Tumors
Phe Gly Leu Ala The Val Lys Ser
P P
594 595 598 601596 599Val Glu
Leu
585
Gly
465
Gly
465
Gly
463
Prevalence of BRAF Mutations in Thyroid Tumors
PC FC PDC AC
Mean
N of cases39%
227/580
0
0/77
13%
2/16
14%
5/35
Nikiforova et al. 2003
Cohen et al., 2003
Xu et al., 2003
Namba et al., 2003
Fukashima et al., 2003
Trovisco et al., 2004
BRAF Mutations Present in Both Well Differentiated and Poorly Differentiated
Carcinoma Areas
Nikiforova et al. (2003)
DNA DNA
BRAF + BRAF +
PC,WD PDC
Prevalence ofBRAF mutations
PDCwith no WD componentwith PC componentwith FC/HCC component
0/82/7 (29%)
0/1
ACwith no WD componentwith PC componentwith FC/HCC component
0/203/5 (60%)
0/4
BRAF Mutations in Poorly Differentiated and Anaplastic Carcinomas
Nikiforova et al. (2003)
BRAF Mutations: Summary PC with BRAF are prone to
dedifferentiation and transformation to PDC and AC
Other genetic mutations are required to direct this process
NNBRAF
PCPC
PDCPDC
ACAC
Additional mutations
RAS
• Point mutations found in many human cancers and in most types of thyroid tumors
• K-RAS, H-RAS, N-RAS genes may be involved
• Hot spots - codons 12, 13 and 61
• N-RAS codon 61 mutations most common in thyroid tumors
RAS Mutations
Mechanism of RAS Activation by Point Mutation
RAS
RAS
GTP
GDP
GAPs
H2O
Pi GTP
GDP
SOSGDSsCDC25
C3G
DownstreamEffectors
Mutationscodons 12/13 or 61
Molecular Pathways Activated by RAS
RASGRB2
SOS
PLC Ral/Cdc42
DAG
PKC
AKT
Rho
Rac
B-RAF
MEK
ERK
PI3K
JNK
P70S6K
MEKK1
BCL
BAD
Apoptosisc-Jun, Fos,c-Myc, Elk-1
Y1062
SHC
FRS2
RET
P
P
P
P
Prevalence of RAS Mutations in Thyroid Tumors
PC FC PDC AC
Mean
N of cases15%
38/253
45%
21/47
24%
14/58
55%
12/22
RAS in Progression of Thyroid Tumors: Case report of AC with areas of FC
FCAC
RAS codon 61
CAA CGA + +
p53 codon 189
GCC GTC - +
Asakawa & Kobayashi (2002)
Mutations found:
• Development of nodules, adenomas, and carcinomas in transgenic mice
• Increased cell proliferation but insufficient for complete transformation of cultured cells
• Increased chromosome instability, i.e. micronuclei, centrosome amplification, chromosome misalignment during mitosis
Consequences of RAS Activation in Thyroid Cells
RAS Mutations: Summary Predispose FC and PC to dedifferentiation,
likely by increasing genomic instability Require additional mutations for
dedifferentiation
NNRAS PCPC PDCPDC
ACAC
Additional mutations
FCFC
RET/PTC Rearrangement
RET/PTC Rearrangements
Wild type RET (10q11.2)
EC TM TK
RET/ PTC1
RET / PTC2 andnovel types
RET / PTC3
H4 (10q21)
CC
TK
TK
TKELE1 (10q11.2)
CC
Gene N
CC
PLCγ
Enigma
SHC
FRS2
SOS
GRB2
RAF
RAS
MEK
ERK
PP
PP
Y1015
Y1062
RET/PTC
c-Jun, Fos ,c-Myc , Elk-1
Molecular Pathways Activated by RET/PTC
PC FC PDC ACSantoro (1992) 19%
33/1770
0/370
0/15Wynford-Thomas(1993)
00/45
00/19
Tallini (1998) 40%81/201
00/22
00/15
00/17
Nikiforov(unpublished)
19%18/93
00/46
00/12
00/11
Santoro (2002) 13%8/62
Prevalence of RET/PTC in Thyroid Tumors
RET/PTC Rearrangements: Summary
No RET/PTC in anaplastic carcinomas Data on PDC not entirely conclusive Likely - PC with RET/PTC have low
potential for dedifferentiation/progression
NNRET/PTC
PCPC
Molecular Pathways in Thyroid Papillary Carcinogenesis
NNRET-PTC
15%15%
40%40%BRAF
RAS
20%20%
PCPC
PCPC
PCPC
PDCPDC ACAC
PAX8-PPARγ Rearrangement
Structure of PAX8-PPAR Fusion Protein
PPARPAX8
PD HD DA/B C E/F
Kroll et al. (2000)
• Results from fusion of PAX8 (2q13) and PPARγ (3p25) genes
• PAX8-PPARγ chimeric protein has dominant negative effect on wild-type PPARγ
• Wild-type PPARγ may inhibit thyroid cell growth
(tumor suppressor gene)
PAX8-PPARγ Rearrangement
Prevalence of PAX8-PPAR in Thyroid Tumors
PC FC PDC AC
Mean
N of cases1%
1/144
36%
45/125
0
0/12
0
0/32
PAX8-PPAR Rearrangements: Summary
No RET/PTC in PDC and AC Likely - FC with PAX8-PPARγ lack
potential for dedifferentiation/ progression
NNPAX8-PPARγ
FCFC
Molecular Pathways in Thyroid Follicular Carcinogenesis
FCFC
PAX8-PPARγ35%35%
FAFA
RAS45%45%
PDCPDC ACAC
NN
FCFC
Mutations Directing Progression/ Dedifferentiation of Thyroid Tumors: p53
PC FC PDC AC
Mean
N of cases1%
1/110
5%
1/21
24%
21/89
74%
14/19
Mutations Directing Progression/ Dedifferentiation of Thyroid Tumors:
β-catenin
PC FC PDC ACGarsia-Rostan(2001)
00/46
00/12
25%7/28
66%19/29
Rosha (2003) 00/17
PC FC PDC AC
BRAF 39% 0 13% 14%
RAS 15% 45% 24% 55%
RET/PTC 35% 0 9% 0
PAX8-PPAR 1% 36% 0 0
P53 1% 5% 24% 74%
β-catenin 0 0 16% 66%
Specific Genetic Events in Thyroid Tumors: Summary
Molecular Evidence for Progression/Dedifferentiation:
LOH Studies
• In the same tumor, WDC and AC components have similar patterns of allelic loss
• Increased LOH rate in AC component
J. Hunt et al. (2003)
Molecular Pathways in Progression of Thyroid Carcinomas: Summary
• Studies of gene mutations and LOH supports the following progression:
WDC PDC AC
• WD tumors with BRAF and RAS mutations are prone for dedifferntiation, but require additional mutations
• p53 and possibly β-catenin directly guide
progression
Nikiforov Lab
Marina Nikiforova
Zhaowen Zhu
Raffaele Ciampi
Christy Caudill
Manoj Gandhi
Acknowledgements
James FaginUniversity of Cincinnati
Todd Kroll Emory University
Giovanni Tallini