TARGETING HSP90 IN IM-RESISTANT GIST: KIT DEGRADATION AS A BROADLY RELEVANT SALVAGE STRATEGY
From micro GIST to GIST: How can it...Distribution of KIT E11 Deletion, clinical GISTs Distribution...
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From micro GIST to GIST: How can it happen? (Why doesn’t it happen?) Jonathan A. Fletcher, M.D. Dept of Pathology Brigham and Women’s Hospital Dana-Farber Cancer Institute Boston Brigham and Women‘s Hospital, Harvard Medical School Dana-Farber/Harvard Cancer Center
Transcript of From micro GIST to GIST: How can it...Distribution of KIT E11 Deletion, clinical GISTs Distribution...
From micro GIST to GIST: How can it happen? (Why doesn’t it happen?)
Jonathan A. Fletcher, M.D.
Dept of Pathology
Brigham and Women’s Hospital
Dana-Farber Cancer Institute Boston
Brigham and Women‘s Hospital, Harvard Medical School
Dana-Farber/Harvard Cancer Center
microGIST (<1cm) Found in 30% of the general population
EG junction, spindle cell type
Dr. Cher-Wei Liang
Why Study MicroGIST???
►One of the most common benign tumors
►Only common benign tumor that results from TK genomic mutation
►Define events responsible for progression
►from TK-mutant ICC hyperplasia to microGIST
►from microGIST to clinical GIST
►Characterize barriers to malignant progression
Oncogenic KIT/PDGFRA
RAS-GDP
RAF
SHC
BAD
SOS
GRB2
14-3-3
BCLXL
Mitochondria
BCLXL
FAK
P
RAS-GTP
SAPK
AKT
14-3-3
BAD
P
RAS-GAP DOK
PI3K
MEK1/2 P P
P
P
MAPK
P PAK1 P
Adhesion,
motility
mTOR P
P
JAK
STATs
P
P
P
ETV1
Mutation Status in Small (<2cm) vs. Clinically-overt GISTs
Drs. Sabrina Rossi, Roberta Maestro, Paolo dei Tos, AJSP, 2010
Genotype Small GISTs (N = 135)
Overt GISTs (N = 101)
P value
Mutant 74% 84% 0.078
KIT exon 11 46% 61% 0.025
Relevant Risk Parameters for Primary
GIST Including Molecular Data
Parameters
Lower risk
Higher risk
Surgery R0 R1, rupture
Location Stomach Small bowel, rectal or other
location
Size < 5 cm > 5 cm
Mitotic count < 5/50 HPFs > 5/50 HPFs
Mutated
gene PDGFRA
KIT
Wildtype (non-PDGFR, non-KIT)
KIT
mutational
type
Duplication/
Insertion
in exon 11
Deletion in exon 11
(esp. in codons W557 and K558);
Duplication/insertion in exon 9
Wardelmann et al., Virchows Archiv 2007
“Worrisome” KIT mutations in benign microGISTs
Dr. Cher-wei Liang
Exon 9 (4mm) Ex 11 del557-558 (3mm)
Ex 11 homozygous (3mm)
aCGH
Microdissection of tumor
tissue
WGA x 4 times
Pool Co-
hybridization Result
Microdissection of normal
tissue
WGA x 4 times
Pool Co-
hybridization
Cher-Wei Liang, MD
DELETIONS
1p 14q
22
GIST Genetic Progression
KIT or PDGFRA mutation→14 →22q →1p
MicroGIST Genome Screen
Cellular region Hyalinized region
FISH evaluation of chr 14 deletion in viable vs. hyalinized regions of microGISTs (N = 11)
Chr 14 deletion evaluated in 200 cells from 11 microGISTs 5 of 11 microGISTs (45%) had chr 14 deletion– present equally in cellular and hyalinized components
Pseudo-amplification of Biologically Crucial GIST Genes
DOG1(ANO1, TMEM16A): RS 0.52
Cher-Wei Liang, MD
DOG1 Pseudo-amplification: exonic and intronic
Courtesy of Cher-Wei Liang, MD
Clinical GIST Non-GIST Sarcomas
Top 30 active-transcription regions in microGISTs
Top 30 Neighbors
Top 30 Genes
IGF2 (0.78), DOG1 (0.52), CD34 (0.50), SPRY4 (0.45), KIT (0.32), PRKCQ (0.27), PROM1 (0.29), ETV1 (0.24)
MicroGISTs and clinical GISTs share gene expression biomarkers
Despite KIT & PDGFRA mutations, and “GIST biology”: MicroGISTs struggle to grow
Dr. Cher-wei Liang
Hyalinization Calcification
B
Distribution of KIT E11 Deletion, clinical GISTs
Distribution of KIT exon 11 deletion in 110 microGISTs (30, reference) collected from 6 series.
KIT exon 11 deletions in clinical GISTs vs. microGISTs
J Lasota & M Miettinen, Histopathology 2008
Distribution of KIT Ex11 deletions, microGISTs (34 cases from present series, and 76 cases from previously published series)
CL Corless et al., AJP 2002 K Kawanowa et al., Hum P 2006 A Agaimy et al., AJSP 2007 A Agaimy et al., AJSP 2008 S Rossi et al., AJSP 2010
MicroGIST Mutations Expressed in KIT-negative GIST48B
Cher-wei Liang
SCF (KIT-LG) dose response
MicroGIST Mutations Expressed in KIT-negative GIST48B
Cher-wei Liang
SCF (KIT-LG) dose response
MicroGIST Mutations Expressed in KIT-negative GIST48B
Cher-wei Liang
SCF (KIT-LG) dose response
MicroGIST Mutations Expressed in KIT-negative GIST48B
Cher-wei Liang
SCF (KIT-LG) dose response
MicroGIST Mutations Expressed in KIT-negative GIST48B
Cher-wei Liang
SCF (KIT-LG) time response
KIT-ligand (SCF): strong expression in smooth muscle; weak-to-no expression in microGIST
Green: Desmin Red: SCF Blue: DAPI
MicroGISTs have infiltrative borders (90.7%) and smooth muscle markers (49%)
GREEN = Desmin RED = DOG1 BLUE = DAPI
RED = Desmin Brown = DOG1
Dr. Jason Hornick
Some microGISTs are smooth muscle-dependent tumors
Dr. Cher-Wei Liang
Cell cycle dysregulation in GIST
TP53 MDM2 CDKN2A RB1 ATM None %mut
0 0 0 0 0 16 0%
TP53 MDM2 CDKN2A RB1 ATM None %mut
4 1 11 1 1 6 75%
Low-risk GIST (N = 16)
High-risk GIST (N = 24)
Conclusions #1
►MicroGISTs are on a biologic continuum with malignant GISTs
►But, they virtually never progress to malignancy
►And, they very often involute
►Certain KIT & PDGFRA mutations cannot sustain malignant progression
Conclusions #2
►Progression from microGIST to clinical problem Ligand-independence or autocrine/paracrine
Further cell cycle dysregulation
Other genetic hits (14q, 22q, 1p…..)
Acknowledgements
Brigham and Women’s Hospital
Department of Pathology
Cher-wei Liang Yuexiang Wang
Adrián Mariño Enríquez
Stephen Swank
Meijun Zhu
Cheng-Han Lee
Christopher D.M. Fletcher
Jason Hornick
Division of Surgical Oncology
Chandrajit P. Raut
Treviso
Angelo Paolo dei Tos
Sabrina Rossi
Aviano
Roberta Maestro
Dana Farber Sarcoma Program
George D. Demetri
Andrew Wagner
Memorial Sloan Kettering Cancer Center
Cristina Antonescu
Virginia and Daniel K.Ludwig Trust for Cancer Research,
GIST Cancer Research Fund, The LifeRaft Group,
National Institutes of Health (1P50CA127003).
