pediatric gist
DESCRIPTION
Pediatric GIST. Genetic progression mechanisms KIT/PDGFRA transforming roles. Katherine Janeway, MD. Objectives. To determine whether the incidence of KIT / PDGFRA mutations in a large group of pediatric patients is similar to that reported previously in smaller patient groups - PowerPoint PPT PresentationTRANSCRIPT
Pediatric GIST
Genetic progression mechanisms
KIT/PDGFRA transforming roles
Katherine Janeway, MD
Characteristic Adult GIST Pediatric GIST
Age Peak 60
Gender distribution Equal
Morphology 70% spindle cell
KIT IHC Positive (except PDGFRA mutant)
KIT/PDGFRA genotype
>85% mutant
Genetic alterations 14q, 22q, 1p loss
Models Cell lines, xenografts, transgenics
Therapy Imatinib, sunitinib, others
Characteristic Adult GIST Pediatric GIST
Age Peak 60 Median 12
Gender distribution Equal
Morphology 70% spindle cell
KIT IHC Positive (except PDGFRA mutant)
KIT/PDGFRA genotype
>85% mutant
Genetic alterations 14q, 22q, 1p loss
Models Cell lines, xenografts, transgenics
Therapy Imatinib, sunitinib, others
Characteristic Adult GIST Pediatric GIST
Age Peak 60 Median 12
Gender distribution Equal 75% female
Morphology 70% spindle cell
KIT IHC Positive (except PDGFRA mutant)
KIT/PDGFRA genotype
>85% mutant
Genetic alterations 14q, 22q, 1p loss
Models Cell lines, xenografts, transgenics
Therapy Imatinib, sunitinib, others
Characteristic Adult GIST Pediatric GIST
Age Peak 60 Median 12
Gender distribution Equal 75% female
Morphology 70% spindle cell 70% epithelioid
KIT IHC Positive (except PDGFRA mutant)
KIT/PDGFRA genotype
>85% mutant
Genetic alterations 14q, 22q, 1p loss
Models Cell lines, xenografts, transgenics
Therapy Imatinib, sunitinib, others
Characteristic Adult GIST Pediatric GIST
Age Peak 60 Median 12
Gender distribution Equal 75% female
Morphology 70% spindle cell 70% epithelioid
KIT IHC Positive (except PDGFRA mutant)
Positive
KIT/PDGFRA genotype
>85% mutant
Genetic alterations 14q, 22q, 1p loss
Models Cell lines, xenografts, transgenics
Therapy Imatinib, sunitinib, others
Characteristic Adult GIST Pediatric GIST
Age Peak 60 Median 12
Gender distribution Equal 75% female
Morphology 70% spindle cell 70% epithelioid
KIT IHC Positive (except PDGFRA mutant)
Positive
KIT/PDGFRA genotype
>85% mutant 15% mutant
Genetic alterations 14q, 22q, 1p loss
Models Cell lines, xenografts, transgenics
Therapy Imatinib, sunitinib, others
Characteristic Adult GIST Pediatric GIST
Age Peak 60 Median 12
Gender distribution Equal 75% female
Morphology 70% spindle cell 70% epithelioid
KIT IHC Positive (except PDGFRA mutant)
Positive
KIT/PDGFRA genotype
>85% mutant 15% mutant
Genetic alterations 14q, 22q, 1p loss ?
Models Cell lines, xenografts, transgenics
Therapy Imatinib, sunitinib, others
Characteristic Adult GIST Pediatric GIST
Age Peak 60 Median 12
Gender distribution Equal 75% female
Morphology 70% spindle cell 70% epithelioid
KIT IHC Positive (except PDGFRA mutant)
Positive
KIT/PDGFRA genotype
>85% mutant 15% mutant
Genetic alterations 14q, 22q, 1p loss ?
Models Cell lines, xenografts, transgenics
None
Therapy Imatinib, sunitinib, others
Characteristic Adult GIST Pediatric GIST
Age Peak 60 Median 12
Gender distribution Equal 75% female
Morphology 70% spindle cell 70% epithelioid
KIT IHC Positive (except PDGFRA mutant)
Positive
KIT/PDGFRA genotype
>85% mutant 15% mutant
Genetic alterations 14q, 22q, 1p loss ?
Models Cell lines, xenografts, transgenics
None
Therapy Imatinib, sunitinib, others ?
Objectives
To determine whether the incidence of KIT / PDGFRA mutations in a large group of pediatric patients is similar to that reported previously in smaller patient groups
To correlate KIT / PDGFRA genotype with the activation status of KIT, PDGFRA and downstream signaling intermediates
To define the chromosomal aberrations in pediatric GIST in relation to those seen in adult GIST
MethodsPatients 27 patients age less than 25 with confirmed GIST
Subset of 15 patients had cryopreserved specimens
KIT and PDGFRA mutation analysis KIT exons 9, 11, 13 and 17 and PDGFRA exons 12
and 18 were PCR amplified and screened for mutations by high performance liquid chromatography
The entire KIT coding sequence was PCR amplified from cDNA and sequenced using the ABI 3730 xl sequencer
SNP assay DNAs were isolated from cryopreserved tumor and
analyzed using an Affymetrix 10K SNP array at the DFCI Microarray Core Facility
Western blotting Whole cell lysates from cryopreserved tumors were
separated by gel electrophoresis using 4 to 12% Bis-Tris gels and blotted to nitrocellulose membranes. Immunostains were detected by enhanced chemiluminesence .
Methods
KIT and PDGFRA genotyping
Mutation analysis Three of 27 patients (11%) with KIT or PDGFRA
mutation KIT exon 11 homozygous deletion VV559-560 (17 yo) KIT exon 9 heterozygous AY502-503 tandem duplication (22 yo) PDGFRA exon 18 D842V point mutation (14 yo)
Four patients with GISTs lacking mutations on genomic DNA sequencing also lacked KIT mutations upon sequencing of the entire coding region from cDNA
Conclusions
Most pediatric GISTs are KIT/PDGFRA - wildtype Our 27 cases plus 31 previously published genotyped
cases: 15% of pediatric GISTs harbor KIT or PDGFRA mutations
Pediatric Adult
KIT exon 11 5% 66%
KIT exon 9 9% 10%
PDGFRA 3% 7%
Mechanisms of genetic progression are significantly different in pediatric KIT-wildtype GISTs versus pediatric and adult KIT-mutant GISTs Biologically different tumors despite KIT expression and
activation
Conclusions
Pediatric KIT-wildtype GISTs display KIT expression and activation at levels comparable with KIT-mutant pediatric and adult GISTs Mechanism is unclear
Therapeutic inhibitors of KIT activation, particularly wildtype-KIT activation and inhibitors of signaling molecules downstream of KIT have the potential to be active in pediatric KIT-wildtype GIST
Conclusions
Thanks!
Brigham and Women’s Hospital Jonathan Fletcher Bernadette Liegl
Oregon Health Sciences University Mike Heinrich Chris Corless
Children’s Hospital, Boston Antonio Perez-Atayde Harry Kozakewich
Big Papi