Project description:Pediatric GIST commonly harbors a disabled succinate dehydrogenase complex (SDH), which yields tumors with highly conserved genomes but characteristic epigenomic signatures. Mysteriously, nearly half of such SDH-deficient GIST, including tumors from Carney Triad patients, lack identifiable mutations in SDH component genes and genes required for complex assembly (SDHA, SDHB, SDHC, SDHD, SDHAF, termed SDHx). Genomic sequencing coupled with DNA methylation and transcriptional profiling have exposed SDHC promoter-specific CpG island epimutation and concomitant gene silencing in the majority of SDHx-WT GIST. We performed whole genome expression profiling on 20 FFPE dSDH GIST tumors using Affymetrix U133P2 arrays which contain >54K gene target probesets. Included here were data from 7 SDHx-w.t. and 13 SDHx mutants that passed array QC.
Project description:Pediatric GIST commonly harbors a disabled succinate dehydrogenase complex (SDH), which yields tumors with highly conserved genomes but characteristic epigenomic signatures. Mysteriously, nearly half of such SDH-deficient GIST, including tumors from Carney Triad patients, lack identifiable mutations in SDH component genes and genes required for complex assembly (SDHA, SDHB, SDHC, SDHD, SDHAF, termed SDHx). Genomic sequencing coupled with DNA methylation and transcriptional profiling have exposed SDHC promoter-specific CpG island epimutation and concomitant gene silencing in the majority of SDHx-WT GIST.
Project description:Purpose: Gastrointestinal stromal tumor (GIST) is the most common sarcoma of the gastrointestinal tract, with mutant succinate dehydrogenase (SDH) subunits (A-D) comprising less than 7.5% (i.e., 150-200/year) of new cases annually in the United States. Contrary to GISTs harboring KIT or PDGFRA mutations, SDH-mutant GISTs affect adolescents/young adults, often metastasize, and are frequently resistant to tyrosine kinase inhibitors (TKI). Lack of human models for any SDH-mutant tumors, including GIST, has limited molecular characterization and drug discovery. Experimental design: We describe methods for establishing novel patient-derived SDH-mutant (mSDH) GIST models and interrogated the efficacy of temozolomide on these tumor models in vitro and in clinical trials of patients with mSDH GIST. Results: Molecular and metabolic characterization of our patient-derived mSDH GIST models revealed that these models recapitulate the transcriptional and metabolic hallmarks of parent tumors and SDH deficiency. We further demonstrate that temozolomide elicits DNA damage and apoptosis in our mSDH GIST models. Translating our in vitro discovery to the clinic, a cohort of patients with SDH-mutant GIST treated with temozolomide (n = 5) demonstrated a 40% objective response rate and 100% disease control rate, suggesting that temozolomide represents a promising therapy for this subset of GIST. Conclusions: We report the first methods to establish patient-derived mSDH tumor models, which can be readily employed for understanding patient-specific tumor biology and treatment strategies. We also demonstrate that temozolomide is effective in patients with mSDH GIST who are refractory to existing chemotherapeutic drugs (namely, TKIs) in clinic for GISTs, bringing a promising treatment option for these patients to clinic.
Project description:Epigenetic aberrations are widespread in cancer, yet the underlying mechanisms and causality remain poorly understood. A subset of gastrointestinal stromal tumors (GISTs) lack canonical kinase mutations but instead have succinate dehydrogenase (SDH)-deficiency and global DNA hyper-methylation. Here we associate this hyper-methylation with changes in genome topology that activate oncogenic programs. To investigate epigenetic alterations systematically, we mapped DNA methylation, CTCF insulators, enhancers, and chromosome topology in KIT-mutant, PDGFRA-mutant, and SDH-deficient GISTs. Although these respective subtypes shared similar enhancer landscapes, we identified hundreds of putative insulators where DNA methylation replaced CTCF binding in SDH-deficient GISTs. We focused on a disrupted insulator that normally partitions a core GIST super-enhancer from the FGF4 oncogene. Recurrent loss of this insulator alters locus topology in SDH-deficient GISTs, allowing aberrant physical interaction between enhancer and oncogene. CRISPR-mediated excision of the corresponding CTCF motifs in an SDH-intact GIST model disrupted the boundary and strongly up-regulated FGF4 expression. We also identified a second recurrent insulator loss event near the KIT oncogene, which is also highly expressed across SDH-deficient GISTs. Finally, we established a patient-derived xenograft (PDX) from an SDH-deficient GIST that faithfully maintains the epigenetic state of the parental tumor, including hyper-methylation and insulator defects. This PDX model is highly sensitive to FGF receptor (FGFR) inhibitor, and more so to combined FGFR and KIT inhibition, validating the functional significance of the underlying epigenetic lesions. Our study reveals how epigenetic alterations can drive oncogenic programs in the absence of canonical kinase mutations, with implications for mechanistic targeting of aberrant pathways in cancers.
Project description:Gene expression profiling of immortalized human mesenchymal stem cells with hTERT/E6/E7 transfected MSCs. hTERT may change gene expression in MSCs. Goal was to determine the gene expressions of immortalized MSCs.
Project description:Transcriptional profiling of human mesenchymal stem cells comparing normoxic MSCs cells with hypoxic MSCs cells. Hypoxia may inhibit senescence of MSCs during expansion. Goal was to determine the effects of hypoxia on global MSCs gene expression.