Phosphoglycerate dehydrogenase diverts glycolytic flux and contributes to oncogenesis

Most tumors exhibit increased glucose metabolism to lactate, however, the extent to which glucose-derived metabolic fluxes are used for alternative processes is poorly understood [1, 2]. Using a metabolomics approach with isotope labeling, we found that in some cancer cells a relatively large amount of glycolytic carbon is diverted into serine and glycine metabolism through phosphoglycerate dehydrogenase (PHGDH). An analysis of human cancers showed that PHGDH is recurrently amplified in a genomic region of focal copy number gain most commonly found in melanoma. Decreasing PHGDH expression impaired proliferation in amplified cell lines. Increased expression was also associated with breast cancer subtypes, and ectopic expression of PHGDH in mammary epithelial cells disrupted acinar morphogenesis and induced other phenotypic alterations that may predispose cells to transformation. Our findings show that the diversion of glycolytic flux into a specific alternate pathway can be selected during tumor development and may contribute to the pathogenesis of human cancer.National Institutes of Health (U.S.)National Cancer Institute (U.S.)Smith Family FoundationDamon Runyon Cancer Research FoundationBurroughs Wellcome Fun

IDH1 and IDH2 mutations in cholangiocarcinoma

Purpose of review Genetic alterations in intrahepatic cholangiocarcinomas have been poorly characterized. Recent studies have discovered that intrahepatic cholangiocarcinomas have recurrent mutations in isocitrate dehydrogenase. We will review the effects of these mutations on several biochemical pathways, as well as potential changes to downstream signaling pathways. Recent findings Hotspot mutations in isocitrate dehydrogenase isoforms 1 or 2 occur in 10% to 23% of intrahepatic cholangiocarcinomas. These tumors have elevated levels of an oncometabolite, 2-hydroxyglutarate, which results in higher DNA CpG methylation and altered histone methylation. Limited experiments in different tumor types have suggested higher epithelial-mesenchymal transition, FGFR signaling or MAPK signaling among IDH1/2-mutated tumors. Summary Tumors with IDH1 or IDH2 mutations may represent a distinct sub-type of cholangiocarcinomas. Further studies are needed to determine whether these mutated genes are responsible for tumorigenesis or tumor maintenance, as well as additional cancer genes that may cooperate with IDH

Erk regulation of pyruvate dehydrogenase flux through PDK4 modulates cell proliferation

In this study, Brugge et al. demonstrate how growth factor signaling regulates a key node of intracellular glucose metabolism, which in turn controls ATP levels, lipogenesis, and cell proliferation. These results identify metabolic changes in normal and transformed cells in response to growth factor deprivation and loss of attachment to the ECM

Isocitrate Dehydrogenase Mutations Promote a ZEB1/mir-200-dependent Epithelial Mesenchymal Transition

Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) occur in a variety of tumor types, and these mutations result in production of the oncometabolite, 2-hydroxyglutarate (2-HG). However it is not clear how mutant IDH and 2-HG alter signaling to promote cancer.To address this question, we created a panel of isogenic IDH1/2 wild-type and mutant colon carcinoma and mammary epithelial cell lines. From this, differences were noted in the ability of different IDH2 mutations to cause robust 2-HG accumulation. We find that IDH1/2 mutants producing high levels of intracellular 2-HG cause an epithelial mesenchymal transition (EMT)-like phenotype, characterized by changes in EMT-related gene expression as well as changes in cellular morphology. Addition of exogenous 2-HG to an IDH wild-type cell line is sufficient on its own to induce an EMT-like phenotype. The mutant IDH-induced EMT is dependent on upregulation of the transcription factor ZEB1 and downregulation of the mir-200 family of micro RNA’s. Knockdown of IDH1 in IDH1 R132H mutant cells is sufficient to reverse the EMT-like phenotype, demonstrating the necessity for continued expression of mutant IDH and 2-HG to maintain this phenotype. These results suggest mutant IDH proteins reversibly deregulate discreet signaling pathways that contribute to tumorigenesis

Abstract LB565: Efficacy of a highly potent and selective KIT V654A inhibitor for treatment of imatinib resistant GIST

Abstract Gastrointestinal stromal tumor (GIST) is the most common type of sarcoma, with approximately 5,000 patients diagnosed per year in the US. Approximately 80% of patients with GIST present with mutations in the c-KIT oncogene at exon 9 or 11, which leads to constitutive, ligand-independent activation of the KIT receptor tyrosine kinase. For patients with metastatic GIST, frontline therapy with imatinib is effective, with a response rate of approximately 51-54% and median progression-free survival (PFS) of 19-23 months, in a molecularly unselected population. Other agents are approved for advanced GIST, without molecular selection, after progression on imatinib, including sunitinib, regorafenib, and ripretinib; however, response rates are less than 10% with PFS of approximately 5-6 months. Notably, patients who progress on imatinib and other tyrosine kinase inhibitors may develop a variety of on-target resistance mutations in the KIT oncogene, such as those in exon 17 (including at amino acids D816 and D820, activation loop mutation), exon 13 (V654A, ATP-binding region mutation), and less frequently in exon 14 (T670I, gatekeeper mutation). Several KIT inhibitors have been developed to potently target the exon 17 resistance mutations (avapritinib and ripretinib); however, there remains an important medical need in 2nd- and 3rd-line therapy in a molecularly unselected population of imatinib-resistant GIST. This suggests more broad-spectrum KIT inhibition is likely required, a hypothesis supported by the observation of large inter- and intra-patient heterogeneity of KIT secondary mutations across hundreds of samples obtained from patients with GIST treated with avapritinib. Sequencing data from the NAVIGATOR phase 1 trial (NCT02508532) revealed that patients with KIT mutant GIST and with the KIT V654A secondary resistance mutation had a poor response to treatment with avapritinib. To address this, we developed a highly potent and selective inhibitor of KIT V654A. This inhibitor showed dose-dependent modulation of downstream pharmacodynamic markers and induced tumor regression in a mastocytoma xenograft model driven by an exon 11 plus 13 V654A resistance mutation. Importantly, this inhibitor was generally well-tolerated and showed high selectivity over wild-type KIT. These findings suggest this novel KIT inhibitor has the potential to be used as a single agent or combination therapy for patients with imatinib-resistant GIST harboring the KIT V654A mutation. Citation Format: Alexandra R. Grassian, Joseph Kim, Omar Ahmad, Kevin Barvian, Alison Davis, Tom Dineen, Wei Hu, Ebby Job, Ludivine Moine, Kate Newberry, Maria Roche, Doug Shorten, Yeon Sook Choi, Francis Wolenski, Sebastian Bauer, Cesar Serrano, Jonathan Trent, Suzanne George. Efficacy of a highly potent and selective KIT V654A inhibitor for treatment of imatinib resistant GIST [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB565

Preclinical Evidence of Anti-Tumor Activity Induced by EZH2 Inhibition in Human Models of Synovial Sarcoma.

The catalytic activities of covalent and ATP-dependent chromatin remodeling are central to regulating the conformational state of chromatin and the resultant transcriptional output. The enzymes that catalyze these activities are often contained within multiprotein complexes in nature. Two such multiprotein complexes, the polycomb repressive complex 2 (PRC2) methyltransferase and the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeler have been reported to act in opposition to each other during development and homeostasis. An imbalance in their activities induced by mutations/deletions in complex members (e.g. SMARCB1) has been suggested to be a pathogenic mechanism in certain human cancers. Here we show that preclinical models of synovial sarcoma-a cancer characterized by functional SMARCB1 loss via its displacement from the SWI/SNF complex through the pathognomonic SS18-SSX fusion protein-display sensitivity to pharmacologic inhibition of EZH2, the catalytic subunit of PRC2. Treatment with tazemetostat, a clinical-stage, selective and orally bioavailable small-molecule inhibitor of EZH2 enzymatic activity reverses a subset of synovial sarcoma gene expression and results in concentration-dependent cell growth inhibition and cell death specifically in SS18-SSX fusion-positive cells in vitro. Treatment of mice bearing either a cell line or two patient-derived xenograft models of synovial sarcoma leads to dose-dependent tumor growth inhibition with correlative inhibition of trimethylation levels of the EZH2-specific substrate, lysine 27 on histone H3. These data demonstrate a dependency of SS18-SSX-positive, SMARCB1-deficient synovial sarcomas on EZH2 enzymatic activity and suggests the potential utility of EZH2-targeted drugs in these genetically defined cancers

Circulating tumor DNA (ctDNA) analyses of the phase III VOYAGER trial: KIT mutational landscape and outcomes in patients with advanced gastrointestinal stromal tumor (GIST)

101 Background: The genotype of primary mutations predicts imatinib response in untreated metastatic GIST. However, the sequence of salvage treatments in metastatic GIST is based solely on the chronological order of registration trials. ctDNA sequencing offers a powerful diagnostic tool to detect resistance mutations in GIST but has not been shown to correlate with outcomes in clinical trials of pretreated patients (pts). We analyzed ctDNA samples collected at baseline in the phase III VOYAGER trial (NCT03465722) to describe the landscape of KIT alterations and its association with outcomes of pts treated with avapritinib or regorafenib. Methods: In VOYAGER, 476 pts with advanced KIT-mutant GIST were randomly assigned to avapritinib (240 pts) or regorafenib (236 pts) in 3rd-4th line. Baseline plasma was collected and ctDNA analyzed with the Guardant 360 (G360), 74-gene panel. KIT molecular subgroups were determined and correlated with outcomes. PDGFRA-mutant GISTs were excluded from outcomes analysis. Results: Baseline ctDNA analysis was performed in 386/476 pts (81%). ctDNA was detected in 333 pts (86%), with 250 and 18 pts showing at least one KIT (75%) or PDGFRA (5%) variant, respectively. KIT primary mutations were detected in 71% pts (exon 11, 56%; exon 9, 14%; exon 13, 1%) and KIT secondary mutations in 55% of pts. Activation loop (AL, exons 17 and 18) was more commonly affected (44%) than the ATP-binding pocket (ABP, exons 13 and 14; 23%). Among KIT-mutant tumors, multiple KIT mutations were commonly detected within individual tumors (mean, 2.56; range, 1-14). Notably, 17% of pts had > 3 mutations (mean, 6.07; range, 4 to 14). Median PFS and OS were shorter for patients whose ctDNA was positive for V654A or T670I (ABP hot spots) when treated with avapritinib vs. regorafenib: mPFS, 1.9 mo vs. 7.4 mo; log-rank p <.001; mOS, 8.3 mo vs. 11.7 mo; log rank p =.0651. mPFS was shorter for patients with ctDNA positive for KIT exon 17 mutation if concurrently KIT V654A/T670I was absent when treated with avapritinib, with no difference in OS: mPFS, 4.7 mo vs. 6.7 mo; log-rank p =.03; mOS, 19.2 mo vs. NR; log-rank p =.628. mPFS on avapritinib was longer when ABP mutations were absent when compared to those with ABP present (5.6 vs. 1.9 mo; log-rank p <.001). There were no differences considering AL mutations vs. no AL mutations (3.8 vs. 3.9 mo; log-rank p =.622) when treated with avapritinib. Regorafenib showed similar activity regardless of KIT mutational status and the location of KIT mutation. Conclusions: Hybrid capture-based plasma sequencing detects ctDNA in the majority of patients with advanced TKI-resistant GIST, including heterogeneity of KIT mutations. This study is the first to show that ctDNA sequencing correlates with outcomes in pretreated GIST. Identification of ABP (exon13/14) KIT mutations negatively correlates with avapritinib activity