Phosphoglycerate dehydrogenase is dispensable for breast tumor maintenance and growth

Cancer cells have the ability to use aerobic glycolysis to maintain cell growth and proliferation via the Warburg effect. Phosphoglycerate dehydrogenase (PHDGH) catalyzes the first step of the serine biosynthetic pathway, which is a metabolic gatekeeper both for macromolecular biosynthesis and serine-dependent DNA synthesis. PHGDH is amplified or overexpressed in a subset of breast cancer and melanoma, and critical for the viability of those cells. Here, we report that PHDGH is overexpressed in many ER-negative human breast cancer cell lines and PHGDH knockdown in these cells leads to a decrease in the levels of serine production and impairment of cancer cell proliferation. However, PHGDH knockdown does not affect tumor maintenance and growth in established xenograft tumor mouse models, suggesting that PHGDH-dependent cell growth is only observed in the in vitro context. Our finding indicates that PHGDH is dispensable for tumor maintenance and growth in vivo, which suggests that other mechanisms or pathways may bypass the function of PHGDH in human breast cancer cells

Tumor intrinsic efficacy by SHP2 and RTK inhibitors in KRAS mutant cancers

KRAS, an oncogene mutated in nearly one-third of human cancers, remains a pharmacological challenge for direct inhibition except in the case of recent advances in selective inhibitors targeting the KRAS-G12C variant. Here, we report that selective inhibition of the protein tyrosine phosphatase, SHP2, is effective in treating KRAS mutant cancer cell lines in vitro and in vivo. In vitro, sensitization of KRAS-driven cancers towards the allosteric SHP2-inhibitor, SHP099, is revealed when cells are grown as multicellular spheroids and correlates with activity in mouse models but is not apparent in standard 2D cell culture conditions. Interrogation of the MAPK pathway in SHP099 treated KRAS-mutant cancer models suggested relevance of both MAPK and non-MAPK pathway dependent mechanisms correlating with SHP099 sensitivity as phospho-ERK and DUSP6 modulation were equivalent in 2D, 3D and in vivo models despite differences in compound sensitivity. We demonstrate that efficacy is tumor-intrinsic due to the lack of anti-angiogenic activity of SHP099 and recapitulation of efficacy by genetic depletion of SHP2 in cancer cells, suggesting a dependence on RTK signaling upstream of RAS. Furthermore, KRAS mutants with low intrinsic GTP hydrolysis, e.g. KRAS-G13D and Q61H, also are sensitive to SHP099 in vivo. Taken together, these data reveal that many KRAS-mutant cancers depend on upstream signaling from RTK and SHP2, and provide a new therapeutic strategy for treating KRAS mutant cancers with SHP2 inhibitors

Optimization of 3-Pyrimidin-4-yl-oxazolidin-2-ones as Orally Bioavailable and Brain Penetrant Mutant IDH1 Inhibitors

Mutant isocitrate dehydrogenase 1 (IDH1) is an attractive therapeutic target for the treatment of various cancers such as AML, glioma and glioblastoma. We have evaluated 3-pyrimidin-4-yl-oxazolidin-2-ones as mutant IDH1 inhibitors that bind to an allosteric, induced pocket of IDH1R132H. This letter describes SAR exploration focused on improving both the in vitro and in vivo metabolic stability of the compounds, leading to the identification of 19 as a potent and selective mutant IDH1 inhibitor that has demonstrated brain penetration and excellent oral bioavailability in rodents. In a preclinical patient-derived IDH1 mutant xenograft tumor model study, 19 efficiently inhibited the production of the biomarker, 2-HG

IDH1 mutations alter citric acid cycle metabolism and increase dependence on oxidative mitochondrial metabolism.

Oncogenic mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) occur in several types of cancer, but the metabolic consequences of these genetic changes are not fully understood. In this study, we performed (13)C metabolic flux analysis on a panel of isogenic cell lines containing heterozygous IDH1/2 mutations. We observed that under hypoxic conditions, IDH1-mutant cells exhibited increased oxidative tricarboxylic acid metabolism along with decreased reductive glutamine metabolism, but not IDH2-mutant cells. However, selective inhibition of mutant IDH1 enzyme function could not reverse the defect in reductive carboxylation activity. Furthermore, this metabolic reprogramming increased the sensitivity of IDH1-mutant cells to hypoxia or electron transport chain inhibition in vitro. Lastly, IDH1-mutant cells also grew poorly as subcutaneous xenografts within a hypoxic in vivo microenvironment. Together, our results suggest therapeutic opportunities to exploit the metabolic vulnerabilities specific to IDH1 mutation

Identification of NVP-TNKS656: The use of structure-efficiency relationships to generate a highly potent, selective, and orally active tankyrase inhibitor

Tankyrase 1 and 2 have been shown to be redundant, druggable nodes in the Wnt pathway. As such, there has been intense interest in developing agents suitable for modulating the Wnt pathway in vivo by targeting this enzyme pair. By utilizing a combination of structure-based design and LipE-based structure efficiency relationships, the core of XAV939 was optimized into a more stable, more efficient, but less potent dihydropyran motif 7. This core was combined with elements of screening hits 2, 19, and 33 and resulted in highly potent, selective tankyrase inhibitors that are novel three pocket binders. NVP-TNKS656 (43) was identified as an orally active antagonist of Wnt pathway activity in the MMTV-Wnt1 mouse xenograft model. With an enthalpy-driven thermodynamic signature of binding, highly favorable physicochemical properties, and high lipophilic efficiency, NVP-TNKS656 is a novel tankyrase inhibitor that is well suited for further in vivo validation studies. © 2013 American Chemical Society

Optimization of the in vitro Cardiac Safety of Hydroxamate-Based Histone Deacetylase Inhibitors

Histone deacetylase (HDAC) inhibitors have shown promise in treating various forms of cancer. However, many HDAC inhibitors from diverse structural classes have been associated with QT prolongation in humans. Inhibition of the human ether a-go-go related gene (hERG) channel has been associated with QT prolongation and fatal arrhythmias. In order to determine if the observed cardiac effects of HDAC inhibitors in humans is due to hERG blockade, a highly potent HDAC inhibitor devoid of hERG activity was required. Starting with dacinostat (LAQ824), a highly potent HDAC inhibitor, we explored the SAR to determine the pharmacophores required for HDAC and hERG inhibition. We disclose here the results of these efforts where a high degree of pharmacophore homology between these two targets was discovered. This similarity prevented traditional strategies for mitigating hERG binding/modulation from being successful and novel approaches for reducing hERG inhibition were required. Using a hERG homology model, two compounds, 11r and 25i, were discovered to be highly efficacious in vivo with weak affinity for the hERG and other ion channels