Abstract 3932: Metabolic biomarkers predict the sensitivity to phosphatidylinositol 3-kinase pathway inhibitor in small-cell lung carcinoma

Abstract

Abstract Comprehensive genomic analysis has revealed that the PI3K/AKT/mTOR pathway is a feasible therapeutic target in small-cell lung carcinoma (SCLC). However, biomarkers to identify patients likely to benefit from inhibitors of this pathway have not been identified. Here we show that metabolic features determine sensitivity to the PI3K/mTOR dual inhibitor gedatolisib in SCLC cells. We analyzed the phosphatidyl lipid profile including the acyl groups of 11 SCLC cell lines using electrospray ionization mass spectrometry. We found that a specific phosphatidylinositol (3,4,5)-triphosphate (PIP3) subspecies lipid product, PIP3 (38:4), is predictive in assessing sensitivity to gedatolisib. We generated a large-scale metabolomic dataset for 28 SCLC cell lines. Notably, we found that higher amounts of purine-related aqueous metabolites such as hypoxanthine led to resistance to PI3K pathway inhibition. The levels of the mRNA encoding hypoxanthine phosphoribosyl transferase 1 (HPRT1), a key component of the purine salvage pathway, differed significantly between SCLC cells sensitive or resistant to gedatolisib. Loss of HPRT1 in SCLC cells decreased cellular proliferation in the presence of gedatolisib compared with a control. Further, complementation with purine metabolites could reverse the vulnerability to targeting of the PI3K pathway in SCLC cells normally sensitive to gedatolisib. These results indicate that the mechanism of resistance to PI3K pathway inhibitors is mediated by activation of the purine salvage pathway, which supplies purine resources for nucleotide biosynthesis. Metabolic profiles of clinical samples of SCLC revealed that purine-related metabolites were higher in SCLC tumor tissues, suggesting that higher amounts of purine-related aqueous metabolites might be characteristic of SCLC biology. Metabolomics is a powerful approach for identifying novel therapeutic biomarkers applicable to SCLC treatment. Citation Format: Shigeki Umemura, Hideki Makinoshima, Genichiro Ishii, Takehiko Sasaki, Hiroyasu Esumi, Koichi Goto, Katsuya Tsuchihara. Metabolic biomarkers predict the sensitivity to phosphatidylinositol 3-kinase pathway inhibitor in small-cell lung carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3932.