Suppression of p16 increases nucleotide synthesis via mTORC1

Abstract

Reprogrammed metabolism and cell cycle dysregulation are two cancer hallmarks. p16 is a cell cycle inhibitor and tumor suppressor that is upregulated during oncogene-induced senescence (OIS). Loss of p16 allows for uninhibited cell cycle progression, bypass of OIS, and tumorigenesis. Whether p16 loss affects pro-tumorigenic metabolism is unclear. We report that suppression of p16 plays a central role in reprogramming metabolism by increasing nucleotide synthesis. This occurred via activation of mTORC1 signaling, which directly mediated increased translation of the mRNA encoding ribose-5-phosphate isomerase A (RPIA), a pentose phosphate pathway enzyme. p16 loss correlated with activation of the mTORC1-RPIA axis in multiple cancer types. Suppression of RPIA inhibited proliferation only in p16-low cells by inducing senescence both in vitro and in vivo. These data reveal the molecular basis whereby p16 loss modulates pro-tumorigenic metabolism through mTORC1-mediated upregulation of nucleotide synthesis and reveals a metabolic vulnerability of p16-null cancer cells.\n\nHighlightsO_LImTORC1 is activated by p16 knockdown to increase nucleotide synthesis and bypass senescence\nC_LIO_LImTORC1 directly increases translation RPIA to increase ribose-5-phosphate\nC_LIO_LIActivation of mTORC1 pathway downstream of p16 suppression is independent of RB\nC_LIO_LIRPIA suppression induces senescence only in cells and tumors with low p16\nC_LI