CBMS-02 Phosphoglycerate mutase 1 (PGAM1) controls DNA damage repair via regulation of WIP1 activity

Abstract Phosphoglycerate Mutase 1 (PGAM1) is overexpressed in different forms of cancer and has been suggested to have additional functions beyond its role in metabolism. We here report that PGAM1 is overexpressed in GBMs and indirectly regulates activation of ATM, Chk1 and Chk2 but not ATR, thereby increasing the efficiency of DNA damage repair and resistance to radiation (IR) and temozolomide (TMZ) treatment. Genetic suppression of PGAM1 in multiple GBM cell lines resulted in decrease proliferation, apoptosis and colony formation after radiation and temozolomide treatment compared to parental cells. Moreover, parental cells demonstrated DNA damage (gH2AX foci) whereas isogenic PGAM1 knockdown cells exhibited no DNA damage repair activation and a significant increase in sub-G0 apoptotic cells that expressed annexin-V, cleaved caspase-3 and cleaved PARP-1. Mechanistically, suppression of PGAM1 expression inhibited phosphorylation of ATM at s1981 and the subsequent downstream phosphorylation of Chk2 and cdc25C. Moreover, PGAM1 co-immunoprecipitated with WIP1, a phosphatase reported to bind and dephosphorylate ATM, Chk1, and Chk2. Cytoplasmic binding of WIP1 with PGAM1 prevented nuclear localization of WIP1, leaving ATM and its downstream substrates phosphorylated, which is required for DNA damage repair activity. Consistent with these observations, mice intracranially implanted with PGAM1 knockdown GBM cells and treated with TMZ and IR had longer survival than similarly treated mice implanted with matched control cells. These results therefore define PGAM1 as an activator of DNA damage repair pathway and link tumor metabolism to drug response in GBM.