Identifying metabolic alterations and vulnerabilities in therapy-induced senescent cells

Cellular senescence is a tumor suppressive mechanism that leads to cell cycle arrest under stress conditions. A variety of cancer treatments lead to therapy-induced senescence (TIS), which has traditionally been considered irreversible and hence a positive outcome. However, senescent cells secrete cytokines that enhance inflammation and cancer progression; a phenomenon referred to as senescence-associated secretory phenotype (SASP). Furthermore, new evidence suggests mechanisms of senescence escape which could lead to relapse. Our research aims to identify cellular metabolic alterations associated with TIS which could be drug targeted. We used LC-MS based metabolomics and isotope tracing to characterize metabolic alterations in melanoma cells treated with clinically relevant therapeutic agents inducing TIS: the chemotherapeutic drug Cisplatin, and radiation. ­Our analysis reveals major metabolic alterations in TIS related to amino acid and lipid metabolism associated with the SASP phenotype: Isotope tracing experiments revealed increase in the relative contribution of glucose versus glutamine-derived TCA cycle anaplerosis (supporting amino acid biosynthesis) via pyruvate carboxylase (PC) in all studied TIS models, versus in proliferating cells. Additionally, proteomic analysis showed a significant increase in PC expression, suggesting this alteration to be regulated in the protein level. Our hypothesis is that TIS cells are dependent on PC activity for senescence maintenance, and we are currently exploring the effect of PC-silencing on TIS cells. Our research is expected to lead to the identification of a metabolic enzyme targeted for eliminating TIS cells and improve anticancer short-term, as well as long-term, therapy.