Characterization of Amplified Malate Dehydrogenase 1 (MDH1) in the Context of Squamous Cell Lung Cancer

Abstract

Cancer cells often reroute or stimulate their metabolism to support proliferation, which requires a change in the activity or regulation of key metabolic residues. Malate dehydrogenase 1 (MDH1) catalyzes the NADH‐dependent conversion of oxaloacetate to malate, which can help drive glycolysis through the production of NAD+. MDH1 is amplified in many squamous cell lung carcinomas, the second leading cause of cancer related death, and this amplification is associated with a poor prognosis of 50% reduced survival. The precise role of MDH1 in driving squamous cell lung cancer and the mechanisms that regulate this protein are not yet well understood.Here, we develop a tool to examine the effect of MDH1 amplification in an in vitro model. We aim to examine MDH1 amplification in squamous cell lung carcinoma with an isogenic control. It has been previously shown that MDH1 methylation can suppress glutamine metabolism in pancreatic cancers, and that acetylation of MDH1 alters its activity. We will examine how MDH1 amplification affects squamous cell carcinomas by using biochemical kinetics and cellular methods. We have found that MDH1 amplification influences the production of metabolites in the TCA cycle. Through monoclonal single cell isolation, we will generate a squamous epithelial lung cancer cell line stably overexpressing MDH1. We hypothesize that MDH1 has cysteine residues that can be sensitive to oxidative stress which can alter the normal enzymatic activities of MDH1. Through site‐directed mutagenesis, we will mutate a cysteine residue to a serine residue at the 137 position to examine the possible effect of oxidative stress on MDH1. This residue has been shown to be sensitive to oxidation in the mouse form of MDH1. We will also heterologously express and purify MDH1 mutants and perform kinetic assays to examine the impact of amplified MDH1. By understanding the regulatory strategies of MDH1, we hope to identify new pathways that may be targeted therapeutically.Support or Funding InformationThis work was funded by a Research Scholar Grant, RSG‐19‐075‐01‐TBE, from the American Cancer Society (C.D.S.), National Institutes of Health R00 CA187594 (C.D.S.), U54CA132384 (SDSU) & U54CA132379 (UC San Diego), and IMSD 5R25GM058906 (SDSU), as well as the California Metabolic Research Foundation (SDSU).