GSTP1-catalyzed PKM2 S-Glutathionylation Regulates Glycolysis in Non-small Cell Lung Cancer and is Attenuated with a Clinically Relevant inhibitor of Glutathione-S-transferase P

Rationale Lung cancer is the most lethal form of any of the common cancers, resulting in over 160,000 deaths in the US every year. Unfortunately, the 5-year survival rate has remained almost unchanged over the past 3 decades. Glutathione S-transferase P1 (GSTP1) is expressed significantly higher in lung tumor tissue from NSCLC compared to matched non-tumorous lung tissue. Originally this was attributed to its role in phase II drug metabolism. However, GSTP1 was recently described as a catalyst of protein S-glutathionylation (PSSG), a reversible cysteine oxidation and post-translational modification pointing towards a different role of GSTP in lung cancer. The goal of this study is to determine whether GSTP1 expression and subsequent enhanced PSSG are important in tumorigenesis. Methods In a tissue micro array of 106 human NSCLC specimens together with adjacent healthy tissue GSTP1 expression and overall PSSG was evaluated. The most common “driver” mutation in NSCLC occurs in the KRAS gene. To study NSCLC in mice we established an inducible KRAS G12D -driven lung adenocarcinoma model that enables lung-epithelial specific expression of mutant KRAS. Alternatively, primary Mouse Tracheal Epithelial (MTE) Cells derived from KRAS G12D mice were exposed to adeno-Cre to activate mutant KRAS. Results Assessment of 106 NSCLC TMAs revealed that 47% were completely negative and 41% were highly positive for GSTP1, and the lung cancers expressing GSTP1 had high PSSG reactivity. GSTP1 expression and PSSG were associated with a worse prognosis. In a mouse model of NSCLC, activation of mutant KRAS resulted in an increase of GSTP1 protein and PSSG in the lung. Further, lactate content and glycolysis regulators were significantly upregulated in lungs following KRAS G12D activation. Following pharmaceutical inhibition of GSTP with TLK117, a phase II tested compound, KRAS-induced increases in PSSG and lactate were strongly decreased in lungs compared to vehicle- treated animals. KRAS G12D activation in primary lung epithelial cells by adeno-cre resulted in a strong increase of GSTP1 protein and a striking increase in overall protein S-glutathionylation. More specifically Pyruvate kinase M2 (PKM2), an important enzyme in cancer metabolism, was highly S-glutathionylated in KRAS G12D activated mouse lung and in MTE cells and increase in lactate production and expression of glycolysis enzymes was observed. Pharmacological GSTP1 inhibition with TLK117 decreased PKM2-and overall PSSG, glycolysis and tumor migration. Conclusion Together, these data reveal a potential pivotal new role of GSTP1 in regulating lung adenocarcinoma metabolism by promoting glycolysis in part through oxidative inactivation (S-glutathionylation) of PKM2.