Deletion of PGAM5 Downregulates FABP1 and Attenuates Long-Chain Fatty Acid Uptake in Hepatocellular Carcinoma

SIMPLE SUMMARY: Hepatocellular carcinoma is the most common liver cancer. Metabolic dysfunction-associated steatotic liver disease is emerging as a primary cause of hepatocellular carcinoma. Lipid metabolism is altered in hepatocellular carcinoma to promote tumor growth. The mitochondrial membrane protein phosphoglycerate mutase 5 (PGAM5) is overexpressed in hepatocellular carcinoma and may play a role in lipid metabolism. The aim of our research study was to determine whether the expression of PGAM5 modified fatty acid uptake and lipid droplet accumulation in hepatocellular carcinoma cells. We learned that by eliminating PGAM5 expression, lipid droplet accumulation was reduced in hepatocellular carcinoma and that this may be due to reduced fatty acid uptake. Enhanced understanding of fatty acid regulation in cancer supports the rationale design of therapeutics targeting metabolic pathways. ABSTRACT: Phosphoglycerate mutase 5 (PGAM5) is a Ser/His/Thr phosphatase responsible for regulating mitochondrial homeostasis. Overexpression of PGAM5 is correlated with a poor prognosis in hepatocellular carcinoma, colon cancer, and melanoma. In hepatocellular carcinoma, silencing of PGAM5 reduces growth, which has been attributed to decreased mitophagy and enhanced apoptosis. Yet in colon cancer, PGAM5’s pro-tumor survival effect is correlated to lipid metabolism. We sought to identify whether deletion of PGAM5 modulated lipid droplet accrual in hepatocellular carcinoma. HepG2 and Huh7 PGAM5 knockout cell lines generated using CRISPR/Cas9 technology were used to measure cell growth, cellular ATP, and long-chain fatty acid uptake. Expression of hepatocellular fatty acid transporters, cluster of differentiation 36 (CD36), solute carrier family 27 member 2 (SLC27A2), solute carrier family 27 member 5 (SLC27A5), and fatty acid binding protein 1 (FABP1) was measured by quantitative PCR and Western blot. We found that deletion of PGAM5 attenuates hepatocellular carcinoma cell growth and ATP production. Further, PGAM5 knockout ameliorates palmitate-induced steatosis and reduces expression of FABP1 in HepG2 and Huh7 cell lines. PGAM5’s role in hepatocellular carcinoma includes regulation of fatty acid metabolism, which may be related to expression of the fatty acid transporter, FABP1.