Purpose: Almost all colorectal cancer (CRC) cell lines are known to overexpress aspartate aminotransferase (GOT1), which potentially regulates the intracellular levels of reactive oxygen species (ROS) via the production of NADPH, and supports tumor growth. In our study, the role of GOT1 in the anticancer efficacy of 5-fluorouracil (5-FU) was examined.
Methods: HCT116, SW480, and HT-29 cells were transfected with lentiviral vectors expressing short hairpin RNA (shRNA) against GOT1. Following 5-FU treatment, cellular proliferation was evaluated, the NADP+/NADPH ratio was monitored, ROS was measured, and intracellular levels of glutamine (Gln), Aspartate (Asp), oxaloacetate (OAA), malate, and pyruvate were investigated using liquid chromatography-mass spectrometry (LC-MS). A CRC subcutaneous tumor model was performed to determine the impact of GOT1 inhibition on 5-FU efficacy in vivo.
Results: In response to 5-FU administration, CRC cells undergo metabolic adaptation, resulting in increased glutamine flux for the synthesis of aspartate. GOT1 is responsible for the conversion of glutamine-derived aspartate into OAA, which subsequently can be converted into malate and pyruvate. The GOT1-mediated metabolic process is able to maintain the NADP+/NADPH ratio, which counteracts 5-FU-induced oxidative stress. Inhibition of GOT1 impaired the defense against 5-FU-induced ROS, thereby sensitizing cells to 5-FU. The importance of GOT1 in supporting tumor growth during 5-FU treatment was also indicated in an in vivo tumor model of CRC.
Conclusion: These findings show that GOT1 could serve as a promising target for increasing the anticancer efficacy of the conventional therapy in patients with CRC.
Keywords: Chemotherapy; Colorectal cancer; GOT1; Reactive oxygen species.