Demonstration of the effect of hypoxia inducible factor-1 inhibition on GLUT1 and paraoxonase enzyme family in hepatocellular carcinoma cells

Hypoxia-inducible factor-1 (HIF-1) is a transcriptional activator that is the main regulator of adaptation to hypoxia. Cancer cells produce reactive oxygen species which results in oxidative stress. As an antioxidant defense system, the paraoxonase (PON, EC 3.1.8.1) enzyme family (PON1, PON2 and PON3) is involved in oxidative stress. It has been shown that the expression level of GLUT1 from glucose transporters (GLUTs) is associated with the expression levels of HIF-1 in many cancer types. Lactate dehydrogenase (LDH) is an enzyme that facilitates ATP production, which continues through glycolysis, resulting in the production of lactate in the cytosol. The increased expression of GLUTs and LDHA together with HIF-1α provides an excellent adaptation to the needs of highly proliferating tumor cells. In our study; the effect of HIF-1α inhibitor Echinomycin in normoxic and hypoxic conditions in HepG2 cell line on paraoxonase and lactonase activities and HIF-1α, GLUT1, LDHA and PON family protein levels were investigated. The IC50 dose of Echinomycin was determined as 5.7 µM by the WST-1 assay. The exposure time point to hypoxic condition for HIF-1α was determined as "4 hours" according to ELISA and western blot. The PON activity change and PON1, PON2, PON3, HIF-1α, GLUT1, LDHA protein expression levels were found to be statistically significant. Keywords: Hepatocellular carcinoma, HIF-1α, hypoxia, GLUTs, lactate dehydrogenase, lactonase, paraoxonase