Tumour suppressor PTEN enhanced enzyme activity of GPx, SOD and catalase by suppression of PI3K/AKT pathway in non-small cell lung cancer cell lines

Phosphates and tensin homologue deleted on chromosome 10 (PTEN) is a tumour suppressor gene which dephosphorilates phosphoinositol 3,4,5 triphosphates. Therefore PTEN can regulate PI3K/AKT pathway in cells. Because of promoter methylation or gene deletion, PTEN expression is commonly decreased or lost in non-small cell lung cancer (NSCLC) cell lines. Therefore, we hypothesized that PTEN could regulate the activity of superoxide dismutase (CuZnSOD), glutathione peroxidase (GPx) and catalase. We first recreated PTENwt, G129R and G129E expressions in lung cell lines, in which endogenous PTEN expression was not detected. Then, we showed that PTEN could suppress AKT activity by its lipid phosphatase domain. We then examined the effect of recreated PTEN expressions in NSCLC cells. While PTENwt expression caused enhanced activity of SOD, GPx and catalase in transfected cells lines, neither G129R nor G129E expression effected enzyme activities. These results suggest that PTEN can up-regulate SOD, GPx and catalase activity by inhibition of PI3K/AKT pathway in NSCLC cell lines.