High expression levels of MAGE-A9 are correlated with unfavorable survival in lung adenocarcinoma

A variety of melanoma-associated antigen-A (MAGE-A) protein are commonly detected in lung cancers. Their biological function is not well characterized but may involve cell cycle progression and the regulation of apoptosis. We hypothesized that MAGE-A9 is involved in the regulation of apoptosis. To test this hypothesis, we evaluated MAGE-A9 protein expression by immunohistochemical staining and we assessed the relationship between the expression of MAGE-A9 and clinical pathological parameters. In addition, we investigated the effect of MAGE-A9 down-regulation in lung adenocarcinoma. The results showed that a high expression level of MAGE-A9 protein in lung adenocarcinoma tumor cells was related to larger tumor diameter (P = 0.013) and poor differentiation (P = 0.029). Cox regression analysis revealed that the expression of MAGE-A9 in lung adenocarcinoma tumor cells (P < 0.001) is an independent prognostic factor in five-year survival rates. NSCLC cells with silenced MAGE-A9 had decreased cell proliferation, migration and invasion in cell culture compared to corresponding control cells. The NSCLC cells showing down-regulated MAGE-A9 induced the expression of apoptosis-associated proteins. In addition, MAGE-A9 was associated with resistance to conventional chemotherapeutic agents. Our findings provide evidence that MAGE-A9 could be a potential therapeutic target in NSCLC.