Abstract
Background Melanoma-associated antigen C2 (MAGEC2) is an oncogene associated with various cancer types. However, the biological function of MAGEC2 in circulating tumor cells is unclear. In this study, we investigated the role of MAGEC2 using adapted suspension cells (ASCs), which were previously developed to study circulating tumor cells (CTCs).Methods Differential gene expression between adherent cells (ADs) and ASCs was examined using RNA-seq analysis. MAGEC2 expression was assessed using RT-qPCR, immunoblotting, and ChIP-seq analysis. Depletion of MAGEC2 expression was carried out using siRNA. MAGEC2-depleted ADs and ASCs were used to investigate the change in proliferation rate and cell cycle. Then, the protein levels of STAT3, phosphorylated STAT3, and downstream of STAT3 were measured using control and MAGEC2-depleted ADs and ASCs. The direct effect of active STAT3 inhibition with Stattic in ASCs was also assessed in terms of proliferation and apoptosis. Finally, an Annexin V/7-AAD assay was performed to determine the percentage of apoptotic cells in Stattic-treated cells. Results MAGEC2 was highly expressed in ASCs compared to ADs. Depletion of MAGEC2 reduced the proliferation rate and viability of ASCs. To elucidate the underlying mechanism, the level of STAT3 was examined because of its oncogenic properties. Tyrosine-phosphorylated active STAT3 was highly expressed in ASCs and decreased in MAGEC2-depleted ASCs. In addition, when ASCs were treated with Stattic, an active STAT3 inhibitor, they were more sensitive to intrinsic pathway-mediated apoptosis.Conclusions High expression of MAGEC2 may play an important role in the survival of ASCs by maintaining the expression of activated STAT3 to prevent apoptotic cell death.