TM4SF4 and non-small cell lung carcinoma: Based on our findings about the expression and methylation patterns of TM4SF4 in NSCLC cells, we hypothesized that overexpression of TM4SF4 in some aggressive NSCLC adenocarcinoma cells is critical for tumorigenesis and radiation resistance, and we examined this hypothesis using TM4SF4-overexpressing or knockdown A549 NSCLC cells.