TGFB1 and small cell lung carcinoma: Enhancer of zeste homolog 2 (EZH2) expression in SCLC cells is associated with the epigenetic silencing of TGFβRII expression, TGFβ‐SMAD‐ASCL1 (achaete‐scute family bHLH transcription factor 1) pathway suppression, and contributing to SCLC progression.