KMT2D and small cell lung carcinoma: High frequency truncating mutations for the H3K4 histone methyltransferase KMT2D/MLL2 gene have been reported in 17% of SCLC cell lines and 8% of SCLC tumors, and KMTD2/MLL2 loss is associated with reduced H3K4me1 and impaired enhancer function [62].