Finally, KMT2C encodes for a nuclear methyltransferase (MLL3) of the mixed-lineage leukemia family the genes of which are among the more frequently mutated in cancer (74); somatic mutations at MLL3 have been related to different types of cancer (75), while in activated B-cells, deficiencies in the MLL3–MLL4 complex have been shown to manifest defective immunoglobulin class switching (76). The gene discussed is KMT2C; the disease is cancer.