KMT2D maintains neoplastic cell proliferation and global histone H3 lysine 4 monomethylation

The cancer COMPASS: navigating the functions of MLL complexes in cancer

The mixed-lineage leukemia family of histone methyltransferases (MLL1-4, or KMT2A-D) were previously linked to cancer through the founding member, MLL1/KMT2A, which is often involved in translocation-associated gene fusion events in childhood leukemias. However, in recent years, a multitude of tumor exome sequencing studies have revealed that orthologues MLL3/KMT2C and MLL2/KMT2D are mutated in a significant percentage of a large variety of malignancies, particularly solid tumors. These unexpected findings necessitate a deeper inspection into the activities and functional differences between the MLL/KMT2 family members. This review provides an overview of this protein family and its relation to cancers, focusing on the recent links between MLL3/KMT2C and MLL2/4/KMT2D and their potential roles as tumor suppressors in an assortment of cell types.

The epigenetic basis of diffuse large B-cell lymphoma

The pathogenesis of diffuse large B-cell lymphoma (DLBCL) is strongly linked to perturbation of epigenetic mechanisms. The germinal center (GC) B cells from which DLBCLs arise are prone to instability in their cytosine methylation patterns. DLBCLs inherit this epigenetic instability and display variable degrees of epigenetic heterogeneity. Greater epigenetic heterogeneity is linked with poor clinical outcome. Somatic mutations of histone-modifying proteins have also emerged as a hallmark of DLBCL. The effect of these somatic mutations may be to disrupt epigenetic switches that control the GC phenotype and "lock in" certain oncogenic features of GC B cells, resulting in malignant transformation. DNA methyltransferase and histone methyltransferase inhibitors are emerging as viable therapeutic approaches to erase aberrant epigenetic programming, suppress DLBCL growth, and overcome chemotherapy resistance. This review will discuss these recent advances and their therapeutic implications.

PITX2 associates with PTIP-containing histone H3 lysine 4 methyltransferase complex

Pituitary homeobox 2 (PITX2), a Paired-like homeodomain transcription factor and a downstream effector of Wnt/β-catenin signaling, plays substantial roles in embryonic development and human disorders. The mechanism of its functions, however, is not fully understood. In this study, we demonstrated that PITX2 associated with histone H3 lysine 4 (H3K4) methyltransferase (HKMT) mixed-lineage leukemia 4 (MLL4/KMT2D), Pax transactivation domain-interacting protein (PTIP), and other H3K4·HKMT core subunits. This association of PITX2 with H3K4·HKMT complex was dependent on PITX2's homeodomain. Consistently, the PITX2 protein complex was shown to possess H3K4·HKMT activity. Furthermore, the chromatin immunoprecipitation result revealed co-occupancy of PITX2 and PTIP on the promoter of the PITX2's transcriptional target. Taken together, our data provide new mechanistic perspectives on PITX2's functions and its related biological processes.

Autoimmune haematological disorders in two Italian children with Kabuki syndrome

Kabuki syndrome (also called Niikawa-Kuroki syndrome) is a rare genetic disease described for the first time in Japan, characterised by anomalies in multiple organ systems and often associated with autoimmune disorders and impaired immune response. We herein report the clinical history, the therapeutic approach and the outcome of two children with Kabuki syndrome who developed autoimmune haematological disorders (haemolytic anaemia and immune thrombocytopenia). Factors regarding differential diagnosis and interventions in better management of this syndrome and its complications are discussed. This is the first report of Italian children with autoimmune haematological disorders complicating Kabuki syndrome.