Epigenetic Gene Regulation by Janus Kinase 1 in Diffuse Large B Cell Lymphoma (ChIP-Seq)

JAK kinases classically signal by activating STAT transcription factors, but can also regulate gene expression by epigenetically phosphorylating histone H3 on tyrosine 41 (H3Y41-P). In diffuse large B cell lymphomas (DLBCL), JAK signaling is a feature of the ABC subtype and is triggered by autocrine production of IL-6 and IL-10. Whether this signaling involves STAT activation, epigenetic modification of chromatin or both mechanisms is unknown. Here we use genetic and pharmacological inhibition to show that JAK1 signaling sustains the survival of ABC DLBCL cells. While STAT3 contributed to the survival of ABC DLBCL cell lines, forced STAT3 activity could not protect these cells from death following JAK1 inhibition, suggesting epigenetic JAK1 action. JAK1 regulated the expression of nearly 3,000 genes in ABC DLBCL cells, and the chromatin surrounding many of these genes was modified by H3Y41-P marks that were diminished by JAK1 inhibition. These JAK1 epigenetic target genes encode important regulators of ABC DLBCL proliferation and survival, including IRF4, MYD88 and MYC. A small molecule JAK1 inhibitor cooperated with the BTK inhibitor ibrutinib in reducing IRF4 levels and acted synergistically to kill ABC DLBCL cells, suggesting that this combination should be evaluated in clinical trials. Overall design: TMD8 cells were treated with either DMSO or AZD 1480 (2uM) for 16 hours. Chromatin immunoprecipitation was performed with a phospho-H3Y41 antibody (Abcam #ab26310), and normal rabbit IgG (Santa Cruz #sc-2027) as a negative control (n=4).