Triggering necroptosis in cisplatin and IAP antagonist-resistant ovarian carcinoma.

Ovarian cancer patients are typically treated with carboplatin and paclitaxel, but suffer a high rate of relapse with recalcitrant disease. This challenge has fostered the development of novel approaches to treatment, including antagonists of the 'inhibitor of apoptosis proteins' (IAPs), also called SMAC mimetics, as apoptosis-inducing agents whose action is opposed by caspase inhibitors. Surprisingly, IAP antagonist plus caspase inhibitor (IZ) treatment selectively induced a tumor necrosis factor-α (TNFα)-dependent death among several apoptosis-resistant cell lines and patient xenografts. The induction of necroptosis was common in ovarian cancer, with expression of catalytically active receptor-interacting protein kinase-3 (RIPK3) necessary for death, and in fact sufficient to compromise survival of RIPK3-negative, necroptosis-resistant ovarian cancer cells. The formation of a necrosome-like complex with a second critical effector, receptor-interacting serine-threonine kinase-1 (RIPK1), was observed. RIPK1, RIPK3 and TNFα were required for the induction of death, as agents that inhibit the function of any of these targets prevented cell death. Abundant RIPK3 transcript is common in serous ovarian cancers, suggesting that further evaluation and targeting of this RIPK3-dependent pathway may be of clinical benefit

Ectopic expression of PAX5 promotes maintenance of biphenotypic myeloid progenitors coexpressing myeloid and B-cell lineage-associated genes.

The transcription factor PAX5 is a critical regulator of B-cell commitment and development. Although normally not expressed in myeloid progenitors, PAX5 has recently been shown to be frequently expressed in myeloid malignancies and to suppress expression of myeloid differentiation genes, compatible with an effect on the differentiation or maintenance of myeloid progenitors. However, previous studies in which PAX5 was ectopically expressed in normal myeloid progenitors in vivo and in vitro provided conflicting results as to the effect of PAX5 on myeloid development. Herein, we demonstrate that on ectopic expression of PAX5 in bone marrow multipotent stem/progenitor cells, cells with a biphenotypic B220(+)GR-1/MAC-1(+) phenotype are produced. These remain cytokine-dependent, but unlike control-transduced cells they sustain long-term generation of myeloid progenitors in vitro and remain capable of myeloid differentiation. Notably, PAX5(+)B220(+)GR-1/MAC-1(+) myeloid progenitors coexpress, at the single-cell level, myeloid genes and otherwise B-cell-specific PAX5 target genes. These findings establish that ectopic expression of PAX5 introduces extensive self-renewal properties in otherwise short-lived myeloid progenitors. Along with the established ectopic expression of PAX5 in acute myeloid leukemia, this motivates a careful investigation of the potential involvement of ectopic PAX5 expression in myeloid and biphenotypic leukemias

Whole-genome Bisulfite Sequencing of Human Pancreatic Islets Reveals Novel Differentially Methylated Regions in Type 2 Diabetes Pathogenesis

Current knowledge about the role of epigenetics in type 2 diabetes (T2D) remains limited. Only a few studies have investigated DNA methylation of selected candidate genes or a very small fraction of genomic CpG sites in human pancreatic islets, the tissue of primary pathogenic importance for diabetes. Our aim was to characterize the whole-genome DNA methylation landscape in human pancreatic islets, to identify differentially methylated regions (DMRs) in diabetic islets, and to investigate the function of DMRs in islet biology.Here, we performed whole-genome bisulfite sequencing, which is a comprehensive and unbiased method to study DNA methylation throughout the genome on a single nucleotide resolution, in pancreatic islets from donors with T2D and non-diabetic controls. We identified 25,820 DMRs in islets from individuals with T2D. These DMRs cover loci with known islet function e.g. PDX1, TCF7L2 and ADCY5 Importantly, binding sites previously identified by ChIP-seq for islet-specific transcription factors, enhancer regions and different histone marks were enriched in the T2D associated DMRs. We also identified 457 genes, including NR4A3, PARK2, PID1, SLC2A2 and SOCS2 that had both DMRs and significant expression changes in T2D islets. To mimic the situation in T2D islets, candidate genes were overexpressed or silenced in cultured β-cells. This resulted in impaired insulin secretion, thereby connecting differential methylation to islet dysfunction. We further explored the islet methylome and found a strong link between methylation levels and histone marks. Additionally, DNA methylation in different genomic regions and of different transcript types (i.e. protein-coding, non-coding and pseudogenes) was associated with islet expression levels.Our study provides a comprehensive picture of the islet DNA methylome in both non-diabetic and diabetic individuals and highlights the importance of epigenetic dysregulation in pancreatic islets and T2D pathogenesis