Combined PARP and Dual Topoisomerase Inhibition Potentiates Genome Instability and Cell Death in Ovarian Cancer

Although ovarian cancer is a rare disease, it constitutes the fifth leading cause of cancer death among women. It is of major importance to develop new therapeutic strategies to improve survival. Combining P8-D6, a novel dual topoisomerase inhibitor with exceptional anti-tumoral properties in ovarian cancer and compounds in preclinical research, and olaparib, a PARP inhibitor targeting DNA damage repair, is a promising approach. P8-D6 induces DNA damage that can be repaired by base excision repair or homologous recombination in which PARP plays a major role. This study analyzed benefits of combining P8-D6 and olaparib treatment in 2D and 3D cultures with ovarian cancer cells. Measurement of viability, cytotoxicity and caspase activity were used to assess therapy efficacy and to calculate the combination index (CI). Further DNA damage was quantified using the biomarkers RAD51 and γH2A.X. The combinational treatment led to an increased caspase activity and reduced viability. CI values partially show synergisms in combinations at 100 nM and 500 nM P8-D6. More DNA damage accumulated, and spheroids lost their membrane integrity due to the combinational treatment. While maintaining the same therapy efficacy as single-drug therapy, doses of P8-D6 and olaparib can be reduced in combinational treatments. Synergisms can be seen in some tested combinations. In summary, the combination therapy indicates benefits and acts synergistic at 100 nM and 500 nM P8-D6

HP1-β is required for development of the cerebral neocortex and neuromuscular junctions

HP1 proteins are thought to be modulators of chromatin organization in all mammals, yet their exact physiological function remains unknown. In a first attempt to elucidate the function of these proteins in vivo, we disrupted the murine Cbx1 gene, which encodes the HP1-β isotype, and show that the Cbx1−/−-null mutation leads to perinatal lethality. The newborn mice succumbed to acute respiratory failure, whose likely cause is the defective development of neuromuscular junctions within the endplate of the diaphragm. We also observe aberrant cerebral cortex development in Cbx1−/− mutant brains, which have reduced proliferation of neuronal precursors, widespread cell death, and edema. In vitro cultures of neurospheres from Cbx1−/− mutant brains reveal a dramatic genomic instability. Our results demonstrate that HP1 proteins are not functionally redundant and that they are likely to regulate lineage-specific changes in heterochromatin organization

Chemotherapy‐induced release of ADAM17 bearing EV as a potential resistance mechanism in ovarian cancer

Abstract Ovarian cancer (OvCa) is the gynaecological disorder with the poorest prognosis due to the fast development of chemoresistance. We sought to connect chemoresistance and cancer cell‐derived extracellular vesicles (EV). The mechanisms of how chemoresistance is sustained by EV remained elusive. One potentially contributing factor is A Disintegrin and Metalloprotease 17 (ADAM17)—itself being able to promote chemoresistance and inducing tumour cell proliferation and survival via the Epidermal Growth Factor Receptor (EGFR) pathway by shedding several of its ligands including Amphiregulin (AREG). We now demonstrate that upon chemotherapeutic treatment, proteolytically active ADAM17 is released in association with EV from OvCa cells. In terms of function, we show that patient‐derived EV induce AREG shedding and restore chemoresistance in ADAM17‐deficient cells. Confirming that ADAM17‐containing EV transmit chemoresistance in OvCa, we propose that ADAM17 levels (also on EV) might serve as an indicator for tumour progression and the chemosensitivity status of a given patient