Giovanna Damia

Onvansertib and Navitoclax Combination as a New Therapeutic Option for Mucinous Ovarian Carcinoma

Mucinous epithelial ovarian cancer (mEOC) is a rare subtype of epithelial ovarian cancer, characterized by poor responses to standard platinum-based chemotherapy. Polo-like kinase 1 (PLK1) is a key regulator of mitosis and cell cycle progression and its inhibition has been recently identified as a target in mEOC. In this study, we aimed to identify further therapeutic targets in mEOC using a CRISPR/Cas9 library targeting 3015 genes, with and without treatment with onvansertib, a PLK1 inhibitor. We identified twelve genes associated with cell survival (ZC2HC1C, RPA2, KIN17, TUBG1, SMC2, CDC26, CDC42, HOXA9, TAF10, SENP1, MRPS31, and COPS2) and three genes (JUND, CARD9, and BCL2L2) in synthetic lethality with onvansertib treatment. We validated that SENP1 downregulation is important for the growth of mEOC cells through esiRNA interference and the use of a pharmacological inhibitor Momordin Ic. The downregulation of CARD9 and BCL2L2 combined with subtoxic doses of onvansertib interfered with mEOC cell growth. Interestingly, the combination of navitoclax, an inhibitor of BcL2 family members including BCL2L2, was synergistic in all four of the mEOC cell lines tested and substantially induced cell death through apoptosis. These data support the use of a combination of navitoclax and onvansertib as a new therapeutic strategy for mEOC.

Different Patterns of Platinum Resistance in Ovarian Cancer Cells with Homologous Recombination Proficient and Deficient Background

Platinum compounds are very active in first-line treatments of ovarian carcinoma. In fact, high rates of complete remission are achieved, but most patients eventually relapse with resistant disease. Many mechanisms underlying the platinum-resistant phenotype have been reported. However, there are no data in the same isogenic cell system proficient and deficient in homologous recombination (HR) on platinum-acquired resistance that might unequivocally clarify the most important mechanism associated with resistance. We generated and characterized cisplatin (DDP)-resistant murine ovarian ID8 cell lines in a HR-deficient and -proficient background. Specific upregulation of the NER pathway in the HR-proficient and -resistant cells and partial restoration of HR in Brca1−/−-resistant cells were found. Combinations of different inhibitors of the DNA damage response pathways with cisplatin were strongly active in both resistant and parental cells. The data from the ID8 isogenic system are in line with current experimental and clinical evidence and strongly suggest that platinum resistance develops in different ways depending on the cell DNA repair status (i.e., HR-proficient or HR-deficient), and the upregulation and/or restoration of repair pathways are major determinants of DDP resistance.

Basal expression of RAD51 foci predicts olaparib response in patient-derived ovarian cancer xenografts

The search for biomarkers to evaluate ovarian cancer (OC) homologous recombination (HR) function and predict the response to therapy is an urgent clinical need to improve the selection of patients who could benefit from platinum- and olaparib (poly-ADP ribose polymerase inhibitors, PARPi)-based therapies. We used a large collection of OC patient-derived xenografts (PDXs) (n = 47) and evaluated their HR status based on BRCA1/2 mutations, BRCA1 promoter methylation and the HRDetect score. RAD51 foci were quantified in formalin-fixed, paraffin-embedded untreated tumour specimens by immunofluorescence and the messenger RNA expression of 21 DNA repair genes by real-time PCR. Tumour HR deficiency predicted both platinum and olaparib responses. The basal level of RAD51 foci evaluated in geminin-positive/replicating cells strongly inversely correlated with olaparib response (p = 0.011); in particular, the lower the foci score, the greater the sensitivity to olaparib, while low RAD51 foci score seems to associate with platinum activity. The basal RAD51 foci score is a candidate predictive biomarker of olaparib response in OC patients as it can be easily translatable in a clinical setting. Moreover, the findings corroborate the importance of OC-PDXs as a reliable tool to identify and validate biomarkers of response to therapy.

Onvansertib-Based Second-Line Therapies in Combination with Gemcitabine and Carboplatin in Patient-Derived Platinum-Resistant Ovarian Carcinomas

Platinum resistance represents an urgent medical need in the management of ovarian cancer. The activity of the combinations of onvansertib, an inhibitor of polo-like kinase 1, with gemcitabine or carboplatin was tested using patient-derived xenografts of high-grade serous ovarian carcinoma resistant to cisplatin (DDP). Two PDX models were selected from our xenobank: one with acquired resistance to DDP (#266R) and the other (#315) with intrinsic DDP resistance. Tumor-bearing mice were randomized to receive vehicle, single onvansertib, gemcitabine and carboplatin, and their combinations. Onvansertib/gemcitabine and onvansertib/carboplatin combinations were well tolerated. In the #266R model, single drug treatments were completely inactive, while the combinations of onvansertib/gemcitabine and onvansertib/carboplatin resulted in a significant increase in survival compared to controls and single drugs (p < 0.001 versus control, onvansertib, gemcitabine and carboplatin). Similar efficacy was observed in the s.c. #315 PDX model; indeed, onvansertib and carboplatin monotherapies were inactive, gemcitabine monotherapy was marginally active, while both combinations were highly active. The molecular mechanism underlying the efficacy of the combinations suggests a higher induction of DNA damage which seems plausible considering that, in both cases, gemcitabine and carboplatin, respectively, interfere with DNA metabolism and induce alkylation damage. The results suggest that the combinations of onvansertib/gemcitabine and onvansertib/carboplatin are safe and were shown to be of therapeutic value in the platinum-resistant setting of ovarian carcinoma, strongly supporting their clinical translatability.

Onvansertib treatment overcomes olaparib resistance in high-grade ovarian carcinomas

AbstractOccurrence of resistance to olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor (PARPi) approved in ovarian carcinoma, has already been shown in clinical settings. Identifying combination treatments to sensitize tumor cells and/or overcome resistance to olaparib is critical. Polo-like kinase 1 (PLK1), a master regulator of mitosis, is also involved in the DNA damage response promoting homologous recombination (HR)-mediated DNA repair and in the recovery from the G2/M checkpoint. We hypothesized that PLK1 inhibition could sensitize tumor cells to PARP inhibition. Onvansertib, a highly selective PLK1 inhibitor, and olaparib were tested in vitro and in vivo in BRCA1 mutated and wild-type (wt) ovarian cancer models, including patient-derived xenografts (PDXs) resistant to olaparib. The combination of onvansertib and olaparib was additive or synergic in different ovarian cancer cell lines, causing a G2/M block of the cell cycle, DNA damage, and apoptosis, much more pronounced in cells treated with the two drugs as compared to controls and single agents treated cells. The combined treatment was well tolerated in vivo and resulted in tumor growth inhibition and a statistically increased survival in olaparib-resistant-BRCA1 mutated models. The combination was also active, although to a lesser extent, in BRCA1 wt PDXs. Pharmacodynamic analyses showed an increase in mitotic, apoptotic, and DNA damage markers in tumor samples derived from mice treated with the combination versus vehicle. We could demonstrate that in vitro onvansertib inhibited both HR and non-homologous end-joining repair pathways and in vivo induced a decrease in the number of RAD51 foci-positive tumor cells, supporting its ability to induce HR deficiency and favoring the activity of olaparib. Considering that the combination was well tolerated, these data support and foster the clinical evaluation of onvansertib with PARPis in ovarian cancer, particularly in the PARPis-resistant setting.