Patrycja Gralewska

Olaparib Combined with DDR Inhibitors Effectively Prevents EMT and Affects miRNA Regulation in TP53-Mutated Epithelial Ovarian Cancer Cell Lines

Epithelial ovarian cancer (EOC) remains a leading cause of gynecologic cancer mortality. Despite advances in treatment, metastatic progression and resistance to standard therapies significantly worsen patient outcomes. Epithelial–mesenchymal transition (EMT) is a critical process in metastasis, enabling cancer cells to gain invasive and migratory capabilities, often driven by changing miRNA expression involved in the regulation of pathological processes like drug resistance. Targeted therapies like PARP inhibitors (PARPi) have improved outcomes, particularly in BRCA-mutated and DNA repair-deficient tumors; however, resistance and limited efficacy in advanced stages remain challenges. Recent studies highlight the potential synergy of PARPi with DNA damage response (DDR) inhibitors, such as ATR and CHK1 inhibitors, which disrupt cancer cell survival pathways under stress. This study investigated the combined effects of olaparib with ATR and CHK1 inhibitors (ATRi and CHK1i) on migration, invasion, and EMT-related protein expression and miRNA expression in ovarian cancer cell lines OV-90 and SKOV-3. The results demonstrated enhanced cytotoxicity, inhibition of migration and invasion, and modulation of miRNAs linked to metastasis. These findings suggest that combination therapies targeting DNA repair and cell cycle pathways may offer a novel, more effective approach to managing advanced EOC and reducing metastatic spread.

Targeted Nanocarrier-Based Drug Delivery Strategies for Improving the Therapeutic Efficacy of PARP Inhibitors against Ovarian Cancer

The current focus of ovarian cancer (OC) research is the improvement of treatment options through maximising drug effectiveness. OC remains the fifth leading cause of cancer-induced mortality in women worldwide. In recent years, nanotechnology has revolutionised drug delivery systems. Nanoparticles may be utilised as carriers in gene therapy or to overcome the problem of drug resistance in tumours by limiting the number of free drugs in circulation and thereby minimising undesired adverse effects. Cell surface receptors, such as human epidermal growth factor 2 (HER2), folic acid (FA) receptors, CD44 (also referred to as homing cell adhesion molecule, HCAM), and vascular endothelial growth factor (VEGF) are highly expressed in ovarian cancer cells. Generation of active targeting nanoparticles involves modification with ligands that recognise cell surface receptors and thereby promote internalisation by cancer cells. Several poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) are currently used for the treatment of high-grade serous ovarian carcinomas (HGSOC) or platinum-sensitive relapsed OC. However, PARP resistance and poor drug bioavailability are common challenges, highlighting the urgent need to develop novel, effective strategies for ovarian cancer treatment. This review evaluates the utility of nanoparticles in ovarian cancer therapy, with a specific focus on targeted approaches and the use of PARPi nanocarriers to optimise treatment outcomes.

Liposomal Vitamin C as a Modulator of the Efficacy of Ceralasertib Therapy in Ovarian Cancer

Clinical evidence suggests that vitamin C (VitC) may enhance the efficacy of cancer chemotherapy. However, its high oxidating and reducing activity results in low stability in physiological fluids, which may compromise its supportive role in cancer therapies. VitC stability improves when located in a region where water activity is reduced and exposure to a limited amount of ferrous ions. This can be achieved when VitC is encapsulated in liposomes. Here, we present a novel combinatorial effect of a liposomal formulation of vitamin C (LVC, liposomal VitC) and an ataxia-telangiectasia and Rad3-related (ATR) kinase inhibitor (ATRi, ceralasertib) on cancer cells. The cytotoxic effects of vitamin C, LVC and ATRi were evaluated using spectrophotometric and spectrofluorimetric assays, flow cytometry and Western blot. Lipid peroxidation was assessed via fluorescence microscopy and quantified by spectrofluorimetric assays. DNA damage was examined by Western blot. The combination has higher efficacy than ceralasertib alone in genetically diverse ovarian cancer cell lines. LVC offers protective effects when used as an adjuvant during anticancer therapy. We found that the inhibition of the ATR pathway in the presence of LVC results in increased intracellular calcium levels, elevated lipid peroxidation, and higher Fe2+ concentrations. The upregulation of ROS, together with the increased expression of long-chain-fatty-acid—CoA ligase 4 (ACSL4) following co-treatment with ATRi and LVC, indicates the activation of ferroptotic pathways. The formation of DNA double-strand breaks suggests replication fork collapse. Our findings demonstrates that this synthetic targeted therapy, combining a novel liposomal formulation of VitC with an ATR inhibitor, not only enhances DNA damage and the cytotoxic efficacy of ceralasertib but also effectively drives ovarian cancer cells toward cell death.

PARP Inhibition Increases the Reliance on ATR/CHK1 Checkpoint Signaling Leading to Synthetic Lethality—An Alternative Treatment Strategy for Epithelial Ovarian Cancer Cells Independent from HR Effectiveness

Poly (ADP-ribose) polymerase inhibitor (PARPi, olaparib) impairs the repair of DNA single-strand breaks (SSBs), resulting in double-strand breaks (DSBs) that cannot be repaired efficiently in homologous recombination repair (HRR)-deficient cancers such as BRCA1/2-mutant cancers, leading to synthetic lethality. Despite the efficacy of olaparib in the treatment of BRCA1/2 deficient tumors, PARPi resistance is common. We hypothesized that the combination of olaparib with anticancer agents that disrupt HRR by targeting ataxia telangiectasia and Rad3-related protein (ATR) or checkpoint kinase 1 (CHK1) may be an effective strategy to reverse ovarian cancer resistance to olaparib. Here, we evaluated the effect of olaparib, the ATR inhibitor AZD6738, and the CHK1 inhibitor MK8776 alone and in combination on cell survival, colony formation, replication stress response (RSR) protein expression, DNA damage, and apoptotic changes in BRCA2 mutated (PEO-1) and HRR-proficient BRCA wild-type (SKOV-3 and OV-90) cells. Combined treatment caused the accumulation of DNA DSBs. PARP expression was associated with sensitivity to olaparib or inhibitors of RSR. Synergistic effects were weaker when olaparib was combined with CHK1i and occurred regardless of the BRCA2 status of tumor cells. Because PARPi increases the reliance on ATR/CHK1 for genome stability, the combination of PARPi with ATR inhibition suppressed ovarian cancer cell growth independently of the efficacy of HRR. The present results were obtained at sub-lethal doses, suggesting the potential of these inhibitors as monotherapy as well as in combination with olaparib.

The Influence of PARP, ATR, CHK1 Inhibitors on Premature Mitotic Entry and Genomic Instability in High-Grade Serous BRCAMUT and BRCAWT Ovarian Cancer Cells

Olaparib is a poly (ADP-ribose) polymerase inhibitor (PARPi) that inhibits PARP1/2, leading to replication-induced DNA damage that requires homologous recombination repair. Olaparib is often insufficient to treat BRCA-mutated (BRCAMUT) and BRCA wild-type (BRCAWT) high-grade serous ovarian carcinomas (HGSOCs). We examined the short-term (up to 48 h) efficacy of PARPi treatment on a DNA damage response pathway mediated by ATR and CHK1 kinases in BRCAMUT (PEO-1) and BRCAWT (SKOV-3 and OV-90) cells. The combination of ATRi/CHK1i with PARPi was not more cytotoxic than ATR and CHK1 monotherapy. The combination of olaparib with inhibitors of the ATR/CHK1 pathway generated chromosomal abnormalities, independent on BRCAMUT status of cells and formed of micronuclei (MN). However, the beneficial effect of the PARPi:ATRi combination on MN was seen only in the PEO1 BRCAMUT line. Monotherapy with ATR/CHK1 inhibitors reduced BrdU incorporation due to a slower rate of DNA synthesis, which resulted from elevated levels of replication stress, while simultaneous blockade of PARP and ATR caused beneficial effects only in OV-90 cells. Inhibition of ATR/CHK1 increased the formation of double-strand breaks as measured by increased γH2AX expression at collapsed replication forks, resulting in increased levels of apoptosis. Our findings indicate that ATR and CHK1 inhibitors provoke premature mitotic entry, leading to genomic instability and ultimately cell death.