Protein & Cell

Emerging applications of tumour-educated platelets in the detection and prognostication of ovarian cancer

Genome-wide CRISPR-Cas9 screening identifies CLK1 inhibition as a strategy to restore PARP inhibitor sensitivity via ERCC1 isoform switching

Abstract Epithelial ovarian cancer (EOC) is an aggressive malignancy with limited therapeutic options. Poly(ADP-ribose) polymerase inhibitors (PARPi) have shown remarkable efficacy, especially in BRCA-mutant patients, and are approved as maintenance therapy to prevent recurrence after initial response to chemotherapy. However, the development of PARPi resistance poses a major clinical challenge. This study utilized a whole-genome CRISPR-Cas9 genetic screening to identify genes associated with PARPi sensitivity upon knockout. Based on the screening and validated through further experiments, we confirmed that CLK1 knockdown is synthetically lethal with PARPi in ovarian cancer. The combination of the PARPi Olaparib and CLK1 inhibitor TG003 exhibited potent anti-proliferative effects both in vitro and in vivo. Mechanistically, CLK1 inhibition downregulated the functional ERCC1-202 isoform, resulting in enhanced DNA damage and apoptosis. Our findings reveal a novel mechanism underlying PARPi sensitivity and suggest that targeting CLK1 in combination with PARPi may represent a promising therapeutic strategy for PARPi-resistant ovarian cancer.

Loss of 4.1N in epithelial ovarian cancer results in EMT and matrix-detached cell death resistance

AbstractEpithelial ovarian cancer (EOC) is one of the leading causes of death from gynecologic cancers and peritoneal dissemination is the major cause of death in patients with EOC. Although the loss of 4.1N is associated with increased risk of malignancy, its association with EOC remains unclear. To explore the underlying mechanism of the loss of 4.1N in constitutive activation of epithelial-mesenchymal transition (EMT) and matrix-detached cell death resistance, we investigated samples from 268 formalin-fixed EOC tissues and performed various in vitro and in vivo assays. We report that the loss of 4.1N correlated with progress in clinical stage, as well as poor survival in EOC patients. The loss of 4.1N induces EMT in adherent EOC cells and its expression inhibits anoikis resistance and EMT by directly binding and accelerating the degradation of 14-3-3 in suspension EOC cells. Furthermore, the loss of 4.1N could increase the rate of entosis, which aggravates cell death resistance in suspension EOC cells. Moreover, xenograft tumors in nude mice also show that the loss of 4.1N can aggravate peritoneal dissemination of EOC cells. Single-agent and combination therapy with a ROCK inhibitor and a 14-3-3 antagonist can reduce tumor spread to varying degrees. Our results not only define the vital role of 4.1N loss in inducing EMT, anoikis resistance, and entosis-induced cell death resistance in EOC, but also suggest that individual or combined application of 4.1N, 14-3-3 antagonists, and entosis inhibitors may be a promising therapeutic approach for the treatment of EOC.