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Although bevacizumab (BEV) plays a key role in ovarian cancer treatment, BEV resistance is often observed in clinical settings. This study aimed to identify the genes responsible for BEV resistance. C57BL/6 mice inoculated with ID-8 murine ovarian cancer cells were treated with anti-VEGFA antibody or IgG (control) twice weekly for 4 weeks. The mice were sacrificed, then, RNA was extracted from the disseminated tumors. qRT-PCR assays were performed to identify angiogenesis-related genes and miRNAs that were altered by anti-VEGFA treatment. SERPINE1/PAI-1 was found to be upregulated during BEV treatment. Therefore, we focused on miRNAs to elucidate the mechanism underlying the upregulation of PAI-1 during BEV treatment. Kaplan-Meier plotter analysis revealed that higher expression levels of SERPINE1/PAI-1 were associated with poor prognoses among BEV-treated patients, suggesting that SERPINE1/PAI may be involved in the acquisition of BEV resistance. miRNA microarray analysis followed by in silico and functional assays revealed that miR-143-3p targeted SERPINE1 and negatively regulated PAI-1 expression. The transfection of miR-143-3p suppressed PAI-1 secretion from ovarian cancer cells and inhibited in vitro angiogenesis in HUVECs. Next, miR-143-3p-overexpressing ES2 cells were intraperitoneally injected into BALB/c nude mice. ES2-miR-143-3p cells downregulated PAI-1 production, attenuated angiogenesis, and significantly inhibited intraperitoneal tumor growth following treatment with anti-VEGFA antibody. Continuous anti-VEGFA treatment downregulated miR-143-3p expression, which upregulated PAI-1 and activated an alternative angiogenic pathway in ovarian cancer. In conclusion, the substitution of this miRNA during BEV treatment may help overcome BEV resistance, and this may be used as a novel treatment strategy in clinical settings., Implications: Continuous administration of VEGFA antibody upregulates SERPINE1/PAI-1 expression via the downregulation of miR-143-3p, which contributes to acquiring bevacizumab resistance in ovarian cancer., (©2023 American Association for Cancer Research.)

Epithelial ovarian cancer (EOC) cells metastasize within the peritoneal cavity and directly encounter human peritoneal mesothelial cells (HPMC) as the initial step of metastasis. The contact between ovarian cancer cells and the single layer of mesothelial cells involves direct communications that modulate cancer progression but the mechanisms are unclear. One candidate mediating cell-cell communications is exosomes, 30-100 nm membrane vesicles of endocytic origin, through the cell-cell transfer of proteins, mRNAs, or microRNAs. Therefore, the goal was to mechanistically characterize how EOC-derived exosomes modulate metastasis. Exosomes from ovarian cancer cells were fluorescently labeled and cocultured with HPMCs which internalized the exosomes. Upon exosome uptake, HPMCs underwent a change in cellular morphology to a mesenchymal, spindle phenotype. CD44, a cell surface glycoprotein, was found to be enriched in the cancer cell-derived exosomes, transferred, and internalized to HPMCs, leading to high levels of CD44 in HPMCs. This increased CD44 expression in HPMCs promoted cancer invasion by inducing the HPMCs to secrete MMP9 and by cleaning the mesothelial barrier for improved cancer cell invasion. When CD44 expression was knocked down in cancer cells, exosomes had fewer effects on HPMCs. The inhibition of exosome release from cancer cells blocked CD44 internalization in HPMCs and suppressed ovarian cancer invasion. In ovarian cancer omental metastasis, positive CD44 expression was observed in those mesothelial cells that directly interacted with cancer cells, whereas CD44 expression was negative in the mesothelial cells remote from the invading edge. This study indicates that ovarian cancer-derived exosomes transfer CD44 to HPMCs, facilitating cancer invasion., Implications: Mechanistic insight from the current study suggests that therapeutic targeting of exosomes may be beneficial in treating ovarian cancer. Mol Cancer Res; 15(1); 78-92. ©2016 AACR., (©2016 American Association for Cancer Research.)