Koji Nakamura

PI3K/mTOR Dual Inhibitor GSK458 and Arsenic Trioxide Exert Synergistic Antitumor Effects against Ovarian Clear-Cell Carcinoma

Abstract Ovarian clear-cell carcinoma (OCCC), particularly advanced or recurrent settings, is generally resistant to platinum-based chemotherapy, warranting novel therapeutic strategies. Mutations in the PI3K/AKT/mTOR pathway are frequently reported in OCCC. Therefore, we hypothesized that the PI3K/mTOR dual inhibitor, GSK458, and arsenic trioxide (As2O3) may exert synergistic antitumor effects on OCCC. We investigated the effects of GSK458, As2O3, and the combination of GSK458 and As2O3 on cell viability, colony formation, and apoptosis in seven OCCC cells. Mechanistically, transcriptomic differences were assessed among the groups. Additionally, their antitumor effects were evaluated on the three-dimensional cultures of OCCC patient-derived xenografts as well as in vivo. Low-dose combination of GSK458 and As2O3 exerted synergistic antitumor effects in vitro. Viability of the three-dimensional OCCC patient-derived xenograft cultures treated with the combination of GSK458 and As2O3 decreased to 23.8% of that of the control. RNA sequencing revealed that the mechanism was associated with cell cycle and DNA damage repair. The combination of GSK458 and As2O3 synergistically inhibited the PI3K/AKT/mTOR pathway and angiogenesis and increased apoptosis. Compared with any monotherapy, the combination treatment significantly suppressed tumor growth in vivo, thereby enhancing survival. Overall, our findings highlight the potential of the novel combination of GSK458 and As2O3 for OCCC treatment.

Continuous Administration of Anti-VEGFA Antibody Upregulates PAI-1 Secretion from Ovarian Cancer Cells via miR-143-3p Downregulation

Abstract 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.

Exploring the potential of engineered exosomes as delivery systems for tumor-suppressor microRNA replacement therapy in ovarian cancer

MicroRNA (miRNA) plays a pivotal role in cancer biology. Therefore, tumor suppressor (TS) miRNAs are an attractive target for cancer therapy. However, clinical trials have failed due to the difficulties in miRNA delivery, warranting the development of a novel drug delivery system (DDS). Exosomes are stable in circulation and selectively picked up by cancer cells, indicating that they can serve as a miRNA carrier. The aim of this study was to explore the possibility of exosomes as a carrier for miRNA replacement therapy for ovarian cancer (OC). First, exosomes were purified from primary-cultured omental fibroblasts of OC patients. miR-199a-3p was selected as a TS miRNA, and the synthesized miR-199a-3p was loaded into exosomes by electroporation. Treatment with miR199a-3p-loaded-exosomes (miR-199a-3p-Exo) drastically increased miR-199a-3p expression level in OC cell lines (CaOV3; 8592-, SKOV3; 67188-, and OVCAR3; 2280-fold). miR-199a-3p-Exo suppressed c-Met expression, a direct target of miR-199a-3p, and thereby inhibited cell proliferation and invasion. In a xenograft study, miR-199a-3p-Exo also drastically inhibited peritoneal dissemination in OC mice model, and diminished c-Met expression, ERK phosphorylation, and MMP2 expression in tumors. These results suggest that miRNA replacement therapy using exosomes shows promise for treatment of OC. Given that omental fibroblasts can be obtained from most OC patients, patient-derived exosomes can be utilized as a DDS for future molecular-targeted therapies.