Yun Bai

Inhibition of PI3K and Hedgehog Signaling Pathway Inhibits Hypoxia-Induced Vasculogenic Mimicry Formation in Ovarian Cancer Stem Cells

Inhibition of the Hedgehog and phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathways has been shown to suppress tumor proliferation and stem cell activity. However, the precise role of these pathways in vasculogenic mimicry (VM) of ovarian cancer stem cells (OCSCs) remains unclear. To investigate the roles of the PI3K/AKT and Hedgehog signaling pathways in VM formation and the underlying mechanisms in OCSCs. OCSCs were induced through serum-free culture of SK-OV-3. Hypoxia-inducible factor-1α (HIF-1α) knockdown was achieved by transfection with sh-HIF-1α. Cells were treated with the PI3K agonist 740 Y-P, the PI3K inhibitor LY294002, the Hedgehog agonist purmorphamine, and the Hedgehog inhibitor cyclopamine under hypoxic conditions. Expression of HIF-1α, epithelial-to-endothelial transition (EET) markers, and components of the PI3K and Hedgehog pathways was analyzed using immunofluorescence and Western blotting. VM capacity was assessed using a Matrigel three-dimensional (3D) culture assay. Cell proliferation and invasion were evaluated by MTS, EdU, and Transwell assays. VM formation was further examined in an OCSC xenograft model. OCSCs accounted for more than 85% of seventh-generation SK-OV-3 cells cultured under serum-free conditions. Hypoxia markedly increased HIF-1α expression, which activated the PI3K and Hedgehog signaling pathways. HIF-1α knockdown suppressed activation of these pathways. Treatment with LY294002 and cyclopamine, as well as HIF-1α knockdown, inhibited hypoxia-induced upregulation of N-cadherin and VE-cadherin, as well as the formation of branching points and 3D channels. Moreover, both LY294002 and cyclopamine significantly reduced cell proliferation, invasion, and VM formation in vitro and in xenografted OCSCs. HIF-1α knockdown inhibits activation of the PI3K and Hedgehog signaling pathways, thereby reducing EET and VM formation in hypoxia-induced OCSCs.

Ginsenoside Rg6 Improves Cisplatin Resistance in Epithelial Ovarian Cancer Cells via Suppressing Fucosylation and Inducing Autophagy

Platinum-based chemotherapy remains a mainstay of clinical practice in the standard treatment of epithelial ovarian cancer (EOC). Most patients who receive this treatment, however, develop relapse and drug resistance. Ginsenoside Rg6 (G-Rg6), one of the anticarcinogenic active components in the American ginseng berry, may hold promise in the adjuvant chemotherapy of EOC. In this study, the correlation between fucosylation and cisplatin (cDDP) resistance in EOC cells was validated by gene expression profile analysis and lectin blot. We found that G-Rg6 derived from the American ginseng berry inhibits the cell viability and protein fucosylation of cDDP-resistant EOC cells. G-Rg6-induced G2/M-cell cycle arrest was proven to result from the autophagy of cDDP-resistant EOC cells. In addition, we observed that G-Rg6 initiates autophagy in cDDP-resistant EOC cells by inhibiting the GRB2–ERK1/2–mTOR axis, and that high concentration of G-Rg6 treatment leads to cell apoptosis. G-Rg6 also enhances cDDP uptake in A2780CP cells by promoting CTR1 expression and suppressing its core fucosylation. Therapies combining cDDP and G-Rg6 display higher efficacy in inhibiting the cDDP-resistant EOC cells in comparison with the sole application of cDDP, exhibiting strong potential for clinical application. G-Rg6 derived from the American ginseng berry can improve cDDP resistance in EOC cells via suppressing fucosylation and inducing autophagy, suggesting its potential in the adjuvant chemotherapy of EOC patients.