Effects and mechanism of RhoC downregulation in suppressing ovarian cancer stem cell proliferation, drug resistance, invasion and metastasis.

Cancer stem cells are considered to be the root cause of tumor initiation, metastasis, recurrence and therapeutic resistance. Recent studies have reported that RhoC plays a critical role in regulating cancer stem cells; however, its function in ovarian cancer stem cells (OCSCs) remains unknown. The ovarian cancer cell line A2780, and the paclitaxel-resistant A2780 cell line (A2780-PTX) were obtained. A2780 cells were used to isolate and identify the highly invasive A2780-PM cells, and A2780-PTX cells were used to isolate and identify the highly drug-resistant and highly invasive A2780-PTX-PM cells by Transwell assay. MTT, Transwell and wound healing assays were used to compare the differences in cell proliferation, invasion and migration ability among the four cell lines. Immunofluorescence was used to detect the expression of stem cell markers CD117 and CD133. OCSCs were sorted by flow cytometry. Following si-RhoC transfection of the OCSCs, cell proliferation, drug resistance, invasion and migration ability and RhoC, CD117 and CD133 expression levels were assayed. RT-PCR was used to assess RhoC, CD117, CD133 and matrix metalloproteinase 9 (MMP9) mRNA expression levels. A2780-PM and A2780‑PTX-PM cells exhibited higher cell proliferation, drug resistance, and invasion and migration ability than the A2780 and A2780-PTX cell lines. Furthermore, CD133 and CD117 expression levels were higher in the A2780-PM and A2780‑PTX-PM cells than levels in the A2780 and A2780-PTX cells. Transfection of si-RhoC in OCSCs suppressed the proliferation, drug resistance, invasion, migration and CD117 and CD133 expression levels. Furthermore, the expression levels of RhoC, CD117, CD133, MDR1, and MMP9 mRNA were downregulated in the transfected population. Taken together, our results demonstrated that RhoC downregulation may inhibit the proliferation, drug resistance, invasion and migration of OCSCs, and RhoC may play an important role in the formation of OCSCs.