Knocking down RAD51AP1 enhances chemosensitivity by inhibiting the self-renewal of CD133 positive ovarian cancer stem-like cells.

Purpose: This study was designed to investigate the function of RAD51AP1 in the self-renewal and chemosensitivity of CD133 positive (CD133) ovarian cancer (OC) stem-like cells.

Methods: CD133 (CD133 positive) OVCAR4 and CD133 negative (CD133) OVCAR4 cells were separated from OVCAR4 by flow cytometry. Then, the separated CD133OVCAR4 cells were divided into the following groups: Vector group; RAD51AP1 group; siNC group; si-RAD51AP1 group. Next, sphere-formation assay and colony forming assay were used to evaluate the self-renewal and proliferation ability of cells; western blot to detect the expression of RAD51AP1, transforming growth factor beta 1 (TGF-β1) and SMAD4 proteins in tissues and cells; qRT-PCR to assess the mRNA levels of sex-determining region Y-box 2 (SOX2), octamer-binding transcription factor 4 (OCT4), NANOG and Kruppel-like factor 4 (KLF4).

Results: The performance of CD133OVCAR4 cells was much better than that of CD133OVCAR4 cells in sphere-formation assay and colony forming assay. Besides, compared with adjacent group and CD133OVCAR4 cells, the expression level of RAD51AP1 increased significantly in OC group and CD133OVCAR4 cells. Moreover, the over-expression of RAD51AP1 promoted the self-renewal and proliferation of CD133OVCAR4 cells. On the contrary, knocking down the expression level of RAD51AP1 could inhibit the self-renewal and proliferation of CD133OVCAR4 cells and improve the sensitivity of cells to chemotherapy drugs.

Conclusion: The findings of this study showed that RAD51AP1 was highly expressed in OC tissue and CD133OVCAR4 cells, and regulated the self-renewal and chemosensitivity of tumor cells through the TGF-β1/SMAD4 signaling pathway.