Abstract
Endometrial carcinoma (EC) often exhibits resistance to hormone therapies, such as medroxyprogesterone acetate (MPA), highlighting the need for novel strategies to enhance therapeutic efficacy. The present study aimed to investigate the effects of polyphyllin VII (PPVII) on the efficacy of MPA in EC, focusing on the regulatory role of microRNA (miR)-33a-5p. Briefly, an MPA-resistant Ishikawa cell line (Ishikawa/MPA-R), maintained with 10 µM MPA, was established and transfected with negative control (NC) and miR-33a-5p inhibitors. Following treatment with PPVII and MPA, the proliferation capacity and apoptosis levels of the Ishikawa and Ishikawa/MPA-R cells were evaluated using reverse transcription-quantitative polymerase chain reaction, MTT assay, clonogenic assay, flow cytometry, western blotting and dual-luciferase assay. Next, the expression levels of miR-33a-5p and F-box and leucine rich repeat protein 16 (FBXL16) were measured, and the regulatory relationship between miR-33a-5p and FBXL16 was analyzed. Significant reductions in cell viability were observed in all groups following treatment with increased concentrations of MPA and PPVII, with the greatest effect observed in the combined MPA + PPVII group (P<0.01). The apoptosis levels of the Ishikawa/MPA-R cells were significantly increased in all drug treatment groups, particularly in the MPA + PPVII group (P<0.05). PPVII treatment significantly increased the expression level of miR-33a-5p in Ishikawa/MPA-R cells (P<0.01). In the PPVII + miR-33a-5p inhibitor group, the Ishikawa/MPA-R cells exhibited an upregulation in the viability (P<0.01), colony formation ability (P<0.01), proportion in the G1 phase (P<0.05) and the protein expression levels of cyclin D1 (P<0.01) and cyclin-dependent kinase 4 (P<0.01), and a reduction in the miR-33a-5p expression (P<0.01), apoptosis levels (P<0.05), proportion in the S (P<0.05) and G2 phases and the levels of Bcl-2-associated X protein (P<0.001). The FBXL16 protein expression in Ishikawa/MPA-R cells was significantly higher compared with Ishikawa cells, and the mRNA and protein expression levels of FBXL16 were markedly elevated in the PPVII + miR-33a-5p inhibitor group compared with the PPVII + NC group (P<0.01). These findings suggested that PPVII upregulated the expression of miR-33a-5p, enhanced the sensitivity of EC cells to MPA and potentially exerted anticancer effects in EC through the synergistic action of the miR-33a-5p/FBXL16 axis in combination with MPA.