The impact of oleuropein on miRNAs regulating cell death signaling pathway in human cervical cancer cells

Cervical cancer is known as the second most pervasive malignancy in women across the globe. The role played by microRNAs (miRNAs) in the initiation, progression, and metastasis of this cancer has received specific attention. The use of natural compounds leading cancer cells toward apoptosis is a feasible strategy for cancer therapy. Oleuropein, an olive-extracted phenolic substance, displays anticancer properties. Here, it was attempted to assess the role played by oleuropein in cell viability in cervical cancer and changes in the expression of some miRNAs associated with cervical cancer as well as some of their possible target genes selected using bioinformatics analysis. For this purpose, HeLa cell line was exposed to several oleuropein concentrations for 48 and 72 h. After that, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay and flow cytometry were employed to assess cell viability and apoptosis, respectively. In addition, to conduct bioinformatics analysis, Cytoscape computer program was used based on STRING database. Furthermore, to examine the role played by oleuropein in the expression of miRNAs of interest as well as their potential target genes, real-time PCR was employed. The findings indicated that oleuropein reduced cell viability through inducing apoptosis. As a result of treatment with oleuropein, miR-34a, miR-125b, and miR-29a showed increased expression levels, whereas miR-181b, miR-221, and miR-16 showed decreased expression levels. Furthermore, oleuropein reduced the expression of the anti-apoptotic genes Bcl-2 and Mcl1, whereas it elevated the expression of the pro-apoptotic Bid, Fas, and TNFRSF10B genes and the p53 tumor suppressor. Our results indicate that the apoptosis induction is a mechanism of action of oleuropein in HeLa cells. Because of its effect on the reflation of the expression of genes and miRNAs effective in the pathogenesis of cervical cancer, oleuropein shows potential as an effective research tool for developing new natural drugs for treating cervical cancer.