Casticin suppresses self-renewal related stemness via miR-342-3p-mediated FoxM1 downregulation in cervical cancer cells

Background: Casticin (CAS), a natural flavonoid found in Viticis Fructus, Viticis Cannabifoliae Fructus, and Semen Euphorbiae, shows anti-inflammatory activity and efficacy against various cancers. However, its effect on stemness associated with self-renewal in cervical cancer (CC) cells remains unclear, as well as the underlying mechanism. Purpose: The primary objective of this study was to examine the effect of CAS on CC stemness and to explore the underpinning regulatory mechanism. Methods: HeLa cells underwent treatment with varying concentrations of CAS (0, 10, 30, 100 nM). To evaluate the impacts of CAS on CC stemness and tumorigenicity, sphere- and colony-formation assays and a xenograft model were employed. The study involved screening for changes in miRNAs and their target genes. The miRNA array identified an upregulation in miRNAs, whereas the mRNA array detected a downregulation of specific target genes. The latter genes were found to regulate stem cell-related genes through miR-342-3p in HeLa cells administered CAS. Next, whether miR-342-3p directly targets FOXM1 when upregulated by CAS was assessed by the luciferase reporter assay. qRT-PCR was performed to analyze miR-342-3p expression. Additionally, immunoblotting was conducted to assess the protein amounts of FoxM1 and stemness-related factors (CD133, CD49f, Nanog, and Sox2). Function rescue experiments were conducted to determine the mechanism of CAS in stemness regulation. These experiments involved utilizing a miR-342-3p inhibitor and overexpressing FOXM1 in HeLa cells. Results: CAS decreased in vitro stemness, suppressing sphere- and colony-formation capabilities of CC. It also dose-dependently downregulated the expression of stemness-associated proteins, including CD133, CD49f, Nanog, and Sox2. Moreover, CAS inhibited in vivo carcinogenesis, remarkably reducing tumor growth in mice bearing HeLa cell xenografts. Analysis revealed downregulated FOXM1 expression in HeLa cells treated with CAS. In the luciferase reporter assay, miR-342-3p was found to directly target FOXM1 in CAS-treated HeLa cells. Additionally, miR-342-3p inhibitor transfection successfully rescued CAS' suppressive impact on stemness. Furthermore, overexpression of FOXM1 did not induce changes in miR-342-3p expression. However, it effectively rescued CAS' suppressive effects on stemness. Moreover, CAS also inhibited stemness, upregulated miR-342-3p, and lowered FOXM1 expression in the SiHa cell line. Conclusion: CAS suppresses self-renewal-associated stemness by targeting FOXM1 via miR-342-3p upregulation. These findings suggest CAS is promising as a novel therapeutic candidate in CC.