Induction of p27 contributes to inhibitory effect of isorhapontigenin (ISO) on malignant transformation of human urothelial cells

ABSTRACTBladder cancer (BC) is the most expensive cancer to manage on a per-patient basis, costing about $4 billion in total healthcare expenditure per annum in America alone. Therefore, identifying a natural compound for prevention of BC is of tremendous importance for managing this disease. Previous studies have identified isorhapontigenin (ISO) as having an 85% preventive effect against invasive BC formation induced by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). The results showed here that ISO treatment inhibited EGF-induced cell transformation of human urothelial cells through induction of tumor suppressor p27 transcription secondary to activation of an E2F1-dependentpathway.ISOtreatmentrenderedcellsresistanttoEGF-induced anchorage-independent growth concurrent with p27 protein induction in both UROtsa and SV-HUC-1 cells. ISO inhibition of EGF-induced cell transformation could be completely reversed by knockdown of p27, indicating that this protein was essential for the noted ISO inhibitory action. Mechanistic studies revealed that ISO treatment resulted in increased expression of E2F1, which in turn bound to its binding site in p27 promoter and initiated p27 transcription. The E2F1 induction was due to the elevation of its translation caused by ISO-induced miR-205 downregulation. Consistently, miR-205 was found to be overexpressed in human BCs, and ectopic expression of miR-205 mitigated ISO inhibitory effects against EGF-induced outcomes. Collectively, the results here demonstrate that ISO exhibits its preventive effect on EGF-induced human urothelial cell transformation by induction of p27 through a miR-205/E2F1 axis. This is distinct from what has been described for the therapeutic effects of ISO on human BC cells.KEYWORDS: ISOp27urothelial cellsbladder cancertransformation Disclosure statementNo potential conflict of interest was reported by the author(s).Ethical standardsEthical approval: All specimens were obtained with appropriate informed consent from the patients and the Medical Ethics Committee of China. And the comprehensive information of tissues were described in Materials and Methods.Author contributionsMH, XH, JX and JS acquisition and analysis of the data, drafting the manuscript; ZT, JW, HC, XW and PS, acquisition of data, critically reviewed the article; HY and JS analysis and interpretation of the data, critically reviewed the article; and CH conception and design, analysis and interpretation of the data, drafting and revising the manuscript. All the authors have read and approved the final manuscript.Data availabilityThe authors declare that all data supporting the findings of this study are available with the article or from the corresponding author upon reasonable request.Supplementary materialSupplemental data for this article can be accessed online at https://doi.org/10.1080/15384101.2022.2074623Additional informationFundingThis work was partially supported by grants from Natural Science Foundation of China (NSFC81773391 to C.H.); Oujiang Research Project (OJQD2022006 to C.H.); Natural Science Foundation of Ningbo (202003N4205 to J.S.); the Research Foundation of Ningbo Institute of Life and Health Industry, University of Chinese Academy of Sciences (research fund of ningbo institute of life and health industry, university of Chinese academy of sciences 2020YJY0209 to J.S.); the National Natural Science Foundation of China (82003199 to J.S.).