Background: Apigenin (API) is a naturally occurring plant-derived flavone, which is abundantly present in common fruits and vegetables, and shows little or no toxicity of daily diet. The treatment of colorectal cancer is limited by high recurrence rate and multidrug resistance.

Purpose: The purpose of this study was to explore the potential therapeutic effect and possible mechanisms of API on colorectal cancer cells.

Methods: Cell proliferation and apoptosis of human colon cancer cell line HCT116 was assessed after API treatment. A comprehensive transcriptome profile of API-treated HCT116 cells was acquired by high-throughput sequencing. The regulation of miRNA215-5p and E2F1/3 were identified by bioinformatics analyses. An inhibitor of miRNA215-5p, inhibitor 215, was applied to confirm the role of this microRNA played in the anti-cancer effect of API. Luciferase reporter gene assay was performed to identify targeting relationship between miRNA215-5p and E2F1/3.

Result: API significantly promoted cell apoptosis and anti-proliferation of HCT116 cells in a dose-dependent manner. Bioinformatics analyses identified several altered miRNAs among which the expression of miRNA-215-5p showed markedly increased. Meanwhile, the expression of E2F1 and E2F3 was decreased by API, which was associated with miRNA215-5p. Luciferase reporter gene assay showed miRNA-215-5p could directly bind to 3' UTR of E2F1/3. Inhibition of miRNA-215-5p significantly inhibited apoptosis and cell cycle arrest at G0/G1 phase induced by API.

Conclusions: The result of this study confirmed the anti-cancer effect of API on human colorectal cancer cells and investigated the underlying mechanism by a comprehensive transcriptome profile of API-treated cells.

Keywords: Apigenin; Cell cycle; Colorectal cancer; E2F1; High-throughput sequencing; miRNA-215-5p.