Esculetin enhances the inhibitory effect of 5-Fluorouracil on the proliferation, migration and epithelial-mesenchymal transition of colorectal cancer.

Background: Colorectal cancer (CRC) is the most common malignant disease worldwide and thus new therapeutic approaches are needed. 5-Fluorouracil (5-FU) remains the most widely used agent to treat colorectal cancer (CRC). However, its clinical efficacy is currently limited by the development of drug resistance. Esculetin (EST), a coumarin, was found to have anti-proliferative and anti-migration activity in cancer.

Objective: This research aims to evaluated the influence and possible mechanism of EST on the proliferation, migration and epithelial-mesenchymal transition of CRC cell lines.

Materials And Methods: Human CRC cell lines HT-29, SW480, HCT-116, and Caco-2 were treated with various concentrations of EST (0.2, 2, 20, 200, 2000 μg/ml) or 5-FU (0.1, 1, 10, 100, 1000 μg/ml) for 48 h, and cell viability was determined by the MTT and CCK-8 assay. The motility of HCT-116 cells was detected by scratch assay. Western blot was applied to detect the protein expression. Besides, levels of Wnt3a and VEGF in HCT-116 cell culture medium supernatant were analyzed by ELISA. The anti-tumor effect was detected with HCT-116 subcutaneous tumor bearing tumor model by monitoring the tumor vomume in vivo. Finally, the tumoral expression of VEGF was measured by immunohistochemistry, and the expression of Ki67, PCNA, β-catenin, c-Myc, Cyclin D1, MMP2 and MMP7 was measured by Western blot analysis.

Results: EST inhibited HCT-116 cell proliferation in a dose-dependent manner. Western blot analysis revealed that EST decreased the expression of Ki67, PCNA, N-cadherin, E-cadherin, vimentin, fibronectin, β-catenin, c-Myc, Cyclin D1, MMP2 and MMP7. Furthermore, EST reduced the release of Wnt3a and VEGF into HCT-116 cells culture medium. After EST treatment, the tumor volume was significant smaller than that of the control group, and the tumoral levels of VEGF were decreased. Moreover, western blot analysis indicated that the expression of Ki67, PCNA, β-catenin, c-Myc, Cyclin D1, MMP2 and MMP7 were also significantly decreased after treated with EST. In addition, in vitro and in vivo anti-tumor results demonstrated that EST combined with 5-FU could increase the inhibitory effect of 5-FU on HCT-116 cells proliferation, migration and epithelial-mesenchymal transition.

Conclusions: EST enhances the inhibitory effect of 5-FU on the proliferation, migration and epithelial-mesenchymal transition of CRC.