Background

Colorectal cancer (CRC) is an important death-related disease in the world and new therapeutic strategies are urgently needed to reduce mortality. Several studies have demonstrated that emodin, the main ingredient of Rheum palmatum, fights cancer but its potential anti-tumor effect on CRC is still unknown.

Purpose

The present study is aimed to explore the potential anti-tumor effects of emodin against CRC and the underlying molecular mechanism.

Methods

CRC-related datasets were screened according to filter criteria in the GEO database and TCGA database. By using screened differentially expressed genes, GO, KEGG and survival analysis were carried out. The expressions of ACSL4, VEGFR1, and VEGFR2 were examined by immunohistochemistry and western blot. Then, pcDNA-ACSL4, pcDNA-VEGFR1, and pcDNA-VEGFR2 were used to overexpress ACSL4, VEGFR1, and VEGFR2, while ACSL4 siRNA was used to silence ACSL4 expression in HCT116 cells. CCK-8 assay and transwell migration assay were used to detect the cell proliferation and invasion. A docking simulation assay and an MST assay were performed to explore the potential mode of emodin binding to ACSL4. The HCT116 cells and CRC mouse model were established to investigate the effects of emodin on CRC.

Results

The ACSL4, VEGFR1, and VEGFR2 expression were upregulated in CRC tissues and ACSL4 was associated with a shorter survival time in CRC patients. ACSL4 downregulation reduced cell proliferation and invasion, while ACSL4 exhibited a positive correlation with the levels of VEGFR1, VEGFR2, and VEGF. In HCT116 cells, emodin reduced cell proliferation and invasion by inhibiting ACSL4, VEGFR1, and VEGFR2 expression and VEGF secretion. Docking simulation and MST assay confirmed that emodin can directly bind to ACSL4 target. Moreover, ACSL4 overexpression abolished the inhibitory effect of emodin on VEGF secretion and VEGFR1 and VEGFR2 expression, but VEGFR1 and VEGFR2 overexpression did not affect the inhibitory effect of emodin on ACSL4 expression and VEGF secretion. Furthermore, emodin reduced the mortality and tumorigenesis of CRC mice and reduced ACSL4, VEGFR1, VEGFR2 expression, and VEGF content.

Conclusion

Our findings indicate that emodin inhibits proliferation and invasion of CRC cells and reduces VEGF secretion and VEGFR1 and VEGFR2 expression by inhibiting ACSL4. This emodin-induced pathway offers insights into the molecular mechanism of its antitumor effect and provides a potential therapeutic strategy for CRC.