Curcumin as a MicroRNA Regulator in Cancer: A Review

Curcumin is a natural dietary polyphenol for which anti-tumor effects have been documented. Anti-inflammatory and antioxidant properties of curcumin, along with its immunomodulatory, proapoptotic, and antiangiogenic properties, are often referred to as the main mechanisms underlying the anti-tumor effects. At the molecular level, inhibition of NF-kB, Akt/PI3K, and MAPK pathways and enhancement of p53 are among the most important anticancer alterations induced by curcumin. Recent evidence has suggested that epigenetic alterations are also involved in the anti-tumor properties of curcumin. Among these curcumin-induced epigenetic alterations is modulation of the expression of several oncogenic and tumor suppressor microRNAs (miRNAs). Suppression of oncomiRs such as miR-21, miR-17-5p, miR-20a, and miR-27a and over-expression of miR-34 a/c and epithelial-mesenchymal transition-suppressor miRNAs are among the most important effects of curcumin on miRNA homeostasis. The present review will summarize the findings of in vitro and experimental studies on the impact of curcumin and its analogues on the expression of miRNAs involved in different stages of tumor initiation, growth, metastasis, and chemo-resistance.