Curcumin as a therapeutic agent in cancer therapy: Focusing on its modulatory effects on circular RNAs

Curcumin, a natural polyphenol compound, has been identified as an effective therapeutic agent against cancer that exerts its anti-tumor activities by up/downregulating signaling mediators and modulating various cellular processes, including angiogenesis, autophagy, apoptosis, metastasis, and epithelial-mesenchymal transition (EMT). Since almost 98% of genomic transcriptional production is noncoding RNAs in humans, there is evidence that curcumin exerts therapeutic effects through the alterations of noncoding RNAs in various types of cancers. Circular RNAs (circRNAs) are formed by the back-splicing of immature mRNAs and have several functions, including functioning as miRNA sponges. It has been shown that curcumin modulated various circRNAs, including circ-HN1, circ-PRKCA, circPLEKHM3, circZNF83, circFNDC3B, circ_KIAA1199, circRUNX1, circ_0078710, and circ_0056618. The modulation of these circRNAs targeted the expression of mRNAs and modified various signaling pathways and hallmarks of cancer. In this article, we reviewed the pharmacokinetics of curcumin, its anti-cancer activities, as well as the biology and structure of circRNAs. Our main focus was on how curcumin exerts anti-cancer functions by modulating circRNAs and their target mRNAs and pathways.