Molecular Mechanisms of Anti-metastatic Activity of Curcumin

Cancer is the leading cause of death worldwide. Although cancer occurs as a localized disease, its morbidity and mortality rates remain high due to the ability of cancer cells to break-off from the primary tumor and spread to distant organs. Currently, chemotherapy is the main treatment for cancer; however, the increase in proportion of drug-resistant cancer cells and unpleasant side-effects of chemotherapy are still the major challenges in cancer therapy. Curcumin is a natural polyphenol compound and the main bioactive constituent of Indian spice turmeric, widely used in Indian and Chinese medicines. Curcumin has well-known therapeutic actions, including anti-inflammatory, anti-microbial, anti-oxidant and anti-cancer properties. Curcumin induces cancer cell apoptosis through regulating various signaling pathways and arresting tumor cell cycle. Curcumin's therapeutic/ preventative actions on metastatic cancers have not been yet fully understood and studied. The present review explores the potential anti-metastatic mechanisms of curcumin, including inhibition of transcription factors and their signaling pathways (e.g., NF-κB, ApP-1 and STAT3), inflammatory cytokines (e.g., CXCL1, CXCL2, IL-6, IL-8), multiple proteases (e.g., uPA, MMPs), multiple protein kinases (e.g., MAPKs, FAK), regulation of miRNAs (e.g., miR21, miR181b) and heat shock proteins (HLJ1). In addition, possible synergistic actions of combination therapy of curcumin with current chemotherapies are discussed in this review.