Anti-inflammatory and Cytotoxic Activities of Mango (Mangifera indica L. var Keitt) Polyphenols in Cancer and Non-cancer Breast Fibroblasts in Vitro

Breast cancer is the leading cause of cancer death among women worldwide and polyphenols are under investigation as an alternative to conventional treatment approaches of breast cancer. The anti-inflammatory and anti-proliferative activities of polyphenols have been demonstrated in many studies, yet cellular targets and the underlying cellular mechanisms remain unclear.

The overall goal of this study was to investigate the anti-inflammatory and cytotoxic properties of polyphenol compounds extracted from the mango variety Keitt in MCF-12A breast non-cancer and MDA-MB231 breast cancer cells by assessing the modulation of signaling pathways involved in inflammation and carcinogenesis. Mango polyphenols were identified by HPLC-MS analysis. The generation of reactive oxygen species was performed using fluorescence intensity in the DCFH-DA assay. Gene expression was analyzed by qRT-PCR, and protein expression was conducted by Western Blotting and Multiplex Bead assay analysis.

Bioactive compounds identified in the mango pulp by HPLC-MS included a great variety of polyphenols such as gallic acid, galloyl glucosides with different degree of polymerization and other polyphenols. The anti-inflammatory activities of mango polyphenols were evaluated in MCF-12A non cancer breast fibroblasts. An inflammatory microenvironment for MCF-12A breast cells was induced with tumor necrosis factor alpha (TNF-?). The generation of reactive oxygen species was suppressed significantly compared to cells induced with TNF-?, where there was no significant difference between the concentrations of mango polyphenol extract. Results showed a significant down-regulation of mRNA and protein expression of inflammatory genes involved in the PI3K/AKT pathway and related downstream targets such as NF-?B and mTOR involved in biological processes including cell growth, proliferation and survival. Moreover, mango polyphenols had a significant impact on the miRNA-126-PI3K/AKT axis which plays an important role in inflammation and carcinogenesis, suggesting a potential anti-inflammatory underlying mechanism.

The cytotoxic effects of mango polyphenols were investigated in MDA-MB231 breast cancer cells. Mango polyphenols decreased the production of reactive oxygen species; however no significant differences were found between the tested concentrations of mango polyphenols. The gene expression of proapoptotic factors involved in the intrinsic mitochondrial pathway such as cytochrome C and caspase-3 were significantly regulated after mango polyphenol treatment. In addition, the suppression of the PI3K/AKT/mTOR pathway and downstream effectors such as HIF-1? and VEGF as well as the disruption of the miRNA-21-PTEN/AKT axis were identified as potential underlying mechanism of the cytotoxic properties of mango polyphenols.

Overall, findings from this study show that mango polyphenols counteract inflammatory and cancerous cell signaling processes; therefore the potential of mango polyphenols in the prevention of breast-cancer focusing on the PI3K/AKT/mTOR-axis should be further investigated.