Abstract 2823: Honokiol inhibits the invasive potential of melanoma cells by targeting NADPH oxidase 1 and decreasing the binding of core proteins

Melanoma is an aggressive and deadly skin cancer that causes the majority of skin cancer related deaths, and is increasing rapidly in children. As melanoma is a highly metastatic cancer, an approach that could reduce its metastatic potential, may facilitate the development of an effective strategy for its prevention or treatment. To develop more effective chemopreventive agents for the prevention of metastatic melanoma, we determined the effect of honokiol, a phytochemical from Magnolia plant, on the migratory potential of melanoma cells and the molecular mechanisms underlying these effects using Hs294t and SK-Mel 28 cell lines as an in vitro model. Nox1 is a member of NADPH oxidase (Nox) family, consists both cytosolic and membrane bound subunits, and play a role in reactive oxygen species (ROS) generation. Nox1 generated ROS contributes to cell migration through an increase in the expression of matrix metalloproteinases (MMPs). Here, first we checked the protein level (Nox1) and enzymatic activity (Nox) in melanoma cells and compared with normal human epidermal melanocytes (NHEM) and found elevated. Overexpression of Nox1 in melanoma cells was associated with increased migration rate in comparison to NHEM, as determined by cell migration assay. Treatment with diphenyliodonium chloride (DPI, an inhibitor of Nox1) significantly decreases migration potential of melanoma cells. We also found that the treatment of melanoma cells with honokiol reduced the expression of Nox1, and caused significant reduction in cell migration potential. The increased expression of MMPs (2 and 9) is resultant of ROS production by Nox1, which played an important role in cell migration. Honokiol treatment to melanoma cells inhibits MMPs expression. To verify the observations, the Hs294t and SK-Mel 28 cells were treated with DPI, and n-acetyl cysteine, an antioxidant. A reduction in the level of MMPs and cell migration was observed. Further, we examined the effect of honokiol on Nox activity, and the levels of core proteins (p22phox and p47phox) of complex using Hs294t and SK-Mel 28 cells. It was found that treatment of melanoma cells with honokiol not only reduced the Nox activity, but also reduced the binding of p22phox to p47phox proteins through increasing the cytoplasmic accumulation of p47phox protein and decreases the expression level of membrane bound protein p22phox. Together, these results indicate that honokiol acts as a Nox1 inhibitor, and has the ability to inhibit melanoma cell migration by targeting the Nox1-mediated ROS production. This new insight into the anti-melanoma cell migration activity of honokiol could serve as a basis for development of improved chemopreventive or therapeutic strategies for metastatic melanoma. Citation Format: Ram Prasad, Santosh K. Katiyar. Honokiol inhibits the invasive potential of melanoma cells by targeting NADPH oxidase 1 and decreasing the binding of core proteins. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2823. doi:10.1158/1538-7445.AM2015-2823