Curcumin suppresses melanoma cell migration through down-regulating NEDD4 and inhibiting the endocytic degradation of E-cadherin

Abstract Objective Melanoma is one of the most aggressive cancers which tends to metastasize beyond the primary site. To block or delay cancer metastasis is critical for melanoma treatment. Curcumin exerts inhibiting the proliferation and metastasis of melanoma, while its anti-metastasis mechanism is not completely understood. Methods The melanoma cell lines A375 and A875 were used in this experiment. Cell migration was determined by Transwell assay with curcumin. The expression of Neuronal precursor cell-expressed developmentally downregulated 4 (NEDD4), E-cadherin, and vimentin was determined by Western blotting and/or quantitative real-time PCR in the context of NEDD4 knockdown or overexpression or curcumin treatment. The endocytosis of E-cadherin was observed by fluorescence microscopy in the cells with NEDD4 (wild type or mutated) overexpression or curcumin treatment. Results We demonstrated that curcumin inhibited the migration of melanoma cells through upregulating E-cadherin while inhibiting vimentin. The inhibited epithelial-mesenchymal transition (EMT) of the melanoma cells treated with curcumin was associated with the decreased expression of NEDD4. Knockdown of NEDD4 upregulated E-cadherin, while overexpression of NEDD4 depleted E-cadherin. Moreover, NEDD4 promoted the internalization and lysosomal degradation of E-cadherin, while curcumin strengthened the localization of E-cadherin in the plasma membrane and inhibited the delivery of E-cadherin to endosome. NEDD4 colocalized with the internalized E-cadherin, while mutated NEDD4, which still enhanced E-cadherin internalization, did not colocalize with E-cadherin. Conclusions Taken together, curcumin’s inhibition on NEDD4 expression and E-cadherin endocytosis contributes to its anti-migration effect on melanoma cells.