Abstract
Melanoma is the leading cause of death from skin disease due, in large part, to its propensity to metastasize. We have examined the effect of grape seed proanthocyanidins (GSPs) on melanoma cancer cell migration and the molecular mechanisms underlying these effects using highly metastasis-specific human melanoma cell lines, A375 and Hs294t. Using in vitro cell invasion assays, we observed that treatment of A375 and Hs294t cells with GSPs resulted in a concentration-dependent inhibition of invasion or cell migration of these cells, which was associated with a reduction in the levels of cyclooxygenase (COX)-2 expression and prostaglandin (PG) E2 production. Treatment of cells with celecoxib, a COX-2 inhibitor, or transient transfection of melanoma cells with COX-2 small interfering RNA, also inhibited melanoma cell migration. Treatment of cells with 12-O-tetradecanoylphorbol-13-acetate, an inducer of COX-2, enhanced the phosphorylation of ERK1/2, a protein of mitogen-activated protein kinase family, and subsequently cell migration whereas both GSPs and celecoxib significantly inhibited 12-O-tetradecanoylphorbol-13-acetate -promoted cell migration as well as phosphorylation of ERK1/2. Treatment of cells with UO126, an inhibitor of MEK, also inhibited the migration of melanoma cells. Further, GSPs inhibited the activation of NF-κB/p65, an upstream regulator of COX-2, in melanoma cells, and treatment of cells with caffeic acid phenethyl ester, an inhibitor of NF-κB, also inhibited cell migration. Additionally, inhibition of melanoma cell migration by GSPs was associated with reversal of epithelial-mesenchymal transition process, which resulted in an increase in the levels of epithelial biomarkers (E-cadherin and cytokeratins) while loss of mesenchymal biomarkers (vimentin, fibronectin and N-cadherin) in melanoma cells. Together, these results indicate that GSPs have the ability to inhibit melanoma cell invasion/migration by targeting the endogenous expression of COX-2 and reversing the process of epithelial-to-mesenchymal transition.
Highlights
Melanoma is the leading cause of death from skin disease due to its propensity to metastasis [1,2], and is increasing rapidly in children [3]
grape seed proanthocyanidins (GSPs) inhibit human melanoma cancer cell migration We determined whether treatment of A375 and Hs294t human melanoma cells with GSPs inhibited their invasiveness or migration using Boyden chamber cell migration assays
To confirm that the inhibition of cancer cell migration by GSPs was a direct effect on migration ability, and that was not due to a reduction in cell viability, a trypan blue assay was performed using cells that were treated identically to those used in the migration assays
Summary
Melanoma is the leading cause of death from skin disease due to its propensity to metastasis [1,2], and is increasing rapidly in children [3]. Exposure of the skin to UV radiation induces an increase in the expression levels of cyclooxygenase -2 (COX-2), a rate-limiting enzyme that catalyzes the conversion of arachidonic acid to prostaglandins (PGs) [5,6]. These inflammatory mediators have been identified as a risk factor for the development of skin cancers [5,6], and thought to play a central role in orchestrating the multiple events involved in cancer invasion and metastasis [7,8]. Melanoma is a highly malignant cancer with a potent capacity to metastasize distantly, an approach that decreases its metastatic or invasive ability may facilitate the development of an effective strategy for its treatment or prevention
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