ABSTRACT: Skin cancer is one of the most common cancers worldwide. Melanoma accounts for ~5% of skin cancers but causes the large majority of skin cancer?related deaths. Recent discoveries have shown that the mitogen?activated protein kinase (MAPK) signaling pathway is critical for melanoma development and progression. Many oncogenic pathways that cause melanoma tumorigenesis have been identified, most of which are due to RAF/MEK/ERK (MAPK) pathway activation. However, the precise role of p38 remains unclear. Using specific short hairpin (sh) RNA to silence p38? and p38?, the present findings demonstrated that p38? was a crucial factor in regulating cell migration in the A375 melanoma cell line. Silencing p38? downregulated the expression of epithelial?mesenchymal transition markers, such as matrix metallopeptidase (MMP) 2, MMP9, twist family bHLH transcription factor 1, snail family transcriptional repressor 1 and vimentin, while mesenchymal?epithelial transition markers, such as E?cadherin, were upregulated. Of note, the results also demonstrated that p38? silencing impaired vascular endothelial growth factor expression, which regulates tumor angiogenesis. Furthermore, p38? knockdown inhibited cell proliferation in melanoma cells. In addition, silencing p38? induced senescence?like features, but not cell cycle arrest. Expression of the senescence markers p16, p21, p53 and ??galactosidase was upregulated, and an increase in the number of senescence?associated ??galactosidase?positive cells was observed in a p38? knockdown stable clone. However, no significant difference was found between control and p38? stable knockdown cells. Taken together, the present results suggested that p38? knockdown impaired migration and proliferation, and increased senescence, in A375 melanoma cells. However, p38? may not be involved in melanoma tumorigenesis. Therefore, targeting p38? may be a valuable approach towards inhibiting tumor growth and metastasis in patients with melanoma.
