Melanoma coordinates general and cell-specific mechanisms to promote methotrexate resistance

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• 作者：Magal&iacute ; Sá ; ez-Ayala^a ; ¹ ; Mar&iacute ; a Piedad Ferná ; ndez-Pé ; rez^a ; ¹ ; Mar&iacute ; a F. Montenegro^a ; Luis Sá ; nchez-del-Campo^b ; Soledad Chazarra^a ; Antonio Piñ ; ero-Madrona^c ; Juan Cabezas-Herrera^d ; José ; Neptuno Rodr&iacute ; guez-Ló ; pez^a ; ^{neptuno@um.es}
• 关键词：Melanoma ; Methotrexate ; E2F1 ; Chk1 ; DNA damage
• 刊名：Experimental Cell Research
• 出版年：2012
• 期刊代码：292_00144827
• 类别：med
• 出版时间：10 June, 2012
• 卷：318
• 期：10
• 页码：1146-1159
• 文件大小：1989 K

摘要

Melanoma, the most aggressive form of skin cancer, is notoriously resistant to all current modalities of cancer therapy, including to the drug methotrexate. Melanosomal sequestration and cellular exportation of methotrexate have been proposed to be important melanoma-specific mechanisms that contribute to the resistance of melanoma to methotrexate. In addition, other mechanisms of resistance that are present in most epithelial cancer cells are also operative in melanoma. This report elucidates how melanoma orchestrates these mechanisms to become extremely resistant to methotrexate, where both E2F1 and checkpoint kinase 1 (Chk1), two molecules with dual roles in survival/apoptosis, play prominent roles. The results indicated that MTX induced the depletion of dihydrofolate in melanoma cells, which stimulated the transcriptional activity of E2F1. The elevate expression of dihydrofolate reductase and thymidylate synthase, two E2F1-target genes involved in folate metabolism and required for G₁ progression, favored dTTP accumulation, which promoted DNA single strand breaks and the subsequent activation of Chk1. Under these conditions, melanoma cells are protected from apoptosis by arresting their cell cycle in S phase. Excess of dTTP could also inhibit E2F1-mediated apoptosis in melanoma cells.