Chu W, Pak B J, Bani M R, Kapoor M, Lu S J, Tamir A, Kerbel R S, Ben-David Y
Sunnybrook and Women's College Health Sciences Centre, Division of Cancer Biology Research, Toronto, Ontario, Canada.
Oncogene. 2000 Jan 20;19(3):395-402. doi: 10.1038/sj.onc.1203315.
A major obstacle in the systemic treatment of advanced malignant melanoma is its intrinsic resistance to conventionally used chemotherapeutic agents. In order to investigate the mechanisms of this intrinsic resistance, we have previously utilized retroviral insertional mutagenesis on an early-stage, drug sensitive human melanoma cell line (WM35) to establish mutated cell lines that exhibited increased resistance to cis-diammi-nedichloroplatinum(II) (CDDP). Here, we demonstrate that this increased resistance to CDDP is mediated by the over-expression of tyrosinase-related protein-2 (TYRP2), an enzyme that normally functions in the biosynthesis of the pigment, melanin. Northern and Western blot analyses revealed that the expression of TYRP2 in the virally-derived cell lines as well as in a panel of human melanoma cell lines positively correlated with their levels of resistance to CDDP. Furthermore, enforced expression of TYRP2 in WM35 cells by transfection elevated their resistance to CDDP. The increased CDDP resistance in the virally-derived clones and TYRP2 transfectants was accompanied by a reduction in CDDP-induced apoptosis. Interestingly, the virally-derived CDDP-resistant clones also showed cross resistance to carboplatin and methotrexate, but not taxol, suggesting that TYRP2 over-expression may confer resistance specifically to DNA damaging agents. Overall, these results demonstrate a novel mechanism of drug resistance in human melanoma cells that is mediated by the over-expression of TYRP2. Since TYRP2 is expressed only in cells of melanocytic lineage, this may represent the first report of a lineage-specific mechanism of drug resistance. In summary, these findings suggest a significant role for TYRP2 in the intrinsic drug resistance phenotype of human melanoma cells and may have important implications in the development of chemosensitization strategies for the clinical management of this disease.
晚期恶性黑色素瘤全身治疗的一个主要障碍是其对传统使用的化疗药物具有内在抗性。为了研究这种内在抗性的机制，我们之前利用逆转录病毒插入诱变技术处理一种早期的、对药物敏感的人黑色素瘤细胞系（WM35），以建立对顺二氯二氨铂（II）（CDDP）抗性增加的突变细胞系。在此，我们证明这种对CDDP抗性的增加是由酪氨酸酶相关蛋白2（TYRP2）的过表达介导的，TYRP2是一种正常情况下在色素黑色素生物合成中起作用的酶。Northern印迹和Western印迹分析表明，TYRP2在病毒衍生的细胞系以及一组人黑色素瘤细胞系中的表达与它们对CDDP的抗性水平呈正相关。此外，通过转染在WM35细胞中强制表达TYRP2提高了它们对CDDP的抗性。病毒衍生克隆和TYRP2转染细胞中CDDP抗性的增加伴随着CDDP诱导的细胞凋亡的减少。有趣的是，病毒衍生的CDDP抗性克隆对卡铂和甲氨蝶呤也表现出交叉抗性，但对紫杉醇没有交叉抗性，这表明TYRP2的过表达可能特异性地赋予对DNA损伤剂的抗性。总体而言，这些结果证明了人黑色素瘤细胞中由TYRP2过表达介导的一种新的耐药机制。由于TYRP2仅在黑素细胞系细胞中表达，这可能是关于谱系特异性耐药机制的首次报道。总之，这些发现表明TYRP2在人黑色素瘤细胞的内在耐药表型中起重要作用，并且可能对开发针对该疾病临床管理的化学增敏策略具有重要意义。
