Ichihashi N, Kitajima Y
Department of Dermatology, Gifu University School of Medicine, 40 Tukasa-machi, Gifu City 500-8705, Japan.
Br J Dermatol. 2001 Apr;144(4):745-50. doi: 10.1046/j.1365-2133.2001.04129.x.
Human malignant melanoma is notoriously resistant to chemotherapeutic agents. Melanoma-derived cell lines are often markedly chemoresistant, suggesting that cellular mechanisms mediate generation of the multidrug resistance (MDR) phenotype. This phenotype is often due to P-glycoprotein (Pgp) and the MDR-associated protein (MRP), which are drug transporter proteins associated with resistance to a broad spectrum of lipophilic drugs.
To determine the relationships between the expression of the MDR gene MDR-1 (the product of which is Pgp) or the MRP gene, and clinical chemoresistance of malignant melanoma.
We examined changes in the expression of MDR-1 and MRP genes at the mRNA level before and after chemotherapy by reverse transcription-polymerase chain reaction (RT-PCR) analysis using formalin-fixed, paraffin-embedded sections of 18 specimens taken from eight melanoma patients. mRNA expression of the MDR-1 and MRP gene-specific PCR products was quantitatively determined by densitometry and compared with that of an internal standard (beta-actin).
Five of seven primary melanomas were found to express the MRP gene to a certain extent even before chemotherapy. After first and second courses of chemotherapy, six patients had an increased ratio of MRP mRNA to beta-actin mRNA compared with the prechemotherapy levels in the same patients. None of the cases of melanoma expressed MDR-1.
These results suggest that a significant mRNA level of MRP gene was intrinsically present in malignant melanoma even before exposure to chemotherapeutic drugs and increased in its expression after chemotherapy, suggesting that MRP plays a part in increasing the chemoresistance of malignant melanoma during chemotherapy.
人类恶性黑色素瘤对化疗药物具有众所周知的耐药性。黑色素瘤衍生的细胞系通常具有明显的化疗耐药性，这表明细胞机制介导了多药耐药（MDR）表型的产生。这种表型通常归因于P-糖蛋白（Pgp）和多药耐药相关蛋白（MRP），它们是与对多种亲脂性药物耐药相关的药物转运蛋白。
确定多药耐药基因MDR-1（其产物为Pgp）或MRP基因的表达与恶性黑色素瘤临床化疗耐药性之间的关系。
我们使用从8例黑色素瘤患者获取的18个标本的福尔马林固定、石蜡包埋切片，通过逆转录-聚合酶链反应（RT-PCR）分析，检测化疗前后MDR-1和MRP基因在mRNA水平的变化。通过密度测定法定量测定MDR-1和MRP基因特异性PCR产物的mRNA表达，并与内标（β-肌动蛋白）进行比较。
7例原发性黑色素瘤中有5例即使在化疗前就已在一定程度上表达MRP基因。在第一和第二疗程化疗后，与化疗前相比，6例患者的MRP mRNA与β-肌动蛋白mRNA的比值增加。所有黑色素瘤病例均未表达MDR-1。
这些结果表明，即使在接触化疗药物之前，恶性黑色素瘤中就已固有存在显著水平的MRP基因mRNA，且化疗后其表达增加，这表明MRP在化疗期间增加恶性黑色素瘤的化疗耐药性中起作用。
