一株耐阿霉素小鼠白血病L1210细胞系的建立及耐药机制的研究

肿瘤细胞耐药是肿瘤病人治疗失败的主要原因。通过连续递增阿霉素浓度的方法,筛选出一株对阿霉素的耐药性增高91.2倍的小鼠白血病L1210细胞系(L1210/DOX)。该细胞与L1210敏感细胞的增殖速度相似,倍增时间分别为15和15.5h。电子显微镜结果显示L1210/DOX细胞的形状和大小仍保持典型的白血病细胞态,与敏感株相似。该耐药细胞系与高三尖杉酯碱和长春新碱有交叉耐药,其半数抑制浓度(IC_(50))分别为敏感株的31.4和33.4倍,但对烷化剂马法兰无交叉耐药,呈多药耐药性。细胞内药物浓度检测的结果为阿霉素在L1210/DOX细胞内蓄积浓度仅为敏感细胞的9％。斑点杂交的结果显示L1210/DOX的多药耐药基因(MDR-1)mRNA水平显著高于敏感株。然而,二者的谷胱甘肽S-转移酶活性无显著差异。以上结果提示MDR-1基因的过度表达在L1210/DOX细胞耐药中起着重要作用;L1210/DOX细胞可经DBA/2小鼠传代,将成为体内耐药的小鼠模型。

ESTABLISHMENT OF A MOUSE LEUKEMIA CELL LINE (L1210 / DOX) RESISTANT TO DOXORUBICIN AND MECHANISMS OF DRUG RESISTANCE

The development of resistance accounts for failure to chemotherapy in majority of patients with cancer. A mouse leukemia cell line resistant to doxorubicin(L1210 / DOX), the resistance to DOX of whice was intensified by 91.2-fold, was selected by in vitro continuous exposure to increasing drug concentrations. The doubling times of sensitive L1210/S and resistant L1210/DOX were similar (15.5 and 15 hours, respectively). Electron microscopy examination indicated that L1210 / DOX was similar to L1210 / S in cell shape and dimensions. The subline was also cross-resistant to homoharringtonine and vincristine with the IC50s being 31.4 and 33.4 times higher than those of L1210/S respectively, but not to an alkylating agent melphalan. It showed a typical multidrug resistance (MDR) phenotype. Intracellular accumulation of DOX in L1210/DOX was only 9% of that in L1210 / S. The MDR-1 mRNA level in L1210 / DOX cells was markedly higher than that in L1210 / S with dot blot. However, glutathione S-transferase (GST) activity in L1210/DOX was similar to that in L1210 / S. The findings demonstrated that mRNA overexpression of MDR-1 gene in L1210 / DOX may play a role in MDR and L1210 / DOX could be inoculated to DBA / 2 mouse to form a possible drug-resistant mouse model.