Tomida A, Naito M, Tsuruo T
Institute of Molecular and Cellular Biosciences, University of Tokyo.
Jpn J Cancer Res. 1995 Feb;86(2):224-32. doi: 10.1111/j.1349-7006.1995.tb03043.x.
To study the mechanisms of the acute induction of drug resistance in cancer cells, we have established a model system in which adriamycin (ADM) induces immediate drug resistance. In this system, human colon carcinoma HT-29 cells were pretreated for 1 h with a subtoxic dose of ADM (0.3 micrograms/ml) and incubated for 24 h in drug-free medium. Then the cells were treated for 1 h with ADM, and the cell survival was determined in terms of colony-forming ability. The survival of the pretreated cells was increased up to 100-fold, as compared with that of untreated cells. Such increased survival, however, was observed only after high doses of ADM (2 to 8 micrograms/ml); more than 99% of the cells were killed. These results indicate that only a small fraction of ADM-pretreated cells acquire the ADM-resistant phenotype. Similar induced resistance was observed in five of seven subclones isolated from HT-29 cells by limiting dilution, suggesting that the majority of cells in the parental HT-29 population could acquire the ADM-resistant phenotype. In the subclone HT-29T9, the ADM pretreatment induced concomitant resistance to daunomycin, VP-16, and VM-26 but not to agents other than topoisomerase II inhibitors. The ADM-induced drug resistance did not accompany MDR1 gene expression and could not be overcome by verapamil, a P-glycoprotein inhibitor. The present system could be useful to study the acute induction mechanism(s) of ADM-resistance, which could be relevant to clinical resistance in patients.
为了研究癌细胞中急性诱导耐药性的机制，我们建立了一个阿霉素（ADM）诱导即时耐药性的模型系统。在这个系统中，人结肠癌细胞HT-29先用亚毒性剂量的ADM（0.3微克/毫升）预处理1小时，然后在无药物培养基中孵育24小时。接着用ADM处理细胞1小时，并根据集落形成能力测定细胞存活率。与未处理的细胞相比，预处理细胞的存活率提高了100倍。然而，只有在高剂量的ADM（2至8微克/毫升）处理后才观察到这种存活率的提高；超过99%的细胞被杀死。这些结果表明，只有一小部分经ADM预处理的细胞获得了ADM耐药表型。通过有限稀释从HT-29细胞中分离出的7个亚克隆中有5个观察到了类似的诱导耐药性，这表明亲本HT-29群体中的大多数细胞都可以获得ADM耐药表型。在亚克隆HT-29T9中，ADM预处理诱导了对柔红霉素、VP-16和VM-26的伴随耐药性，但对拓扑异构酶II抑制剂以外的药物没有耐药性。ADM诱导的耐药性不伴随MDR1基因表达，也不能被P-糖蛋白抑制剂维拉帕米克服。本系统可能有助于研究ADM耐药性的急性诱导机制，这可能与患者的临床耐药性有关。
