APPROARCH AT MOLECULAR LEVEL FOR MECHANISMS OF MULTIDRUG-RESISTANCE AND ENHANCEMENT OF ANTICANCER DRUGS WITH HYPERTHERMIA

肿瘤细胞对抗癌药物的耐药性是一个重要的问题。因此，我们对多种哺乳动物细胞的耐药机制进行了研究，在我们建立的埃利希腹水瘤细胞中发现了与阿霉素耐药相关的MDR 1基因。其阻力与细胞膜p-gp的外输泵有关，而阿霉素的渗透受Na^+/H^+和Cl^-/HCO 3两种离子通道的影响。加热可明显增强阿霉素的细胞杀伤作用。阿霉素的抗肿瘤作用在体内进行了检测，并与亚温热治疗进行了比较。然而，抗肿瘤作用并不明显。另一方面，千金藤素抑制阿霉素的外排，即千金藤素增强阿霉素的杀伤作用。阿霉素的抗肿瘤作用受细胞内和细胞外pH值的影响，在酸性条件下，阿霉素在细胞内的蓄积量很小。依赖于减缓阿霉素的内流。结果表明，高温对阿霉素抗肿瘤作用的增强作用并不明显，因为肿瘤处于低pH状态，高温诱导的低pH较未高温诱导的低pH更明显。另一方面，这些细胞对阿霉素的耐药机制尚不清楚。提示埃利希腹水瘤阿霉素耐药细胞至少存在两种阿霉素耐药表达过程。抗肿瘤药物耐药的机制有多种。热疗可明显增强烷化剂的体内外杀伤作用。对烷化剂的敏感性与06-甲基鸟嘌呤-DNA甲基转移酶（MGMT）有关。由于甲基化抑制了MGMT的表达，因此研究了甲基化水平与烷化剂对几种人鳞癌细胞杀伤作用的关系。MGMT的甲基化与其对烷化剂的敏感性密切相关。

It is an important problem that tumor cells treated with anticancer drugs expressed multidrug resistance. Therfore, resistant mechanisms of varius mammalian cells were studied, MDR1 gene concerning resistance to adriamycin were appeared in our established cells of Ehrlich ascites tumor. Its resistance related to eflux pump of p-gp which is in cellular membrane, and the penetration of adriamycin into cells was affected by both of ion channels of Na^+/H^+ and Cl^-/HCO_3. Heating showed marked enhancement of cell killing effects of adriamycin. Abtitumor effects of adriamycin were tested on in vivo with or without treatment of mild hyperthermia. However, antitumor effects were shown not so much. On the other hand, efflux of adriamycin was inhibited with cepharanthine, that is, cepharanthine enhanced a killing effect of adriamycin. Antitumor effects of adriamycin were affected with intraa- and extracellure pH. Intracellular accumulation of adriamycin was small amount at acidic condition. It was depended to slow infflux of adriamycin. It is concluded that antitumor effects of adriamycin were not so large enhancement with hyperthermia as it is low pH condition in tumor and hyperthermia induced low pH more than without treatment. On the othe hand, those cells showed the other unknown resistant mechanisims to adriamycin. It is indicated that adriamysin-resistant cells of Ehrlich ascites tumor have at least two expression processes of resistance to adriamycin. There are many mechanisms on resistant to anticancer drugs. Hyperthermia enhanced markedly killing effects of alkylating agents in vitro and in vivo. The sensitivity to alkylating agents related to 06-methylguanine-DNA methyltransferase(MGMT). As MGMT expression was depressed by methylation, it is investigated that relationship between level of methylation and killing effect of alkylating agent in several human squarmous carcinoma cells. Methylation of MGMT is closely related to the sennsitivity for alkylating agents.