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

肿瘤细胞在抗癌药物作用下的多药耐药是一个重要的问题。因此，我们研究了多种哺乳动物细胞对阿霉素的耐药机制，在我们建立的埃利希腹水肿瘤细胞中出现了与阿霉素耐药有关的MDR1基因。其耐药性与细胞膜内p-gp的流泵有关，而阿霉素对细胞的渗透受Na^+/H^+和Cl^-/HCO_3离子通道的影响。加热能明显增强阿霉素的细胞杀伤作用。对阿霉素的抗肿瘤作用进行了体内试验，并对其进行了低温治疗和不低温治疗。然而，抗肿瘤作用并不明显。另一方面，头孢酞酸抑制阿霉素的外排，即头孢酞酸增强了阿霉素的杀伤作用。阿霉素的抗肿瘤作用受细胞内外ph的影响，在酸性条件下，阿霉素在细胞内蓄积较少。这取决于阿霉素的缓慢流入。综上所述，热疗后阿霉素的抗肿瘤作用并没有明显增强，因为肿瘤处于低pH状态，热疗引起的低pH值高于不治疗。另一方面，这些细胞显示出对阿霉素的其他未知耐药机制。提示埃利希腹水肿瘤阿霉素耐药细胞至少有两个对阿霉素耐药的表达过程。抗癌药物的耐药机制有很多。体外和体内热疗均能显著增强烷基化剂的杀伤作用。甲基鸟嘌呤- dna甲基转移酶（MGMT）对烷基化剂的敏感性。由于甲基化可以抑制MGMT的表达，我们研究了甲基化水平与烷基化剂杀伤作用在几种人鳞状癌细胞中的关系。MGMT的甲基化与对烷基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.