The development of multidrug-resistant tumor cell populations is a major problem in the chemotheraphy of human cancer. These cells are often cross resistant to unrelated drugs. Current understanding of the mechanism of development of tumor drug resistance and its reversal, however, is limited. The present study was examined about sensitive Ll210 cell and resistant sublines (L1210AdR, L1210VcR and L1210Cis) for reversal of drug resistance by hyperthermia. Cell survival was determined by MTT assay after exposure to various heat(41, 42, 43¡ÆC) condition and to anticancer drug and heat combination. Survival rate of sensitive and resistant cells as various temperature exposure was revealed fifty percent on 42.8¡ÆC for L1210 cell and 41.4¡ÆC to 41.9¡ÆC for resistant sublines. The 50 percent survival for exposure times on 42¡ÆC was expressed as no change in L1210 cell and as 46 to 48 minutes on resistant cells, on 43¡ÆC, L1210 cell was 48 minutes, resistant cells were 10 to 14 minutes. Cytotoxicity of resistant sublines treated by combination of hyperthermia and adriamycin was not increased. mdr 1 gene of L1210AdR and L1210VcR were well expressed by hyperthermia but expression of hsp 70 gene were increased to compare increasing of exposure time at 41¡ÆC. Expressions of hsP 70 in L1210 and Ll210Cis cells were revealed the peak values at exposure for 45 min and 30 min. The cytotoxic effect of hyperthermia on resistant sublines were more effective than on sensitive L1210 cell. And then the suggestion of correlation between mdr 1 and hsp 70 gene brought about.
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