OBJECTIVETo investigate the expression change of apoptosis-associated genes in human colon cancer cells transplanted into nude mice after hyperthermia, chemotherapy and radiotherapy.

METHODSHuman colon cancer cell line HT29 was transplanted into the hind limbs of nude mice. Under the laboratory-simulated condition of hyperthermia(43 degree centigrade, 60 min), actual radiation doses and MMC doses were calculated in reference to the clinical practice. The mice were divided into 6 groups according to the treatment approaches: hyperthermia (group A), chemotherapy (group B), radiotherapy (group D), thermochemotherapy (group C), thermoradiotherapy (group E) and thermochemoradiotherapy (group F). The mice were sacrificed at different time points and the tumor tissues were taken for further procedures. The morphologic changes of P53, Bcl-2 and Bax expression in membrane, cytoplasm and nucleus of tumor cell after treatment were observed by immunohistochemistry stain (SP method).

RESULTSAll of the six approaches of treatment could down-regulate the expression of P53 and Bcl-2, and up-regulate the expression of Bax in different levels. There was no significant difference in the amount of reduction of P53 expression among group A, C and E. The extent of reduction in the above mentioned groups was significantly different as compared to group B and D. By comparing to group D, the extent of reduction of P53 expression was greater in group B. Down-regulation of Bcl-2 could be enhanced when hyperthermia was combined with chemotherapy (group C) or radiation (group E), but more obvious down-regulation was found in group E as compared to group C. Hyperthermia itself could not obviously up-regulate Bax expression, and it occurred at last. Bax expression increased more by chemotherapy treatment (group B) than that by radiation (group D). By comparing to group C, the greater increase occurred in group E.

CONCLUSIONSHyperthermia enhances the effects of radiosensitivity and chemosensitivity on tumors by changing the expression of apoptosis-associated genes P53, Bcl-2 and Bax. Hyperthermia combined with chemotherapy and/or radiation has a greater effect on down-regulation of P53 and Bcl-2 expression and up-regulation of Bax expression than any single therapy.