人结肠癌裸鼠移植瘤热疗和化疗及放疗后凋亡相关基因的变化

目的探讨热疗、化疗、放疗对人结肠癌裸鼠移植瘤凋亡相关基因表达的影响。方法将人类结肠癌细胞株——HT29移植于裸鼠双侧后肢。于实验室模拟热疗条件（43℃，60rain），并参照人类结肠癌临床化疗及放疗方案。实验共分6组，即热疗、化疗、放疗、热化疗、热放疗及热放化疗组。于治疗前后不同时间点处死裸鼠。取肿瘤组织备用。利用免疫组织化学染色检测肿瘤细胞膜、细胞浆及细胞核Bcl－2和Bax基因及P53表达的形态学变化。结果6种治疗方法均能不同程度下调P53和Bcl－2、上调Bax的表达。热放化疗组治疗后48hP53及Bcl－2达到最低水平，Bax达高峰。与另外5组比较差异有统计学意义（P〈0．01）；热疗、热化疗及热放疗3组间对P53表达的下调作用差异无统计学意义，但均较化疗、放疗组下调明显。治疗后48h热放疗组和热放化疗组Bcl－2的表达明显低于其他各组（P〈0．05），热疗组下调Bcl－2作用最小，与另外5组的差异均有统计学意义（P〈0．05和P〈0．01）。热放化疗组上调Bax基因表达的作用发生时间最早（2h）：作用最强，与另外5组的差异均有统计学意义（P〈0．05和P〈0．01）；热疗组发生时间最晚（24h），作用最小，与另外5组的差异均有统计学意义（P〈0．05和P〈0．01）。结论热疗可能通过增强放化疗对凋亡相关基因的表达发挥其增敏作用。热疗联合应用化疗和（或）放疗对人结肠癌裸鼠移植瘤凋亡相关基因表达的改变更为显著。

Expression change of apoptosis-associated genes after hyperthermia, chemotherapy and radiotherapy in human colon cancer-transplanted nude mice]

OBJECTIVE: To investigate the expression change of apoptosis-associated genes in human colon cancer cells transplanted into nude mice after hyperthermia, chemotherapy and radiotherapy. METHODS: Human 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). RESULTS:All 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. CONCLUSIONS: Hyperthermia 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.