Makizumi Ryouji, Yang Weng-Lang, Owen Randall P, Sharma Rohit R, Ravikumar T S
Int J Clin Exp Med. 2008;1(2):117-29. Epub 2008 Feb 28.
Radiofrequency ablation (RFA) is gaining popularity for treating colorectal liver metastases by inducing image guided tumor hyperthermia. In order to reduce tumor recurrence, adjuvant therapies have been administered post-RFA. We hypothesized that tumor cells escaping RFA cytotoxicity by being in the sublethal zones of tumor might develop differential behavior toward cytotoxic drugs. Here, we used cultured human colorectal cancer cells to evaluate the interaction between heat treatment and chemotherapeutic agents. Human colon cancer cell lines HT29 and HCT116 were subjected to temperatures of 42 degrees to 50 degrees C for 15 min, in combination with 5-fluorouracil, oxaliplatin, or irinotecan at different sequences. Cytotoxicity was determined by MTT assay. The cell cycle progression was analyzed by flow cytometry with propidium iodide staining. The expression of several genes associated with drug sensitivity was quantitated by real-time RT-PCR before and after heat treatment. Either heat treatment at 45 degrees C by simultaneous or pre-treatment with three different chemotherapeutic agents didn't affect the cytotoxicity of the combined treatment to HT29 and HCT116 cells, except for irinotecan treatment in HCT116 cells. However, when pre-exposure to 45 degrees C, HCT116 cells, but not HT29 cells, developed resistance to these three drugs. In an analysis of cell cycle profile after the drug followed heat treatment, a longer delay in cell cycle progression in HCT116 cells was observed in comparison to HT29 cells. Furthermore, HCT116 and HT29 cells exhibited different expression profiles of several drug-related genes in response to heat treatment at 45 degrees C. An observation of a differential response to the drug and heat treatment sequences between two human colon cancer cell lines suggests that tumor heterogeneity and selection of chemotherapeutic agents need to be under consideration in the clinical setting.
射频消融术（RFA）通过诱导影像引导下的肿瘤热疗来治疗结直肠癌肝转移，正越来越受到欢迎。为了降低肿瘤复发率，在RFA术后已采用辅助治疗。我们推测，处于肿瘤亚致死区而逃避RFA细胞毒性的肿瘤细胞，可能会对细胞毒性药物产生不同的反应。在此，我们使用培养的人结肠癌细胞来评估热处理与化疗药物之间的相互作用。将人结肠癌细胞系HT29和HCT116在42℃至50℃的温度下处理15分钟，并与5-氟尿嘧啶、奥沙利铂或伊立替康以不同顺序联合使用。通过MTT法测定细胞毒性。用碘化丙啶染色通过流式细胞术分析细胞周期进程。在热处理前后，通过实时RT-PCR对几种与药物敏感性相关的基因表达进行定量。除了HCT116细胞中的伊立替康治疗外，45℃的热处理与三种不同化疗药物同时使用或预处理均未影响联合治疗对HT29和HCT116细胞的细胞毒性。然而，当预先暴露于45℃时，HCT116细胞而非HT29细胞对这三种药物产生了抗性。在药物处理后再进行热处理的细胞周期分析中，与HT29细胞相比，观察到HCT116细胞的细胞周期进程延迟更长。此外，HCT116和HT29细胞在对45℃热处理的反应中表现出几种药物相关基因的不同表达谱。两种人结肠癌细胞系对药物和热处理顺序的不同反应表明，在临床环境中需要考虑肿瘤异质性和化疗药物的选择。
