己酮可可碱增强(E)-(2′)-脱氧-氟亚甲基胞苷的细胞毒性和对宫颈癌细胞的放射增敏作用

Pentoxifylline Enhances Cytotoxicity and Radiosensitization of (E)-2′-deoxy-2′-(fluoromethylene) Cytidine in Cervical Cancer Cells

目的：观察己酮可可碱(pentoxifylline, PTX)对(E)－(2')－脱氧－氟亚甲基胞苷[(E)－2’－deoxy-2’-(fluoromethylene) cytidine，FMdC]的细胞毒性和放射增敏作用的影响。方法: 在人类宫颈癌细胞系C33-A和C4-I, FMdC和PTX的细胞毒性和放射增敏作用应用MTT和克隆形成分析。两种药物的细胞毒性相互作用应用Isoborogram分析。常规照射剂量2 Gy时的放射增敏比（sensitive enhancement ratio, SER）定义为2 Gy时对照组存活分数（survival fraction, SF）和药物处理组SF之比(SER2Gy)。结果：PTX增加FMdC 对C33-A和C4-I 细胞的细胞毒性，并呈剂量依赖关系。单药FMdC对C4-I和C33-A的50％抑制浓度（50％inhibition concentration, IC50）分别为139.5 nmol/L和46.7 nmol/L。在C4-I细胞，0.25 mmol/L、0.5 mmol/L和1.0 mmol/L PTX降低FMdC的IC50至58.0 nmol/L、40.6 nmol/L和20.9 nmol/L。在C33-A细胞，0.25 mmol/L、0.5 mmol/L和1.0 mmol/L PTX降低FMdC的IC50至32.1 nmol/L、23.3 nmol/L和9.1 nmol/L。Isoborogram分析表明, FMdC和PTX的细胞毒性效应为相乘作用。应用克隆形成分析，照射前用30 nmol/L FMdC处理指数生长期C33-A和C4-I细胞48 h或照射后立即单用0.25～1.0 mmol/L PTX, 均能观察到各自的放射增敏作用;

Objectives: This study was designed to investigate the effect of pentoxifylline on (E)-2'-deoxy-2'-(fluoromethylene) cytidine (FMdC)-induced cytotoxicity and radiosensitization.Methods：The cytotoxicity and radiosensitizing effect of FMdC and PTX were investigated by MTT assay and clonogenic assay on two human cervical cancer cell lines C33-A and C4-I. The cytotoxic activity of the drug combination was evaluated by isobologram analysis. The change in radiosensitivity was quantified by calculating the sensitive enhancement ratio (SER) at a clinically relevant dose of 2 gray, defined as the mean survival fraction (SF) for control/mean SF for drug (SER2Gy). Results：Pentoxifylline enhanced the cytotoxic effect of FMdC in C33-A and C4-I in a dose dependent manner. The 50％inhibition concentration (IC50) of FMdC was 139.5 nmol/L for C4-I and 46.7 nmol/L for C33-A. Pentoxifylline at the concentrations of 0.25 mmol/L, 0.5 mmol/l, and 1.0 mmol/L lowered the IC50 of FMdC to 58 nmol/L, 40.6 nmol/L，and 20.9 nmol/L for C4-I, and 32.1 nmol/L, 23.3 nmol/L, and 9.1 nmol/L for C33-A, respectively. Isobologram analysis showed that the cytotoxic effect of FMdC and pentoxifylline was supra-additive. Using clonogenic assay, pre-irradiation exposure of exponentially growing C4-I and C33-A cells to 30 nmol/L FMdC for 48 h or post-irradiation to 0.25－1.0 mmol/L pentoxifylline alone resulted in an increase in radiation-induced cytotoxicity. The SER2Gy of 30 nmol/L FMdC alone and 0.5 mmol/L pentoxifylline alone were 2.08 and 1.76 for C4-I, 1.32 and 1.36 for C33-A,respectively. Pentoxifylline enhanced the radiosensitizing effect of FMdC. The corresponding SER2Gy of a combination of 30 nmol/L FMdC and 0.5 mmol/L pentoxifylline was increased to 3.18 for C4-I and 1.96 for C33-A, respectively. Conclusion：Pentoxifylline may be able to potentiate the cytotoxicity and radiosensitization of FMdC in vitro.