Xu Peng, Huang Jian-Ming, Ren Yuan, Zha Xiao, Deng Bi-Fang, Wu Jun-Hui, Lang Jin-Yi
Guangxi Medical University, Nanning, Guangxi 530021, PR China.
Chin J Cancer. 2010 Feb;29(2):126-30. doi: 10.5732/cjc.009.10500.
Combined hypoxic cytotoxic drugs and chemoradiotherapy is an important mean of oncotherapy, and Tirapazamine (TPZ) is one of the most remarkable drugs. It has been shown that TPZ has a synergistic effect with radiotherapy on tumor cells, but whether TPZ would down-regulate the expression of the hypoxia-induced genes has not been reported. This study was to investigate the hypoxia-induced mRNA expressions of hypoxia inducible factor-1alpha (HIF-1alpha) and osteopontin (OPN) in human nasopharyngeal carcinoma HNE-1 and CNE-1 cells and the radiosensitization of TPZ, a hypoxia-specific drug, on HNE-1 and CNE-1 cells in vitro.
The IC50 values of TPZ for HNE-1 and CNE-1 cells were measured using MTT assay, and the mRNA expressions of HIF-1alpha and OPN in HNE-1 and CNE-1 cells was determined using RT-PCR under aerobic and hypoxic conditions, respectively. The survival rates of HNE-1 and CNE-1 cells treated with or without TPZ at IC10 in the presence or absence of oxygen for 6 h were determined using colony formation assay following exposure to 1-6 Gy of 60Co radiation. The dose-survival curves were plotted and the values of D0, Dq and SER were calculated as a single-hit multitarget model.
The IC50 values of TPZ were 34.81 μmol/L and 35.02 μmol/L in HNE-1 and CNE-1 cells under aerobic condition, and 30.20 μmol/L and 28.48 μmol/L under hypoxic condition, respectively. The expressions of HIF-1alpha and OPN mRNA were reduced by TPZ in HNE-1 cells, but not in CNE-1 cells under hypoxic condition. For the HNE-1 cells, the respective values of D0 and Dq were 0.89 Gy and 0.28 Gy following normoxic irradiation versus 1.47 Gy and 0.44 Gy following hypoxic irradiation. For the CNE-1 cells, the respective values of D0 and Dq were 0.72 Gy and 0.68 Gy following normoxic irradiation versus 0.95 Gy and 0.56 Gy following hypoxic irradiation. The values of D0 and Dq for HNE-1 and CNE-1 cells treated with TPZ under hypoxic condition following irradiation were 0.66 Gy, 0.21 Gy and 0.85 Gy, 0.79 Gy, respectively.
TPZ can down-regulate hypoxia-induced expression of HIF-1alpha and OPN mRNA of HNE-1 cells and radiosensitize the HNE-1 cells but not CNE-1 cells, and act as a hypoxia modifier.
低氧细胞毒性药物与放化疗联合应用是肿瘤治疗的重要手段，替拉扎明（TPZ）是其中最引人注目的药物之一。已有研究表明TPZ与放疗对肿瘤细胞有协同作用，但TPZ是否会下调低氧诱导基因的表达尚未见报道。本研究旨在探讨低氧诱导的缺氧诱导因子-1α（HIF-1α）和骨桥蛋白（OPN）在人鼻咽癌HNE-1和CNE-1细胞中的mRNA表达，以及低氧特异性药物TPZ对HNE-1和CNE-1细胞的体外放射增敏作用。
采用MTT法测定TPZ对HNE-1和CNE-1细胞的IC50值，分别在有氧和低氧条件下，用RT-PCR法检测HNE-1和CNE-1细胞中HIF-1α和OPN的mRNA表达。用集落形成法测定在有或无氧气存在的情况下，用IC10剂量的TPZ处理或不处理HNE-1和CNE-1细胞6小时后，经1-6 Gy 60Co辐射后的细胞存活率。绘制剂量-存活曲线，并按照单击多靶模型计算D0、Dq和SER值。
在有氧条件下，TPZ对HNE-1和CNE-1细胞的IC50值分别为34.81 μmol/L和35.02 μmol/L，在低氧条件下分别为30.20 μmol/L和28.48 μmol/L。在低氧条件下，TPZ可降低HNE-1细胞中HIF-1α和OPN mRNA的表达，但对CNE-1细胞无此作用。对于HNE-1细胞，常氧照射后D0和Dq值分别为0.89 Gy和0.28 Gy，低氧照射后分别为1.47 Gy和0.44 Gy。对于CNE-1细胞，常氧照射后D0和Dq值分别为0.72 Gy和0.68 Gy，低氧照射后分别为0.95 Gy和0.56 Gy。照射后在低氧条件下用TPZ处理的HNE-1和CNE-1细胞的D0和Dq值分别为0.66 Gy、0.21 Gy和0.85 Gy、0.79 Gy。
TPZ可下调HNE-1细胞低氧诱导的HIF-1α和OPN mRNA表达，并使HNE-1细胞放射增敏，而对CNE-1细胞无此作用，可作为低氧修饰剂。
