Radiother Oncol: 山东大学研究者发现缺氧诱导CDUPRT/5-FC基因治疗方案能特异性靶向缺氧肿瘤细胞

对于绝大多数的实体肿瘤而言，缺氧是其显著特征。有证据提示，在局部晚期实体肿瘤中，50%-60%的实体肿瘤表现出缺氧区域分布的不均匀。既往进行的临床研究提示与氧供好的肿瘤相比，治疗对乏氧肿瘤的局部控制较差，并且患者的总体生存情况显著降低。鉴于缺氧在肿瘤进展和对治疗的耐药中所起到的主要作用，研究者考虑到能将缺氧作为一个治疗靶点对肿瘤的治疗方案进行新的探究。为了探究当与5-氟胞嘧啶方案联用时，缺氧是否能通过靶向作用于双功能自杀基因的胞嘧啶脱氨酶和尿嘧啶磷酸核糖基转移酶表达而增强肿瘤对放疗的反应，来自中国山东大学的Xiaorong Sun等设计了相关研究并将其研究结果发表在Radiother Oncol 2012年10月的期刊上。
在诱导缺氧的启动子的控制下，研究者制备了稳定转染的R3327-AT细胞，该细胞表达三重融合基因——CD、UPRT和mDsRed。研究者通过蛋白质印迹法、流式细胞技术、荧光显微镜技术和对5-FU和5-FC的细胞毒性测定来验证缺氧所诱导的CDUPRTmDsRed的表达/功能。随之，研究者采用5-FC和局部放疗对荷瘤小鼠进行治疗。同时，研究者对肿瘤的体积进行了监测，并且比较了同时接受5-FC和放疗的小鼠和仅接受5-FC或放疗的小鼠在治疗前后肿瘤体积的变化情况。此外，研究者还采用荧光显微镜记录了在肿瘤组织中CDUPRTmDsRed在缺氧区的分布情况。
研究结果显示缺氧所诱导的CDUPRTmDsRed蛋白可增高肿瘤对5-FC和5-FU的敏感性。在缺氧情况下，经过5-FC治疗后放疗增敏效应显著增高。在肿瘤的异种移植物中，荧光显微镜下的CDUPRTmDsRed表达与缺氧标记物（哌莫硝唑染色阳性的细胞）相互局限。此外，与仅接受5-FC或放疗治疗的荷瘤小鼠相比，接受联合5-FC和放疗的荷瘤小鼠的肿瘤体积缩小更加明显。
来自本研究的数据提示，缺氧诱导的CDUPRT/5-FC基因治疗方案能特异性的针对缺氧肿瘤细胞，并且与放疗联合时能显著改善对肿瘤的控制。
与缺氧相关的拓展阅读：

• Neural Regen Res ：三七总皂苷减轻缺氧复氧所致神经元的氧化应激损伤
• Circulation：间充质干细胞分泌外染色体抑制缺氧性肺动脉高压
• J Cell Biochem：脂肪酸合酶减少促进缺氧HepG2细胞死亡
• J. Cell. Mol. Med：杨宝峰等发现缺氧调控心肌肥厚新机制
• Int J Oncol：阻断缺氧调控的TMPRSS4治疗肿瘤
• PLoS ONE:缺氧调节的溶瘤腺病毒基因治疗
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Hypoxia targeted bifunctional suicide gene expression enhances radiotherapy in vitro and in vivo.
PURPOSE
To investigate whether hypoxia targeted bifunctional suicide gene expression-cytosine deaminase (CD) and uracil phosphoribosyltransferase (UPRT) with 5-FC treatments can enhance radiotherapy.
MATERIALS AND METHODS
Stable transfectants of R3327-AT cells were established which express a triple-fusion-gene: CD, UPRT and monomoric DsRed (mDsRed) controlled by a hypoxia inducible promoter. Hypoxia-induced expression/function of CDUPRTmDsRed was verified by western blot, flow cytometry, fluorescent microscopy, and cytotoxicity assay of 5-FU and 5-FC. Tumor-bearing mice were treated with 5-FC and local radiation. Tumor volume was monitored and compared with those treated with 5-FC or radiation alone. In addition, the CDUPRTmDsRed distribution in hypoxic regions of tumor sections was visualized with fluorescent microscopy.
RESULTS
Hypoxic induction of CDUPRTmDsRed protein correlated with increased sensitivity to 5-FC and 5-FU. Significant radiosensitization effects were detected after 5-FC treatments under hypoxic conditions. In the tumor xenografts, the distribution of CDUPRTmDsRed expression visualized with fluorescence microscopy was co-localized with the hypoxia marker pimonidazole positive staining cells. Furthermore, administration of 5-FC to mice in combination with local irradiation resulted in significant tumor regression, as in comparison with 5-FC or radiation treatments alone.
CONCLUSIONS
Our data suggest that the hypoxia-inducible CDUPRT/5-FC gene therapy strategy has the ability to specifically target hypoxic cancer cells and significantly improve the tumor control in combination with radiotherapy.