缝隙连接在非肿瘤和肿瘤细胞对顺铂细胞毒性的不同影响及机理研究

Gap junctions(GJ) can propagate toxic effects among tumor cells during chemotherapy, which had been considered as a new method to treat tumor. But there are inherent drawbacks due to gap junctions exist in both tumor cells and normal cells. Enhancement of GJ to increase the efficacy of chemotherapy could also enhance toxic effects on normal cells. Recently our study shows for the first time that the effect of GJ composed of Cx43 on cisplatin toxicity differs between normal and tumor testicular cells. Upregulation of GJ function increased cisplatin cytotoxicity in tumor cells but decreased it in normal cells, however the related mechanisms is unknown. The GJ protects normal cells from cisplatin toxicity while enhancing it in tumor cells, suggesting that enhancement/maintenance of GJ could increase therapeutic efficacy while decreasing off-target toxicity. If we find this role of GJ in other tumor and normal cells of the same origin, it will greatly increase the clinical value of GJ as a new tumor therapic target. In order to verify this phenomenon universal or not, we will investigate the effect of GJ on the cytotoxicity of cisplatin on several tumors and normal cells of the same origin. Based on these works, we will study the possible mechanisms involved in. Our works will provide the pivotal data and a new clue to develop new drugs targeted on GJ to enhance the therapeutic efficiency of radiotherapy and chemotherapy

通过增强缝隙连接（GJ）增加肿瘤对化疗的敏感性被公认为是一种潜在的肿瘤治疗新途径。但是该途径有一个关键障碍：GJ在正常细胞也存在；因此增强GJ的方法，在增强药物对肿瘤作用的同时，也可能增加对正常细胞的毒性。研究表明，GJ能够减轻某些有害刺激对正常细胞的伤害。我们的研究首次发现，在睾丸癌细胞Cx43组成的GJ能增强顺铂的细胞毒性；而在正常睾丸细胞则降低顺铂的毒性；提示GJ可能在增强药物对肿瘤细胞的毒性同时，降低其对非肿瘤细胞的毒性。据此本课题提出"顺铂刺激细胞产生能通过GJ传递的保护信号和死亡信号；在非肿瘤细胞，GJ传递保护信号，减弱顺铂的细胞毒性；而在肿瘤细胞GJ传递死亡信号，增强顺铂的细胞毒性"这一假说；并拟在肿瘤细胞及同一组织来源的非肿瘤细胞，研究GJ对顺铂细胞毒性的影响；探讨GJ对顺铂作用产生不同影响的机理；为验证该假说提供证据；为研制以GJ为靶点,增强肿瘤化疗疗效的药物提供依据。

我们发现，GJ在增强药物对肿瘤细胞毒性的同时，可降低其对非肿瘤细胞的毒性。本课题在大鼠肝脏来源的非肿瘤细胞（BRL-3A）和肝癌细胞（CBRH-7919），及人胚肺细胞（HLF）和肺小细胞癌细胞（A549），研究了Cx32或Cx43组成GJ对细胞内顺铂含量及顺铂-DNA交联物形成的影响；探讨了GJ在非肿瘤和肿瘤细胞对顺铂细胞毒性不同影响的机理，以及的GJ对宫颈癌细胞凋亡的影响。本研究发现，（1）GJ可以在增强药物作用的同时， 降低药物对正常组织的毒性；GJ对肿瘤和正常细胞的这种不同影响在许多器官中存在。（2）在肝非肿瘤细胞，GJ能够通过稳定MRP2在细胞膜上的分布，增强其作用，促进顺铂转出细胞而降低细胞内顺铂含量，减少铂-DNA交联物形成，进而降低了顺铂的细胞毒性。但在肝癌细胞，GJ通过稳定CTR1在细胞膜上的分布，增强其作用，促进顺铂转入细胞而增加细胞内顺铂的含量，增加了铂-DNA交联物形成而增强顺铂的细胞毒性。（3）在宫颈癌细胞Cx32能拮抗SN或顺铂诱导的内源性凋亡，同时也能拮抗TNFα或TRAIL诱导的外源凋亡；Cx32的这些抗凋亡作用与GJ无关。Cx32和Cx43组成的GJ有促进凋亡的作用。本研究为证明GJ可以成为增强抗肿瘤药物疗效和防治耐药性的新靶点提供了重要的理论依据。