Mechanism Of The Hsp90 Inhibitor SNX-2112 In Combination With CDDP Induced Cell Death In Esophageal Squamous Carcinoma

Esophageal cancer is a malignant tumor with high morbidity and mortality in the worldwide, and chemotherapy is the main treatment straegies of patients with advanced esophageal cancer. Cisplatin(CDDP) is a cytotoxic drug, which can inhibit the DNA replication and damage to the cell membrane structure of cancer cell lead to strong toxicity, poor selectivity and drug resistance for patients. Therefore, it is very important to develop the new molecular targeted drugs and explore treatment methods which has the more effcient and the low toxicity for patients with esophageal carcinoma.Many studies reported that Hsp90 was highly expressed in esophaeal carcinoma tissues, indicating that Hsp90 might become a new theraty target of esophageal cancer. SNX-2112 is a novel Hsp90 inbitor which can inhibit the function of Hsp90. In our previous study, we found that SNX-2112 can inhibit the growth of esophaeal carcinoma. The aim of this paper is to study the effect of SNX-2112 combined with CDDP on human esophaeal carcinoma cell proliferation and the mechanisms of action, not only broaden SNX-2112 to become a clinical anti-esophaeal cancer drug, but also to offer the basis of the combination of SNX-2112 and CDDP to treatment the paitent with esophaeal cancer.MTT examine the growth inhibiton of SNX-2112 combined CDDP in esophaeal carcinoma cells, Calculating the combined index(CI) by Compusyn software. PI staining was done to analyze the change of cell cycle in esophaeal cancer when SNX-2112 combined with CDDP, Quantitative Real-time PCR was used to detect the changes of cycle related genes. Annexin V/PI double staining were used to detect apoptosis; Western blot to detect the expression and activation of apoptosis related proteins. Laser confocal and Western blot observe the effect of related signaling pathway of the DNA damage and the repair of DNA damage when SNX-2112 combined with CDDP. Examine the vivo effects and mechanisms of SNX-2112 combined with CDDP in esophageal carcinoma xenograft model. H&E and TUNEL staining were used to detect the apoptosis induced by SNX-2112 and CDDP. Immunofluorescence to detect the change of the related proteins expression of DNA damage in tumor tissue.The results showed that the combination of SNX-2112 and CDDP can inhibit proliferation of esophageal cancer cells more significantly, the most of the combined index(CI) <1. SNX-2112 can inhibit the arrest of G2/M phase induced by CDDP in esophageal cancer cell, SNX-2112 with a low concentration can enhance the esophageal carcinoma cells apoptosis induced by CDDP and downregulate of the ratio of Bcl-2/Bax, and increase the cleavaged of PARP. SNX-2112 can enhance the DNA damage induced by CDDP, which can activate the associated protein of DNA damage and inhibition of the repair DNA damage. The solid tumor inhibitory rate of the treatment group of Eca-109 and EC-9706 were 60% and 68% respectively when SNX-2112 combined with CDDP(p<0.01), the expression of the related protein of DNA damage was increased in the combination group compared with the single group in vivo.Conclusion: The Hsp90 inhibitor SNX-2112 can promote the effect of growth inhibition induced by CDDP in esophageal cancer both in vitro and in vivo, and also can promote apoptosis of esophageal carcinoma cells induced by CDDP in vitr o and in vivo. SNX-2112 can inhibit the G2/M arrest induced by CDDP and apoptosis though enhancing DNA damage and inhibiting the repair of DNA damage induced by CDDP in esophageal carcinoma cells.