The Expression Of Drug-Resisitance Gene In CNE1 Cells After High-dose X-ray Irradiation And The Preliminary Research On Its Mechanism

Multidrug resistance is always considered to be a cause of tumor therapy failures and now is a hotspot on tumor therapy. MDR is the result of multiple factors,involved possible mechanism of MDR include the multi-drug resistance gene (multidrug resisitance gene, MDR1) and the protein of P-glycoprotein (p-glycoprotein,P-gp) overexpression.Clinical investigation indicated the patients chemotherapy-sensitivity is cut down after radiation therapy. Further analysis showed that after ionizing radiation of tumor cells or tissues MDR1 and P-gp expression were higher than before.Induction of MDR1 and P-gp expression after ionizing radiation suggested that radiation might cause tumors have certain multidrug resistance, but so far, research in this area also relatively small. Lucubrate the passway regulated the expression of MDR1 can provide new target of tumor therapy.Objective: The aim of this study was to invstigate the effect of radiation treatment,given in high-dose,on the expression of MDR1 gene.Use gene chip technology to find differentially expressed genes about tumor occurrence and development before and after radiation in CNE1 cell lines , initially explore the mechanism of the expression change of MDR1 .Method:Our studies were conducted with CNE1 cells cultured in vitro.Exponentially growing CNE1 cell were exposed to 5000cGy ionizing radiation administered in 25 fractions,respectively,at 200cGy per fraction/day.Collected Nasopharyngeal carcinoma cell line CNE1 cells and CNE1/R cells which were exposed to 5000cGy ionizing fraction. Used RT-PCR to detect the expression of MDR1mRNA. Extracted the total RNA from the cells which group have the most obvious increased expression of MDR1.Antisense transcribed mRNA into cDNA to hybridizated with Catalog No.OHS-044 chip ,and analysis differentially expressed genes.Result:A statistically significant increase in MDR1 gene detectd by RT-PCR.The semi-quantitative OD value of MDR1 mRNA is 0.47±0.04, semi-quantitative OD value of CNE1/R cells (1th, 7th, 21th, 28th, 35th, 42th,49th days after irradiation) were 0.67±0.04, 0.70±0.02, 0.73±0.02, 0.63±0.03, 0.63±0.09, 0.62±0.05,0.62±0.02(P<0.05).Detected with gene chips as CNE1 and CNE-1/R.There are 27 genes significantly up-regulated in CNE1/R than CNE1 gene,8 genes are significantly down-regulated.These genes distributed in many signaling pathway including cell apoptosis, inflammation,stress,and androgen signaling pathway. RT-PCR indicated the BCL-2 mRNA of CNE1 cells and CNE1/R cells in expression by semi-quantitative OD values were:0.55±0.02,1.05±0.04;MMP7mRNA expression by semi-quantitative OD values were:0.51±0.01,0.82±0.02Conclusions:There is low expression of MDR1 before X-rays irradiated, and the cumulative does of 5000cGy ionizing radiation can induce cell CNE1 MDR1 mRNA expressed continuity.X-ray irradiation caused multi-channel and multi-gene changes in CNE1,they may be the cause of MDR.