The Study Of Expression And Transcription Of Multidrug Resistance Gene 1 In Pancreatic Cancer

Tumor cells resistant to multiple anti-cancer agents, so called multidrug resistance(MDR), was the main cause of chemotherapy failure. The mechanism of MDR was complicated, and MDR1 (multidrug resistance gene 1) has considered to be the main cause of MDR. The expression and roles of MDR1 were studied in pancreatic cancer patients, including clinical and experimental aspect.Clinical study: The expression of MDR1 in pancreatic cancer was detected at gene level by Reverse transcription-polymerase chain reaction (RT-PCR) and at protein level by immunohistochemical analysis respectively, and the relationship of MDR1 and postoperative survival time was also observed. MDR1 expression was significantly higher(79.3%) in pancreatic cancer than that in normal pancreatic tissues, normal pancreas tissues around tumor and benign pancreatic tumors. The expression of MDR1 in pancreatic cancer was also obviously higher than that in normal pancreatic tissues and pancreas tissues around tumor tested by RT-PCR. No special correlation was found between the expression of MDR1 with the sex, age, location, size, differentiation, the stage of tumor or preoperative local intra-arterial chemotherapy respectively. But the expression of P-gp was correlated with postoperative survival time of the patients with pancreatic cancer.Experimental study: MDR1 expression level was detected by method of RT-PCR in two pancreatic cancer cell lines, AsPC-1 and BxPC-3. The expression of MDR1 was higher in two cell lines. BxPC-3 was cultured from pancreatic cancer in situ, and the expression of MDR1 was slightly higher than that in AsPC-1. So BxPC-3 was chosen as further research platform. Multidrug resistance cell line of pancreatic cancer, BxPC-3/ADM, was constructed successfully by increasing theconcentration of ADM gradually. During the inducing course, MDR1 had main contribution to MDR at the early stage, whereas at the late stage MDR1 and MRP had co-contributed action. MDR1 cDNA vector was transfected into pancreatic cancer cell BxPC-3 by liposome, and the expression of MDR1 was significantly increased. But during the anaphase of screening, it was very difficult to obtain stable transfection of positive clone of MDR1 cDNA vector.The special siRNA was designed and synthesized which aimed at the MDR1 gene by RNA interference(RNAi) technique. Bgl II and HindIII restriction enzyme sites were introduced into the 5'and 3' of MDR1 gene siRNA respectively, then inserted into polylinker site of plasmid Retro pSuper, and MDR1 siRNA eukaryotic expression vector Retro pSuper-MDR1 siRNA was constructed. MDR1 siRNA had been successfully integrated into the plasmid. MDR1 siRNA vector was transfected into pancreatic cancer cell BxPC-3 by liposome, and the expression of MDR1 was significantly down-regulated.Conclusion: the expression of MDR1 in pancreatic cancer was higher, and that of P-gp may be concerned with postoperative survival time of the patient. The expression of MDR1 in pancreatic cancer cells was also higher, and multidrug resistance cell line of pancreatic cancer, BxPC-3/ADM, was constructed successfully by increasing the concentration of ADM gradually. The expression of MDR1 of BxPC-3 could be effectively inhibited By MDR1 siRNA. The RNAi technique is an effective method of MDR1 gene regulation.