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Objective:To discuss effect of ionizing radiation on transcription of colorectal cancer multidrug resistance(MDR) 1 gene of HCT-8 cells.Methods:Total RNA was extracted by guanidine thiocyanate one-step method.Northern blot was applied to detect transcription level of MDR1 gene.The expression of P-gp protein was detected by flow cytometry.Results:The expression of MDRl of normal colorectal cancer HCT-8 cells was low.It was increased by 8.35 times under stimulus with 2 Gy.When treated with low doses in advance,high expressed MDR was decreased significantly under 0.05,0.1 Gy,which was 69.00%,62.89%in 2 Cy group and 5.77 times,5.25 times in sham irradiation group.No obvious difference was detected between(0.2+2) Gy group and 2 Gy group.Compared with sham irradiation group,the percentage of P-gp positive cells after radiation of a high 2 Gy dose was increased significantly(P<0.01).When treated with high radiation dose following low radiation dose(0.05 Gy,0.1 Gy) in advance,the percentage of P-gp positive cells were also increased significantly.The percentage of P-gp positive cells were increased obviously in 0.2 Gy and 2 Gy groups.Compared with simple high radiation 2 Gy group,the percentage of P-gp positive cells was decreased significantly(P<0.05).Conclusions: Low radiation dose can reverse multidrug resistance of colorectal cancer cells caused by high radiation dose.
Objective: To discuss effect of ionizing radiation on transcription of colorectal cancer multidrug resistance (MDR) 1 gene of HCT-8 cells. Methods: Total RNA was extracted by guanidine thiocyanate one-step method. Northern blot was applied to detect transcription level of MDR1 gene. The expression of P-gp protein was detected by flow cytometry. Results: The expression of MDR1 of normal colorectal cancer HCT-8 cells was low. It was increased by 8.35 times under stimulus with 2 Gy.When treated with low doses in advance, high expressed MDR was decreased significantly under 0.05, 0.1 Gy, which was 69.00%, 62.89% in 2 Cy group and 5.77 times, 5.25 times in sham irradiation group. Non difference was detected between (0.2 + 2) Gy group and 2 Gy group. Compared with sham irradiation group, the percentage of P-gp positive cells after radiation of a high 2 Gy dose was increased significantly (P <0.01) .When treated with high radiation dose following low radiation dose (0.05 Gy, 0.1 Gy) in advance, the percentage of P-gp positive cells were also increased significantly. The percentage of P-gp positive cells were increased obviously in 0.2 Gy and 2 Gy groups. Compared with simple high radiation 2 Gy group, the percentage of P-gp positive cells was decreased significantly ( P <0.05) .Conclusions: Low radiation dose can reverse multidrug resistance of colorectal cancer cells caused by high radiation dose.