title: Effect of ionizing radiation on transcription of colorectal cancer MDR1 gene of HCT-8 cells.
abstract: 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 Gy 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.
authors.affiliation: Gastroenterology Department, Fifth Hospital of Sun Yat-sen University Zhuhai 51900, China.
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Ma
authors.forename: Jing
authors.initials: J
authors.lastname: Lu
authors.forename: Li-Xia
authors.initials: LX
authors.lastname: Kong
authors.forename: Xiao-Hua
authors.initials: XH
authors.lastname: Long
authors.forename: Su-Huan
authors.initials: SH
authors.lastname: Liao
authors.forename: Bao-Rong
authors.initials: BR
authors.lastname: Chi
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D011839:Radiation, Ionizing; D014158:Transcription, Genetic / Q000528:radiation effects*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D012333:RNA, Messenger; D012334:RNA, Neoplasm