title: [Association of epithermal growth factor receptor expression and its downstream gene mutation status with radiosensitivity of colorectal carcinoma cell lines in vitro].
abstract: OBJECTIVE
  To investigate the effect of epithermal growth factor receptor (EGFR) expression and K-ras, B-raf and PIK3CA mutation status on the radiosensitivity of human colorectal carcinoma (CRC) cell lines in vitro.
  
  
  METHODS
  Real-time RT-PCR was used to measure EGFR mRNA expression in nine human CRC cell lines, and K-ras, B-raf and PIK3CA mutation status of each CRC cell line was also identified respectively. After treatment with irradiation at graded dose, the cell viability was measured by clonogenic survival assay. The rate of cell apoptosis and cell cycle distribution were tested by flow cytometry. The cell morphology was observed with hoechst 33258 staining to analyze the correlation between EGFR mRNA expression and radiosensitivity of CRC cell lines.
  
  
  RESULTS
  A positive correlation between EGFR mRNA expression and survival fraction of 2 Gy(SF2) was observed (r=0.717, P=0.030). Association was also identified between the mutation status of PIK3CA and radiosensitivity (t=2.401, P=0.047), while mutation status of K-ras and B-raf was not associated with radiosensitivity. At 48-hour after exposing to irradiation, the apoptosis rate of radiosensitive cell line (HCT116) was significantly increased in a dose-dependent manner (P<0.05), while the apoptosis rate of radioresistant cell line (HT29) was significantly increased only when radiation dose increased to 6 Gy. The ratio of G0/G1 phase was reduced significantly with the increase of radiation dose in radiosensitive cell line (HCT116, P<0.05), while this trend was not observed in radioresistant cell line (HT29, P>0.05).
  
  
  CONCLUSIONS
  Over-expression of EGFR mRNA is correlated to radioresistance of human CRC cell lines, and mutation status of PIK3CA is closely related with radiosensitivity of CRC cells. The inhibition of apoptosis and G0/G1 arrest may induce the radioresistance of CRC cell lines.
authors: Department of Colorectal Surgery, Changhai Hospital, The Second Military Medical University, Shanghai 200433, China. fugang416@126.com.
authors: Zhi-gui
authors: ZG
authors: Zuo
authors: Zhi-qi
authors: ZQ
authors: Yu
authors: Xian-hua
authors: XH
authors: Gao
authors: Hao
authors: H
authors: Wang
authors: Chang
authors: C
authors: Zhang
authors: Qi-zhi
authors: QZ
authors: Liu
authors: Yi-fang
authors: YF
authors: Han
authors: Li-ping
authors: LP
authors: Chen
authors: Xiao-qing
authors: XQ
authors: Zhang
authors: Chuan-gang
authors: CG
authors: Fu
mesh_terms: D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects; D002453:Cell Cycle / Q000235:genetics / Q000528:radiation effects; D045744:Cell Line, Tumor; D058534:Class I Phosphatidylinositol 3-Kinases; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D066246:ErbB Receptors / Q000378:metabolism*; D011905:Genes, ras / Q000235:genetics; D006801:Humans; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D011836:Radiation Tolerance
chemical_list: D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors; D048493:Proto-Oncogene Proteins B-raf