title: Different responses of tumor and normal cells to low-dose radiation.
abstract: OBJECTIVE
  We demonstrated stimulation of both erythrocyte immune function and superoxide dismutase activity in tumor-bearing mice in response to whole-body 75 mGy X-rays. In addition, we enhanced the chemotherapeutic effect by exposing tumor-bearing mice to low-dose radiation (LDR). This study aims to investigate the different responses of tumor cells and normal cells to LDR.
  
  
  METHODS
  Survival fraction, micronucleus frequency, and cell cycle of Lewis cells and primary human fibroblast AG01522 cells were measured. S180 sarcoma cells were implanted in mice, and tumor sizes were measured in vivo.
  
  
  RESULTS
  In response to LDR exposure in vitro, a stimulating effect was observed in AG01522 cells but not in Lewis cells. Low-dose radiation did not cause an adaptive response in the Lewis cell cycle. Lack of an LDR-induced radioadaptive response in tumor cells was observed in tumor-bearing mouse models. Furthermore, a higher apoptotic effect and lower expression of the anti-apoptosis gene Bcl-2 were found in tumor cells of tumor-bearing mice exposed to D1 + D2 than those in tumor cells of tumor-bearing mice exposed to D2 alone.
  
  
  CONCLUSIONS
  Different responses of tumor cells and normal cells to LDR were found. Low-dose radiation was found to stimulate the growth of normal cells but not of tumor cells in vitro and in vivo, which is a very important and clinically relevant phenomenon.
authors.affiliation: Department of Oncology, the Affiliated Hospital of Qingdao University Medical College, Qingdao, China.
authors.forename: Hongsheng
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Oncology, the Affiliated Hospital of Qingdao University Medical College, Qingdao, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Liu
authors.affiliation: Department of Oncology, the Affiliated Hospital of Qingdao University Medical College, Qingdao, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Oncology, the Affiliated Hospital of Qingdao University Medical College, Qingdao, China.
authors.forename: Qingjun
authors.initials: Q
authors.lastname: Shang
authors.affiliation: Department of Oncology, the Affiliated Hospital of Qingdao University Medical College, Qingdao, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Jiang
authors.affiliation: Department of Oncology, the Affiliated Hospital of Qingdao University Medical College, Qingdao, China.
authors.forename: Yuanmei
authors.initials: Y
authors.lastname: Zhang
keywords: adaptive response; cell cycle; clonogenic survival; low dose radiation; tumor cells