title: The tumor suppressor, p53, contributes to radiosensitivity of lung cancer cells by regulating autophagy and apoptosis.
abstract: OBJECTIVE
  Cell death is one of the most important endpoints of radiosensitivity. The tumor suppressor p53 participates not only in regulation of apoptosis, but also in autophagy mechanism. In this study, H1299-P53 (with wild-type p53) and H1299-175H (with mutant 175H) were used, and the effects of p53 on radiosensitivity were analyzed.
  
  
  METHODS
  Cell models with different p53 status were established by gene engineering, and cell viability was examined by colony formation assay, and cell counting kit-8 (CCK-8), 3-Methyladenine, and Z-VAD were used to block autophagy and apoptosis, respectively. Western blot was used to detect protein expression; monodansylcadaverine (MDC) staining was used to analyze autophagy rate; DAPI/Propidium Iodide (PI) staining and flow cytometry were used to assess apoptosis and necrosis.
  
  
  RESULTS
  In parental H1299, H1299-P53, and H1299-175H cells, radiosensitivity exhibited different by colony formation and CCK-8 assay (D0: 1.764 Gy, 1.407 Gy and 1.695 Gy; Dq: 2.977 Gy, 1.199 Gy and 2.312 Gy in turn). The radiosensitization of p53 was associated with the increase of MDM2 and P21 expression. The ionizing radiation (IR)-induced apoptosis was significant in H1299-P53 compared with in H1299 and H199-175H (p < 0.05) by flow cytometry, and the expression of cleaved-caspase3 was increased in H1299-P53 cells. While the IR-induced autophagy was significant in H1299 cells (p < 0.01) and decreased in H1299-P53 and H1299-175H cells (p < 0.01) by MDC staining, the expression of MAPLC3II and Beclin-1 increased in H1299, but not in H1299-p53 and H199-175H cells. The IR-induced cell survival was significantly increased by Z-VAD-FMK and decreased by 3MA in H1299-P53 cells; IR- induced autophagy was significantly increased by Z-VAD-FMK in H1299-P53 cells (p < 0.01), but not changed in H1299 cells.
  
  
  CONCLUSIONS
  p53 could regulate radiosensitivity by inhibiting autophagy and activating apoptosis; autophagy provides a prosurvival mechanism, and p53 potently abrogated the IR-induced autophagy, while mutant 175H shown no effect on radiosensitivity, suggesting that individual treatment strategies should be based on p53 status in patients.
authors.affiliation: Department of Radiation Oncology, China-Japan Union Hospital, Jilin University, Changchun, China.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Cheng
authors.forename: Dejuan
authors.initials: D
authors.lastname: Kong
authors.forename: Xue
authors.initials: X
authors.lastname: Hou
authors.forename: Bing
authors.initials: B
authors.lastname: Liang
authors.forename: Mengzi
authors.initials: M
authors.lastname: He
authors.forename: Nan
authors.initials: N
authors.lastname: Liang
authors.forename: Shumei
authors.initials: S
authors.lastname: Ma
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Liu
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D001343:Autophagy / Q000528:radiation effects*; D015153:Blotting, Western; D003114:Colony-Forming Units Assay; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy; D011836:Radiation Tolerance / Q000502:physiology*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism*; D014965:X-Rays
chemical_list: C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53