title: Synergistic cytotoxic effects of recombinant human adenovirus p53 and radiation at various time points in A549 lung adenocarcinoma cells.
abstract: The aim of this study was to evaluate the effects of recombinant human adenovirus p53 (rAd-p53; Gendicine) transfection and radiation at various time points following transfection. Cytotoxic effects and p53 protein expression levels were analyzed. rAd-p53 containing the human wild-type p53 gene was introduced into the human lung adenocarcinoma cell line A549, and cells were irradiated with a single dose of 6 MeV 4 Gy β rays. According to the time interval between rAd-p53 transfection and radiotherapy (RT), A549-transfected rAd-p53 cells were divided into 5 groups: radiation administered immediately after transfection (0 h-RT) group, after 3 h group (3 h-RT), after 6 h group (6 h-RT), after 24 h group (24 h-RT) and after 48 h group (48 h-RT). Cells with rAd-p53 transfection alone (Ad-p53) and with empty adenovirus (Ad) were included as the two control groups. Following 72 h of transfection, cell viability and growth were analyzed using MTT assays and flow cytometry, and p53 protein expression was analyzed using western blot analysis. From 0 h-RT to 48 h-RT, cell viability gradually decreased, while percentage of apoptotic cells and p53 protein expression gradually increased. The cell viability suppression rates in the 6 h-RT, 24 h-RT and 48 h-RT groups were 56.7±5.4, 60.8±6.0 and 68.9±6.6, respectively, which were significantly greater compared to that of the Ad-p53 (40.8±4.7), 0 h-RT (45.0±3.5) and 3 h-RT groups (47.0±4.3). No statistically significant differences were observed in the cell viability suppression rates among the 6 h-RT, 24 h-RT and 48 h-RT groups (P>0.05). Similar changes were observed in the percentage of apoptotic cells. The p53 protein expression level in the 6 h-RT group (0.856±0.092) was higher compared to that in the 3 h-RT group (0.643±0.089) (t=2.882; P=0.045), but not significantly different from that of the 24 h-RT group (1.193±0.202). The cell viability suppression rate and percentage of apoptotic cells was positively correlated with p53 protein expression in the A549 cells (P<0.05). Radiation may inhibit or damage p53 protein expression at the early stage of rAd-p53 transfection. To sensitize tumor cells to irradiation and achieve maximal cytotoxic effects, it is recommended to conduct RT at least 6 h following transfection with rAd-p53.
authors.affiliation: Department of Oncology, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110022, P.R. China.
authors.forename: Jie-Tao
authors.initials: JT
authors.lastname: Ma
authors.forename: Cheng-Bo
authors.initials: CB
authors.lastname: Han
authors.forename: Jian-Zhu
authors.initials: JZ
authors.lastname: Zhao
authors.forename: Wei
authors.initials: W
authors.lastname: Jing
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhou
authors.forename: LE-Tian
authors.initials: LT
authors.lastname: Huang
authors.forename: Hua-Wei
authors.initials: HW
authors.lastname: Zou