Abstract
To determine whether p53 plays a role as a modulator of chemo- and radio- therapeutic agents in NSCLC, the stable transfection of wild-type p53 into H1299 cells were performed. In this study, the role of both wild-type and null p53 in modulating the sensitivity of H1299 cells to three therapeutic agents, cisplatin, X-ray, and sodium arsenite, is examined. The sensitivity to the three agents was tested in the sulforhodamine B (SRB) cell viability assay. The data showed that H1299 cells transfected with wild-type p53 gene had an increase in susceptibility to the three agents (2.3-fold to cisplatin, 1.7-fold to X-ray, and 2.2-fold to sodium arsenite) in comparison with parental or neo-transfected H1299 cells. Furthermore, the apoptotic cell fraction was also determined by dual-parameter flow cytometry after treatment with the three agents. By growing cells in the presence of cisplatin, X-ray, and sodium arsenite, respectively, the apoptotic fractions of H1299-S40 cells increased to 22%, 28%, and 27%, respectively. The expressions of p53, Bak (pro-apoptotic protein) and caspase3 (apoptotic proteolytic enzyme) were examined by Western blot. In p53-transfected H1299-S40 cells p53 proteins were obviously increased after treated individually with the three agents. The results showed similar Bak protein expression was found in both p53-transfected H1299-S40 and null-H1299 cells following cisplatin treatment, but not sodium arsenite treatment or X-ray exposure. In comparison, the active patterns of caspase 3 protein in H1299-S40 cells after above mentioned three agents were dramatically expressed but not in parental H1299 cells. These indicated that the p53 enhanced sensitivities to above three agents in cells through Bak-dependent or Bak-independent (cisplatin) apoptotic pathway. These observations suggest that the increase in chemo- or radio-sensitivity was attributable to wild-type p53 mediation of the process of apoptosis. In the future, the model cell line system could be used in other drugs investigation or p53 molecule related research.