Changes in p21(WAF1), pRb, Mdm-2, Bax and Bcl-2 expression in cervical cancer cell lines transfected with a p53 expressing adenovirus

The aim of this study was to provide some insights into the molecular mecha nisms involved in p53-dependent apoptosis and growth arrest. Changes in the levels of p53 protein and proteins regulated by p53 were studied in relati on to events of the cell cycle and apoptosis in cervical cancer cell lines upon transfection with a p53 expressing adenovirus (Ad5-p53). The post-tran sfection level of p53 protein in SiHa cells was found to be unchanged durin g the 24-48 h period. In contrast. the level of p21(WAF1) protein was shown to increase to its highest level at 24 h, and decreased gradually up to 48 h after the Ad5-p53 transfection. We further noted that the increase of p2 1(WAF1) was accompanied by G1 arrest at 24 h and the decrease of p21(WAF1) was associated with apoptosis at 36-48 h after transfection. An anti-p21(WA F1) antibody cross-reactive protein band of approximately 14 kDa was observ ed in HeLa and C-33A cells when these cells were committed to apoptosis upo n Ad5-p53 transfection. In SiHa cells phosphorylation of pRb was inhibited during the early stage of Ad5-p53 transfection. This was followed by the cl eavage of pRb. However, Ad5-p53 transfection did not change the levels of B ar and Bcl-2 proteins. Our results suggested that. Bar and Bcl-2 may not be important for the apoptosis of these cells. whereas cleavage of Rb, and th e decrease of p21(WAF1) could play important roles in p53-dependent apoptos is. (C) 2000 Elsevier Science Ltd. All rights reserved.