EFFECTS OF p53 OVEREXPRESSION ON NEOPLASTIC CELL PROLIFERATION AND APOPTOSIS IN THYMIC CARCINOMA
Abstract
Objective: To investigate p53 overexpression and its correlation with neoplastic cell proliferation and apoptosis in 20 thymic carcinomas.
Methods: 20 surgical samples of thymic carcinoma were collected randomly during the past 15 years in the Guangzhou area. lmmunohistochemlcal staining was performed using LSAB method with anti-p53 monoclonal antibody (DO-7) and proliferating cell nuclear antigen (clone PC 10) as primary antibodies. The p53 index was indicated by the number of p53 positive cells among 100 carcinoma cells. More than 25 percentage of p53 positive cells found in tissue sections was recognized as p53 overexpression. Carcinoma cell proliferation activity was assayed by PCNA index (PI), and apoptosis degree was evaluated by TUNEL (TdT-mediated dUTP-X nick end labeling) index (TI) using Boehringer Mannheim In Situ Death Detection Kit.
Results: P53 positive cells could be found in vast majority of thymic carcinomas (19/20) and the overexpression rate reached 35% (7•20). The median PI (40%) of 7 cases with p53 overexpression was higher than that (31%) of 13 cases without p53 overexpression, but there was no statistical significance that existed between these two data (P>0.05). The median TI (0.5/HPF) of 7 p53 overexpression cases was much lower than that (4.5/HPF) of 13 non-overexpression cases, and there was a significant difference statistically (P<0.05).
Conclusion: p53 exPression was a frequent finding in thymic carcinoma cells, and the p53 overexpression which might represent p53 inactivation or gene mutation was often involved in thymic carcino-genesis. The median PCNA index of p53 overexpression group was higher than that of non-overexpression group though there existed no statistical difference. This indicates that the inhibiting function of p53 on cell proliferation seemed lost in p53 overexpressed thymic carcinomas. It is worthy to be specially mentioned that the inducing function of p53 on cell apoptosis was markedly lost in p53 overexpressed thymic carcinomas. Taken together, the overexpressed p53 that could represent aberrant p53 protein had not only lost its proliferation-inhibiting but also its apoptosis-inducing function in thymic carcinomas which might play an important role in thymic carcinogenesis.
Methods: 20 surgical samples of thymic carcinoma were collected randomly during the past 15 years in the Guangzhou area. lmmunohistochemlcal staining was performed using LSAB method with anti-p53 monoclonal antibody (DO-7) and proliferating cell nuclear antigen (clone PC 10) as primary antibodies. The p53 index was indicated by the number of p53 positive cells among 100 carcinoma cells. More than 25 percentage of p53 positive cells found in tissue sections was recognized as p53 overexpression. Carcinoma cell proliferation activity was assayed by PCNA index (PI), and apoptosis degree was evaluated by TUNEL (TdT-mediated dUTP-X nick end labeling) index (TI) using Boehringer Mannheim In Situ Death Detection Kit.
Results: P53 positive cells could be found in vast majority of thymic carcinomas (19/20) and the overexpression rate reached 35% (7•20). The median PI (40%) of 7 cases with p53 overexpression was higher than that (31%) of 13 cases without p53 overexpression, but there was no statistical significance that existed between these two data (P>0.05). The median TI (0.5/HPF) of 7 p53 overexpression cases was much lower than that (4.5/HPF) of 13 non-overexpression cases, and there was a significant difference statistically (P<0.05).
Conclusion: p53 exPression was a frequent finding in thymic carcinoma cells, and the p53 overexpression which might represent p53 inactivation or gene mutation was often involved in thymic carcino-genesis. The median PCNA index of p53 overexpression group was higher than that of non-overexpression group though there existed no statistical difference. This indicates that the inhibiting function of p53 on cell proliferation seemed lost in p53 overexpressed thymic carcinomas. It is worthy to be specially mentioned that the inducing function of p53 on cell apoptosis was markedly lost in p53 overexpressed thymic carcinomas. Taken together, the overexpressed p53 that could represent aberrant p53 protein had not only lost its proliferation-inhibiting but also its apoptosis-inducing function in thymic carcinomas which might play an important role in thymic carcinogenesis.