Background: Cyclin-dependent kinase inhibitors (CDKI), including p21, p27 and p57 of the KIP family, are negative regulators of cell cycle progression and potentially act as tumor suppressors. The expression of p21 is induced by tumor suppressor gene p53. Mutations of p53 are common and found in various human cancers. Thus, the function of p21 as a tumor suppressor may be not retained after p53 mutation in human cancers. The aim of our study was to evaluate the tumor suppressive activity of p21 and p53 in human gastric cancer.
Methods: One hundred and two patients who underwent surgery for gastric cancer at Chonnam National University Hospital were selected retrospectively for this study. The primary selection criteria were the availability of formalin-fixed and paraffin-embedded blocks and sufficient clinical follow-up for tumor-specific survival analysis. In this study, we examined the expression of p21 and p53 in human gastric cancer tissue by immunohistochemistry and the correlation between their expression and clinicopathological variables.
Results: p21 and p53 immunoreactivities were localized in the nuclei of carcinoma cells. Positive nuclear expression of p21 and p53 was demonstrated in 63.7 and 33.3% of cancer tissues, respectively. No apparent correlation was noted between p21 and p53 expression. Negative expression of p21 correlated with advanced stage and lymph node metastasis (p = 0.028 and 0.017, respectively). Moreover, negative expression of p21 correlated with poor survival (p = 0.037). Positive expression of p53 correlated with depth of tumor invasion (p = 0.029). However, no significant correlation could be observed between the status of p53 expression and survival. Combined analysis of p21 and p53 status showed that p21 negative and p53 positive tumors had a poorer survival than other group tumors (p = 0.026).
Conclusion: These results suggest that the status of p21 and p53 expression may help in predicting the aggressive behavior of gastric cancer. However, further studies are warranted to clarify the impact of p53 on the function of p21 as a tumor suppressor.