Significance of the expression of p27Kip1 in esophageal squamous cell carcinomas

Recent observations have demonstrated that the reduced expression of p27Kip1 (p27) is correlated with progression and poor prognosis of breast, colon, and gastric carcinomas. These observations led us to examine the expression of p27 and cyclin D1 and E protein in six esophageal carcinoma cell lines and 81 esophageal carcinoma tissues by Western blot analysis and immunohistochemistry. The expression levels of cyclin D1 and p27 were correlated clearly in esophageal carcinoma cell lines by Western blot analysis. Immunohistochemical analysis revealed that the high-grade expression of p27 protein was detected in 61% of esophageal carcinomas, and it was correlated with tumor invasion, lymph node metastasis, and poor patient prognosis. This observation was different from the results reported in other organs. Cell cycle regulation is a very complicated process. Homeostatic feedback mechanisms against the overexpression of cyclin D1 may exist in esophageal carcinomas, and there can be organ-specific regulations in the progression of carcinomas.