p16, cyclin D1 and Rb expression in colorectal carcinomas: Correlations with clinico-pathological parameters and prognosis.

In an immunohistochemical study, 200 colorectal carcinomas were stained with monoclonal antibodies recognizing the cell cycle regulators p16, cyclin D1 and Rb, in order to study their expression and prognostic impact. Cyclin D1 and Rb were generally expressed in a nuclear pattern, whereas p16 also exhibited cytoplasmic reactivity. Immunoreactivity was observed in 94% (p16), 75% (cyclin D1) or 91% (Rb) of the carcinomas. Cytoplasmic p16 and cyclin D1 correlated with the extent of the mucinous tumor component. The cytoplasmic expression of p16 was reduced in advanced pN stages. At a cut-off point of 20%, cyclin D1 was significantly upregulated in tumors of the right colon. Further correlations with gender, growth pattern, staging, grading or prognosis were not revealed. The three cell cycle regulators do not represent useful markers of prognosis or predictors of colorectal carcinoma.