Abstract

The retinoblastoma (Rb)/cyclin D1/p16 pathway is an important constituent of cell cycle regulation. Perturbations in this pathway due to a variety of genetic aberrations have been reported in many human cancers including breast cancer. We examined the significance of immunoexpression of p16 protein, cyclin D1 protein, Rb protein (pRb), and p53 protein in 128 cases of invasive breast carcinoma. The results were correlated with survival rate and clinicopathological variables, including age, histologic grade, lymph node status, tumor size, estrogen receptor (ER), and progesterone receptor (PR) content. Abnormal expressions of p16 and pRb which were defined as negative staining were seen in 21% and 43% of tumors, respectively. There was a significant inverse relationship between p16 and pRb expression. There was no correlation between p16 staining and any other parameters, including survival rate, cyclin D1, p53, and clinicopathologic variables. Surprisingly, there was a trend for tumors which were positive for pRb to be grade III ductal carcinomas. Cyclin D1 positivity was noted in 46% of cases. The expression of cyclin D1 protein was significantly higher in lower histologic grade, higher ER and PR expression. The expression of p53 protein showed a significant correlation with high tumor grade. In a Cox multivariate analysis, neither p16, pRb, cyclin D1 nor p53 was an independent predictor, but tumor size and lymph node status were independent predictors of patient outcome.

• Keywords: Invasive breast carcinoma;Cell cycle related protein;Survival rate;Clinicopathological variables