p16INK4a protein expression is associated with poor survival of the breastcancer patients after CMF chemotherapy

Immunohistochemical assay for p16 protein expession was performed in 192 br east carcinoma patients treated with adjuvant chemotherapy. p16 expression was observed in 78 cases (40.6%). The frequency of p16 expression significa ntly decreased in moderately differentiated (histologic grade II) cancers, 20 (19.6%) of 102. In poorly differentiated cancers (histologic grade III), p16 expression was not observed in all 16 cases. p16 expression was signif icantly associated with histologic grade of the breast carcinomas (p < 0.00 1). The proliferative index (PI: S + G2/M) of individual tumors was measure d by DNA flow cytometry. In 114 tumors with PI less than 20%, p16 expressio n was observed in 59 tumors (49.1%). In the tumors with PI equal or more th an 20%, p16 expression was observed in 22 (28.2%) of 78 cases. p16 expressi on was significantly decreased in the tumor with higher PI (p = 0.003). For the other clinicopathologic variables, no significant association was foun d with p16 expression status. Immunohistochemical assay for p53 protein exp ression was performed on the same breast carcinomas. There was no significa nt association between p16 and p53 expression in breast carcinomas. During median follow-up period of 52 months (range: 40-72 months), 46 patients (25 .8%) had recurrent disease and 32 patients (18.91%) died of recurrent disea se. p16 expression was observed in 20 (43.5%) of 46 patients with recurrent disease, while its expression was observed in 58 patients (39.7%) of 146 p atients who were free of recurrence during the study period. p16 expression had no significant impact on predicting recurrence of breast carcinoma. Fo urteen patients (12.2%) of 114 patients whose tumors did not show p16 expre ssion died of recurrent breast carcinoma, whereas 18 patients (23.1%) of 78 patients with p16 expressing tumor died during the follow-up period. There was a significant difference of patient survival according to p16 expressi on status (p = 0.039). These results indicate that p16 expression is useful in predicting response to chemotherapy in breast cancer patients. p16 prot ein seems to have a role in tumor growth and differentiation of the breast carcinoma.