An Analysis of p53, bcl-2 and Ki-67 Expressions, and Apoptosis in Rectal Cancer: Their Correlation with the Tumor Response after Preoperative Radiochemotherapy

ABSTRACT

Background: Preoperative radiochemotherapy (RCT) has been administered for locally advanced rectal cancer to increase the therapeutic benefits, and to preserve the sphincter in low-lying tumors, however, tumor responses after RCT are variable. Methods: Apoptotic index (AI), and expressions of Ki-67, p53 and bcl-2 were analyzed in pretreatment biopsies from 69 patients with rectal cancer by immunohistochemistry. Tumor response was graded in surgically resected specimens by using a three-scale grading system no response (NR), partial remission (PR) and complete remission (CR). Results: CR was identified in 19 cases (28%), PR in 24 cases (35%), and NR in 26 cases (38%) of 69 cases. p53 protein was expressed in 49 cases (71%), whereas bcl-2 was in 42 cases (61%). The pretreatment Ki-67 labeling index was 65.4+/-3.4%. The tumor response was not associated with any of these markers. Tumors with CR/PR showed a higher AI (0.84+/-.84%/0.66+/-.52%) than that of tumors with NR (0.58+/-0.54%). There was a significant correlation between tumor response and the histologic differentiation (p=0.008) or recurrence (p=0.039). Conclusions: The AI revealed a tendency to increase in tumors with CR/PR, while expressions of p53 and bcl-2, and Ki-67 labeling index had little direct association with tumor response.