Expression of the p73 protein in rectal cancers with or without preoperative radiotherapy

Purpose: To investigate p73 expression in normal mucosa, primary tumor, and metastasis in relation to radiotherapy (RT) response and clinicopathologic/biologic variables in rectal cancers. Methods and Materials: p73 was immunohistochemically examined on biopsies (unirradiated, n = 102), distant (from the large bowel, n = 82), and adjacent (adjacent to primary tumor, n = 89) normal mucosa samples, primary tumors (n = 131), and lymph node metastasis (n = 32) from rectal cancer patients participating in a clinical trial of preoperative RT. Seventy-four patients received surgery alone and 57 received additional RT. Results: Cytoplasmic p73 was increased in the primary tumor compared with the distant or adjacent mucosa (p ≤ 0.0001). Nuclear (p = 0.02) and cytoplasmic (p = 0.003) p73 was higher in irradiated distant mucosa samples than in unirradiated ones, and nuclear p73 tended to be increased in irradiated primary tumors compared with unirradiated ones (p = 0.06). p73 was positively related to cyclooxygenase-2 expression in irradiated tumors (p = 0.03). p73-negative tumors tended to have a lower local recurrence after RT compared with unirradiated cases (p 0.06). Conclusions: Normal epithelial cells seem more sensitive to RT than tumor cells regarding p73 expression. Patients with p73-negative rectal tumors may have a lower risk of local recurrence after RT