Immunohistochemical study of p53 expression in cancer tissues from patients undergoing radiation therapy.

Immunostaining using p53 monoclonal antibodies (p53(Ab-3) recognizes mutant type and p53(Ab-6) the wild type of p53 protein) was performed on frozen sections of biopsy specimens obtained before and during preoperative radiotherapy from 23 patients with head and neck squamous cell carcinoma. The positive staining rates of p53(Ab-3) before radiotherapy and at radiation doses of 4Gy, 10Gy and 20Gy were 30.0%, 38.9%, 25.0% and 6.25%, and those of p53(Ab-6) 10.5%, 11.8%, 5.0% and 0% respectively. The relationship between the immunohistochemical findings and antitumor effect at radiation dose of 20Gy was examined on the correspondent haematoxylin-eosin sections. In patients whose p53(Ab-3) stainings were positive at any doses of radiotherapy, the antitumor effect at the cumulative dose of 20Gy waas either remarkable or effective. Moreover, the frequency of the expression of mutant type p53 protein tended to increase in rather radiosensitive tumors. As for wild type p53 protein, there was no remarkable relationship between the staining of p53(Ab-6) and the antitumor effect.