IMMUNOHISTOCHEMICAL STUDY OF P53 EXPRESSION IN CANCER TISSUES FROM PATIENTS UNDERGOING RADIATION-THERAPY

Immunostaining using p53 monoclonal antibodies (p53(Ab-3) recognizes m utant type and p53(Ab-6) the wild type of p53 protein) was performed o n frozen sections of biopsy specimens obtained before and during preop erative radiotherapy from 23 patients with head and neck squamous cell carcinoma. The positive staining rates of p53(Ab-3) before radiothera py 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% respect ively. The relationship between the immunohistochemical findings and a ntitumor effect at radiation dose of 20Gy was examined on the correspo ndent haematoxylin-eosin sections. In patients whose p53(Ab-3) stainin gs were positive at any doses of radiotherapy, the antitumor effect at the cumulative dose of 20Gy was either remarkable or effective. Moreo ver, the frequency of the expression of mutant type p53 protein tended to increase in rather radiosensitive tumors. As for wild type p53 pro tein, there was no remarkable relationship between the staining of p53 (Ab-6) and the antitumor effect.