Over‐expression of p53 protein in human laryngeal carcinoma

We examined the expression of tumor-suppressor protein p53 in a variety of laryngeal carcinomas from 43 patients (25 primary, 13 metastatic and 5 recurrent cases), 13 normal laryngeal tissues and 7 benign laryngeal nodule biopsy specimens, using the polyclonal antibody CM-1. Previously we have reported a high incidence of ras mutations (51%) and human papillomavirus (HPV) infection (37%) in these laryngeal carcinomas. p53 protein was detected by immunohistochemistry in 65% of laryngeal carcinomas (60% of primary, 69% of metastatic and 80% of recurrent cases). No correlation was found between p53 over-expression and histological grading of the tumors. None of the specimens from normal larynx and laryngeal nodules revealed any detectable level of this protein. Furthermore, 11 (69%) of 16 HPV-positive cases and 17 (77%) of 22 cases with ras mutation showed variable grades of p53 expression. Twelve (71%) of 17 laryngeal carcinomas in current study having both p53 over-expression and ras mutation were moderately or poorly differentiated. Likewise, positivity for these 2 parameters was significantly increased in metastatic tumors (9 of 13 cases, 69%) as compared with primary and recurrent tumors (8 of 30 cases, 27%) (p < 0.01). Our results suggest that multiple factors are involved in this malignancy, and that the simultaneous over-expression of p53 and the presence of ras mutation may be related to the progression stage of laryngeal carcinoma.