Cathepsin D in laryngeal carcinoma: preliminary report

The biological activity of tumor cells seems to be related to some peptides produced in the same neoplastic cytoplasms. Cathepsin D is considered one of these proteins, which is able to promote mitosis and tumor invasion. The effects of cathepsin D have been studied in tumors of the breast, ovary and endometrium, and in few cases of laryngeal cancer. Using an immunohistochemical method, we have attempted to evaluate cathepsin D expression in 17 cases of laryngeal squamous cell carcinoma in comparison with the presence of the same protein in the adjacent normal laryngeal mucosa and in inflammatory cells surrounding the tumor. In 11 cases, cathepsin D was present in more than 50% of neoplastic cells, in 4 cases positive cells were 30-50% of all neoplastic cells, in the last 2 cases less than 30% of neoplastic cells expressed the antigen. In normal respiratory epithelium the expression of cathepsin D was limited to the apex of cells. In flat metaplastic epithelium, we observed a positive reaction of basal and parabasal cells. Such positivity became diffuse to all cellular layers in dysplastic foci. A minimal positivity was also detected in salivary glands and ducts. A strong positivity was present in macrophages around and among tumor cells. Our findings suggest that cathepsin D plays a role in cancerogenesis and growth of laryngeal squamous cell carcinoma. The expression of cathepsin D also in normal and inflammatory cells may influence the quantitation of this antigen in studies in which cytosolic levels of cathepsin D are measured after protein extraction.