Vitamin A status and retinoid-binding proteins in carcinomas of the head and neck region.

The serum levels of retinol, RBP (retinol-binding protein) and PALB (prealbumin) were found to be significantly lower in patients with malignant tumors of the head and neck region than in controls. In tumor tissues as well as in normal laryngeal mucosa, specific binding sites for retinol and retinoic acid were found. Whereas retinol-binding (CRBP = cellular retinol-binding protein) could only be detected in a few cases, binding for retinoic acid (CRABP = cellular retinoic acid-binding protein) was present in all specimens investigated. The presence or lack of binding sites was not dependent on the actual serum retinol levels. With regard to the antineoplastic role of vitamin A, the reduced serum levels are considered as a possible factor in tumor development and growth. CRBP and CRABP are assumed to be mediating factors for the retinol and retinoic acid action. Since the presence of CRABP is a constant finding, we propose that retinoic acid and its synthetic derivatives with high affinity for CRABP could be appropriate antineoplastic drugs in these tissues.