Retinoic-acid-binding protein in normal and neoplastic human esophagus

The concentration of cellular retinoic acid binding proteins (CRABP) was determined in the cytosol of normal esophageal tissue and in esophageal carcinomas. Unlike the reported results for human breast, colon, melanoma, or oropharynx cancers, the CRABP levels in esophageal cancers were either undetectable or contained levels of CRABP which were significantly lower than that of adjacent histologically disease-free tissue (P less than 0.005). Moreover, there was no difference between the normal mucosa of cancer or noncancer patients with regards to the CRABP concentration. The absence of CRABP in the cancer tissue was not dependent on the degree of differentiation. These results indicate that the CRABP disappears when the normal mucosa becomes malignant. If such a change is also demonstrated in known premalignant conditions of the esophagus, CRABP could serve as a diagnostic biochemical marker for early detection of this cancer.