Cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein are present in the cytosol of normal human uterine cervical tissues, as detected by ultracentrifugation analysis. Both binding proteins have characteristically high specificity for their respective ligands. In sucrose gradients, both proteins sediment in the 2S region and are of similar molecular weight (M.W. ∼14,000). In blind analyses of cervical biopsies, obtained under direct vision by colposcopy of normal women (control) or from patients histopathologically diagnosed to have dysplasias or carcinoma in situ (study group), CRBP was not detectable by sucrose gradient analysis in 78.8% of the 33 abnormal biopsies, compared to 23.5% of the 34 controls. This difference was statistically significant (p < 0.005). In biopsies in which CRBP was detected, the mean levels were 2.76 and 0.72 pmol/mg protein in the cytosol for the control and study groups, respectively. In some subjects from each group, cellular retinoic acid-binding protein but not CRBP was detected in the biopsied tissue. The presence and role of these binding proteins in vitamin A metabolism, epithelial maturation and differentiation in cervical dysplasias, and in situ lesions remain to be investigated.
This work was supported by Contract NCI 1 CP-65788 from the Diet, Nutrition and Cancer Program, Division of Cancer Cause and Prevention, National Cancer Institute.