Regulation and turnover of cellular retinol-binding protein in a xenografted human ovarian tumour.

A human ovarian mesodermal mixed heterologous carcinoma, with a high content of cellular retinol-binding protein (CRBP), was used to study the effects of retinoid and hormonal treatment on tumour CRBP content, tumour growth rate, differentiation and turnover of CRBP. Tumour growth in general was accompanied by an increase in the CRBP concentration of the xenografted tumours. This was related to the appearance of more mature epithelial cells, showing CRBP immunoreactivity. The increase in CRBP concentration was more pronounced in retinyl palmitate-treated tumours than in tumour tissue from etretinate- (an aromatic retinoid) treated mice and controls, suggesting that CRBP synthesis is under the influence of its ligand. Various hormonal treatments had no influence on the CRBP concentration in these tumour cells. The CRBP turnover was similar to that of the bulk of cellular proteins.