Retinoid binding lipoprotein in neoplastic cells.

A lipid-protein aggregate (LPA), binding both retinol and retinoic acid, was detected in the cytosols of several human and murine tumor cells by gel filtration after incubation of cell extracts with labelled retinoids. In addition to this high Mr lipoprotein (Mr 2 X 10(6)) the cytosols also contained low Mr retinoid binding proteins (Mr 14,500). The amounts of retinoids bound to these 2 distinct components were similar and both bound some 40-200-fold more retinol than retinoic acid. Retinyl palmitate hydrolase, copper and zinc were found in association with LPA. The LPA may be involved in subcellular compartmentalization, transport and function of retinoids.