Specific high-affinity binding and biologic action of retinoic acid in human neuroblastoma cell lines.

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Abstract
Neuroblastoma cells are a good model for neuronal development because of their ability to extend neurites in response to various stimuli, including retinoic acid. In the present experiments, 5 human neuroblastoma cell lines (LA-N-1, IMR-32, LA-N-5, SK-N-MC, and CHP-100) were examined for the presence of cellular retinoic acid binding protein (CRABP), a receptor-like protein implicated in the molecular functioning of vitamin A. CRABP is identified and quantitated by sucrose gradient centrifugation, selective inhibition by the mercurial reagent p-chloromercuribenzene sulfonic acid (PCMBS), and saturation analysis. All 5 lines contain significant levels of cytosolic CRABP (2.5-7.5 pmol/mg of protein), which dispaly typical properties of specific high affinity retinoic acid binding, a sedimentation coefficient of 2 S, and inhibition by PCMBS. Three of the lines (LA-N-1, IMR-32, and LA-N-5) are strongly growth inhibited by 1 .mu.M retinoic acid in monolayer culture, whereas 2 (LA-N-1 and La-N-5) undergo marked differentiation to a stellate, fusiform morphology with characteristic neurite outgrowths. The SK-N-MC and CHP-100 lines are relatively resistant to the antiproliferative effects of retinoic acid under these conditions. Nevertheless, all 5 lines are effectively inhibited by retinoic acid in their ability to form anchorage-independnet colones in soft agar. Thus, although CRABP is not necessarily correlated with growth inhibition in monolayer culture, it is associated with retinoic acid''s ability to inhibit neuroblastoma colony formation in soft agar. More experiments will be required to determine if this effect on growth in soft agar reflects the putative ability to retinoic acid to convert tumorigenic neuroblastoma cell lines into the normal differentiated phenotype.