Expression of neurotransmitter receptors and myc protooncogenes in subclones of a human neuroblastoma cell line

Abstract

Phenotypic variability of the human neuroblastoma cell line SK-N-SH was studied with the use of three subclones that interconvert at a slower rate than the parent cell line, i.e., a neuroblast-type subclone (SH-SY5Y), a nonneuronal, strongly substrate adherent subclone (SH-EP), and an intermediate type subclone (SH-IN). Rhodamine-phalloidin staining of actin fibers revealed differences in the cytoskeleton morphology of the three subclones, while the clathrin subunit proteins (heavy and light chains), components of coated vesicles, were invariant. Dramatic differences were observed for the expression of neurotransmitter systems, i.e., the mu and delta opioid receptor, the muscarinic cholinergic receptor and its effect on phosphatidylinositol turnover, and the uptake1 transporter for catecholamines. While these systems were strongly expressed in the parent line and the neuroblast-like clones SH-SY5Y and SH-IN, they were absent or barely detectable in the nonneuronal EP clone. Furthermore, the protooncogenes N- and c-myc were only expressed in the neuroblast containing lines, consistent with their growth characteristics of fully transformed cells. The strong c-myc expression in the absence of c- or N-myc amplification in SK-N-SH, adds a new form of high protooncogene activity in neuroblastoma cell lines. The remarkable differences of neurotransmitter systems and myc expression among the various phenotypes of human neuroblastoma cells should be considered in the therapy of neuroblastoma.