The fine structure of continuous human neuroblastoma lines SK-N-SH, SK-N-BE(2), and SK-N-MC

Cell cultures of the continuous human neuroblastoma lines SK-N-SH, SK-N-BE(2), and SK-N-MC at exponential and stationary growth phase have been examined by electron microscopy. At the level of fine structure these cells did not show typical neuronal differentiation such as extensive granular endoplasmic reticulum or neurites with microtubules and neurofilaments. Instead they were characterized by abundant free ribosomes, moderate Golgi complexes, and usually scant granular endoplasmic reticulum, features similar to the fine structure of early normal embryonic autonomic neurons. However, in several respects appearance of differentiated features of the neuroblastoma cells did not follow the pattern observed for normal neurons, suggesting noncoordinate, expression of neuronal phenotypic properties. First, an occasional neuroblastoma cell had as extensive granular endoplasmic reticulum as would be found at later stages in normal developing neurons. Second, the cellular processes of these neuroblastoma cells did not have the fine structure of developing or mature axons in vivo. Third, few dense core vesicles were found in SK-N-SH and SK-N-BE(2), though these organelles are numerous in early normal adrenergic neurons and the adrenergic character of these two lines is apparent from other studies that have demonstrated expression of neurotransmitter synthesizing enzymes (SK-N-MC is cholinergic). The fine structural characterization of these continuous human neuroblastoma cell lines will allow this parameter to be utilized with other approaches in future experimental studies.