In Vitro Activation of Distinct Molecular and Cellular Phenotypes after Induction of Differentiation in a Human Neuroblastoma Cell Line

In this report we provide evidence for the activation of distinct differentiation pathways during treatment of the neuroblastoma cell line SMS-KCNR with 1 mm dibutyryl cyclic AMP (dbcAMP) and/or 5 µm retinoic acid (RA). Our results show that the adrenal gland specific gene pG2 is induced only during dbcAMP treatment, while RA induces a neuronal phenotype and expression of all neural related genes while decreasing the expression of many chromaffin related genes. Furthermore dbcAMP does not affect the DNA content distribution of SMS-KCNR cells [G₁=61.8 ± 4.1% (SD); S = 20.3 ± 6.3%; G₂-M = 18 ± 5.4%] despite morphological and molecular signs of cellular differentiation. Conversely, RA arrests cell growth causing a decrease in cells in the growth fraction (S + G₂ + M = 15.6 ± 6.1%) and an increase in cells in G₁ (G₁ = 84.3 ± 5%). Using cyclic AMP and RA in combination, we found that RA inhibited expression of adrenal gland specific gene pG2 and induced a neuronal phenotype. Since dbcAMP does not cause a significant G₁ block in SMS-KCNR cells we propose that this agent may be able to induce SMS-KCNR only to an intermediate stage of chromaffin differentiation in which cells retain their proliferative potential.