PHENOTYPIC AND MORPHOLOGICAL CHARACTERIZATION OF NEUROBLASTOMA-CELLS CONSTITUTIVELY EXPRESSING B-MYB

B-myb gene is expressed in neuroblastoma cells and down-regulated duri ng differentiation. We used B-myb-transfected LAN-5 cells, which const itutively express high level of B-myb, to detect changes at phenotypic and morphological levels in basal and differentiation conditions. Our results demonstrate that the overexpression of B-myb markedly affects the cytoskeletal composition, the pattern of neurotransmitter enzymes and the extracellular matrix expression. In general, B-myb transfecte d neuroblastoma cells show a broad potentiality without a direction to ward a specific neuroectodermal differentiation pathway. On the other hand, we confirm inhibition of the neuronal differentiation upon retin oic acid (RA) treatment of B-myb transfected cells. Furthermore, the u ltrastructural analyses are supportive of a change in the metabolism i n B-myb transfected cell treated with RA. Our data suggest that B-myb expression is compatible with an early phase of differentiation of neu roectodermal cells, but must be down-regulated for the completion of t he differentiative programme.