LAMIN A/C AND N-MYC INTERPLAY IN NEUROBLASTOMA CELL DIFFERENTIATION

Neuroblastoma is a childhood tumor of the peripheral sympathetic nervous system thought to arise from highly proliferative migratory cells of the neural crest. Amplification of the MYCN gene occurs in a number of neuroblastomas representing a hallmark of a highly aggressive subgroup. Most malignant neuroblastoma cells have retained their capacity to differentiate in vitro. The type-V intermediate-filament lamins A/C have an expression pattern in some organs dependent on the differentiation states. In adult tissues, lamin A/C is observed only in final differentiated cells. Our aim was to study the interplay between MYCN and LMNA genes in the neuronal differentiation. We employed the neuroblastoma cell lines SHSY5Y, with high lamin A/C and absent N-Myc expression, and LAN-5, with high N-Myc and low lamin A/C. Both cell lines were induced to differentiate by retinoic acid. Differentiated SHSY5Y cells reduced c-Myc protein expression, as expected and increased lamin A/C, suggesting an involvement of the lamins in the differentiation process. To better understand the role of lamin A/C in the SHSY5Y differentiation we silenced the LMNA gene. The decrease of lamin A/C determined an inhibition of the neurites formation, even though a decrease of the c-Myc protein was still evidenced. We then inhibited c-Myc protein activity by using a validated peptide which interferes with the Myc-Max dimerization. An increase of the neurofilament and of lamin A/C expressions was observed after exposure to the peptide, further indicating that lamin A/C is needed to differentiate SHSY5Y cells. By contrast, LAN-5 cells significantly increased N-Myc during their differentiation, while no increase of lamin A/C was observed, strongly indicating an interplay between NMYC and LMNA genes.