All-trans-retinoic acid induces nuclear factor kappaB activation and matrix metalloproteinase-9 expression and enhances basement membrane invasivity of differentiation-resistant human SK-N-BE 9N neuroblastoma Cells.

A comparison between retinoic acid (RA) differentiation-resistant and differentiation-sensitive SK-N-BE neuroblastoma (NB) cell lines revealed an association between resistance to differentiation, exhibited by N-myc stable transfected SK-N-BE 9N cells, with sensitivity to RA induction of p50/p65 nuclear factor kappaB (NF-kappaB) transcription factor activity and induction of matrix metalloproteinase (MMP)-9 expression leading to enhanced invasive behavior in vitro. These effects were not observed in differentiation-sensitive parental SK-N-BE or control-transfected SK-N-BE 2N counterparts. RA activated a MMP-9 promoter reporter gene construct in SK-N-BE 9N but not parental SK-N-BE or SK-N-BE 2N cells through a NF-kappaB element (-600) in association with enhanced p50 mRNA expression, reduced cytoplasmic inhibitor of nuclear factor kappaBalpha protein levels, and the induction of nuclear p50/p65 containing MMP-9 NF-kappaB site binding activity. RA activation of the MMP-9 promoter was inhibited by transient overexpression of a dominant-negative inhibitor of nuclear factor kappaBalpha protein and stimulated by transient p50 but not p65 overexpression in the absence of RA. A limited, nonessential function for activator protein 1 (-74), Ets (-540), and SP1 (-560) elements within the MMP-9 promoter was revealed by point mutation but was not associated with changes in the binding or position of complexes constitutive to differentiation-sensitive or -resistant cells. Our data indicates that in this model of NB resistance to differentiation that results from uncoupled RA regulation of N-myc expression, RA stimulates malignant NB cell behavior by inducing nuclear NF-kappaB transcription factor activity, which in turn induces MMP-9 expression and stimulation of basement membrane invasive capacity involving MMP-9 activity.