OMS is a rare paraneoplastic disorder that affects adults and children. Pediatric OMS is often associated with NB, a common, solid
tumor of childhood, derived from the sympathetic nervous system. The detection of
autoantibodies and lymphocytic infiltration in NB patients led to advance an autoimmune hypothesis for the pathogenesis of OMS-related NB. BAFF is a potent modulator of B cell growth and survival upon interaction with its receptors BAFF-R and
BCMA. The aim of this study was to investigate mechanism(s) involved in ectopic lymphoid neogenesis in OMS-associated NB. We investigated BAFF, BAFF-R, and
BCMA expression in NB
tumors associated or not with OMS. Furthermore, we evaluated BAFF expression and secretion in NB cell lines, treated or untreated with differentiating agents. Immunohistochemically, lymphocytes infiltrating NB
tumors from patients, with or without OMS, expressed BAFF, BAFF-R, and
BCMA, whereas neuroblasts expressed BAFF and
BCMA but not BAFF-R. By flow cytometry, BAFF was found to be consistently expressed in NB cell lines. Similarly to the results obtained in tissue lesions,
BCMA but not BAFF-R was detected on the surface of all NB cell lines under basal conditions. De novo synthesis of BAFF-R and up-regulation of
BCMA were observed in NB cell lines upon treatment with IFN-γ or 13-cis
retinoic acid. This study provides new insights in the mechanisms driving the neogenesis of lymphoid follicles and in the functional interactions between
tumor and immune cells in OMS-associated NB.