Flt-3 and its ligand are expressed in neural crest-derived tumors and promote survival and proliferation of their cell lines

Flt-3 ligand (FL) is a cytokine that promotes the survival, proliferation, and differentiation of hematopoietic progenitors in synergy with other grow th factors, such as stem cell factor. Previously we have demonstrated that stem cell factor and its receptor c-kit are expressed in neural crest-deriv ed tumor cells and that a c-kit block induces their apoptosis. Here we have evaluated the expression of flt-3 and its ligand in 12 neuroectodermal tum or cell lines from neuroblastoma (NB), neuroepithelioma (NE), Ewing sarcoma (ES), and peripheral neuroectodermal tumor (PNET) and in 38 biopsies: 19 f rom NE and 19 from ES and PNET. RT-PCR demonstrated the expression of flt-3 and FL in all lines. Coexpression was observed in 42% of NE and in 74% of ES and PNET biopsies. Flow cytometry confirmed the presence of membrane and cytoplasmic flt-3 and membrane FL in all lines, whereas soluble FF protein was not measurable in their supernatants. Microphysiometric demonstration of acidification of the medium provided evidence of the specific response o f cell lines to FL stimulation. Specific flt-3 phosphorylation after FL tre atment was also demonstrated by Western blotting analysis. In cells growing in RPMI plus 1% fetal calf serum, FL revealed a significant proliferating activity, more evident in NE and NE lines (mean increase of Viable cells, 7 3 +/- 26% after 1 day). Treatment with flt-3 antisense oligonucleotides sig nificantly inhibited cell growth. FL also displayed an antiapoptotic activi ty: after a 12-hour culture in the presence of 0.1% fetal calf serum, FL ca used a 50% reduction of apoptotic cells. These results provide further evid ence that neuroectodermal and hematopoietic cells share common regulatory p athways, and could be of interest in the clinical management of neuroectode rmal tumors.