“…However, we have previously shown that cultivated NB cells can eliminate amplified MYCN gene copies by micronucleus formation, and that this process results in the formation of F-cells [24]. This fact, together with other properties of F-cells, which also occur in histogenetically distinct tumour cell lines [25][26][27][28], led us to conclude that the F-cells in the NB cell lines we have investigated so far represent a 'revertant' or senescent cell type and not a cell type differentiating along the glial/Schwannian lineage [24]. The results of the in vitro experiments presented in this paper show that NB cells, tumours, and cell lines are able to stimulate SC proliferation.…”