SPP1 and neoplasm: Given that we observed significant differences in the expression level of SPP1 in MPNSTs as compared with the benign plexiform neurofibromas and the fact that SPP1 plays significant roles in both tumorigenesis and metastasis [33], we knocked down expression of the SPP1 gene in four MPNST cell lines (ST8814, S462, S1844.1 and S1507.2) and examined both the ability of these cell lines to form tumours (Figure 3a) and the effect of knockdown on wound healing and invasion.