knockdown reduces tumour size in soft agar. Stable ST8814, S462, S1844.1 and S1507.2 cell lines, expressing either non-target or SPP1 shRNA as indicated, were subjected to tumour spheroid growth assays. a) Photographs of 40 tumours were taken after 2 weeks of incubation. The diameter of all tumours was measured using ImageJ software; the scale bar on images represents 250 μm. b) The percentage of tumour size was calculated from the 40 tumours for both the control and SPP1 shRNA. SPP1 knockdown significantly reduced tumour size in all four MPNST cell lines, consistent with a role for SPP1 in tumour growth (P = 0.0001), *P < 0.05 when comparing treated vs. untreated cells.