NTRK1 and neoplasm: In contrast, the TrkA specific inhibitor GW441756, at concentrations of 1 μM and 100 nM, did not significantly inhibit spheroid growth of TrkA SH-SY5Y cells but significantly reduced tumour spheroid growth of TrkAIII SH-SY5Y cells, reducing mean spheroid volume from 0.42±0.23 mm3 (control) to 0.029±0.014 mm3 (t-test, p<0.05, df = 4) with 1 μM GW441756 and 0.05±0.015 mm3 with 100 nM GW441756 (t-test, p<0.05, df = 4; One way ANOVA comparison: F (2, 6) = 8.16; p<0.019) (Fig. 8B).