A 3D Spheroid Model of Tumour Angiogenesis Figure 4. Minitumour spheroids growth factor dependency. A – Direct incubation of function blocking antibodies for VEGF or PDGF within the collagen-I gel decreases endothelial cell sprouting from the Minitumour spheroids. B – Minitumour spheroids incubated with function blocking antibodies to IL6 and IL8 show similar levels of sprout formation to EndoFib spheroids. C - Minitumour and EndoFib spheroids show a differential response to inhibition of growth factor signaling using small molecule growth factor receptor inhibitors. D – Increase in endothelial cell sprouting in both Minitumour and EndoFib spheroids after 40 h incubation with the gamma-secretase inhibitor DAPT. E – Representative images from Minitumour and EndoFib spheroids incubated in collagen-I for 40 h with the addition of different growth factor receptor inhibitors. doi:10.1371/journal.pone.0030753.g004 PLoS ONE | www.plosone.org 8 February 2012 | Volume 7 | Issue 2 | e30753