It would be interesting to assess the production of HGF by fibroblasts within the 3D co-culture format proposed by Jacobi et al. and to understand how the presence of the ECM may affect the concentration of HGF in the extracellular milieu and the proximity of the tumour cells, given the role of ECM in regulating HGF/c-MET signalling [137]. Here, HGF is linked to neoplasm.