Given that other growth factors like basic fibroblast growth factor (FGF2) and hepatocyte growth factor (HGF) also activate proliferation following internalisation of their receptors into endosomes [11], our data suggests that endosomal ROS may influence growth factor receptor signalling per se, representing a critical point of convergence of this type of signalling, which is then able to promote tumour development. The gene discussed is HGF; the disease is neoplasm.