ERRFI1 and neoplasm: In contrast, HER2 tumours exhibited a protein–protein interaction network that reflected the relationship between HER2 and its associating substrates (for example, Cbl, Ptpn11, Plcγ1), but it is noteworthy that Egfr and Pdgfrα, as well as the feedback inhibitor Errfi1, are also components of this network (Figure 5).