ERBB4 and neoplasm: The regressed tumours had significantly reduced ratio of pEGFR:EGFR (p<0.05) (Fig. 6D) and pHER4:HER4 (p<0.001) (Fig. 6E) compared to the tumours without regression, suggesting the inhibition on EGFR and HER4 might be the cause of tumour regression.