ERBB2 and neoplasm: The partial anti-tumor efficacy conferred by scIgG-T in the mouse xenograft model can be attributed to the direct HER2 engagement by the Fab region of scIgG-T, as indicated by downregulation of HER2 in tumor tissues and inhibition of pHER2 (Y1248), pAKT (S473), and pErk1/2.