STAG1 and neoplasm: To examine whether the scFv–HSA fusion antibodies could specifically internalize into HER2-positive tumor cells and study the internalization efficiency, the uptake of T-SA1 and T-SA2 in three kinds of HER2 high-expression cells (that is, BT474, SKBR-3 and SKOV3) was semi-quantified by flow cytometry assay.