To investigate target cell specificity, binding of the antibodies to HER2- and HER3-expressing cell lines was analyzed by flow cytometry using tumor cell lines expressing different surface levels of HER2 and HER3 (BT474: >572,000 HER2/cell and ~11,000 HER3/cell; LIM1215: ~33,000 HER2/cell and ~20,000 HER3/cell; MDA-MB-468: ~1,700 HER2/cell and ~6,000 HER3/cell). This evidence concerns the gene ERBB2 and neoplasm.