Bar graph of Her2/neu protein in tissue samples quantified by ELISA. (A) Her2/neu normalized for total protein for each tissue sample tested. Sufficient quantities of only 32 of the 40 tissue samples were available for testing. Error bars show SDs for duplicate ELISA plates. The inset compares the total amount of Her2/neu protein in two breast cancer cell lines: MCF-7 cells, which have fewer than five copies of the Her2/neu gene, and HCC1954 cells, which overexpress the Her2/neu protein. Overexpression in this cell line leads to a 40-fold increase in Her2/neu protein level relative to that in MCF-7 cells. (B) Relative amounts of Her2/neu protein in tumor tissue compared with the paired normal tissue, showing the fold increase in Her2/neu for tumor tissues ranging from about 5-fold to more than 30-fold.