ERBB2 and breast cancer: For this, we analyzed four different breast cancer cell lines (MDA-MB-453, MDA-MB-361, SK-BR-3 and BT-474) each representing different copy number of the ERBB2 locus (FISH ERBB2 to CEP17 ratios equal 2.15, 3.60, 4.42, 5.79, respectively).