ERBB2 and breast cancer: Increasing the proportion of MDA-MB-468 human BC cells (EGFR-positive/HER2-negative) mixed with SK-OV-3 human ovarian cancer cells (HER2-positive/EGFR-negative) from 0% to 100% provided a cell population that was homogeneously HER2-positive, or exhibited an increasing gradient of EGFR-positive cells, or was homogeneously EGFR-positive.