ERBB2 and breast cancer: The analysis was performed using MDA‐MB‐231 cell line (basal B, TP53 + +m, triple negative: ER‐, PR‐, HER2‐) that is highly invasive human analogue of murine 4T1 breast cancer cells, nonresponsive on endocrine therapy and poorly responsive on chemotherapy, T47D cell line (luminal A, TP53 + +m, ER+, PR±, HER2‐), which is less invasive and MCF‐7 cell line (luminal A, TP53 + /‐wt, ER+, PR±, HER2‐) that is the least invasive, endocrine and chemotherapy responsive.