Purpose: Previous studies have drawn controversial conclusions for the expression of erb-b2 receptor tyrosine kinase 4 also known as Human Epidermal Growth Factor Receptor 4 (ERBB4/HER4) in breast cancer. Accordingly, in the present study, ERBB4/HER4 expression was analyzed in healthy breast, invasive ductal triple-negative breast cancer (TNBC), and non-TNBC tissues. Materials and Methods: The expression level of ERBB4/HER4 was evaluated in 10 normal breast, 20 TNBC, and 20 non-TNBC tissue samples using real-time polymerase chain reaction (Real-Time PCR). Results and Discussion: The ERBB4/HER4 expression level was downregulated in TNBC compared to the healthy tissue (P value, < 0.0001; fold change, -2.1); in contrast, upregulated in non-TNBC versus the healthy tissue (P value, < 0.0001; fold change, 1.7). Noticeably, without categorization of breast cancer samples, ERBB4/HER4 was not significantly dysregulated (TNBC + non-TNBC vs normal; P value, 0.9816). What's more, according to the area under the curve (AUC) and receiver operating characteristic (ROC) curves analysis, ERBB4/HER4 is significantly and strongly able to distinguish TNBC from healthy and non-TNBC from healthy. To put it in a nutshell, downregulation of ERBB4/HER4 in TNBC vs healthy tissue and its upregulation in non-TNBC vs healthy tissue may explain contentious findings in previous studies. This study sheds new lights on expression pattern of ERBB4/HER4 in breast cancer.
