Stromal expression of matrix metalloproteinase 2 in cancer-associated fibroblasts is strongly related to human epidermal growth factor receptor 2 status in invasive breast carcinoma.

The peritumoral stroma and cancer-associated fibroblasts (CAFs) have been suggested to play an important role in breast tumorigenesis. The specific immunohistochemical characteristics of the stromal component according to the breast carcinoma subtype surrogates of molecular classes is poorly understood. In the present study, immunohistochemical staining was used to evaluate the expression of matrix metalloproteinase 2 (MMP2), which is one of the most important proteins considered to facilitate tumor invasion, in a series of invasive breast carcinomas according to subtype: Luminal A, luminal B, luminal-HER2, HER2-enriched and triple-negative. A significant increase in MMP2 expression was demonstrated in tumors known to exhibit a more aggressive metastatic behavior, such as luminal HER2 (37%), HER2-enriched (30%) and triple-negative tumors (17%), compared with the luminal A (6%) or luminal B (13%) subtypes. Our data indicated that the CAFs associated with different breast subtypes exhibit different specific properties to facilitate tumor invasion.