Immunohistochemical Study of Matrix Metalloproteinase 9 and Tissue Inhibitor of Matrix Metalloproteinase 1 in Benign and Malignant Breast Tissue – Strong Expression in Intraductal Carcinomas of the Breast

Abstract

Objective: Matrix metalloproteinases (MMPs) are involved in carcinogenesis due to their tissue remodeling capability, and there is convincing evidence linking gelatinase B (MMP-9) with malignant cell invasion. Tissue inhibitor 1 of MMP (TIMP-1) is a strong inhibitor of MMP-9 but has also tumor-enhancing effects. Only few data exist on MMP-9 or TIMP-1 expression in tissue samples of different breast histology. Methods: MMP-9 and TIMP-1 immunoreactivity was examined in a wide range of breast tissue samples differing in histology from usual ductal hyperplasia (UDH) to fully developed ductal breast carcinoma. Immunohistochemical expression of MMP-9 was studied in 178 samples: 31 UDH samples, 29 atypical ductal hyperplasia (ADH) samples, 28 ductal carcinoma in situ (DCIS) samples and 90 ductal invasive carcinoma samples (30 samples of malignancy grades I, II and III, respectively). TIMP-1 expression was also analyzed in 178 breast tissue samples: 41 UDH, 21 ADH and 34 DCIS lesions, and 82 invasive ductal breast carcinomas (25 in grade I, 30 in grade II and 27 in grade III). Results: A significantly distinctive pattern of MMP-9 protein expression was shown in DCIS samples, where 85.7% of the cases showed moderate or strong positivity and negative staining was rare (p = 0.021). Negative or weakly positive MMP-9 staining was the most prominent finding in UDH (71%), ADH (69%) as well as in invasive carcinoma samples (64.4%). Various degrees of TIMP-1 expression were seen in 86.5% of all cases. DCIS and invasive carcinoma samples revealed similar immunostaining: at least some positivity was seen in 91.1% of the DCIS samples and 91.5% of infiltrative carcinomas. Thus, TIMP-1 negativity (22.2%) was significantly associated with hyperplastic lesions (p = 0.026). Conclusions: These results suggest that MMP-9 and TIMP-1 overexpression are early markers of breast carcinogenesis preceding tumor invasion. Apparently, DCIS carries the risk to evolve into a malignant phenotype according to these markers. The clinical importance of these findings is discussed.