Abstract: Objective To examine the expression pattern of membrane type-1 matrix metalloproteinase (MT1-MMP) in breast
carcinomas. Methods Forty-three breast cancer tissues were collected and examined for MT1-MMP protein and mRNA
expressions using immunohistochemistry, semi-quantitative RT-PCR and in situ hybridization. Results Immunohistochemistry
of the breast cancer specimens showed MT1-MMP immunoreactivity on the cancer cell membrane. MT1-MMP mRNA was
located in the stromal cells surrounding the breast cancer nest as shown by in situ hybridization. MT1-MMP mRNA expression
was detected in all of the carcinomas, but its level was significantly lower in immunohistochemically negative specimens than
in positive ones (0.547 ± 0.0886 vs 0.759 ± 0.0802, P<0.01). Conclusion MT1-MMP is very likely produced by stromal cells
surrounding the breast cancer nest and anchored on the cell membrane after activation.