Validation of immunolocalization of the urokinase receptor expression in ductal carcinoma in situ of the breast: Comparison with detection by non-isotopic in-situ hybridization

Aims: Ductal carcinoma in situ (DCIS) is a pre-invasive form of mammary carcinoma with no microscopic evidence of cancer cell invasion through the basement membrane. However, for initiation of invasion, tumour cells have to acquire and focus proteolytic activity on to the cell surface in order to infiltrate the surrounding extracellular matrix. The receptor (uPA-R or CD87) for the serine protease urokinase-type plasminogen activator (uPA) plays a central role in invasion and metastasis. This study was performed to determine and localize m-RNA and protein of uPA-R in ductal carcinoma in situ of the breast. Methods and results: We analysed uPA-R mRNA and protein expression by in-situ hybridization and immunohistochemistry, respectively in 50 formalin-fixed, paraffin-embedded specimens of DCIS. Three different antibodies were used to stain cell-associated uPA-R; chicken polyclonal antibody (pAb) HU277 and monoclonal antibodies (mAb) IID7 and 3936. In all cases, myoepithelial and stromal cells reacted with either antibody. Especially, reaction of macrophage-like cells with mAb 3936 resulted in a well-marked and bright staining. Applying mAb IID7, in 46 of the 50 breast specimens tumour cells showed a positive immunoreaction. Likewise pAb HU277 stained tumour cells in 40 of the 50 cases, whereas mAb 3936 reacted with only 24 of the 50 tissue sections. Endothelial cells were marked by both mAb IID7 and pAb HU277 (46/50 and 35/50, respectively); mAb 3936 did not label at all. All of the cell types stained by mAb IID7 and pAb HU277 also displayed reactivity with uPA-R mRNA-specific antisense oligonucleotides in in-situ hybridization. Conclusions: Our results reveal the presence of the tumour invasion-related receptor for the protease uPA not only in invasive ductal breast carcinoma but also in different types of DCIS.