Stromal cells associated with early invasive foci in human mammary ductal carcinoma in situ coexpress urokinase and urokinase receptor

Abstract

The transition from ductal carcinoma in situ (DCIS) of the breast to invasive ductal carcinoma is facilitated by proteolytic degradation of basement membrane. The transition can be identified as microinvasive foci in a small proportion of DCIS lesions. We have previously found that MMP-13 is frequently expressed in such foci. To establish whether plasmin-directed proteolysis is likely to be involved in early invasion, we have here studied the expression of urokinase plasminogen activator (uPA) and its receptor (uPAR) in human DCIS lesions with and without microinvasion. uPA mRNA was detected in periductal stromal cells in all of 9 DCIS lesions with microinvasion and in 2 of 9 DCIS lesions without microinvasion by in situ hybridization. The uPA mRNA signal was seen in numerous stromal cells in microinvasive areas together with MMP-13 mRNA expressing cells. Double immunofluorescence analyses, using emission fingerprinting, showed that the uPA expressing stromal cells included both myofibroblasts and macrophages. The early invasive carcinoma cells were negative for uPA. uPAR immunoreactivity was focally upregulated in periductal stromal cells in all of the 9 DCIS lesions with microinvasion and in only 2 of the 9 DCIS lesions without microinvasion. uPAR was seen in both macrophages and myofibroblasts in microinvasive areas, and it was evident that uPA and uPAR colocalized in both fibroblast-like cells and macrophage-like cells. We conclude that periductal macrophages and myofibroblasts are strongly involved in the initial steps of breast cancer invasion by focally upregulating the expression of the plasminogen activation system and MMP-13. ' 2007 Wiley-Liss, Inc.Key words: breast cancer; DCIS; microinvasion; uPA; uPAR Ductal carcinoma in situ (DCIS) of the human breast is a preinvasive lesion where the intraductal neoplastic epithelial cells are situated on a layer of myoepithelial cells and a basement membrane. After introduction of systematic mammography screening the frequency of diagnosed DCIS has increased from around 1% to 20% of the detected cancers.1 Up to 20% of the DCIS lesions contain minor foci of early invasion 2 and therefore display an important tool for studying the transition from noninvasive to invasive carcinoma.The transition from DCIS to invasive ductal breast cancer is accompanied by degradation of the extracellular matrix (ECM) including the basement membrane, allowing the neoplastic cells to invade the interstitial tissue. In a previous study, we found that the expression of the mRNA for the potent collagenase, matrix metalloprotease 13 (MMP-13), is uniquely associated with early invasive events.3 Plasmin is another potent protease, which degrades basement membrane laminin and a number of other ECM proteins like fibrin and fibronectin and also activates several MMPs, including MMP-13. [4][5][6] Plasmin is generated in situ from its proenzyme, plasminogen, after proteolytic cleavage by plasminogen activators (PA). Urokinase-type PA (uPA) is secreted from cells as pro-uPA and binds to cell s...

Direct evidence of the importance of vitronectin and its interaction with the urokinase receptor in tumor growth

“…32 In ductal cancer in situ VN colocalize with collagen IV in the basement membrane and in adjacent periductal zones. 32,33 This location coincides with areas where a prominent expression of uPA, PAI-1, and uPAR is observed by myofibroblasts located in the vicinity of microinvasive lesions, 34 supporting a possible functional link between the biological activity of these molecules and the onset of invasive tumor growth. Expression of uPAR by malignant epithelial cells is the exception in ductal breast cancer, 35 and further experiments are required to determine if the importance of VN is restricted to uPAR-positive tumors cells or if it also acts on the stromal compartment.…”

Prognosis in adenocarcinomas of lower oesophagus, gastro‐oesophageal junction and cardia evaluated by uPAR‐immunohistochemistry

“…34 In colorectal adenocarcinomas, gastric carcinomas and breast carcinomas uPAR is localised to macrophages and myofibroblasts as well as to some cancer cells. 9,17,35 In squamous cell carcinoma (SCC) of the oral cavity, the receptor is predominantly observed in macrophages but also in fibroblasts and neutrophils. 36,37 uPAR-positive neoplastic cells found in areas with incipient and invasive SCC are in addition reported to express laminin-5c2, 37 which is a marker for invasiveness.…”

Structure-based Engineering of Species Selectivity in the Interaction between Urokinase and Its Receptor

“…Covalently immobilized muPAR (231 resonance units (RU) ϳ 7 fmol/mm 2 ) on the sensor chip was initially saturated by injection of 200 nM mATF (yielding a B max of 50 RU ϳ 3.1 fmol/mm 2 ), and the interaction of this mATF⅐muPAR complex with hSMB was subsequently probed by additional injections of a 2-fold dilution of hSMB (10 uPAR in xenotransplanted tumors do not take into account the different targeting efficiency that is encountered by cancer cells and the host-derived tumor-associated stromal cells. This is of paramount importance as most human cancers indeed exhibit a pronounced expression of uPAR by such "tumor-educated stromal cells" (11,55). A general uPAR antagonist engaging the binding pocket normally occupied by site 1 residues would thus circumvent the need for such precautions.…”

“…Several independent studies have correlated uPAR expression in vivo to e.g. neutrophil infiltration (8 -10) and to various pathological conditions such as cancer invasion and metastasis (11)(12)(13), hepatic fibrin deposition (14,15), and kidney barrier function (16). Accordingly, uPAR has been proposed as a promising molecular target for intervention and/or cytotoxin-based cancer therapies (14,17,18).…”