Introduction 1 2 Matrix Metalloproteases and Plasminogen Activators 1 Figure 1 86 87 2 2 88 2 2  3 4 5 6 7 3 4 8 9 8 10 11 http://web.uniovi.es/degradome/ 12 13 14 15 7 13 16 Several members of the MMP and PA systems are involved in breast cancer progression. We will focus on the role played by these extracellular protease families during the various stages of breast cancer progression, from the initial hyperplastic lesion to disseminated disease, with particular emphasis on the insight gained from transgenic mouse models. Mouse Models of Breast Cancer 17 18 19 20 21 22 23 17 17 24 http://emice.nci.nih.gov/ 23 1 1 25 26 27 28 23 29 32 29 32 1 25 30 32 30 32 31 25 30 32 31 32 33 34 33 34 Table 1 PA system and MMP intervention studies in transgenic and chemically induced breast cancer models. Proteolytic intervention Mouse br.ca. model Phenotypic effect on mammary neoplasia Reference   tumor incidence tumor onset tumor growth rate final tumor size lung metastasis incidence lung metastasis burden comments and additional phenotypes  Plg activation system Plg null MMTV-PymT ↔ ↔ (↓ trend) ↔ ↔ ↓ ↓ reduced metastasis in 129:BSw:FVB mixed strain but not in FVB mice 44 uPA null MMTV-PymT ↔ ↔(↓ trend) ↔ ↔ ↔ ↓ + reduced lymph node metastasis 31 PAI-1 null MMTV-PymT ↔ ↔ ↔ ↔ ↔ ↔ (↑ trend) tumor vascularization not affected 45 uPAR null MMTV-PymT ↔ ↔ ↔ ↔ ↔ ↔ no phenotype in the FVB strain unpublished data MMP protease family  MMP overexpression MMTV-MMP-3 transgene none yes*      *tumors develop in the CD1 mouse strain but not in mixed B6:DBA mice 33 61 90 WAP-MMP-3 transgene none yes*      *tumors develop in the CD1 mouse strain but not in FVB mice 62 90 MMTV-MMP-7 transgene none no      hyperplasia in multiparous mice but no tumors develop spontaneously 29 MMTV-MMP-14 transgene none yes      tumors develop spontaneously 63 MMTV-MMP-3 transgene DMBA gavage ↓ ↓     opposite expectation 33 MMTV-MMP-3 transgene DMBA gavage + MMTV-TGFα ↔ ↔      33 MMTV-MMP-7 transgene MMTV-neu ↑ ↑ ↔  ↔   29 MMTV-MMP-7 transgene ApcMin + ENU ↔       91  MMP inhibition MMP inhibitor-treatment (galardin/GM6001) MMTV-PymT    ↓ ↓ ↓  unpublished data MMP-2 null MMTV-PymT ↔ ↔ ↔ ↔ ↓ ↓  Fingleton and Matrisian, pers. comm. MMP-7 null MMTV-PymT ↔ ↔ ↔ ↔ ↔ ↔  Fingleton and Matrisian, pers. comm. MMP-7 null ApcMin + ENU ↓      transient reduction in number of mammary tumors 91 MMP-9 null MMTV-PymT ↔ ↔ ↔ ↔ ↓ ↓ reduced metastasis in mixed B6:FVB mouse strain but not in FVB mice Fingleton and Matrisian, pers. comm. MMP-9 null MMTV-neu  ↑      67 MMP-11 null MMTV-ras ↔ ↓  ↓ ↑  bidirectional effect 30 MMP-11 null DMBA gavage ↓   ↓   ovarian and mammary carcinomas 66 MMP-13 null MMTV-PymT ↔ ↔ ↔ ↔ ↔ ↔  unpublished data WAP-TIMP-1 transgene WAP-MMP-3 ↓      reduced incidence of hyperplasias, no tumors develop 62 Albumin-TIMP-1 transgene DMBA gavage + MPA ↓      early hyperplasia not affected 34 Albumin-TIMP-1 transgene MMTV-PymT ↔   ↓ ↓ ↔  34 MMTV-TIMP-1 transgene DMBA gavage + MPA    ↔    34 MMTV-TIMP-1 transgene MMTV-PymT    ↔ ↔ ↔  34 MMTV-TIMP-2 transgene MMTV-Wnt1 ↓ ↓ ↓ ↓   reduced mean vessel size in tumors 32 TIMP-2 gene therapy MMTV-neu    ↓ ↓   92 ApcMin Apc BSw DMBA ENU N MMP MMTV MPA PAI-1 Plg PymT TIMP uPA uPAR WAP 35 36 20 mammary intraepithelial neoplasia 37 38 39 17 Protease Expression in Transgenic Breast Cancer Models 5 40 42 2 43 31 43 46 46 47 48 49 50 49 35 51 10 52 3 35 43 3 45 48 3 53 Figure 2 31 45 43 46 47 48 52 49 50 89 72 89 49 35 51  Figure 3 a b c d arrows e f arrows a c f b 35 Bars a c b d f  32 35 51 3 35 54 3 36 Thus, the extracellular proteases expressed in transgenic breast cancer models generally mirror those identified in human breast cancer both in terms of expression and localization. These findings suggest that transgenic models are useful tools for the study of protease involvement in breast cancer invasion and metastasis. Functional Studies of Proteases in Breast Cancer Progression Proteases in Post-lactational Mammary Gland Involution 55 5 40 56 luminal 16 57 stromal 40 58 57 59 16 57 Proteases in Hyperplasia and Carcinogenesis 60 29 61 63 62 63 64 65 46 61 1 29 30 32 66 34 33 67 68 44 31 45 34 Proteases in Tumor Growth and Vascularization 69 3 47 48 52 1 44 31 45 45 11 70 71 72 1 34 32 66 30 73 74 Proteases in Cancer Metastasis 28 25 75 75 77 78 79 28 31 1 31 45 31 44 45 80 81 76 77 82 83 10 84 34 43 84 29 30 73 85 Conclusion and Future Perspectives Transgenic breast cancer models are invaluable research tools because they recapitulate the entire process from the initial genetic events in normal cells to metastatic disease. Furthermore, the very similar expression patterns of extracellular proteases in human and mouse breast cancer samples suggest that transgenic mouse models are ideally suited to study the role of proteases in carcinogenesis and the progression to invasion and metastasis. delayed slower reduced prevention Another area that has so far only been thoroughly examined in one or two transgenic models is the expression patterns of proteases. Using protease array data, it may be possible to draw some more detailed parallels between individual mouse models and certain histopathological subtypes of human breast cancers. It is very possible that the collective of transgenic breast cancer models available, rather than any single transgenic, will be needed to adequately model the heterogenous human disease. Another open question is whether certain proteases or inhibitors are up- or downregulated in response to certain gene deficiencies. This may provide vital information on functional overlap between individual proteases. Transgenic breast cancer mice may prove to be very reliable models not only for basic research but also for testing experimental anti-proteolytic therapeutics, due to the high degree of similarity with human breast cancer. However, the transgenic models also present some significant challenges. A key issue is that the experimental drug has to cross-react with the mouse version of the protease. Therefore, it may be necessary in some cases to develop two drugs in parallel, one for each species. Due to the extracellular nature of the PA and MMP systems, these represent excellent targets for therapeutic monoclonal antibodies. An elegant method for targeting extracellular proteases in transgenic mice is the development of monoclonal anti-mouse antibodies by immunizing protease-deficient mice with the target protease. In conclusion, transgenic breast cancer models will further the identification of extracellular proteases critical to cancer invasion and metastasis, and aid the development of new agents against the spread of cancer.