title: Proteolysis-a characteristic of tumor-initiating cells in murine metastatic breast cancer.
abstract: Tumor initiating cells (TICs) have been identified and functionally characterized in hematological malignancies as well as in solid tumors such as breast cancer. In addition to their high tumor-initiating potential, TICs are founder cells for metastasis formation and are involved in chemotherapy resistance. In this study we explored molecular pathways which enable this tumor initiating potential for a cancer cell subset of the transgenic MMTV-PyMT mouse model for metastasizing breast cancer. The cell population, characterized by the marker profile CD24+CD90+CD45-, showed a high tumorigenicity compared to non-CD24+CD90+CD45- cancer cells in colony formation assays, as well as upon orthotopic transplantation into the mammary fat pad of mice. In addition, these orthotopically grown CD24+CD90+CD45- TICs metastasized to the lungs. The transcriptome of TICs freshly isolated from primary tumors by cell sorting was compared with that of sorted non-CD24+CD90+CD45- cancer cells by RNA-seq. In addition to more established TIC signatures, such as epithelial-to-mesenchymal transition or mitogen signaling, an upregulated gene set comprising several classes of proteolytic enzymes was uncovered in the TICs. Accordingly, TICs showed high intra- and extracellular proteolytic activity. Application of a broad range of protease inhibitors to TICs in a colony formation assay reduced anchorage independent growth and had an impact on colony morphology in 3D cell culture assays. We conclude that CD24+CD90+CD45- cells of the MMTV- PyMT mouse model possess an upregulated proteolytic signature which could very well represent a functional hallmark of metastatic TICs from mammary carcinomas.
authors.affiliation: Institute of Molecular Medicine and Cell Research, Medical Faculty, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|Faculty of Biology, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|BIOSS Centre for Biological Signalling Studies, Freiburg, Germany.
authors.forename: Larissa E
authors.initials: LE
authors.lastname: Hillebrand
authors.affiliation: Institute of Molecular Medicine and Cell Research, Medical Faculty, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
authors.forename: Fee
authors.initials: F
authors.lastname: Bengsch
authors.affiliation: Institute of Molecular Medicine and Cell Research, Medical Faculty, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|Systems Biology of the Cellular Microenvironment Group, Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|Comprehensive Cancer Center Freiburg, Freiburg, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Hochrein
authors.affiliation: Institute of Molecular Medicine and Cell Research, Medical Faculty, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Hülsdünker
authors.affiliation: Institute of Molecular Medicine and Cell Research, Medical Faculty, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Bender
authors.affiliation: Department of Hematology/Oncology, Core Facility, University Medical Center, Freiburg, Germany.
authors.forename: Marie
authors.initials: M
authors.lastname: Follo
authors.affiliation: Institute of Molecular Medicine and Cell Research, Medical Faculty, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|Systems Biology of the Cellular Microenvironment Group, Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|Comprehensive Cancer Center Freiburg, Freiburg, Germany.|German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Hauke
authors.initials: H
authors.lastname: Busch
authors.affiliation: Institute of Molecular Medicine and Cell Research, Medical Faculty, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|Systems Biology of the Cellular Microenvironment Group, Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|Comprehensive Cancer Center Freiburg, Freiburg, Germany.|German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Boerries
authors.affiliation: Institute of Molecular Medicine and Cell Research, Medical Faculty, Albert-Ludwigs-University Freiburg, Freiburg, Germany.|BIOSS Centre for Biological Signalling Studies, Freiburg, Germany.|Comprehensive Cancer Center Freiburg, Freiburg, Germany.|German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Reinheckel
mesh_terms: D000818:Animals; D051927:CD24 Antigen / Q000378:metabolism; D063646:Carcinogenesis; D018929:Cell Culture Techniques; D049109:Cell Proliferation; D002469:Cell Separation; D002471:Cell Transformation, Neoplastic / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D017493:Leukocyte Common Antigens / Q000378:metabolism; D015674:Mammary Neoplasms, Animal / Q000473:pathology* / Q000628:therapy; D053511:Matrix Metalloproteinase 14 / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009362:Neoplasm Metastasis; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D010447:Peptide Hydrolases / Q000378:metabolism; D059748:Proteolysis; D017423:Sequence Analysis, RNA; D015398:Signal Transduction; D018800:Thy-1 Antigens / Q000378:metabolism; D059467:Transcriptome
chemical_list: D051927:CD24 Antigen; C497890:Cd24a protein, mouse; C507096:Mmp14 protein, mouse; D018800:Thy-1 Antigens; D017493:Leukocyte Common Antigens; C516770:Ptprc protein, mouse; D010447:Peptide Hydrolases; D053511:Matrix Metalloproteinase 14
keywords: breast cancer; degradome; matrix metalloproteinase; proteolysis