title: Fibroblast activation protein-α, a stromal cell surface protease, shapes key features of cancer associated fibroblasts through proteome and degradome alterations.
abstract: Cancer associated fibroblasts (CAFs) constitute an abundant stromal component of most solid tumors. Fibroblast activation protein (FAP) α is a cell surface protease that is expressed by CAFs. We corroborate this expression profile by immunohistochemical analysis of colorectal cancer specimens. To better understand the tumor-contextual role of FAPα, we investigate how FAPα shapes functional and proteomic features of CAFs using loss- and gain-of function cellular model systems. FAPα activity has a strong impact on the secreted CAF proteome ("secretome"), including reduced levels of anti-angiogenic factors, elevated levels of transforming growth factor (TGF) β, and an impact on matrix processing enzymes. Functionally, FAPα mildly induces sprout formation by human umbilical vein endothelial cells. Moreover, loss of FAPα leads to a more epithelial cellular phenotype and this effect was rescued by exogenous application of TGFβ. In collagen contraction assays, FAPα induced a more contractile cellular phenotype. To characterize the proteolytic profile of FAPα, we investigated its specificity with proteome-derived peptide libraries and corroborated its preference for cleavage carboxy-terminal to proline residues. By "terminal amine labeling of substrates" (TAILS) we explored FAPα-dependent cleavage events. Although FAPα acts predominantly as an amino-dipeptidase, putative FAPα cleavage sites in collagens are present throughout the entire protein length. In contrast, putative FAPα cleavage sites in non-collagenous proteins cluster at the amino-terminus. The degradomic study highlights cell-contextual proteolysis by FAPα with distinct positional profiles. Generally, our findings link FAPα to key aspects of CAF biology and attribute an important role in tumor-stroma interaction to FAPα.
authors: Institute of Molecular Medicine and Cell Research, University of Freiburg, D-79104 Freiburg, Germany.
authors: M M
authors: MM
authors: Koczorowska
authors: Institute of Molecular Medicine and Cell Research, University of Freiburg, D-79104 Freiburg, Germany.
authors: S
authors: S
authors: Tholen
authors: University Eye Hospital Freiburg, Killianstrasse 5, 79106 Freiburg, Germany.
authors: F
authors: F
authors: Bucher
authors: Institute of Surgical Pathology, Department of Pathology, University Medical Center, Freiburg, Germany.
authors: L
authors: L
authors: Lutz
authors: Centre for Blood Research, University of British Columbia, Vancouver, BC V6T 1Z3, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC V6T 1Z3, Canada; Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
authors: J N
authors: JN
authors: Kizhakkedathu
authors: Laboratory of Experimental Cancer Research, Ghent University Hospital, 1P7, De Pintelaan 185, 9000 Gent, Belgium.
authors: O
authors: O
authors: De Wever
authors: Clinic for Surgery, UKSH Campus Lübeck, Lübeck, Germany.
authors: U F
authors: UF
authors: Wellner
authors: Institute of Molecular Medicine and Cell Research, University of Freiburg, D-79104 Freiburg, Germany.
authors: M L
authors: ML
authors: Biniossek
authors: University Eye Hospital Freiburg, Killianstrasse 5, 79106 Freiburg, Germany.
authors: A
authors: A
authors: Stahl
authors: Institute of Surgical Pathology, Department of Pathology, University Medical Center, Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany; German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors: S
authors: S
authors: Lassmann
authors: Institute of Molecular Medicine and Cell Research, University of Freiburg, D-79104 Freiburg, Germany; BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany; German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany. Electronic address: oliver.schilling@mol-med.uni-freiburg.de.
authors: O
authors: O
authors: Schilling
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000473:pathology*; D010450:Endopeptidases; D005347:Fibroblasts / Q000378:metabolism; D018093:Gelatinases / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D009363:Neoplasm Proteins / Q000378:metabolism*; D059748:Proteolysis; D020543:Proteome; D012697:Serine Endopeptidases / Q000502:physiology*; D017154:Stromal Cells / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D000099167:Fibroblast Activation Protein Alpha
chemical_list: D014408:Biomarkers, Tumor; D010450:Endopeptidases; D018093:Gelatinases; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D020543:Proteome; D012697:Serine Endopeptidases; D016212:Transforming Growth Factor beta; D000099167:Fibroblast Activation Protein Alpha
keywords: Angiogenesis; CAFs; Degradome; FAPα; Secretome; TGFβ