title: High expression of the cysteine proteinase legumain in colorectal cancer - implications for therapeutic targeting.
abstract: BACKGROUND
  The cysteine proteinase legumain is highly expressed in cancer. Legumain is a potential biomarker and has been suggested to be utilised for prodrug activation in cancer therapy. However, to define the suitability of legumain for such purposes, detailed knowledge of cell type-specific and subcellular expression together with proteolytic activity patterns in tumour tissue is necessary.
  
  
  METHODS
  Expression of legumain was examined in a panel of 277 primary tumours from colorectal cancer (CRC) patients using immunohistochemistry. Tumour (cytoplasmic diffuse, cytoplasmic granulated, and nuclear) and stromal cell expression of legumain was quantified, and associations with clinicopathological parameters and outcome were analysed. Additionally, normal colon tissue and spontaneous mouse tumours were stained for legumain.
  
  
  RESULTS
  Legumain was highly expressed in tumour and stromal cells. Nuclear legumain was detected in 30% of the tumours. In colon cancer patients, high legumain expression was associated with overall and metastasis-free survival (OS; MFS) in uni- and multivariate analysis. Nuclear legumain was associated with poor OS, but not MFS in the colon cancer subgroup. Cytoplasmic granulated or diffuse expression was not associated with OS or MFS. Normal epithelial cells exhibited granulated legumain mainly at the apical pole, and legumain was highly expressed in CD68 positive macrophages.
  
  
  CONCLUSIONS
  Legumain is a highly expressed proteinase in CRC and associated with poor outcome in colon cancer. Diversified localisation of legumain expression in tumour and stromal cells suggests multiple functions in CRC, representing both a challenge and an opportunity for use in therapeutic targeting.
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway; Focus Area HEALTH, Research Center MOLIFE - Molecular Life Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany. Electronic address: mads.haugen@rr-research.no.
authors.forename: Mads H
authors.initials: MH
authors.lastname: Haugen
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway; Department of Oncology, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway.
authors.forename: Kjetil
authors.initials: K
authors.lastname: Boye
authors.affiliation: Department of Pathology, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway; Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, PO Box 1171 Blindern, 0318 Oslo, Norway.
authors.forename: Jahn Martin
authors.initials: JM
authors.lastname: Nesland
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway.
authors.forename: Solveig J
authors.initials: SJ
authors.lastname: Pettersen
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway.
authors.forename: Eivind Valen
authors.initials: EV
authors.lastname: Egeland
authors.affiliation: Focus Area HEALTH, Research Center MOLIFE - Molecular Life Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
authors.forename: Tripti
authors.initials: T
authors.lastname: Tamhane
authors.affiliation: Focus Area HEALTH, Research Center MOLIFE - Molecular Life Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
authors.forename: Klaudia
authors.initials: K
authors.lastname: Brix
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway; Department of Pharmacy, Faculty of Health Sciences, University of Tromsø, N-9037 Tromsø, Norway.
authors.forename: Gunhild M
authors.initials: GM
authors.lastname: Maelandsmo
authors.affiliation: Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway; Department of Gastrointestinal Surgery, Oslo University Hospital, The Norwegian Radium Hospital, PO Box 4953 Nydalen, N-0424 Oslo, Norway.
authors.forename: Kjersti
authors.initials: K
authors.lastname: Flatmark
mesh_terms: D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000473:pathology / Q000628:therapy*; D003546:Cysteine Endopeptidases / Q000009:adverse effects / Q000378:metabolism*; D057056:Cysteine Proteases / Q000009:adverse effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D011355:Prodrugs; D011379:Prognosis; D000099240:Asparaginyl Endopeptidase
chemical_list: D003546:Cysteine Endopeptidases; D057056:Cysteine Proteases; D011355:Prodrugs; D000099240:Asparaginyl Endopeptidase
keywords: Asparaginyl endopeptidase (AEP); Cell nuclei; Colorectal cancer; Cysteine proteinase; Legumain; Prodrugs; S100A4