Cathepsin B (CTSB)

Author: Nat Pernick, M.D. (see Authors page)

Revised: 23 November 2015, last major update September 2012

Copyright: (c) 2003-2015,, Inc.

PubMed Search: cathepsin b[title]
  • Lysosomal cysteine protease associated with focal adhesions, inhibited by cystatin C, an endogenous cysteine protease inhibitor
  • Usually acts only in cell cytoplasm, but in malignant tumors is secreted extracellularly and degrades extracellular matrix so tumor cells can invade
  • Highest staining at invasive edge of tumor
  • Acts as effector of invasion in HER2+ breast cancer (Mol Cell 2012;45:764), inflammatory breast cancer (Breast Cancer Res 2011;13:R115), prostate cancer (Int J Cancer 2012;131:2034)
  • In gliomas, radiation treatment increases cathepsin B levels, suggesting that inhibition may be useful therapy (Neuro Oncol 2012;14:745, Mol Carcinog 2012;52:777)
  • Inhibition may limit breast cancer metastases (Cancer Res 2012;72:1199)
Clinical Features
Uses by Pathologists
Micro Images

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Skin: normal

Breast: inflammatory carcinoma and breast cancer NOS

Colon cancer

Prostate: benign and malignant

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Lung: nonsmall cell lung cancer-tumor associated macrophages

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Salivary glands (minor) in patients with Sjögren's Syndrome (fig C/D)

Positive Staining - Normal
  • Bowel, prostate, skin, thyroid; some endothelial cells
Positive Staining - Disease