Reevaluating cathepsin D as a biomarker for breast cancer: serum activity levels versus histopathology

Abbott, D. E.; Margaryan, N. V.; Jeruss, J. S.; Khan, S.; Kaklamani, V.; Winchester, D. J.; Hansen, N.; Rademaker, A.; Khalkhali-Ellis, Z.; Hendrix, M. J.

Cancer Biol Ther. 2009 Nov 20; 9(1):23-30

Abstract

Cathepsin D is a lysosomal hydrolase involved in intra- and extracellular proteolysis. This enzyme is aberrantly produced and processed in malignancy, and most notably is over-secreted into the tumor cell microenvironment. This hyper-secretion may lead to excessive degradation of the extracellular matrix, and contribute to tumor progression and metastases. These phenomena have been established in vitro, and there is evidence that Cathepsin D is similarly dysregulated in human breast cancer patients. Because breast cancer lacks an effective screening or surveillance biomarker, here we address the hypothesis that serum Cathepsin D activity may be useful to assess the presence or progression of breast cancer in females. While representative histologic sections from various disease-specific cohorts confirm previous findings that increased Cathepsin D production and secretion correlate with tumor progression, we report no difference in serum Cathepsin D activity between patients who are disease free, patients with pre-invasive or limited invasive disease, and patients with metastatic disease. Furthermore, in patients with known metastatic disease, there were no clinical variables associated with significantly different serum Cathepsin D activity. However, the immunohistochemical localization of Cathepsin D expression in histopathologic sections from breast cancer patients correlates with disease progression. Based on the serum results, and in contradistinction to Cathepsin D localization in breast cancer tissues, our findings support using Cathepsin D as a reliable histopathology biomarker for disease progression, but not for serum screening.

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