The Clinical Significance of Cathepsin S Expression in Human Astrocytomas

Abstract

Early local invasion by astrocytoma cells results in tumor recurrence even after apparent total surgical resection, leading to the poor prognosis associated with malignant astrocytomas. Proteolytic enzymes have been implicated in facilitating tumor cell invasion and the current study was designed to characterize the expression of the cysteine proteinase cathepsin S (CatS) in astrocytomas and examine its potential role in invasion. Immunohistochemical analysis of biopsies demonstrated that CatS was expressed in astrocytoma cells but absent from normal astrocytes, oligodendrocytes, neurones and endothelial cells. Microglial cells and macrophages were also positive. Assays of specific activity in 59 astrocytoma biopsies confirmed CatS expression and in addition demonstrated that the highest levels of activity were expressed in grade IV tumors. CatS activity was also present in astrocytoma cells in vitro and the extracellular levels of activity were highest in cultures derived from grade IV tumors. In vitro invasion assays were carried out using the U251MG cell line and the invasion rate was reduced by up to 61% in the presence of the selective CatS inhibitor 4-Morpholineurea-LeuHomoPhe-vinylsulphone. We conclude that CatS expression is up-regulated in astrocytoma cells and provide evidence for a potential role for CatS in invasion. Astrocytomas are the commonest primary brain tumors and within this group the malignant grade III and IV tumors predominate (anaplastic astrocytomas and glioblastomas). Despite their non-metastatic nature, prognosis is poor because tumor infiltration of surrounding brain leads to recurrence even after apparently radical surgery. Multiple stereotactic biopsies of astrocytomas have demonstrated isolated tumor cells at considerable distances from the main tumor mass, 1 and recent investigations 2 have shown that tumor cells may be cultured from histologically normal brain at a distance greater than 4 cm from the gross tumor. Astrocytoma invasion is an active process that involves interactions with the host extracellular matrix (ECM), proteolytic modification of the ECM, and migration of the tumor cells into the modified matrix. 3 Members of the metalloproteinase, serine proteinase, and cysteine proteinase superfamilies have been linked to glioma invasion. 4 The cysteine proteinase cathepsin B (CatB) is expressed in gliomas in vitro 5 and immunohistochemical studies have demonstrated its presence in astrocytomas and glioblastomas in contrast to its absence from astrocytes in normal brain. 6,7 The expression and activity of CatB is higher in anaplastic astrocytomas and glioblastomas compared with low-grade tumors and normal brain 8 and high levels of CatB are positively correlated with poor survival. 9 Human glioblastoma cell lines also exhibit higher levels of CatB expression than lower grade astrocytomas 10 and the functional relevance of the enzyme is confirmed by a marked reduction in in vitro invasiveness of a glioblastoma cell line transfected with antisense CatB cDNA. 11 There is evide...

Cathepsin S is aberrantly overexpressed in human hepatocellular carcinoma

“…overexpression of cathepsin S has been reported in several types of human cancer in the lung (7), prostate (8), brain (9) and pancreas (4). In the present study, we showed for the first time that cat S was not expressed or expressed at a very low basal level in the hepatocytes of normal human livers, but was greatly elevated in cancerous hepatocytes in a significant percentage of human hepatocellular carcinoma livers.…”

“…in addition, cat S was found to be overexpressed in endothelial cells in a late-stage liver tumor in a genetic mouse model of Hcc (6), suggesting a role for cat S in angiogenesis and cancer metastasis. in humans, cat S has been implicated in several types of cancers, including lung cancer (7), prostate cancer (8) and astrocytoma (9). Based on this new evidence, cat S was proposed as a potential drug target for cancer therapy (3,10).…”

Effects of novel human cathepsin S inhibitors on cell migration in human cancer cells

“…The expression of Cat S together with Cat B was found in neoplastic prostatic cells from pre-invasive to invasive and clinically detectable stage 8 . Cat S is expressed in astrocytoma derived from brain tumor cell cultures, but not in those cells from normal astrocytes, oligodendrocytes, neurons and endothelial cells 9 . The highest levels of Cat S activity were also found in grade IV tumors among 59 astrocytoma biopsies 10 .…”

“…The invasive and pro-angiogenic effects in preclinical and clinical evaluation were blocked by antibody Fsn0503 against Cat S 6 . The invasive behavior in U251MG glioblastoma cells was disrupted by a peptidic, irreversible Cat S inhibitor, 4-morpholineureaLeu-HomoPhe-vinylsulphone 9 . These studies indicate that Cat S correlates with cancer migration and invasion and is a potential target for anti-migration and anti-invasive therapy 14,15 .…”

Recombinant cathepsin S propeptide attenuates cell invasion by inhibition of cathepsin L–like proteases in tumor microenvironment

“…In vitro Invasion Assays In vitro invasion assays were done as described previously (18). Briefly, cells were incubated in the presence of predetermined concentrations of rCatSPP, rCatSPP-Fc, or appropriate controls, and invasion plates were incubated at 37jC and 5% CO 2 for 24 h. Noninvaded cells were removed and invaded cells were fixed in Carnoy's fixative for 15 min.…”