Cathepsin B and D are localized at the surface of human breast cancer cells

Abstract

Alterations in trafficking of cathepsins B and D have been reported in human and animal tumors. In MCF10 human breast epithelial cells, altered trafficking of cathepsin B occurs during their progression from a preneoplastic to neoplastic state. We now show that this is also the case for altered trafficking of cathepsin D. Nevertheless, the two cathepsins are not necessarily trafficked to the same vesicles. Perinuclear vesicles of immortal MCF10A cells label for both cathepsins B and D, yet the peripheral vesicles found in ras-transfected MCF10AneoT cells label for cathepsin B, cathepsin D or both enzymes. Studies at the electron microscopic level confirm these findings and show in addition surface labeling for both enzymes in the transfected cells. By immunofluorescence staining, cathepsin B can be localized on the outer surface of the cells. Similar patterns of peripheral intracellular and surface staining for cathepsin B are seen in the human breast carcinoma lines MCF7 and BT20. We suggest that the altered trafficking of cathepsins B and D may be of functional significance in malignant progression of human breast epithelial cells. Translocation of vesicles containing cathepsins B and D toward the cell periphery occurs in human breast epithelial cells that are at the point of transition between the pre-neoplastic and neoplastic state and remains part of the malignant phenotype of breast carcinoma cells.

Cathepsin B localizes to plasma membrane caveolae of differentiating myoblasts and is secreted in an active form at physiological pH

“…These results are similar to those reported for catB in human breast carcinoma cells (Sameni et al, 1995) and in U87 human glioma cells (Rempel et al, 1994).…”

“…To determine if catB is localized on the surface of differentiating myoblasts, we used an established protocol for the staining of surface proteins that does not permeabilize the cells and permits the differentiation of cell surface catB from lysosomal catB (Sameni et al, 1995) (Figure 6). Using this method, catB was detected as discrete containing Z-Arg-Arg-NHMec substrate and pericellular catB activity was measured continuously for 10-15 min at 378C.…”

“…Cells were seeded onto glass coverslips in differentiation medium and were used during proliferation (day 2), postmitotic (day 4) and fusing (day 6) stages of differentiation for intracellular or surface staining as previously described (Sameni et al, 1995). Intracellular staining was carried out at room temperature using saponin-permeablized cells, whereas surface staining was carried out at 48C using unpermeabilized cells.…”

The Clinical Significance of Cathepsin S Expression in Human Astrocytomas

“…11 There is evidence of altered trafficking of CatB in glioblastomas, with a redistribution of enzyme to the cell periphery. 12 In addition, a potential role in invasion has been suggested by high levels at the tumor periphery and in infiltrating cells. 6 The closely related cysteine proteinase cathepsin L (CatL) has also been implicated in glioblastoma invasion in an in vitro model.…”

Role of the Conserved Oligomeric Golgi Complex in the Abnormalities of Glycoprotein Processing in Breast Cancer Cells

“…Cathepsin D (CathD), an aspartyl lysosomal protease expressed in all tissues is secreted from carcinomas. A large number of independent clinical studies associated high Cath-D concentrations in primary breast cancers with increased risk of subsequent metastasis (14). Analysis of glycosylation of Mucinl and trafficking of the lysosomal enzyme Cath-D in COG3 KD breast cells line revealed that disturbance of COG complex function in HB2 cells lead to abnormalities of glycoprotein processing for Mucinl and its secretion into the medium ( Figure 5).…”