Localization of cathepsin B in two human lung cancer cell lines.
We demonstrated the cysteine proteinase cathepsin B in two human lung tumor cell lines by cytochemical and immunocytochemical methods. The cell lines were derived from a squamous cell carcinoma of the lung (HS-24) and a metastasis to the adrenal gland from an adenocarcinoma of the lung (SB-3). For comparison and control, normal human lung fibroblasts cells (Wi-38) were also investigated. Intracellular cathepsin B activity was detected in all three cell lines. SB-3 and the normal fibroblast cells showed almost equal cathepsin B activity, which was considerably stronger than that in the HS-24 cells. Specific inhibitors for cathepsin B (E64, leupeptin, antipain) suppressed its activity completely. Stefin A, the physiological cathepsin B inhibitor, was less effective; this might depend on its limited penetrability into living cells. Localization of the cathepsin B was performed by conventional immunofluorescence microscopy and laser scanning microscopy. With specific anti-cathepsin B antibodies, the enzyme was localized in HS-24, SB-3, and Wi-38 fibroblast cells within perinuclear granules representing the lysosomal compartment. In the SB-3 cells, we additionally localized a minor fraction of the enzyme bound to the plasma membrane in a speckled distribution, accessible to the antibodies from the outside. This direct demonstration of cathepsin B distribution supports biochemical data about the dual localization of the enzyme in tumor cells. It also supports the possibility of a direct involvement of cathepsin B in the degradation of the extracellular matrix, and thus a contribution of the enzyme in invasion and metastasis.
Thoraxklinik Heidelberg-Rohrbach, Federal Republic of Germany.
M
M
Erdel
G
G
Trefz
E
E
Spiess
S
S
Habermaas
H
H
Spring
T
T
Lah
W
W
Ebert
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D002401:Cathepsin B / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D005347:Fibroblasts / Q000378:metabolism / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D008247:Lysosomes / Q000378:metabolism / Q000648:ultrastructure; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure
D002401:Cathepsin B