Cathepsin B/cystatin C complex levels in sera from patients with lung and colorectal cancer.
A sandwich-type ELISA has been developed for quantification of the complex between the cysteine proteinase cathepsin B (CB) and its reversible tight-binding inhibitor cystatin C (CC) in normal and pathological sera. The assay is based on a combination of catching Ab (3E1), raised against CB, and a horseradish peroxidase-labelled detection Ab (1A2), raised against CC. Only the CB/CC complex is able to evoke a signal in this assay. The detection limit of the assay was 15.5 nM and the working range between 31.3-200 nM. The within and between-run coefficients of variance (CV) varied from 4.7% to 9.4% and 11% to 12.8%, respectively, demonstrating satisfactory reproducibility of the method. The concentration of the CB/CC complex was determined in sera from 90 healthy controls, 32 patients with non-cancerous lung diseases, 148 patients with lung and 32 patients with colorectal cancer. The CB/CC complex was significantly less abundant in sera of patients bearing malignant lung tumours than in those with non-cancerous lung diseases or healthy controls (p<0.001). In colorectal cancer sera its level was significantly lower in advanced stages C and D than in early Dukes' stages A and B (p=0.02). Our results show that the increased levels of CB in malignant sera are not impaired effectively by CC and support the hypothesis of hindered inhibitory capability during cancer progression.
Zore
I
I
Krka, d.d., R & D Division, Department of Biochemical Research and Drug Design, Ljubljana, Slovenia.
Krasovec
M
M
Cimerman
N
N
Kuhelj
R
R
Werle
B
B
Nielsen
H J
HJ
Brünner
N
N
Kos
J
J
D016022:Case-Control Studies; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000097:blood*; D015179:Colorectal Neoplasms / Q000097:blood / Q000201:enzymology*; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D015853:Cysteine Proteinase Inhibitors / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000592:standards; D006801:Humans; D008175:Lung Neoplasms / Q000097:blood / Q000201:enzymology*; D011485:Protein Binding; D012680:Sensitivity and Specificity
C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D002401:Cathepsin B