A two‐site enzyme‐linked immunosorbent assay for cytokeratin 8

A monoclonal enzyme-linked immunosorbent assay (ELISA) was developed for the determination in biological fluids of cytokeratin 8, a potential marker for malignant diseases. Two monoclonal antibodies (MAbs), TS 3 and TS 4, with different epitope specificity, were selected from 4 cytokeratin-8 reactive antibodies. TS 3 was used for coating and TS 4 as HRP-conjugate, respectively. Antibodies were selected with the aim of optimizing the discriminatory capacity between cytokeratin 8 levels in sera from healthy persons and from patients with malignant diseases. In sera from healthy individuals the mean value was determined to be 3.1 +/- 2.3 ng/ml with an upper cut-off level of 7.8 ng/ml (+ 2 SD) using purified cytokeratin 8 as standard. Sera from patients with colon cancer and pancreatic cancer were found to have significantly elevated levels, showing a 4- to more than 10-fold increase compared with the normal level. In patients with ovarian cancer no significant elevation was seen. Cytokeratin 8 monitoring may be of value for patients with colon and pancreatic cancer.