The calcium-binding protein calretinin-22k is detectable in the serum and specific cells of cancer patients.

BACKGROUND

Calretinin-22k (CR-22k), an alternatively spliced form of calretinin (CR) belongs to the EF-hand family of calcium-binding proteins and is expressed in several colon adenocarcinoma cell lines (e.g. WiDr, HT-29).

MATERIALS AND METHODS

Serum samples of cancer patients were screened with a sandwich ELISA technique using the CR-specific antiserum 7696. Highly positive samples were analyzed by Western blots and immunohistochemistry.

RESULTS

CR-22k was detected in the serum of several patients and values were as high as 0.19 microgram/ml. Western blot analysis confirmed the identity of the bound protein as CR-22k. The highest concentrations were detected in patients with colon or breast cancer, but also in a patient with ischemic necrosis of the gut. CR immunoreactivity was localized to epithelial cells, nerve fibres, cells of the connective tissue and to mesothelial cells.

CONCLUSIONS

Our results establish that CR-22k is detectable in the serum of cancer patients under specific pathological conditions.