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Chromogranin A in Physiology and Oncology

Publication at First Faculty of Medicine |
2011

Abstract

Chromogranin A (CgA) is a hydrophilic acidic one-chain peptide containing 439 amino acids, preceded by NH(2)-terminal 18-amino-acid signal peptide; the complete pre-chromogranin A molecule thus encompasses 457 amino acids. It is a member of the chromogranin family that comprises several proteins.

The CgA gene is a single-copy gene localized in the locus 14q32. Chromogranin A is produced by endocrine and neuroendocrine cells.

The largest amount of CgA occurs in chromaffin granules of adrenal medulla and in the dense-core vesicles of sympathetic nerves. Its biological functions have not been completely elucidated, but it is known that it acts as a precursor of many biologically active peptides generated by cleavage at specific sites.

It is the major soluble protein co-stored and co-released along with resident catecholamines and polypeptide hormones or cell-specific neurotransmitters. Because of its widespread distribution in neuroendocrine tissue, it can be used both as immunohistochemical marker and serum marker of neuroendocrine tumours.

CgA has been used as a rather reliable tumour marker because its level is significantly increased in neuroendocrine tumours and changes of its level reflect the tumour response to therapy or tumour recurrence.