English

Prostate Cancer

Chromoa (CHROMOGRANIN A)

Chromogranin A

Free prostate specific antigen

Prostate specific antigen

Prostatic acid phosphatase

Chromogranin A (CGA)

Reference :

CGA-RIACT

For research use in the USA.

Chromogranin A (CGA) is an acid protein of 439 aa (49kD). One of the granin family, it is located in the secretion granules of the neuroendocrine cells. CGA is a pro-hormone which undergoes maturation by proteolytic cleavage. This gives bio-active peptides (vasostatins, chromostatin, pancreastatin, parastatin etc.) which have paracrine and autocrine functions. Circulating CGA is present in healthy subjects, and the values obtained are independent of age and of sex. CGA is a specific marker for neuroendocrine tumors.

Sequence of human CGA and position of the different epitopes The stars and the corresponding numbers indicate the potential dibasic cleavage sites for human CGA:

Clinical interest :

The interest of seric CGA assay was first shown in pheochromocytoma, then rapidly extended to other endocrine cancers with particularly significant high rates in intestinal carcinoids and in neuroendrocrine tumors of the pancreas. Unlike other biological markers, for example plasmatic catecholamines, the rates of CGA are affected by neither stress nor the drugs used in the treatment of pheochromocytomas. The rate of circulating CGA is associated with a neuroendocrine differentiation and linked to the tumor mass. Some authors have also shown that the presence of CGA in prostate cancers indicates an unfavorable evolution. These pathological rates can be associated with a decreased survival, independently of the disease’s stage.

Clinical interest :

Immunoradiometric technique, the assay is carried out on samples of serum or of plasma (attention : for plasma, the values are systematically higher). The CGA-RIACT kit is based on a sandwich technique, using a solid phase. Two monoclonal antibodies were prepared against two different antigenic sites of CGA. · The first antibody is bound to the solid phase · The second, labeled with 125 Iodine, is used as the tracer The assay takes place in 2 steps, with a first incubation overnight at room temperature, and a further 2-hour incubation under shaking.