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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 dots 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.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 :
The CHROMOGRANIN A kit is an ELISA-type immunoassay. A first monoclonal antibody, immobilized on the microplate, captures
the CGA proteins contained in the calibrators and samples. After washing, the fixed proteins are then recognized by a second
monoclonal antibody conjugated to HRP (Horse-Radish-Peroxidase). After a second incubation, the unfixed reagents are
eliminated by washing. Then the colorimetric reaction is started by the addition of an HRP substrate, TMB (3, 3', 5, 5' Tetramethyl
benzidine). After the reaction is stopped, the optical density (OD) of each well is read at 450 nm. The OD values measured are
proportional to the CGA protein concentration contained in the calibrators and samples.
Method advantageous :
- Secure patient follow-up :
Intra-assay CVs<6%
Inter-assays CVs<12% Thanks to highly specific antibodies against the unprocessed central domain of CGA (145-245) 2 protocoles available, 2h+2h or ON+2h Easy to automate
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