Catestatin--a novel neuropeptide in carcinoid tumors of the appendix

The aim of the study was to investigate the immunohistochemical distribution of the novel neuropeptide catestatin in carcinoid tumors. Catestatin, a novel 21 amino acid neuropeptide derived from chromogranin A, was determined immunohistochemically in 30 carcinoid tumors of the appendix and various carcinoid tumors of other localities.

Paraffin-embedded tissues from 30 carcinoid tumors of the appendix and 16 other carcinoid tumors (5 bronchus-, 5 stomach-, 2 small bowel-, 4 large bowel carcinoid tumors) were incubated with antibodies specific for catestatin, chromogranin A and chromogranin B. Immunohistochemical staining of catestatin was compared to staining with chromogranin A and B. Western blot analysis was performed in one patient with ileal carcinoid.

Thirty patients (20 women, 10 men) with carcinoid tumors of the appendix and 16 patients with other localized carcinoid tumors were investigated. Twenty-six of the appendiceal tumors were localized in the apex of the appendix and 4 tumors in the midportion; none of the tumors was localized at the base of the appendix. Median tumor diameter was 10.7 mm (range 4-18 mm). Immunoreactivity to catesatatin was positive in 28 patients (negative in 2, 0-10% in 11 patients, 11-50% in 14 patients, 51-100% in 3 patients). In 16 patients with carcinoid tumors in various other localizations, catestatin was also expressed. Western blot analysis of ileal carcinoid showed abundant catestatin reactivity with accelerated processing of chromogranin A in the tumor tissue.

Catestatin derived from chromogranin A, which is the most widely distributed marker of neuroendocrine tumors, is expressed in high frequency in carcinoid tumors of the appendix (93.3%).