Tachykinin production by carcinoid tumours in culture

Tissue specimens from 5 patients with metastatic midgut carcinoid tumours were kept in organ culture for up to 6 months. The tumour cells were confined to the suspension in the form of condensed cell clusters and appeared to retain their endocrine characteristics. Radioimmunoassay for tachykinin immunoreactivity showed high concentrations in 4 out of 5 culture media. The concentrations were highest in the beginning of the experiment, but subsequently decreased. The 4 patients from which these tumours were taken had all elevated tachykinin concentrations in extracted plasma. The fifth culture medium had low tachykinin concentration, and the concentration in extracted plasma from this patient was within the normal range. Reversed-phase high-performance liquid chromatography of the culture media with elevated tachykinin concentrations revealed immunoreactive components with the characteristics of synthetic neuropeptide K, neurokinin A and eledoisin, components also found in plasma and tumour tissues of carcinoid patients. Our findings indicate that carcinoid tumour cells produce tachykinins. These peptides are biologically very active, resulting in flush and hypotension when infused intravenously into normals, and might contribute to the clinical symptoms of the carcinoid syndrome.