Human pheochromocytoma cells studied in culture contain large amounts of DSIP-like material

Pre-clinical phaeochromocytoma and paraganglioma models: Cell lines, animal models, and a human primary culture model

While the establishment of human phaeochromocytoma and paraganglioma (PPGL) cell lines has proven to be particularly difficult over several decades of research, there are other reliable pre-clinical PPGL models currently available. This review provides a summary of these models, together with our recently established personalised drug screening platform using patient-derived PPGL primary cultures. Such currently available PPGL models include murine and rat PPGL cell lines, of which only one cell line (PC12) is publicly accessible through a cell repository, and PPGL animal models, of which the patient-derived xenograft models are promising but complex to establish. We have developed next-generation implementation of human PPGL primary cultures, enabling reliable and personalised drug screening and an individualised analysis of tumour drug responsivity based on the tumour's unique genetic, biochemical, immunohistochemical and clinical profile. Overall, reliable PPGL models, including patient-derived primary culture models, are essential to advance pre-clinical research in the field of PPGLs.

Interleukin-6 (IL-6) producing phaeochromocytoma: direct IL-6 suppression by non-steroidal anti-inflammatory drugs

A 35-year-old Japanese woman presented with a phaeochromocytoma and demonstrated marked inflammatory reactions and pyrexia as a result of excessive production of interleukin-6 (IL-6) by the tumour. Serum IL-6 level was 262 ng/l (normal; < 4.0 ng/l). Fever and inflammatory markers were largely overcome by the administration of the nonsteroidal anti-inflammatory drug, naproxen, and all symptoms disappeared soon after the tumour was excised. Immunohistochemical study revealed positive staining using an antihuman IL-6 antibody and Northern analysis showed increased IL-6 mRNA levels in the tumour. Cultured tumour cells showed IL-6 protein synthesis, and nonsteroidal anti-inflammatory drugs such as naproxen and indomethacin directly inhibited IL-6 release. These results indicate that the effects of naproxen in vivo were due, at least in part, to direct suppression of IL-6 secretion from the tumour.

Secretory patterns of tryptophan metabolites in midgut carcinoid tumor cells

Hormonal overproduction is a significant problem in patients with disseminated midgut carcinoid tumors. Serotonin (5-HT) is one major product secreted from such tumors and the urinary excretion of its metabolite (5-hydroxyindoleacetic acid, 5-HIAA) serves as an important tumor marker. The present study aimed at elucidating mechanisms of tryptophan metabolite secretion to facilitate the treatment of the carcinoid syndrome. When midgut carcinoid tumors were studied in primary cell cultures, several similarities with adrenergic neurons could be demonstrated. A marked dose-dependent depletion of intracellular 5-HT could be induced by reserpine, and monoamine oxidase-activity was revealed both in functional studies and by immunocytochemistry. Differences between tumors in the ratios of tryptophan metabolites released indicated that enzymes for synthesis and degradation of 5-HT were individually expressed. Treatment with the somatostatin analogue octreotide or with dexamethasone decreased the extracellular levels of tryptophan metabolites, but the mechanisms were partly different. In some tumors octreotide also decreased the synthesis of 5-HT, while dexamethasone markedly increased the intracellular 5-HIAA levels. It is of clinical interest to further elucidate these mechanisms, since the two drugs may have complementary actions in carotid crisis reactions.

Characterization of the release and metabolism of delta sleep-inducing peptide (DSIP) in the rat brain

In the present study, we examined whether delta sleep-inducing peptide (DSIP) was (1) secreted from neurons on depolarization and (2) degraded by membrane-associated peptidases. Incubation of DSIP with rat brain membrane resulted in the degradation of DSIP with liberation of tryptophan, an N-terminal amino acid of DSIP. Bestatin and puromycin, aminopeptidase inhibitors, significantly inhibited the degradation of DSIP and release of tryptophan. The releases of immunoreactive DSIP-like substance (irDSIP) from rat brain slices and synaptosomes were significantly stimulated by high K(+)-evoked depolarization. The released irDSIP was coeluted with native DSIP on gel filtration chromatography. High K(+)-evoked release of irDSIP did not show extracellular Ca(2+)-dependency. This Ca(2+)-independency suggests that the secretory pathway of DSIP may be different from that of other neurotransmitters. These results demonstrate that DSIP is released from nerve endings on depolarization and inactivated by membrane-associated puromycin-sensitive aminopeptidase. Therefore, DSIP may serve as a neuropeptide-like material in the central nervous systems.