High-dose treatment with a long-acting somatostatin analogue in patients with advanced midgut carcinoid tumours.

OBJECTIVE: High-dose somatostatin analogue treatment has shown an antiproliferative effect in one study including patients with neuroendocrine tumours. To explore this therapeutic strategy further, we have studied the effect of a high-dose formula of octreotide, octreotide pamoate, in midgut carcinoid patients. DESIGN AND METHODS: Twelve patients with advanced midgut carcinoid tumours with a median duration of disease of more than 5 years were included. All were in a progressive state despite several previous treatment modalities. Octreotide pamoate (160 mg) was given as an intramuscular injection every 2 weeks for 2 months and then monthly. Radiological and biochemical responses were monitored. RESULTS: Tumour size and biochemical markers were stabilised for a median of 12 months in 75% of the patients. Ten patients had symptomatic improvement of flush and diarrhoea. CONCLUSION: In this group of patients with advanced midgut carcinoid tumours and progressive disease, octreotide pamoate managed to improve symptoms, and stabilise hormone production and tumour growth in 75% of the patients. We believe that high-dose treatment with somatostatin analogues can be an important addition to the therapeutic arsenal for patients with advanced progressive midgut carcinoid tumours.

Expression of trkB in human neuroblastoma in relation to MYCN expression and retinoic acid treatment.

Expression of full-length trkB can be found in some highly malignant neuroblastoma tumors with an amplified MYCN gene. This contrasts sympathetic neuroblasts, from which neuroblastomas are thought to arise, which neither express trkB nor are dependent on the p145(trkB) ligands, brain-derived neurotrophic factor (BDNF) or neurotrophin-4/5, for their normal development. In this study we show that trkB was expressed in two out of five neuroblastoma tumors with amplified MYCN, while no trkB expression was observed when the MYCN gene was overexpressed in a non-MYCN-amplified neuroblastoma cell line. This shows that MYCN overexpression per se is not sufficient to induce trkB expression. trkB expression and BDNF responsiveness in neuroblastoma cells can be induced by all-trans-retinoic acid (RA). When SH-SY5Y cells were stimulated with a combination of RA and BDNF, norepinephrine and tyrosine hydroxylase levels were unaltered, showing that the cells did not change toward a more catecholaminergic sympathetic phenotype. However, expression of growth-associated protein 43, indicative of a neuronal phenotype, was elevated. Vesicular acetylcholine transporter, choline acetyl transferase, and neuropeptide tyrosine mRNA levels also increased in RA-BDNF-treated cells, which could suggest that these cells develop into a sympathetic cholinergic phenotype. In addition, treatment with RA-induced expression of the platelet-derived growth factor receptor-alpha. As previously shown for BDNF, platelet-derived growth factor stimulated growth of the RA-treated cells, findings that could have clinical relevance. If these receptors mediate a mitogenic signal in vivo also, this might limit the effect of RA treatment on neuroblastoma patients.