1,720,996 research outputs found
Somatostatin receptors: from basic science to clinical approach. Unlabeled somatostatin analogues-1: Prostate cancer
No full textNeuroendocrine cells have been found in all the stages of prostate cancer, but their clinical significance is not completely understood. Neuroendocrine cells are androgen receptor- and prostate-specific antigen-negative, do not proliferate, and secrete many neuropeptides, such as chromogranin A. Neuroendocrine differentiation of prostate cancer correlates with an advancing tumour stage, poor prognosis and tumour progression after androgen deprivation. Furthermore, neuroendocrine phenotype is associated with the increased expression of neo-angiogenesis and vascular endothelial growth factor and with an over-expression of survivin, a new anti-apoptosis protein. Chromogranin A is the quantitatively major secretory protein of the vesicles inside neuroendocrine prostate cells and it is the marker most frequently used to detect neuroendocrine features, both in tissues and in general circulation. Tumours displaying neuroendocrine phenotype tend to be more aggressive and resistant to hormone-therapy. Neuroendocrine differentiation seems to be a dynamic phenomenon: in vitro and in vivo data suggest that it can be induced by androgen suppression. Moreover, the differences in the expression of somatostatin receptors between primary and hormone-refractory prostate cancer are likely to be related to the changes in neuroendocrine phenotype during androgen deprivation. Circulating chromogranin A levels seem to be scarcely affected by endocrine- and chemotherapy, while they significantly decreased after treatment with somatostatin analogs
Selective alkylation and acylation of alpha and epsilon amino groups with PEG in a somatostatin analogue: Tailored chemistry for optimized bioconjugates
No full textThe effects of the type and location of polymer grafting on the biological activity of different mono-PEG derivatives of the somatostatin analogue RC160 were evaluated. A chemical strategy to obtain mono-PEG alkylation or acylation of the peptide's alpha-terminal or lysil-epsilon primary amines was devised. Selective BOC protection of the two available primary amines, followed by reaction with two different PEG reagents and removal of the protecting group, was carried out. Chemical characterization, structural studies, and the evaluation of the biological activity of the bioconjugates synthesized allowed the identification of the one having characteristics more suitable for therapeutic application. This corresponds to the mono-epsilon-lysil-pegylated form, obtained by reductive alkylation, where the amine's positive charge is preserved. The results obtained suggest the importance of preliminary studies in the development of new polymer-peptide conjugates with improved pharmacological properties
The role of somatostatin and somatostatin analogs in the pathophysiology of the human immune system.
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In vivo and in vitro expression of somatostatin receptors in two human thymomas with similar clinical presentation and different histological features
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