Somatostatin Analogs and Tumor Localization Do Not Influence Vitamin D Concentration in Patients with Neuroendocrine Tumors.

Patients with neuroendocrine tumors (NETs), malignancies of rare but still rising incidence, may be a group at higher risk of vitamin D insufficiency. The gastrointestinal tumor prevalence and somatostatin analog (SSA) therapy may cause vitamin D malabsorption. The aim of this study was to evaluate the serum level of vitamin D in NET patients. A total of 36 NET patients were enrolled into the experimental group and 16 individuals were enrolled into the control group. All patients were further classified into subgroups according to primary tumor localization (gastropancreatic, lung, and other NETs) or therapy (with or without SSA treatment). The concentrations of total 25(OH)D were assayed with Electrochemiluminescence immunoassay (ECLIA). Serum concentration of 25(OH)D in NET patients did not differ significantly from that of the control group. However, the average level of 25(OH)D in both groups met the criteria of vitamin D deficiency. Importantly, SSA therapy did not aggravate vitamin D deficiency. Moreover, the concentration of 25(OH)D in the studied group was not significantly influenced by primary tumor localization, patient age, or season. Vitamin D deficiency is a widespread disorder affecting both NET patients and individuals without other health problems, and SSA and gastrointestinal tumor localization do not exacerbate this condition.

Interferon alpha and rapamycin inhibit the growth of carcinoid and medullary thyroid cancer in vitro.

Neuroendocrine tumors (NETs) are highly vascularized neoplasms characterized by rising incidence. Moreover, the neuroendocrine cells were shown to express vascular endothelial growth factor (VEGF) and VEGF receptors. Therefore, angiomodulators could be potentially a new group of drugs enhancing still unsatisfactory effectiveness of NET therapy. The aim of this study was to assess the direct influence of angiomodulators: VEGF and five endogenous and exogenous antiangiogenic compounds (endostatin, interferon alpha [IFNα], rapamycin, JV1-36, semaxinib [SU5416]) on the growth of two NET cell lines: lung carcinoid H727 cell line and medullary thyroid cancer TT cell line in vitro. IFNα and rapamycin induced the inhibitory effect on H727 and TT cell viability and proliferation, increasing apoptosis and arresting the cell cycle. Also semaxinib (10(-5)M) inhibited proliferation of both cell lines. VEGF and endostatin did not influence the growth of H727 and TT cells. The inhibitory effect of IFNα, rapamycin and semaxinib on carcinoid and medullary thyroid cancer growth was revealed in our in vitro study, although some other antiangiogenic agents did not directly influence H727 and TT cell growth. Thus, IFNα and mTOR inhibitors as multidirectionally acting drugs with antiangiogenic effect could be potentially efficient in treatment of neuroendocrine tumors and are worth further studies.

Interferon alpha and rapamycin inhibit the growth of pheochromocytoma PC12 line in vitro.

INTRODUCTION: Pheochromocytomas are benign or malignant neuroendocrine tumours. The unsatisfactory efficacy of the traditional therapeutic methods for patients with metastatic disease results in a continuing search for more effective and targeted agents. Due to the increased vascularisation of these tumours, inhibitors of angiogenesis could be potentially a new group of drugs in pheochromocytoma/paraganglioma therapy. MATERIAL AND METHODS: The aim of this study was to evaluate the influence of angiomodulators: VEGF (vascular endothelial growth factor) and five endogenous and exogenous antiangiogenic compounds (endostatin; IFN-alpha [interferon alpha]; rapamycin - mTOR [mammalian target of rapamycin] inhibitor; JV1-36 and SU5416 (semaxinib]) on the growth of rat pheochromocytoma PC12 cell line. RESULTS: IFN-alpha (10(5) U/mL) strongly inhibited PC12 growth in a 72 h culture, increasing apoptosis and arresting the cell cycle. Rapamycin in a wide range of concentrations (10(-5) to 10(-8) M) induced a slight inhibitory effect on PC12 viability and decreased cell proliferation at the concentration of 10(-5) M. VEGF, endostatin and JV1-36 did not influence the growth of PC12. CONCLUSIONS: The study has shown for the first time that IFN-a inhibited the growth of pheochromocytoma PC12 line and confirmed the inhibitory action of rapamycin on these cells. The results suggest that IFN-alpha and mTOR inhibitors could be potentially effective in the therapy of malignant pheochromocytoma, and encourage further study in this field.

Elevated peripheral blood plasma concentrations of tie-2 and angiopoietin 2 in patients with neuroendocrine tumors.

BACKGROUND: Gastro-entero-pancreatic/neuroendocrine (NET) tumors are highly vascularized neoplasms. However, our knowledge concerning circulating levels of the angiogenic factors in NET patients still remains insufficient. METHODS: The aim of this study was to measure plasma concentrations of VEGF, angiopoietin 1 (Ang-1), angiopoietin 2 (Ang-2), soluble Tie-2, endostatin, osteopontin (OPN) and chromogranin A (CgA) in 36 NET patients and 16 controls. RESULTS: Only the plasma concentrations of Tie-2 and CgA were higher in NET patients as compared to controls. These levels were within the reference range in controls; however one control demonstrated slightly elevated Tie-2 and 4 elevated CgA. Similarly, in the subgroup of patients with carcinoid syndrome, only Tie-2 and CgA concentrations were higher than those in patients with non-functioning NETs. In turn, in the subgroup of metastatic patients, only Ang-2 levels were higher than in those with localized disease. A positive correlation was found between Ang-2 and Tie-2 levels in metastatic patients and between Ang-1 and Tie-2 in localized NETs. CONCLUSIONS: The plasma concentration of Tie-2 is proposed as an additional marker for NET patients and seems to be similarly effective as the currently used CgA level. Moreover, higher plasma levels of Ang-2 together with the positive correlation between Ang-2 and Tie-2 levels in metastatic subjects, implies that cases with a Tie-2 level above the upper limits, together with higher level of Ang-2 seem to be highly predictive of metastases.