Abstract
BackgroundGastro-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.MethodsThe 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.ResultsOnly 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.ConclusionsThe 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.
Highlights
Tumor angiogenesis is a highly complicated process consisting of several steps, known as the angiogenesis cascade, regulated by many pro- and antiangiogenic factors, both of endogenous and exogenous origin [1,2]
The group of endogenous angiogenic factors comprise, among others, the family of vascular endothelial growth factors (VEGFs) and their receptors (VEGF-A, VEGF-B, VEGF-C, VEGF-D and VGFR-2, VEGFR-3), the family of angiopoietins (Ang) and their receptors (Ang-1, angiopoietin 2 (Ang-2), Ang3/4 and Tie-1, Tie-2), other growth factor families, as well as endostatin and osteopontin (OPN). Some of these angiogenic factors are responsible for early activation of the angiogenic cascade, in which the VEGF signaling pathway acts as the most important early regulator of angiogenesis
The aim of the study was to search for new auxiliary diagnostic markers for patients with neuroendocrine tumors based on the analysis of six circulating angiogenic factors in plasma
Summary
Tumor angiogenesis is a highly complicated process consisting of several steps, known as the angiogenesis cascade, regulated by many pro- and antiangiogenic factors, both of endogenous and exogenous origin [1,2]. The group of endogenous angiogenic factors comprise, among others, the family of vascular endothelial growth factors (VEGFs) and their receptors (VEGF-A, VEGF-B, VEGF-C, VEGF-D and VGFR-2, VEGFR-3), the family of angiopoietins (Ang) and their receptors (Ang-1, Ang-2, Ang3/4 and Tie-1, Tie-2), other growth factor families, as well as endostatin and osteopontin (OPN). Some of these angiogenic factors are responsible for early activation of the angiogenic cascade, in which the VEGF signaling pathway acts as the most important early regulator of angiogenesis. In the subgroup of patients with carcinoid syndrome, only Tie-2 and CgA concentrations were higher than those in patients with non-functioning
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