The IGF pathway is activated in insulinomas but downregulated in metastatic disease.

Clinical and molecular studies have implicated epidermal growth factor receptor (EGFR), insulin-like growth factor (IGF) and target of rapamycin (mTOR) signaling pathways in the regulation of pancreatic neuroendocrine tumor (PanNET) growth. Interpretation and comparison of these studies is complex due to clinical and molecular tumor heterogeneity. We therefore focused in this study on insulinomas, which we examined for mRNA and protein expression of EGFR, IGF and mTOR signaling pathway components by quantitative real-time PCR (n=48) and immunohistochemistry (n=86). Findings were compared with normal pancreatic islets and correlated with histopathological data and clinical outcome. Insulinomas showed low EGFR and high IGF2 expression. IGFBP2, IGFBP3 and IGFBP6 mRNA levels were 2-4 folds higher than in islets. High protein expression of IGF2, IGF1R and INSR (in 51-92% of the tumors) and low to moderate expression of mTORC1 pathway proteins p-PS6k and p-4EBP1 (7-28% of the tumors) were observed. Correlations were found between 1) ERK1 mRNA expression and that of numerous IGF pathway genes, 2) p-ERK and IGF1R protein expression and 3) decrease of IGF pathway components and both metastatic disease and shorter 10 years disease free survival. In conclusion, our observations suggest that high expression of IGF signaling pathway components is a hallmark of insulinomas, but does not necessarily lead to increased mTOR signaling. Reduced expression of IGF pathway components may be an adverse prognostic factor in insulinomas.

Effects of interferons α/ß on the proliferation of human micro- and macrovascular endothelial cells.

Synthetic interferons (IFNs) are used in the treatment of several types of cancer. In addition to an antitumor effect, IFNs show antiangiogenic activity. The aim of this study was to investigate the effects of IFN-α and IFN-ß on human micro- and macrovascular endothelial cells in vitro [human micro vascular lung endothelial cells (HMVEC-L) and human umbilical cord endothelial cells (HUVEC)]. By immunohistochemical staining and quantitative reverse transcriptase (RT)-polymerase chain reaction, we studied expression of type I IFN receptors. We evaluated the effects of IFN-α and IFN-ß on the proliferation (DNA content), apoptosis (DNA fragmentation by enzyme-linked immunosorbent assay), and cell cycle distribution (flow-cytometric analysis) of endothelial cells. HUVEC and HMVEC-L cells show comparable expression level of the distinct IFN receptor subtypes. Proliferation of HMVEC-L and HUVEC was inhibited by IFN-ß (the half maximal inhibitory concentration [IC(50)] = 60 and 90 IU/mL, respectively), but not by IFN-α at a dose up to 1,000 IU/mL. An interesting and unexpected observation was an inhibition of apoptosis by IFN-ß. After 72 h of treatment with IFN-ß. Cell cycle inhibition occurs in late S-phase in both cell lines. In conclusion, only IFN-ß, not IFN-α (10-1,000 IU/mL), has an inhibitory activity on endothelial cell proliferation. Surprisingly, apoptosis was decreased by IFN treatment, whereas inhibition of proliferation is caused by cell cycle arrest in late S-phase.

Coexpression of dopamine and somatostatin receptor subtypes in corticotroph adenomas.

CONTEXT: Previous studies have demonstrated the expression of somatostatin receptor subtypes (mainly sst(5)) and dopamine (DA) receptor subtypes (mainly D(2)) in smaller series of human corticotroph adenomas. In line with these findings, sst(5) and D(2)-targeting agents have already been used clinically in patients with Cushing's disease (CD) and have shown promising results in subsets of patients. To what extent these receptor subtypes are coexpressed within individual adenomas, is not known however. OBJECTIVE: The aim of the study was to investigate the (co-)expression of both sst and DA receptors in a large series of human corticotroph adenomas. DESIGN: We performed in vitro analysis of corticotroph adenoma tissue obtained via transsphenoidal adenomectomy. SETTING: The study was conducted at two university medical centers. PATIENTS: Adenoma tissue from 30 patients with CD was analyzed in this study. RESULTS: Analyzed by quantitative RT-PCR, D(2) and sst(5) were significantly (co-) expressed in the majority (60%) of adenomas, whereas 23% of adenomas only expressed D(2), but not sst(5). The remaining 17% of adenomas did not significantly express either sst(5) or D(2). Overall, expression of sst(1-4) and D(4) was low to nondetectable. Corticotroph adenomas with invasive growth invariably showed loss of sst(5) and D(2) expression. Autoradiography revealed clear D(2) and/or SS-14 binding in a subset of cases, which correlated well with their respective mRNA data. CONCLUSIONS: Sst(5) and especially D(2) are highly expressed in the majority of human corticotroph adenomas, with coexpression of sst(5) and D(2) being a common phenomenon. These findings support the current studies with sst(5) and D(2)-targeting agents in patients with CD and highlight the rationale behind sst(5)-D(2) combination therapy.