Daniele Alaimo

A multianalyte PCR blood test outperforms single analyte ELISAs (chromogranin A, pancreastatin, neurokinin A) for neuroendocrine tumor detection

A critical requirement in neuroendocrine tumor (NET) management is a sensitive, specific and reproducible blood biomarker test. We evaluated a PCR-based 51 transcript signature (NETest) and compared it to chromogranin A (CgA), pancreastatin (PST) and neurokinin A (NKA). The multigene signature was evaluated in two groups: i) a validation set of 40 NETs and controls and ii) a prospectively collected group of NETs (n=41, 61% small intestinal, 50% metastatic, 44% currently treated and 41 age-sex matched controls). Samples were analyzed by a two-step PCR (51 marker genes) protocol and ELISAs for CgA, PST and NKA. Sensitivity comparisons included χ(2), non-parametric measurements, ROC curves and predictive feature importance (PFAI) analyses. NETest identified 38 of 41 NETs. Performance metrics were: sensitivity 92.8%, specificity 92.8%, positive predictive value 92.8% and negative predictive value 92.8%. Single analyte ELISA metrics were: CgA 76, 59, 65, and 71%; PST 63, 56, 59, and 61% and NKA 39, 93, 84, and 60%. The AUCs (ROC analysis) were: NETest: 0.96±0.025, CgA: 0.67±0.06, PST 0.56±0.06, NKA: 0.66±0.06. NETest significantly outperformed single analyte tests (area differences: 0.284-0.403, Z-statistic 4.85-5.9, P<0.0001). PFAI analysis determined NETest had most value (69%) in diagnosis (CgA (13%), PST (9%), and NKA (9%)). Test data were consistent with the validation set (NETest >95% sensitivity and specificity, AUC =0.98 vs single analytes: 59-67% sensitivity, AUCs: 0.58-0.63). The NETest is significantly more sensitive and efficient (>93%) than single analyte assays (CgA, PST or NKA) in NET diagnosis. Blood-based multigene analytic measurement will facilitate early detection of disease recurrence and can predict therapeutic efficacy.

A mechanistic role for the chromatin modulator, NAP1L1, in pancreatic neuroendocrine neoplasm proliferation and metastases

BackgroundThe chromatin remodeler NAP1L1, which is upregulated in small intestinal neuroendocrine neoplasms (NENs), has been implicated in cell cycle progression. As p57Kip2 (CDKN1C), a negative regulator of proliferation and a tumor suppressor, is controlled by members of the NAP1 family, we tested the hypothesis that NAP1L1 may have a mechanistic role in regulating pancreatic NEN proliferation through regulation of p57Kip2.ResultsNAP1L1 silencing (siRNA and shRNA/lipofectamine approach) decreased proliferation through inhibition of mechanistic (mammalian) target of rapamycin pathway proteins and their phosphorylation (p < 0.05) in the pancreatic neuroendocrine neoplasm cell line BON in vitro (p < 0.0001) and resulted in significantly smaller (p < 0.05) and lighter (p < 0.05) tumors in the orthotopic pancreatic NEN mouse model. Methylation of the p57Kip2 promoter was decreased by NAP1L1 silencing (p < 0.05), and expression of p57Kip2 (transcript and protein) was upregulated. For methylation of the p57Kip2 promoter, NAP1L1 bound directly to the promoter (−164 to +21, chromatin immunoprecipitation). In 43 pancreatic NEN samples (38 primaries and 5 metastasis), NAP1L1 was over-expressed in metastasis (p < 0.001), expression which was inversely correlated with p57Kip2 (p < 0.01) on mRNA and protein levels. Menin was not differentially expressed.ConclusionNAP1L1 is over-expressed in pancreatic neuroendocrine neoplasm metastases and epigenetically promotes cell proliferation through regulation of p57Kip2 promoter methylation.

The clinical implications and biologic relevance of neurofilament expression in gastroenteropancreatic neuroendocrine neoplasms.

Although gastroenteropancreatic neuroendocrine neoplasms (GEP‐NENs) exhibit widely divergent behavior, limited biologic information (apart from Ki‐67) is available to characterize malignancy. Therefore, the identification of alternative biomarkers is a key unmet need. Given the role of internexin alpha (INA) in neuronal development, the authors assessed its function in neuroendocrine cell systems and the clinical implications of its expression as a GEP‐NEN biomarker.

Chromogranin A and its fragments as regulators of small intestinal neuroendocrine neoplasm proliferation.

Introduction Chromogranin A is a neuroendocrine secretory product and its loss is a feature of malignant NEN de-differentiation. We hypothesized that chromogranin A fragments were differentially expressed during NEN metastasis and played a role in the regulation of NEN proliferation. Methods Chromogranin A mRNA (PCR) and protein (ELISA/western blot) were studied in 10 normal human mucosa, 5 enterochromaffin cell preparations, 26 small intestinal NEN primaries and 9 liver metastases. Cell viability (WST-1 assay), proliferation (bromodeoxyuridine ELISA) and expression of AKT/AKT-P (CASE ELISA/western blot) in response to chromogranin A silencing, inhibition of prohormone convertase and mTOR inhibition (RAD001/AKT antisense) as well as different chromogranin A fragments were examined in 4 SI-NEN cell lines. Results Chromogranin A mRNA and protein levels were increased (37-340 fold, p<0.0001) in small intestinal NENs compared to normal enterochromaffin cells. Western blot identified chromogranin A-associated processing bands including vasostatin in small intestinal NENs as well as up-regulated expression of prohormone convertase in metastases. Proliferation in small intestinal NEN cell lines was decreased by silencing chromogranin A as well as by inhibition of prohormone convertase (p<0.05). This inhibition also decreased secretion of chromogranin A (p<0.05) and 5-HT (p<0.05) as well as expression of vasostatin. Metastatic small intestinal NEN cell lines were stimulated (50-80%, p<0.05) and AKT phosphorylated (Ser473: p<0.05) by vasostatin I, which was completely reversed by RAD001 (p<0.01) and AKT antisense (p<0.05) while chromostatin inhibited proliferation (~50%, p<0.05). Conclusion Chromogranin A was differentially regulated in primary and metastatic small intestinal NENs and cell lines. Chromogranin A fragments regulated metastatic small intestinal NEN proliferation via the AKT pathway indicating that CgA plays a far more complex role in the biology of these tumors than previously considered.

The stimulatory adenosine receptor ADORA2B regulates serotonin (5-HT) synthesis and release in oxygen-depleted EC cells in inflammatory bowel disease.

Objective We recently demonstrated that hypoxia, a key feature of IBD, increases enterochromaffin (EC) cell 5-HT secretion, which is also physiologically regulated by the ADORA2B mechanoreceptor. Since hypoxia is associated with increased extracellular adenosine, we wanted to examine whether this nucleotide amplifies HIF-1α-mediated 5-HT secretion. Design The effects of hypoxia were studied on IBD mucosa, isolated IBD-EC cells, isolated normal EC cells and the EC cell tumor derived cell line KRJ-1. Hypoxia (0.5% O2) was compared to NECA (adenosine agonist), MRS1754 (ADORA2B receptor antagonist) and SCH442146 (ADORA2A antagonist) on HIF signaling and 5-HT secretion. Antisense approaches were used to mechanistically evaluate EC cells in vitro. PCR and western blot were used to analyze transcript and protein levels of HIF-1α signaling and neuroendocrine cell function. An animal model of colitis was evaluated to confirm hypoxia:adenosine signaling in vivo. Results HIF-1α is upregulated in IBD mucosa and IBD-EC cells, the majority (∼90%) of which express an activated phenotype in situ. Hypoxia stimulated 5-HT release maximally at 30 mins, an effect amplified by NECA and selectively inhibited by MRS1754, through phosphorylation of TPH-1 and activation of VMAT-1. Transient transfection with Renilla luciferase under hypoxia transcriptional response element (HRE) control identified that ADORA2B activated HIF-1α signaling under hypoxic conditions. Additional signaling pathways associated with hypoxia:adenosine included MAP kinase and CREB. Antisense approaches mechanistically confirmed that ADORA2B signaling was linked to these pathways and 5-HT release under hypoxic conditions. Hypoxia:adenosine activation which could be reversed by 5′-ASA treatment was confirmed in a TNBS-model. Conclusion Hypoxia induced 5-HT synthesis and secretion is amplified by ADORA2B signaling via MAPK/CREB and TPH-1 activation. Targeting ADORA2s may decrease EC cell 5-HT production and secretion in IBD.

Comparison of PCR-based detection of chromogranin A mRNA with traditional histological lymph node staging of small intestinal neuroendocrine neoplasia

BackgroundAccurate neuroendocrine neoplasia (NEN) staging is vital for determining prognosis and therapeutic strategy. The great majority of NENs express chromogranin A (CgA) which can be detected at a protein or transcript level. The current standards for lymph node metastasis detection are histological examination after Hematoxylin and Eosin (H&E) and CgA immunohistochemical (IHC) staining. We hypothesized that detection of CgA mRNA transcripts would be a more sensitive method of detecting these metastases.FindingsWe compared these traditional methods with PCR for CgA mRNA extracted from formalin fixed paraffin embedded slides of lymph nodes (n = 196) from small intestinal NENs, other gastrointestinal cancers and benign gastrointestinal disease. CgA PCR detected significantly more NEN lymph nodes (75%) than H&E (53%) or CgA IHC (57%) (p = 0.02). PCR detected CgA mRNA in 50% (14 of the 28) of SI-NEN lymph nodes previously considered negative. The false positive rate for detection of CgA mRNA was 19% in non-neuroendocrine cancers, and appeared to be due to occult neuroendocrine differentiation or contamination by normal epithelium during histological processing.ConclusionsMolecular pathological analysis demonstrates the limitations of observer-dependent histopathology. CgA PCR analysis detected the presence of CgA transcripts in lymph nodes without histological evidence of tumor metastasis. Molecular node positivity (stage molN1) of SI-NEN lymph nodes could confer greater staging accuracy and facilitate early and accurate therapeutic intervention. This technique warrants investigation using clinically annotated tumor samples with follow-up data.

GNA15 expression in small intestinal neuroendocrine neoplasia: Functional and signalling pathway analyses

Gastroenteropancreatic neuroendocrine neoplasia (GEP-NEN) comprises a heterogeneous group of tumours that exhibit widely divergent biological behaviour. The identification of new targetable GPCR-pathways involved in regulating cell function could help to identify new therapeutic strategies. We assessed the function of a haematopoietic stem cell heterotrimeric G-protein, Gα15, in gut neuroendocrine cell models and examined the clinical implications of its over expression. Functional assays were undertaken to define the role of GNA15 in the small intestinal NEN cell line KRJ-I and in clinical samples from small intestinal NENs using quantitative polymerase chain reaction, western blot, proliferation and apoptosis assays, immunoprecipitation, immunohistochemistry (IHC) and automated quantitative analysis (AQUA). GNA15 was not expressed in normal neuroendocrine cells but was overexpressed in GEP-NEN cell lines. In KRJ-I cells, decreased expression of GNA15 was associated with inhibition of proliferation, activation of apoptosis and differential effects on pro-proliferative ERK, NFκB and Akt pathway signalling. Moreover, Gα15 was demonstrated to couple to the ß1 adrenergic receptor and modulated proliferative signals through this GPCR. Transcript and protein levels of GNA15 were significantly elevated in primary and metastatic tumours compared to normal mucosa and were particularly increased in low Ki-67 expressing tumours. IHC and AQUA revealed that a higher Gα15 expression was associated with a poorer survival. GNA15 may have a pathobiological role in SI-NENs. Targeting this signalling mediator could provide an opportunity for the development of new therapeutic strategies for this tumour type.

Neuroendocrine gene transcript analysis of blood to define the completeness of surgical resection and identify stable or progressive neuroendocrine tumor disease.

293 Background: A critical requirement in NET management is a sensitive, specific, reproducible blood biomarker test. Surgery and somatostatin analogs (SSAs) are widely used but efficacy is difficult to determine. Imaging is relatively insensitive for residual/recurrent disease determination and symptoms remains the only way to determine SSA efficacy. We evaluated a PCR-based 51 transcript signature (NETest) comparing it to CgA to determine whether biomarkers were effective in defining surgical resection and SSA efficacy. Methods: GEP-NETs (n=50) [M:F 19:31; median age: 58 years, small intestine: n=35, pancreas n=9, rectum n=3, appendix: n=2, stomach n=1] were evaluated. Groups included surgery (n=15, R0-no disease), and SSA therapy (n=35). qRT-PCR was used for transcript measurement, ELISA (DAKO) for CgA and imaging (RECIST) for clinical status. NETest defined risk of disease activity (low disease activity risk <47%, high risk 47-100%). Results: Resection decreased NETest (pre-surgery: 80±6%; 1 post-surg...

Prognostication by multigene proliferative marker panel compared with Ki-67 in small-intestinal NENs.

242 Background: Ki-67 is the major proliferative marker in clinical use to determine neuroendocrine neoplasm (NEN) prognosis. Ki-67 is unable to predict the outcome of SI-NENs, as the majority have a low (≤2) Ki-67%. Therefore, we aimed to identify a sensitive panel of proliferative markers using qRT-PCR to more accurately define the proliferation of these slow growing tumors. METHODS We identified genes with a mechanistic function in cell cycle progression that were over-expressed in RNA microarrays of SI-NENs (n=8) compared to adjacent normal tissue (n=4) (dCHIP, annotation databases). Timing of marker gene expression (qRT-PCR) in proliferating cell-cycle phases (S, G2, M) was determined in flow-sorted SI-NEN cell lines (KRJ-1, H-STS) after propidium iodide staining. RNA expression of candidate proliferative markers was then investigated using an in vivo model and two independent tumor datasets, and transcript level compared to Ki-67% protein expression (immunohistochemical staining). RESULTS Twenty genes with a mechanistic role in proliferation were identified and 17 confirmed to be expressed in proliferating cell cycle phases. Each tumor expressed a unique profile of the 17 proliferative markers. Both Ki-67 protein and Ki-67 RNA transcript levels failed to differentiate in vivo SI-NEN models or patient samples despite variable proliferative capacity (e.g., WDNETs versus WDNECs). Although most tumors showed low levels of Ki-67 expression, the tumors expressed high levels of select alternative proliferative markers. Hierarchical clustering provided a novel and clinically meaningful prognostic classification. CONCLUSIONS Proliferation of individual SI-NENs is regulated by unique combinations of multiple genes with a mechanistic role in cell-cycle progression. Regulation of proliferation in SI-NENs is therefore complex and cannot accurately be defined by Ki-67 as a single marker. A panel of proliferative RNA markers has potential to significantly improve prognostication in patients with SI-NENs.