Expression In Neuroendocrine Tumors Research Articles

The Notch1 pathway is a critical regulator of SSTR2 expression in neuroendocrine tumors

The Notch1 pathway is a critical regulator of SSTR2 expression in neuroendocrine tumors

The Wnt pathway protein Dvl1 targets somatostatin receptor 2 for lysosome-dependent degradation

The Somatostatin receptor 2 (Sstr2) is a heterotrimeric G protein-coupled receptor that is highly expressed in neuroendocrine tumors and is a common pharmacological target for intervention. Unfortunately, not all neuroendocrine tumors express Sstr2, and Sstr2 expression can be downregulated with prolonged agonist use. Sstr2 is rapidly internalized following agonist stimulation and, in the short term, is quantitatively recycled back to the plasma membrane. However, mechanisms controlling steady state expression of Sstr2 in the absence of agonist are less well described. Here, we show that Sstr2 interacts with the Wnt pathway protein Dvl1 in a ligand-independent manner to target Sstr2 for lysosomal degradation. Interaction of Sstr2 with Dvl1 does not affect receptor internalization, recycling, or signaling to adenylyl cyclase but does suppress agonist-stimulated ERK1/2 activation. Importantly, Dvl1-dependent degradation of Sstr2 can be stimulated by overexpression of Wnts and treatment of cells with Wnt pathway inhibitors can boost Sstr2 expression in neuroendocrine tumor cells. Taken together, this study identifies for the first time a mechanism that targets Sstr2 for lysosomal degradation that is independent of Sstr2 agonist and can be potentiated by Wnt ligand. Intervention in this signaling mechanism has the potential to elevate Sstr2 expression in neuroendocrine tumors and enhance Sstr2-directed therapies.

Abstract 5305: Delta-like ligand 3 immunohistochemical expression landscape in high-grade lung neuroendocrine tumors

Abstract Background: High-grade lung neuroendocrine tumors are a heterogeneous group of cancers with aggressive common features and a lack of effective therapeutic options. Recently, efforts have been made to identify new targets and drugs to improve clinical outcomes in these patients. Because of its high expression in neuroendocrine tumors compared to normal tissue, delta-like ligand 3 (DLL3) has emerged as a new therapeutic target in this setting.1,2 Targeting DLL3 with the half-life extended bispecific T cell engager (HLE BiTE®) immune therapy, tarlatamab, in a phase 1 clinical trial has demonstrated promising anti-tumor activity in small cell lung cancer (SCLC) patients.3 In order to more precisely guide patient selection and clinical trial design, a better understanding and quantification of DLL3 expression is required. Thus, we investigated DLL3 immunohistochemical expression across SCLC, large cell neuroendocrine carcinoma (LCNEC), and neuroendocrine carcinoma with combined histology (CNEC), and its associations with clinicopathological characteristics. Design: Formalin-fixed and paraffin-embedded surgically resected lung neuroendocrine carcinomas (SCLC, n=17; LCNEC, n=20; CNEC, n=8) were selected based on tissue availability at MD Anderson Cancer Center and stained with a commercially available immunohistochemistry assay for DLL3 (clone SP347, Ventana). Total percentage and intensity of DLL3 expression of neuroendocrine carcinoma cells were scored and the results were presented as H-Score (0-300) and percentage (%) of DLL3 positive tumor cells. We correlated DLL3 expression with clinicopathological characteristics. Results: DLL3 expression was observed in 37/45 (82%) of all cases (SCLC: %, median=65%, 0-100%; H-score, median=95, 0-175; LCNEC: %, median=65%, 0-100%; H-score, median=100, 0-180; CNEC: %, median=55%, 0-95%; H-score, median=90, 0-175). In patients with LCNEC, DLL3 % was higher in male patients (p=0.0500) and former smokers (p=0.0298) compared to females and current smokers, respectively. No other clinicopathological associations were found with age, Tumor-Node-Metastasis (TNM) staging system, recurrence, neoadjuvant therapy or overall survival. Conclusion:Our work confirms that most high-grade neuroendocrine tumors express DLL3 across histology types and TNM stage. Our results suggest that a large subset of patients with high-grade lung neuroendocrine tumors may be a target population of interest for DLL3-targeted therapies.

ACTH-Dependent Cushing’s Syndrome in an Elderly Woman with Pituitary, Adrenal, and Intrathoracic Lesions

A 77-year-old female with rheumatoid arthritis on etanercept, depression on venlafaxine, and treated hypothyroidism presented with easy bruising and muscle weakness. She denied any steroid use. She had normal BP and BMI, but appeared mildly Cushingoid with round facies, and increased dorsocervical and supraclavicular fat.Laboratory evaluation showed: ACTH 70.8 pg/mL (< 63.3), cortisol 24.3 ug/dL, 24 h urine free cortisol 223 ug (< 50), salivary cortisol 0.428 ug/dL, DHEA-S 165.7 ug/dL (< 142.8), LH 0.1 mIU/mL, FSH 2.7 mIU/mL, and hgbA1C 6.1 % (< 5.6 %). All other hormonal testing was normal. MRI of the pituitary showed a 4 x 2 x 3 mm hypoenhancing defect of the anterior pituitary. CT of the chest and abdomen showed a 1.1 cm left adrenal nodule, and a 1 cm non-specific right middle lobe lung nodule. Inferior petrosal sinus sampling (IPSS) with CRH did not show a central ACTH step-up. PET/CT with DOTATATE showed mildly increased tracer uptake in the right middle lobe measuring 1 cm with SUV max 3.7, and a 0.6 cm left apical subpleural nodule with SUV max 1.9.The patient underwent a right middle lobectomy and pathology was positive for typical carcinoid. Post-operatively, she needed hydrocortisone replacement for 9 months. ACTH was 19.7 pg/dL, cortisol 9.5 ug/dL, DHEA-S 31.3 ug/dL, LH 61.8 mIU/mL, and FSH 112.4 mIU/mL. Her Cushingoid features and myopathy resolved.This case highlights several challenges in the diagnosis and source localization in patients with ACTH-dependent Cushing’s Syndrome (CS). In this slim, elderly female, the typical features of CS were subtle. In addition, dynamic biochemical testing with high dose dexamethasone does not reliably distinguish eutopic from ectopic ACTH-dependent CS, as the sensitivity and specificity range from 60–80%. Thus, the diagnosis largely depends on sophisticated imaging and IPSS.The patient had pituitary, adrenal, and lung lesions. The pituitary lesion initially pointed towards a central ACTH source, but IPSS was negative. The prevalence of pituitary incidentalomas is high, at 10.6% based on autopsy data, with an increasing proportion being recognized in the elderly. Adrenal incidentalomas are also often noted in older individuals, but that was clearly not the cause of CS in this patient with a non-suppressed DHEA-S and elevated ACTH. PET/CT with DOTATATE has emerged as a sensitive test for the detection of often small tumors producing ectopic ACTH and was positive in the lung lesion. In spite of newer localization techniques, the source of ectopic ACTH often remains unidentified (12.5% in a large retrospective case-record study). False negatives on PET/CT with DOTATATE imaging may be due to cortisol’s suppressive effect on the somatostatin receptor expression in neuroendocrine tumors. Thus, in cases of ACTH-dependent CS with negative IPSS, ectopic ACTH must remain as a likely source, and be re-explored after medical treatment of the hypercortisolism.

Imaging Somatostatin Positive Tumors with Tyr3-Octreotate/Octreotide Conjugated to Desferrioxamine B Squaramide Radiolabeled with either Zirconium-89 or Gallium-68.

Radiolabeled derivatives of Tyr3-octreotide and Tyr3-octreotate, synthetic analogues of the peptide hormone somatostatin, can be used for positron emission tomography (PET) imaging of somatostatin receptor expression in neuroendocrine tumors. In this work, a squaramide ester derivative of desferrioxamine B (H3DFOSq) was used attach either Tyr3-octreotide or Tyr3-octreotate to the metal binding ligand to give H3DFOSq-TIDE and H3DFOSq-TATE. These new peptide-H3DFOSq conjugates form stable complexes with either of the positron-emitting radionuclides gallium-68 (t1/2 = 68 min) or zirconium-89 (t1/2 = 3.3 days). The new complexes were evaluated in an AR42J xenograft model that has endogenous expression of SSTR2. All four agents displayed good tumor uptake and produced high-quality PET images. For both radionuclides, the complexes formed with H3DFOSq-TATE performed better, with higher tumor uptake and retention than the complexes formed with H3DFOSq-TIDE. The versatile ligands presented here can be radiolabeled with either gallium-68 or zirconium-89 at room temperature. The long radioactive half-life of zirconium-89 makes distribution of pre-synthesized tracers produced to certified standards feasible and could increase the number of clinical centers that can perform diagnostic PET imaging of neuroendocrine tumors.

Asphericity of Somatostatin Receptor Expression in Neuroendocrine Tumors: An Innovative Predictor of Outcome in Everolimus Treatment?

Background: in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NET), the mTOR inhibitor everolimus is associated with significant improvement in progression-free survival (PFS). This study evaluated the lesional asphericity (ASP) in pretherapeutic somatostatin receptor (SSR) imaging as the first imaging-based prognostic marker for PFS. Methods: this retrospective bicentric cohort study included 30 patients (f = 13, median age, 66.5 (48–81) years) with pretherapeutic [111In-DTPA0]octreotide scintigraphy (Octreoscan®). ASP of functional volumes of up to three leading lesions per patient (n = 74) was calculated after semiautomatic, background-adapted segmentation. Uni- and multivariable Cox regression regarding PFS for clinical factors and the maximum ASP per patient was obtained. Results: all 30 patients showed metachronous or progressive liver metastases. ASP, primary tumor site, metastases pattern, and prior peptide receptor radionuclide therapy (PRRT) were significantly associated with PFS in univariable Cox regression. Only ASP > 12.9% (hazard ratio (HR), 3.33; p = 0.024) and prior PRRT (HR, 0.35; p = 0.043) remained significant in multivariable Cox. Median PFS was 6.7 months for ASP > 12.9% (95% confidence interval (CI), 2.1–11.4 months) versus 14.4 (12.5–16.3) months for ASP ≤ 12.9% (log-rank, p = 0.028). Conclusion: pretherapeutic ASP of SSR positive lesions independently predicted PFS for treatment with everolimus in GEP-NET. ASP may supplement risk-benefit assessment before patient inclusion to treatment.

Phase II study of ONC201 in pheochromocytoma-paragangliomas (PC-PG), medullary thyroid carcinoma (MTC), and other neuroendocrine tumors.

e16703 Background: ONC201 is an imipridone with specificity for the dopamine-like DRD2 receptor. Anti-cancer effects involve up-regulation of TRAIL/DR5, dual AKT/ERK pathway inhibition, and integrated stress response. Because TCGA analysis showed very high DRD2 expression in neuroendocrine tumors, especially pheochromocytoma-paragangliomas (PC-PG), an investigator initiated IND study of ONC201 in neuroendocrine tumors (CCF IRB17-808; CASE2716; IND132665; NCT03034200) was done. Methods: ONC201 dose was 625 mg po/wk. Metastatic PG-PG were enrolled in cohort A. Other neuroendocrine patients were entered in cohort B. Two additional patients had single patient IND. Because hypertension is an issue from catecholamine producing PC-PG, all PC-PG patients had combined alpha + beta blockade and bp was monitored in the clinical research unit after dose #1 ONC201. Additional data was obtained with daily home bp monitoring, often with a wireless cuff which connects into EPIC via MyChart. Labs, scans, and clinic visits were done at week 6, then every 3 months from initial ONC201 dose. Patients with clinical benefit remained on study and could get radiation for bone metastases. Results: Neuroendocrine tumors were treated with ONC201 included 10 PC-PG, 3 with MTC 13 with other varieties including sarcomas, adrenal cortical carcinoma (ACC), neuroblastoma, and GI neuroendocrine tumor (NET). ONC201 was exceptionally well tolerated. All patients were able to maintain or improve KPS while on study. No adverse effects on bp were seen. The only ONC201-related AE was temporary grade 1 neurocognitive dysfunction for ~36 hours after weekly ONC201 dosing in 2/10 PC-PG patients. 4/10 PC-PG patients remain on study at 28, 22, 22, and 4 month. 1 DSRCT patient achieved a PR at 3 months and has been treated 28 months. An ACC patient was initially responsive (PR), but rapidly progressed in liver; 1 GI NET patient had -10% reduction by RECIST at 3 months and remains on treatment. MTC may be responsive (1 no response, 2 stable and improving by RECIST at 3 months). Conclusions: ONC201 is very well tolerated with excellent quality of life and extended clinical benefit against neuroendocrine tumors. Although ONC201 has activity against neuroendocrine tumors, especially PC-PG, increased efficacy will likely require combination therapy. Clinical trial information: NCT03034200 . [Table: see text]

Insulinoma-Associated-1: From Neuroendocrine Tumor Marker to Cancer Therapeutics.

Insulinoma-associated-1 (IA-1 or INSM1) encodes a zinc-finger transcription factor, which was isolated from a human insulinoma subtraction library, with specific expression patterns, predominantly in developing neuroendocrine tissues and tumors. INSM1 is key in early pancreatic endocrine, sympatho-adrenal lineage, and pan-neurogenic precursor development. Insm1 gene ablation results in impairment of pancreatic β cells, catecholamine biosynthesis, and basal progenitor development during mammalian neocortex maturation. Recently, INSM1 has emerged as a superior, sensitive, and specific biomarker for neuroendocrine tumors. INSM1 regulates downstream target genes and exhibits extranuclear activities associated with multiple signaling pathways, including Sonic Hedgehog, PI3K/AKT, MEK/ERK1/2, ADK, p53, Wnt, histone acetylation, LSD1, cyclin D1, Ascl1, and N-myc. Novel strategies targeting INSM1-associated signaling pathways facilitate the suppression of neuroendocrine tumor growth. In addition, INSM1 promoter-driven reporter assay and/or suicide gene therapy are promising effective therapeutic approaches for targeted specific neuroendocrine tumor therapy. In this review, the current knowledge of the biological role of INSM1 as a neuroendocrine tumor biomarker is summarized, and novel strategies targeting multiple signaling pathways in the context of INSM1 expression in neuroendocrine tumors are further explored. IMPLICATIONS: Neuroendocrine transcription factor (INSM1) may serve as a neuroendocrine biomarker for the development of novel cancer therapeutics against neuroendocrine tumors.

PD-L1 expression in neuroendocrine tumors of the lung

BackgroundVarious tumors express programmed cell death ligand 1 (PD-L1), an immune checkpoint ligand, the expression of which correlates with certain effects of anti-programmed cell death 1 (PD-1)/PD-L1 drugs. The aim of this study was to assess the frequency of PD-L1 expression in each of the types of neuroendocrine tumors of the lung. MethodsThe subjects enrolled in this study were patients who had been diagnosed with neuroendocrine tumors of the lung and had been treated at the National Cancer Center Hospital (Tokyo, Japan) between 1982 and 2010. We performed immunohistochemical analysis on a tissue microarray (TMA) of the surgical specimens using the validated PD-L1 antibody clone, E1L3N. Tumor PD-L1 expression scores were calculated semiquantitatively (staining intensity [0–3]×stained area [0–100%]). A score of 1 was used as a cut-off to determine the presence or absence of PD-L1 expression. ResultsAmong the 227 patients included in this study, the patient demographics were as follows: median age (range), 65 years (19–84); sex (male/female), 168/59; pStage (IA, IB, IIA, IIB, IIIA, IIIB, IV): 79, 36, 25, 29, 47, 6, 5, respectively; and histology was typical carcinoid (TC), atypical carcinoid (AC), large cell neuroendocrine carcinoma (LCNEC), small cell lung cancer (SCLC): 46, 6, 106, 69, respectively. The numbers (proportions) of PD-L1-expression tumors were as follows: TC/AC/LCNEC/SCLC, 0/0/11 (10.4%)/4 (5.8%). ConclusionsPD-L1 expression was apparent in 10.4% of LCNEC and 5.8% of SCLC tumors, and was not observed in carcinoid tumors.

68Ga-Pentixafor-PET/CT for Imaging of Chemokine Receptor 4 Expression in Neuroendocrine Tumors - a head-to-head comparison with DOTATOC and FDG PET/CT

68Ga-Pentixafor-PET/CT for Imaging of Chemokine Receptor 4 Expression in Neuroendocrine Tumors - a head-to-head comparison with DOTATOC and FDG PET/CT

212 - New approach to analyzing gene expression in neuroendocrine tumors

212 - New approach to analyzing gene expression in neuroendocrine tumors

Nestin and Klotho protein expression in neuroendocrine tumors of the lung

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Imaging of chemokine receptor 4 expression in neuroendocrine tumors in comparison to DOTATOC and FDG PET/CT

Introduction: Diagnostic imaging of neuroendocrine tumors (NETs) is the domain of somatostatin receptor (SSTR) agonists as well as FDG PET/CT in dedifferentiated tumors. SSTR also serves as target for receptor directed peptide therapy. More recently, specific ligands targeting the chemokine receptor 4 (CXCR4) for diagnostic and therapeutic purposes were introduced potentially offering an additional theranostic option in NETs. Here we evaluated the CXCR4 expression using 68Ga-Pentixafor PET/CT in NET patients in comparison to 68Ga-DOTATOC and 18F-FDG PET/CT.

Abstract 3406: Enhancer of zeste homolog 2 (EZH2) expression and proliferation index (Ki-67) in neuroendocrine tumors of the gastrointestinal tract and pancreas

Abstract EZH2 is a polycomb group protein that is involved in the progression of multiple human cancers including prostatic, endometrial, and colonic adenocarcinomas. Its expression has been shown to increase from typical carcinoid to atypical carcinoid and further to small cell/large cell neuroendocrine carcinomas of the lung. Here we examine the EZH2 expression and the proliferation index (PI) by Ki-67 expression in neuroendocrine tumors of the gastrointestinal tract (GI) and pancreas. We retrieved 72 cases of GI and pancreatic neuroendocrine tumors of grades G1 (n = 56), G2 (n = 6) and G3 (n = 10) which were graded according to the WHO classification. Expression of EZH2 and Ki-67 was analyzed by immunohistochemistry using monoclonal antibodies (EZH2 at 1:200; Ki-67 at 1:70). Expression of EZH2 was determined to be low (10%), and was compared with the respective PI. All G1 tumors had low EZH2 expression and a low PI (20%). In G2 tumors, EZH2 expression was intermediate (1-10%) and PI was between 0-8%. One of the G2 tumors had a low PI of 0, however, the EZH2 expression was intermediate (3%). There was increased EZH2 expression relative to increasing tumor grade from G1 to G3 (p &amp;lt;0.05). EZH2 expression increases incrementally from G1 neuroendocrine tumors to G2 and further to G3 tumors, suggesting an association or a role in progression of neuroendocrine tumors. There is strong correlation between the expression of EZH2 and PI in G1, G2 and G3 tumors. EZH2 appears to be a better predictor of tumor grade in G2 tumors as compared to PI. Thus, EZH2 could be used as an additional diagnostic marker in examining atypical GI neuroendocrine tumors. Citation Format: Jia Qin, Raag Agrawal, Miguel G. Echevarria, LAura A. Martello, M.A Haseeb, Raavi Gupta. Enhancer of zeste homolog 2 (EZH2) expression and proliferation index (Ki-67) in neuroendocrine tumors of the gastrointestinal tract and pancreas. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3406. doi:10.1158/1538-7445.AM2015-3406

Down-Regulation of miR-129-5p and the let-7 Family in Neuroendocrine Tumors and Metastases Leads to Up-Regulation of Their Targets Egr1, G3bp1, Hmga2 and Bach1.

Expression of miRNAs in Neuroendocrine Neoplasms (NEN) is poorly characterized. We therefore wanted to examine the miRNA expression in Neuroendocrine Tumors (NETs), and identify their targets and importance in NET carcinogenesis. miRNA expression in six NEN primary tumors, six NEN metastases and four normal intestinal tissues was characterized using miRNA arrays, and validated by in-situ hybridization and qPCR. Among the down-regulated miRNAs miR-129-5p and the let-7f/let-7 family, were selected for further characterization. Transfection of miR-129-5p inhibited growth of a pulmonary and an intestinal carcinoid cell line. Analysis of mRNA expression changes identified EGR1 and G3BP1 as miR-129-5p targets. They were validated by luciferase assay and western blotting, and found robustly expressed in NETs by immunohistochemistry. Knockdown of EGR1 and G3BP1 mimicked the growth inhibition induced by miR-129-5p. let-7 overexpression inhibited growth of carcinoid cell lines, and let-7 inhibition increased protein content of the transcription factor BACH1 and its targets MMP1 and HMGA2, all known to promote bone metastases. Immunohistochemistry analysis revealed that let-7 targets are highly expressed in NETs and metastases. We found down-regulation of miR-129-5p and the let-7 family, and identified new neuroendocrine specific targets for these miRNAs, which contributes to the growth and metastatic potential of these tumors.

Establishment of robust controls for the normalization of miRNA expression in neuroendocrine tumors of the ileum and pancreas

There is need to determine tissue-specific robust controls for normalization of microRNA expression to avoid false results and misinterpretation. The aim of this study was to evaluate the expression of different small RNAs in neuroendocrine tumors (NETs) and their suitability as normalizers in miRNA real-time PCR experiments. We investigated the expression of the nine small RNAs miR-93, miR-191, SNORD48, SNORD61, SNORD68, SNORD72, SNORD95, SNORD96a, and RNU6-2 in formalin-fixed, paraffin-embedded tissue samples of 25 ileal NETs by real-time PCR determining the most stable controls for expression normalization using four different algorithms. This analysis was expended to ten pancreatic NETs. Finally, five small RNAs were further tested as normalizers for miRNA-133a expression, which is known to be downregulated in metastases of ileal NETs, in ten matched pairs of ileal NETs and their metastases. Ranking of the expression results revealed the following order of stability from high to low: SNORD61 < SNORD95 < SNORD72 < SNORD96a < SNORD68 < miR-191 < miR-93 < RNU6-2 < SNORD48 for ileal NETs and SNORD95 < miR-93 < SNORD96a < SNORD61 < SNORD68 < SNORD72 < RNU6-2 < miR-191 < SNORD48 for pancreatic NETs. The determination of SNORD61 and SNORD95 for ileal NETs and SNORD95 and miR-93 for pancreatic NETs as good normalizers presents a useful tool for experiments involving the analysis of miRNA expression.

Peptide receptor radionuclide therapy of neuroendocrine tumors with 90Y-DOTATOC: Is treatment response predictable by pre-therapeutic uptake of 68Ga-DOTATOC?

PET with (68)Ga-DOTATOC allows for imaging and quantitative assessment of somatostatin receptor expression in neuroendocrine tumors (NET). The aim of this retrospective study was to analyze whether pre-therapeutic (68)Ga-DOTATOC PET/CT is able to predict response to Peptide Receptor Radionuclide Therapy (PRRT). Forty patients with advanced stage NET were treated with a fixed dose of (90)Y-DOTATOC (5550 or 3700MBq). Prior to PRRT, each patient received (68)Ga-DOTATOC PET/CT. Treatment results were evaluated after 3months by CT, tumor marker levels and clinical course and correlated with (68)Ga-DOTATOC uptake (SUVmax) and the assumed uptake of (90)Y-DOTATOC in tumor manifestations (MBq/g). ROC analysis and pairwise comparison of area under the curve (AUC) were performed with pre-treatment uptake of (68)Ga-DOTATOC, assumed uptake of (90)Y-DOTATOC and treatment activity alone and in relation to body weight as continuous variables, and response/no response as classification variable. According to conventional criteria (tumor shrinkage, decrease of tumor markers, improved or stable clinical condition), 20 patients were classified as responders, 16 as non-responders and in four patients findings were equivocal. Using a SUV more than 17.9 as cut-off for favorable outcome, PET was able to predict treatment response of all responders and 15 out of 16 non-responders. All four patients with equivocal findings showed SUV less than or equal to 17.9 and soon experienced tumor progression. The assumed uptake of (90)Y-DOTATOC in tumor manifestations using a cut-off more than 1.26MBq/g as predictor of response was able to correctly classify 19 out of 20 responders, and 14 out of 16 non-responders. In all patients with equivocal findings, the assumed uptake of (90)Y-DOTATOC was below 1.26MBq/g. Pre-therapeutic (68)Ga-DOTATOC tumor uptake as well as assumed uptake of (90)Y-DOTATOC are strongly associated with the results of subsequent PRRT. The defined cut-off values should be confirmed by prospective studies and may then provide the rationale for individual dosing and selecting patients with high likelihood of favorable treatment outcome.

Expression of Notch-1 and alteration of the E-cadherin/β-catenin cell adhesion complex are observed in primary cutaneous neuroendocrine carcinoma (Merkel cell carcinoma)

Increasing evidence indicates that Notch signaling contributes to physiological processes, including development and differentiation, as well as tumorigenesis, either as a tumor promoter or suppressor, depending on cellular context, expression levels and cross talk with other signaling systems. Recent studies reported absent or minimal Notch-1 expression in neuroendocrine tumors of the lung and gastrointestinal tract, suggesting a tumor-suppressor function of Notch-1. Merkel cell carcinoma is a rare and highly aggressive primary cutaneous neuroendocrine carcinoma. Because no information is available on Notch-1 expression in this tumor, we have investigated a series of 31 Merkel cell carcinoma for Notch-1 immunoreactivity. Immunoreactivities for E-cadherin and β-catenin were also analyzed. All but 1 Merkel cell carcinoma (30 of 31) retained cytoplasmic and membrane Notch-1 expression in more than 50% of cells. β-Catenin displayed a prevalent membrane-associated staining in 30 of 31 cases, and 22 cases showed more than 50% of immunoreactive cells whereas nuclear β-catenin was seen only in 2 of 31 cases. E-cadherin membranous expression was remarkably low, as only 1 of 26 cases was found positive in more than 50% of cells. In contrast with neuroendocrine tumors in other tissues, evident Notch-1 expression was found in Merkel cell carcinoma. This finding does not support a tumor-suppressor function of Notch-1 in Merkel cell carcinoma. Downregulation of E-cadherin and diffuse membranous β-catenin expression suggest a dysregulation of the E-cadherin/β-catenin complex in Merkel cell carcinoma. This may contribute to local invasion and distant metastasis.

Immunohistochemical Expression of Estrogen and Progesterone Receptors in Primary Pulmonary Neuroendocrine Tumors

Lung and breast carcinomas are among the most prevalent cancers. Advances in cancer therapies can provide survival benefit and be potentially curative, even in metastatic disease. Due to the high prevalence of these carcinomas, it is not unusual to encounter lung nodule(s) in a patient with breast carcinoma, and distinguishing between primary and metastatic disease is critical for management/treatment. Occasionally neuroendocrine differentiation is present in breast carcinoma, making its distinction from pulmonary/nonpulmonary neuroendocrine tumors in the lung difficult. To assess estrogen and progesterone receptor expression in the entire spectrum of pulmonary neuroendocrine tumors. Seventy-one neuroendocrine neoplasms including typical carcinoids (42), atypical carcinoids (7), small cell carcinomas (14), large cell neuroendocrine carcinomas (2), and combined small cell carcinomas (6) were evaluated for estrogen and progesterone receptors. Mammary and non-small cell lung carcinomas were also stained for comparison. The entire spectrum of neuroendocrine neoplasms demonstrated focal to diffuse estrogen (typical carcinoid, 23; atypical carcinoid, 6; small cell carcinoma, 8; large cell neuroendocrine carcinoma, 2; combined small cell carcinoma, 4) and progesterone (typical carcinoid, 11; atypical carcinoid, 2; small cell carcinoma, 7; large cell neuroendocrine carcinoma, 0; combined small cell carcinoma, 2) expression. There was no correlation between sex and estrogen/progesterone status. Estrogen and progesterone staining were also noted in endothelial cells. Relative to neuroendocrine carcinomas, mammary carcinomas expressed estrogen and progesterone more frequently. Non-small cell carcinomas had greater and similar immunoreactivity for estrogen and progesterone, respectively. Although estrogen and progesterone receptor staining is frequently associated with breast and gynecologic primaries, it can also be observed in "nontarget" organs. Therefore, presence of estrogen and/or progesterone expression in neuroendocrine tumors involving the lung should not exclude a primary pulmonary neoplasm.

LKB1 protein expression in neuroendocrine tumors of the lung

During a recent investigation of LKB1 gene abnormality in lung lesions, strong expression of LKB1 protein in normal neuroendocrine (NE) cells of the bronchial epithelium was found. Because LKB1 functions as a tumor suppressor gene, the question of whether alteration of LKB1 expression is related to the development of pulmonary NE tumors of various grades was investigated. LKB1 immunohistochemistry was examined in a total of 68 primary pulmonary NE tumors consisting of 30 specimens of small cell lung carcinoma (SCLC), 23 large cell neuroendocrine carcinomas (LCNEC), two atypical carcinoids, and 13 typical carcinoids. Loss or low expression (<20% immunoreactive cells) of LKB1 protein expression was more frequently observed in high-grade NE tumors (SCLC and LCNEC; 45/53, 84.9%) than in typical and atypical carcinoids (3/15; 20%). The difference in LKB1 immunoreactivity between the high-grade NE tumors and the carcinoid group was statistically significant (P < 0.0001). In conclusion, marked reduction of LKB1 expression in high-grade NE tumors of the lung suggests a possible role of LKB1 inactivation in its tumorigenesis. Although a few previous studies indicated rare genetic alterations of LKB1 in SCLC, further studies including analysis of other NE tumors and focusing on epigenetic abnormalities of LKB1 gene are warranted.