Heterogeneous expression of neuroendocrine marker proteins in human undifferentiated carcinoma of the colon and rectum

A "conversion-deterioration-double mutation" theory for the evolution and progression of colorectal cancer

In this study, based on some clinical phenomena and recently published knowledge, we proposed our "conversion-deterioration-double mutation" theory, which provides a possible unifying explanation for the evolutionary process of colorectal cancer cells in the human body. In this theory, we proposed that there is a partial interconversion and a jump conversion relationship among normal colorectal epithelial cells, colorectal cancer cells, stem cells, and cancer stem cells (conversion). This conversion leads to tumor heterogeneity. We also proposed that well-differentiated cancer cells converted from cancer stem cells have a more aggressive pattern than primary cancer cells (deterioration). The deterioration of primary cancer cells leads to differences in treatment responses and prognosis. Finally, we speculate a double mutation theory, indicating that for metastasis to occur, both mutations of cancer cells and mutations of target organs are needed and should match and meet. All these three points constitute the "conversion-deterioration-double mutation" theory.

Prognostic relevance of neuroendocrine differentiation in colorectal cancer: a population-based, propensity score matching study

PURPOSE

Neuroendocrine differentiation (NED) may serve as a prognostic factor in colorectal cancer; however, the prognostic relevance of NED remains controversial. The aim of the present study was to determine whether NED influenced the survival of patients in colorectal cancer while exploring its potential interactions with other clinicopathological features.

METHODS

Patients with primary stage I to IV colorectal adenocarcinoma ranging between 2010 and 2015 were identified using the Surveillance, Epidemiology, and End Results database. The Kaplan-Meier technique, Cox proportional hazards model, propensity score matching, and stratification analyses were employed in this study.

RESULTS

A total of 94,291 patients (including 101 patients with NED and 94,190 patients without NED) were included. In the univariable analyses, NED was found to be correlated with a significantly poorer overall survival (hazard ratio (HR) of death = 3.09, 95% CI 2.42-3.95, P < 0.001) and cancer-specific survival (HR of death = 3.77, 95% CI 2.94-4.83, P < 0.001). Moreover, NED remained independently correlated with overall survival (HR of death = 1.84, 95% CI 1.34-2.51, P < 0.001) and cancer-specific survival (HR of death = 2.01, 95% CI 1.45-2.79, P < 0.001) after adjusting in multivariable and propensity score analyses. Furthermore, further stratification analyses indicated that the influence of NED on survival was not affected by tumor location, differentiation, T stage, and distant metastasis status; however, it was found to be associated with lymph node metastasis.

CONCLUSIONS

NED is associated with poor survival outcomes among colorectal cancer patients, especially in those with positive lymph nodes.

Optimal Bayesian Filtering for Biomarker Discovery: Performance and Robustness

Optimal Bayesian feature filtering (OBF) is a fast and memory-efficient algorithm that optimally identifies markers with distributional differences between treatment groups under Gaussian models. Here, we study the performance and robustness of OBF for biomarker discovery. Our contributions are twofold: (1) we examine how OBF performs on data that violates modeling assumptions, and (2) we provide guidelines on how to set input parameters for robust performance. Contribution (1) addresses an important, relevant, and commonplace problem in computational biology, where it is often impossible to validate an algorithm's core assumptions. To accomplish both tasks, we present a battery of simulations that implement OBF with different inputs and challenge each assumption made by OBF. In particular, we examine the robustness of OBF with respect to incorrect input parameters, false independence, imbalanced sample size, and we address the Gaussianity assumption by considering performance on an extensive family of non-Gaussian distributions. We address advantages and disadvantages between different priors and optimization criteria throughout. Finally, we evaluate the utility of OBF in biomarker discovery using acute myeloid leukemia (AML) and colon cancer microarray datasets, and show that OBF is successful at identifying well-known biomarkers for these diseases that rank low under moderated t-test.

Limited role of Chromogranin A as clinical biomarker for pancreatic neuroendocrine tumors

BACKGROUND

Serum Chromogranin A (CgA) is widely used as a biomarker for pancreatic neuroendocrine tumors (PanNETs). The aim of this study was to investigate the value of CgA as a diagnostic and prognostic marker for well-differentiated PanNETs.

METHODS

Patients with well-differentiated PanNET and a baseline CgA measurement, between 2011 and 2016 were reviewed. The diagnostic value was determined by comparing CgA values from patients with PanNETs to those with other pancreatic neoplasms and healthy controls. The Kaplan-Meier method was used to investigate the CgA prognostic significance.

RESULTS

Ninety-nine patients met inclusion criteria. As a diagnostic marker, CgA had a sensitivity of 66%, specificity of 95%, and overall accuracy of 71%. The use of PPIs was associated with a higher CgA level (p = 0.015). When excluding patients on PPIs, CgA accuracy in distinguishing PanNETs from other pancreatic neoplasms was 66%, the sensitivity and specificity were 60% and 75% respectively. Elevated CgA (p = 0.004), Ki67% (p < 0.001), tumor grade (p < 0.001) and stage of disease (p = 0.036) were associated with disease-specific survival.

CONCLUSION

CgA has a limited role as a diagnostic biomarker for well-differentiated PanNETs. An elevated CgA level may have prognostic value but its role should be further investigated with respect to other known pathological factors.

Differential expression of neurogenes among breast cancer subtypes identifies high risk patients

The nervous system is now recognized to be a relevant component of the tumor microenvironment. Receptors for neuropeptides and neurotransmitters have been identified in breast cancer. However, very little is known about the role of neurogenes in regulating breast cancer progression. Our purpose was to identify neurogenes associated with breast cancer tumorigenesis with a potential to be used as biomarker and/or targets for treatment. We used three databases of human genes: GeneGo, GeneCards and Eugenes to generate a list of 1266 relevant neurogenes. Then we used bioinformatics tools to interrogate two published breast cancer databases SAGE and MicMa (n=96) and generated a list of 7 neurogenes that are differentially express among breast cancer subtypes. The clinical potential was further investigated using the GOBO database (n=1881). We identified 6 neurogenes that are differentially expressed among breast cancer subtypes and whose expression correlates with prognosis. Histamine receptor1 (HRH1), neuropilin2 (NRP2), ephrin-B1 (EFNB1), neural growth factor receptor (NGFR) and amyloid precursor protein (APP) were differentially overexpressed in basal and HER2-enriched tumor samples and syntaxin 1A (STX1A) was overexpressed in HER2-enriched and luminal B tumors. Analysis of HRH1, NRP2, and STX1A expression using the GOBO database showed that their expression significantly correlated with a shorter overall survival (p < 0.0001) and distant metastasis-free survival (p < 0.0001). In contrast, elevated co-expression of NGFR, EFNB1 and APP was associated with longer overall (p < 0.0001) and metastasis-free survival (p < 0.0001). We propose that HRH1, NRP2, and STX1A can be used as prognostic biomarkers and therapeutic targets for basal and HER2-enriched breast cancer subtypes.

The Prognostic Significance of Neuroendocrine Differentiation in Colorectal Carcinomas: Our Experience

INTRODUCTION

Neuroendocrine differentiation in colorectal carcinomas, detected using immunohistochemistry and ultrastructural techniques, has been studied as a prognostic marker for invention of targeted therapy. There are a few studies done on this aspect which have shown conflicting results ranging from poor prognosis to no prognostic significance.

AIM

The aim of the study was to determine the clinical significance of neuroendocrine differentiation in colorectal carcinomas using immunohistochemical stains such as chromogranin A & synaptophysin in relation to its prognostic significance.

MATERIALS AND METHODS

A retrospective study was conducted wherein all the colorectal carcinomas, received in the Department of Pathology, over a period of 3 years, were reviewed. Neuroendocrine markers were done on 53 cases of moderately, poorly and undifferentiated adenocarcinomas. Based on the degree of immunoreactivity for these markers, tumours were divided into group 0, group 1, group 2, group 3 & group 4. Group 0 & 1 were categorized as neuroendocrine differentiation absent & group 2, 3 & 4 as present. Neuroendocrine differentiation was correlated with age, sex, grade, stage, diagnosis & survival. Follow up data of the cases was recorded.

RESULTS

Neuroendocrine differentiation was present in 18 cases (33.9%). The degree of immunoreactivity for neuroendocrine markers in present study were; group 0- 58%, 1- 7.5%, 2- 9%, 3- 13% & 4- 11%. The mean age of patients was 54 years with a slight male preponderance {M:F::1.6:1}. Most of the carcinomas with neuroendocrine differentiation belonged to Grade II (61%) & Stage II & III (83%). Neuroendocrine differentiation did not show any significant association with age, sex, location, histological type, grade, stage & survival.

CONCLUSION

The above results indicate that the presence of neuroendocrine differentiation cannot be recommended as a prognostic marker in colorectal carcinomas.

Manganese superoxide dismutase (SOD2/MnSOD)/catalase and SOD2/GPx1 ratios as biomarkers for tumor progression and metastasis in prostate, colon, and lung cancer

The role of manganese-dependent superoxide dismutase (SOD2/MnSOD) during tumor progression has been studied for several decades with controversial results. While SOD2 downregulation was initially associated with tumor initiation and was proposed as a tumor suppressor gene, recent studies have reported that SOD2 might favor tumor progression and dissemination. To our knowledge this is the first time that changes in SOD2 expression in three different types of tumors, i.e., prostate, lung, and colon cancer, are studied by analyzing both SOD2 mRNA and protein levels in a total of 246 patients' samples. In prostate samples, SOD2 protein levels were also increased, especially in middle stage tumors. In the case of colon and lung tumors both mRNA and protein SOD2 levels were increased in malignant tissues compared to those in nontumor samples. More importantly, all metastases analyzed showed increased levels of SOD2 when compared to those of normal primary tissue and healthy adjacent tissue. Together, these results suggest that a common redox imbalance in these three types of tumor occurs at intermediate stages which then might favor migration and invasion, leading to a more aggressive cancer type. Consequently, the ratios SOD2/catalase and SOD2/Gpx1 could be considered as potential markers during progression from tumor growth to metastasis.

Identification of a multi-cancer gene expression biomarker for cancer clinical outcomes using a network-based algorithm

Cancer types are commonly classified by histopathology and more recently through molecular characteristics such as gene expression, mutations, copy number variations, and epigenetic alterations. These molecular characterizations have led to the proposal of prognostic biomarkers for many cancer types. Nevertheless, most of these biomarkers have been proposed for a specific cancer type or even specific subtypes. Although more challenging, it is useful to identify biomarkers that can be applied for multiple types of cancer. Here, we have used a network-based exploration approach to identify a multi-cancer gene expression biomarker highly connected by ESR1, PRKACA, LRP1, JUN and SMAD2 that can be predictive of clinical outcome in 12 types of cancer from The Cancer Genome Atlas (TCGA) repository. The gene signature of this biomarker is highly supported by cancer literature, biological terms, and prognostic power in other cancer types. Additionally, the signature does not seem to be highly associated with specific mutations or copy number alterations. Comparisons with cancer-type specific and other multi-cancer biomarkers in TCGA and other datasets showed that the performance of the proposed multi-cancer biomarker is superior, making the proposed approach and multi-cancer biomarker potentially useful in research and clinical settings.

Role of SNARE proteins in tumourigenesis and their potential as targets for novel anti-cancer therapeutics

The function of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) in cellular trafficking, membrane fusion and vesicle release in synaptic nerve terminals is well characterised. Recent studies suggest that SNAREs are also important in the control of tumourigenesis through the regulation of multiple signalling and transportation pathways. The majority of published studies investigated the effects of knockdown/knockout or overexpression of particular SNAREs on the normal function of cells as well as their dysfunction in tumourigenesis promotion. SNAREs are involved in the regulation of cancer cell invasion, chemo-resistance, the transportation of autocrine and paracrine factors, autophagy, apoptosis and the phosphorylation of kinases essential for cancer cell biogenesis. This evidence highlights SNAREs as potential targets for novel cancer therapy. This is the first review to summarise the expression and role of SNAREs in cancer biology at the cellular level, their interaction with non-SNARE proteins and modulation of cellular signalling cascades. Finally, a strategy is proposed for developing novel anti-cancer therapeutics using targeted delivery of a SNARE-inactivating protease into malignant cells.

Stem cell dynamics in homeostasis and cancer of the intestine

Intestinal stem cells (ISCs) and colorectal cancer (CRC) biology are tightly linked in many aspects. It is generally thought that ISCs are the cells of origin for a large proportion of CRCs and crucial ISC-associated signalling pathways are often affected in CRCs. Moreover, CRCs are thought to retain a cellular hierarchy that is reminiscent of the intestinal epithelium. Recent studies offer quantitative insights into the dynamics of ISC behaviour that govern homeostasis and thereby provide the necessary baseline parameters to begin to apply these analyses during the various stages of tumour development.

Prognostic significance of neuroendocrine differentiation in colorectal adenocarcinoma after radical operation: a meta-analysis

BACKGROUND

The phenomenon of neuroendocrine differentiation has been observed in colorectal adenocarcinoma. However, the ability of neuroendocrine differentiation to predict the outcome of colorectal adenocarcinoma remains controversial.

METHODS

We conducted an extensive search of research studies related to neuroendocrine differentiation using scientific databases, including the PubMed, Embase, OVID, BIOSIS Previews, and Cochrane Central Register of Controlled Trials (up to July, 2013), according to the established search terms. RevMan version 5.2 statistical program was used to analyze the data. An odds ratio (OR) with a 95% confidence interval (CI) was used for the dichotomous data.

RESULTS

Eleven studies with a total of 1,587 patients were included. Patients with neuroendocrine differentiation who underwent a radical operation had a lower 5-year survival rate (pooled OR 0.60, 95% CI 0.37-0.97) compared with those without neuroendocrine differentiation, with evidence of moderate heterogeneity (I (2) = 37%, p = 0.10). A sensitivity analysis and meta-regression showed that the different classification criteria of neuroendocrine differentiation used in these studies were the main source of heterogeneity. When the strong positive rates of neuroendocrine differentiation indicators between the higher (stage III + IV) and the lower (stage I + II) clinical stages were compared, the pooled OR was 1.84 (703 patients; 95% CI 0.98-3.43) without evidence of heterogeneity (I (2) = 0 %, p = 0.89). However, comparisons between consecutive stages showed different ORs: stage II vs. I (203 patients; OR = 0.52, 95% CI 0.17-1.56), stage III vs. II (569 patients; OR = 2.27, 95% CI 1.03-4.98), and stage IV vs. III (375 patients; OR = 1.81, 95% CI 1.00-3.29).

CONCLUSION

The patients with strong positive indicators of neuroendocrine differentiation had a lower 5-year survival rate. The ability to detect neuroendocrine indicators using conventional methods could improve the prognosis judgment of colorectal adenocarcinoma.

Long term outcomes of neuroendocrine carcinomas (high-grade neuroendocrine tumors) of the colon, rectum, and anal canal

INTRODUCTION AND AIM

Neuroendocrine carcinomas (NEC) of the large intestine are rare and aggressive neoplasms. This study was designed to review the experience at a single institution and analyze the outcomes to improve our understanding of these tumors.

METHODS

The patients with NEC (high-grade neuroendocrine tumor) of the colon, rectum, and anal canal were identified from June 1993 to April 2011. Clinical features studied were patient demographics, presenting symptoms, tumor location, tumor stage, treatment status and length of follow-up.

RESULTS

Twenty-five patients were identified. Stages of the diseases were I (n=5), II (n=1), III (n=10) and IV (n=9). Locations of the tumors were: colon (36%); rectum (28%) and anal canal (36%). Rectal bleeding (36%) and pain (32%) were the most common symptoms but 16% of patients were asymptomatic. Among the patients with local or locally advanced disease, only five patients had surgery alone. The remainder of the patients underwent chemotherapy with/without radiation. Mean follow-up was 33.7 ± 8.4 months after diagnosis. NEC of the large bowel and anal canal has very distinctive pathologic features and a very poor prognosis. More than one third of the patients with NEC had metastatic disease at the time of diagnosis. When these tumors are in an advanced stage none of the treatment modalities impact on survival.

CONCLUSION

The present study showed the poor prognosis of these rare tumors.

INSL5 is a novel marker for human enteroendocrine cells of the large intestine and neuroendocrine tumours

We report for the first time the distribution of human INSL5 and its cognate leucine rich G-protein coupled receptor RXFP4 in the large intestine and in neuroendocrine/carcinoid tissues. Immunoreactive INSL5 was uniquely expressed by enteroendocrine cells (EECs) located within the colonic mucosa, whereas colonocytes were immunopositive for RXFP4. INSL5+ and RXFP4+ cells were also detected in human neuroendocrine/carcinoid tissues. We employed a recently described Insl5 knockout mouse model and 2 mouse models of induced colitis to address the relevance of Insl5 in EEC development and in acute inflammation of the colon. We identified INSL5 as a specific marker for synaptophysin+ EECs in the mucosa of the normal human and mouse colon. Insl5 was not essential for the development of mouse synaptophysin+ EECs. The mouse models of chemically induced colitis (dextran sulfate sodium and dinitrobenzene-sulfonic acid) failed to show changes in the numbers of Insl5+ EECs at inflammatory sites during the acute phase of colitis. In conclusion, we showed that INSL5 is a novel marker of colorectal EECs and provide first evidence for the presence of a potentially autocrine/paracrine INSL5-RXFP4 signaling system in the normal human and mouse colon and in rare human neuroendocrine tumours.

Characterization of mammary cancer stem cells in the MMTV-PyMT mouse model

Breast cancer stem cells, the root of tumor growth, present challenges to investigate: Primary human breast cancer cells are difficult to establish in culture and inconsistently yield tumors after transplantation into immune-deficient recipient mice. Furthermore, there is limited characterization of mammary cancer stem cells in mice, the ideal model for the study of breast cancer. We herein describe a pre-clinical breast cancer stem cell model, based on the properties of cancer stem cells, derived from transgenic MMTV-PyMT mice. Using a defined set of cell surface markers to identify cancer stem cells by flow cytometry, at least four cell populations were recovered from primary mammary cancers. Only two of the four populations, one epithelial and one mesenchymal, were able to survive and proliferate in vitro. The epithelial population exhibited tumor initiation potential with as few as 10 cells injected into syngeneic immune-competent recipients. Tumors initiated from injected cell lines recapitulated the morphological and physiological components of the primary tumor. To highlight the stemness potential of the putative cancer stem cells, B lymphoma Mo-MLV insertion region 1 homolog (Bmi-1) expression was knocked down via shRNA targeting Bmi-1. Without Bmi-1 expression, putative cancer stem cells could no longer initiate tumors, but tumor initiation was rescued with the introduction of a Bmi-1 overexpression vector in the Bmi-1 knockdown cells. In conclusion, our data show that primary mammary cancers from MMTV-PyMT mice contain putative cancer stem cells that survive in culture and can be used to create a model for study of mammary cancer stem cells.

The clinical relevance of chromogranin A as a biomarker for gastroenteropancreatic neuroendocrine tumors

Chromogranin A, although it exhibits limitations, is currently the most useful general tumor biomarker available for use in the diagnosis and management of gastroenteropancreatic neuroendocrine tumors (NETs). The value of the chromogranin A lies in its universal cosecretion by the majority of neuroendocrine cells that persists after malignant transformation. Clinicians aware of the physiologic role of chromogranin A and its secretion in a variety of non-NET-related pathologic conditions can use this protein as a moderately effective tumor biomarker in the management of GEP-NETs.

Colon cancer stem cells: implications in carcinogenesis

The cancer stem cell model was described for hematologic malignancies in 1997 and since then evidence has emerged to support it for many solid tumors as well, including colon cancer. This model proposes that certain cells within the tumor mass are pluripotent and capable of self-renewal and have an enhanced ability to initiate distant metastasis. The cancer stem cell model has important implications for cancer treatment, since most current therapies target actively proliferating cells and may not be effective against the cancer stem cells that are responsible for recurrence. In recent years great progress has been made in identifying markers of both normal and malignant colon stem cells. Proteins proposed as colon cancer stem cell markers include CD133, CD44, CD166, ALDH1A1, Lgr5, and several others. In this review we consider the evidence for these proteins as colon cancer stem cell markers and as prognostic indicators of colon cancer survival. Additionally, we discuss potential functions of these proteins and the implications this may have for development of therapies that target colon cancer stem cells.

Single-cell cloning of colon cancer stem cells reveals a multi-lineage differentiation capacity

Colon carcinoma is one of the leading causes of death from cancer and is characterized by a heterogenic pool of cells with distinct differentiation patterns. Recently, it was reported that a population of undifferentiated cells from a primary tumor, so-called cancer stem cells (CSC), can reconstitute the original tumor on xenotransplantation. Here, we show that spheroid cultures of these colon CSCs contain expression of CD133, CD166, CD44, CD29, CD24, Lgr5, and nuclear beta-catenin, which have all been suggested to mark the (cancer) stem cell population. More importantly, by using these spheroid cultures or freshly isolated tumor cells from multiple colon carcinomas, we now provide compelling evidence to indicate that the capacity to propagate a tumor with all differentiated progeny resides in a single CSC. Single-cell-cloned CSCs can form an adenocarcinoma on xenotransplantation but do not generate the stroma within these tumors. Moreover, they can self-renew and are capable of multilineage differentiation. Further analysis indicated that the lineage decision is dictated by phosphoinositide 3-kinase (PI3K) signaling in CSCs. These data support the hypothesis that tumor hierarchy can be traced back to a single CSC that contains multilineage differentiation capacity, and provides clues to the regulation of differentiation in colon cancers in vivo.

Poorly differentiated neuroendocrine cell carcinoma of the rectum: report of a case and literal review

A 56-year-old man was admitted to our hospital because of anal bleeding. Colonoscopy and barium enema revealed type 4 tumor in the rectum. Biopsy revealed poorly differentiated adenocarcinoma. Low anterior resection with total mesorectal excision and lymph node dissection was performed. In immunohistochemical staining, chromogranin A and synaptophysin were positive at major lesion, and CEA were focal positive. The resected tumor was diagnosed pathologically as neuroendocrine cell carcinoma. The Ki-67 labeling index (LI) was 87.8%, so proliferative activity and potential malignancy was very high. Multiple metastatic tumors appeared in pelvis and lung eight months after operation. Treatment for neuroendocrine cell carcinoma of the rectum was controversial. Surgical resection and adjuvant chemotherapy might be one of the methods for gastrointestinal neruroendocrine cell carcinoma.

Identification of differentially expressed proteins in colorectal cancer by proteomics: Down-regulation of secretagogin

To identify proteins with colorectal cancer-specific regulation, comparative 2-DE of individual-matched normal and neoplastic colorectal tissue specimens was performed. We found 15 protein spots with concordantly increased and 20 protein spots with concordantly decreased intensity in tumor tissue (expression regulation more than fivefold). Nine of these proteins were identified by MS/MS. Interestingly, one of the proteins, which exhibited a marked down-regulation in colorectal cancer tissues, was the recently identified endocrine cell-expressed protein secretagogin. The reduction of the secretagogin content in colorectal cancer tissues was confirmed by comparative immunoblotting (n = 17) and RT-PCR (n = 22) as well as by immunohistochemistry (n = 45) of individual-matched neoplastic and normal colorectal tissue specimens. Immunohistochemistry revealed absence of secretagogin-expressing cells in most of the colorectal cancer tissue specimens. However, some colorectal cancers were characterized by secretagogin-expressing cells. In normal mucosa, positively stained cells exhibited a neuroendocrine cell-characteristic morphology and mucosal location. In colorectal cancer tissues, secretagogin-expressing cells were characterized by a malignant morphology. Our findings might represent the basis for the clinical application of secretagogin as a biomarker for a distinct subgroup of colorectal cancers.

Secretagogin is a novel marker for neuroendocrine differentiation

Our previous microarray-based studies identified secretagogin to be highly expressed in normal colon mucosa compared to basal expression in colon adenocarcinomas. The aim of this study was to analyze the differential expression of secretagogin in normal mucosa, adenocarcinomas, and neuroendocrine tumors. Western blotting, immunohistochemistry, immunofluorescence microscopy and ELISA were applied. Western blot analysis detected a 32-kDa secretagogin band in samples from normal mucosa. Immunohistochemical analyses on tissue specimens showed that secretagogin is exclusively expressed in neuroendocrine cells and nerve cells in normal mucosa of the digestive tract. Tissues adjacent to benign hyperplasic polyps and adenomas showed a decreased number of secretagogin-expressing neuroendocrine cells. Secretagogin co-localized with neuroendocrine markers (chromogranin A, neuron-specific enolase, synaptophysin) in neuroendocrine cells in crypts of normal mucosa, and in tumor cells of carcinoids. Secretagogin was strongly expressed in the cytosol and the nucleus of 19 well-differentiated neuroendocrine carcinoids and carcinoid metastases, as well as in neuroendocrine tumors from the lung, pancreas and adrenal gland. Secretagogin was detected in plasma from carcinoid patients with distant metastasis. Combined immunohistochemical analysis of secretagogin and FK506-binding protein 65, a protein de novo synthesized in adenocarcinomas, distinguished well-differentiated carcinoids, adenocarcinoids and undifferentiated carcinomas. We conclude that secretagogin is a novel marker for neuroendocrine differentiation.