Detection of chromogranin A mRNA in small cell lung carcinoma using a new, highly sensitive in situ hybridization method with a non-radioisotope oligonucleotide probe

Three Molecular Subtypes of Gastric Adenocarcinoma Have Distinct Histochemical Features Reflecting Epstein-Barr Virus Infection Status and Neuroendocrine Differentiation

Current histopathologic classification schemes for gastric adenocarcinoma have limited clinical utility and are difficult to apply due to tumor heterogeneity. Elucidation of molecular subtypes of gastric cancer may contribute to our understanding of gastric cancer biology and to the development of new molecular markers that may lead to improved diagnosis, therapy, or prognosis. We previously demonstrated that Epstein-Barr virus (EBV)-infected gastric cancers have a distinct human gene expression profile compared with uninfected cancers. We now examine the histopathologic features characterizing infected (n=14) and uninfected (n=89) cancers; the latter of which are now further divided into 2 major molecular subtypes based on expression patterns of 93 RNAs. One uninfected gastric cancer subtype was distinguished by upregulation of 3 genes with neuroendocrine (NE) function (CHGA, GAST, and REG4 encoding chromogranin, gastrin, and the secreted peptide REG4 involved in epithelial cell regeneration), implicating hormonal factors in the pathogenesis of a major class of gastric adenocarcinomas. Evidence of NE differentiation (molecular, immunohistochemical, or morphologic) was mutually exclusive of EBV infection. EBV-infected tumors tended to have solid-type morphology with lymphoid stroma. This study reveals novel molecular subtypes of gastric cancer and their associated morphologies that demonstrate divergent NE features.

The PAS positive material in gastric cancer cells of signet ring type is not mucin

PURPOSE

The purpose of this study is to assess the exocrine and neuroendocrine properties of tumour cells in diffuse gastric cancer with signet ring cell differentiation.

MATERIAL AND METHODS

Mucin mRNA and protein expressions (MUC1, 2, 3, 4, 5AC, 6 and MUC13) were assessed by immunohistochemistry and in situ hybridization. The neuroendocrine properties were evaluated by protein and mRNA expression of the general neuroendocrine markers chromogranin A and synaptophysin.

RESULTS

No MUC expression was observed in signet ring tumour cells including the amorphous substance in any of the nine cases. All cases showed immunoreactivity to synaptophysin, and seven out of nine cases immunoreactivity to chromogranin A in signet ring and non-signet ring tumour cells. Chromogranin A mRNA expression was observed in tumour cells in all samples with retained mRNA.

CONCLUSIONS

The lack of MUC protein and mRNA in signet ring tumour cells suggests the amorphous substance is not mucin. The lack of MUC mRNA expression in non-signet ring tumour cells questions exocrine differentiation in this tumour group. The abundant protein expression of the general neuroendocrine markers CgA and synaptophysin, and mRNA expression in tumour cells strengthens the hypothesis that this tumour group may be of neuroendocrine origin.

In situ hybridization in human and rodent tissue by the use of a new and simplified method

In situ hybridization (ISH) is a method that detects and localizes DNA or RNA in morphologically preserved tissue and cell preparations. The method is based on the principle that DNA or RNA will undergo hydrogen binding to complimentary sequences. Selective probes are labeled and used in order to detect specific sequences in tissues or cell preparations. Even though the method has improved over the past decades, there are still issues with sensitivity and specificity. The protocols are nonstandardized, and often time consuming due to multiple steps. In this paper, we have used a new and commercially available ISH kit for the detection of mRNA in formalin-fixed paraffin-embedded tissue. We have used both human and Mongolian gerbil tissue, and we evaluated mRNA expression of the neuroendocrine markers chromogranin A and histidine decarboxylase in both normal tissue and poorly differentiated tumor. In our experience, this method offers excellent sensitivity and specificity. The protocol is more standardized, and our results have been consistent. It is also less time consuming than conventional ISH protocols.

Consensus diagnoses and mode of action for the formation of gastric tumors in rats treated with the chloroacetanilide herbicides alachlor and butachlor

A panel of pathologists (Panel) was formed to evaluate the pathogenesis and human relevance of tumors that developed in the fundic region of rat stomachs in carcinogenicity and mechanistic studies with alachlor and butachlor. The Panel evaluated stomach sections stained with hematoxylin and eosin, neuron-specific enolase, and chromogranin A to determine the presence and relative proportion of enterochromaffin-like (ECL) cells in the tumors and concluded all tumors were derived from ECL cells. Biochemical and pathological data demonstrated the tumor formation involved a nongenotoxic threshold mode of action (MOA) initially characterized by profound atrophy of the glandular fundic mucosa that affected gastric glands, but not surface epithelium. This resulted in a substantial loss of parietal cells and a compensatory mucosal cell proliferation. The loss of parietal cells caused a marked increase in gastric pH (hypochlorhydria), leading to sustained and profound hypergastrinemia. The mucosal atrophy, together with the increased gastrin, stimulated cell growth in one or more ECL cell populations, resulting in neoplasia. ECL cell autocrine and paracrine effects led to dedifferentiation of ECL cell tumors. The Panel concluded the tumors develop via a threshold-dependent nongenotoxic MOA, under conditions not relevant to humans.

Presence of chromogranin-derived antimicrobial peptides in plasma during coronary artery bypass surgery and evidence of an immune origin of these peptides

Chromogranin A (CGA) and chromogranin B (CGB) are acidic proteins stored in secretory organelles of endocrine cells and neurons. In addition to their roles as helper proteins in the packaging of peptides, they may serve as prohormones to generate biologically active peptides such as vasostatin-1 and secretolytin. These molecules derived from CGA and CGB, respectively, possess antimicrobial properties. The present study demonstrates that plasmatic levels of both vasostatin-1 and secretolytin increase during surgery in patients undergoing cardiopulmonary bypass (CPB). Vasostatin-1 and secretolytin, initially present in plasma at low levels, are released just after skin incision. Consequently, they can be added to enkelytin, an antibacterial peptide derived from proenkephalin A, for the panoply of components acting as a first protective barrier against hypothetical invasion of pathogens, which may occur during surgery. CGA and CGB, more commonly viewed as markers for endocrine and neuronal cells, were also found to have an immune origin. RNA messengers coding for CGB were amplified by reverse transcription-polymerase chain reaction in human monocytes, and immunocytochemical analysis by confocal microscopy revealed the presence of CGA or CGB or both in monocytes and neutrophils. A combination of techniques including confocal microscopic analysis, mass spectrometry measurement, and antibacterial tests allowed for the identification of the positive role of interleukin 6 (IL-6) in the secretolytin release from monocytes in vitro. Because IL-6 release is known to be strongly enhanced during CPB, we suggest a possible relationship between IL-6 and the increased level of secretolytin in patients undergoing CPB.

Neuroendocrine differentiation in gastric adenocarcinomas associated with severe hypergastrinemia and/or pernicious anemia

Patients with hypergastrinemia secondary to achlorhydria have an increased risk of developing ECL cell carcinoids and gastric adenocarcinomas. Hypergastrinemia is central in the pathogenesis of ECL cell carcinoids, but the link between gastrin and gastric carcinomas is controversial. During neoplastic transformation ECL cells may, however, lose many of their neuroendocrine characteristics, making them difficult to recognise as neuroendocrine with conventional immunohistochemical techniques. Neuroendocrine differentiation was therefore examined in eight gastric adenocarcinomas found in seven patients with severe hypergastrinemia and/or pernicious anemia using a monoclonal antibody towards chromogranin A and immunohistochemistry without and with a sensitive signal amplification technique. The Sevier-Munger method was used as a more specific marker of ECL cells. Seven of the carcinomas contained scattered neuroendocrine tumour cells. When using signal amplification, an increase in the number of immunoreactive neoplastic cells was seen. In many tumours, clusters or confluent sheets of such cells were disclosed, suggesting a neuroendocrine and ECL cell origin. These tumours may therefore be ECL cell carcinomas and hypergastrinemia may thus be involved in the tumourigenesis.

34betaE12 cytokeratin immunodetection in the differential diagnosis of neuroendocrine carcinomas of the breast

Neuroendocrine (NE) carcinomas of the breast share morphologic and immunohistochemical features with NE tumors of other sites, either resembling typical carcinoids or the highly aggressive small cell carcinoma. In addition, some mucinous carcinomas or solid/papillary carcinomas may show a major NE component. This is generally recognized by specific immunodetection of pan-endocrine markers, although this approach may fail to recognize NE tumors lacking immunoreactivity for some NE products, because the antigen is produced but not retained in the cytoplasm. It has recently been reported that high molecular weight (HMW) cytokeratin (CK), recognized by clone 34betaE12, immunostaining selectively labels non-NE carcinomas (squamous-cell and adenocarcinomas) of the aerodigestive tract and lung. The role of such CK immunodetection in the differential diagnosis of NE carcinoma of the breast was evaluated. Twenty-four cases of breast carcinomas having NE differentiation were selected. Twenty-four cases of non-NE invasive breast carcinomas served as controls. HMW CK immunoreactivity was found in all but one case of non-NE carcinomas, but in only two NE tumors (having scattered positive cells only). The authors conclude that in breast carcinomas the presence of HMW CK immunoreactivity favors the diagnosis of non-NE carcinoma, whereas its absence supports that of a NE tumor (either a carcinoid or a small cell carcinoma or a mucinous carcinoma). HMW CK can be added to the list of markers useful in the differential diagnosis of NE from non-NE tumors.

34betaE12 Cytokeratin Immunodetection in the Differential Diagnosis of Small Cell Tumors of Lung

The group of small cell tumors of the lung includes fine following: (1) small cell carcinoma (SCC) of neuroendocrine (NE) origin, (2) poorly differentiated squamous carcinoma, (3) the rare basaloid (basal cell) carcinomas, and (4) malignant lymphomas, primitive neuroectodermal tumors (PNETs), and rhabdomyosarcomas. The differential diagnosis among these entities carries a heavy therapeutic impact but may be difficult in small biopsy specimens or in cytologic material, especially if necrosis or artifactual alterations are present. The use of additional techniques such as immunostaining for NE markers is not always helpful, since immunoreactive chromogranin A is detectable in only a small percentage of small cell carcinomas. It has recently been reported that in the aerodigestive tract 34betaE12 cytokeratin (CK) immunostaining selectively labels non-NE carcinomas, including squamous cell carcinoma, adenocarcinoma, and the rare basaloid carcinoma. We evaluated the role of such CK immunodetection in the differential diagnosis of small cell lung tumors in cytologic and biopsy specimens. Eighty-one lung tumors diagnosed by means of endoscopic bronchial biopsy, fine needle aspirate, or bronchial washing were collected. They included 43 small cell NE carcinomas and 38 cases used as controls (comprehensive of 2 large cell neuroendocrine carcinomas, 4 carcinoid tumors, 30 cases of non-NE lung carcinomas, 2 cases of bronchial infiltration by non-Hodgkin lymphomas). 34betaE12 CK immunoreactivity was found in 29/30 cases of non-NE carcinomas, but in only 3/43 SCCs. The latter showed positivity in only a few scattered cells. The 2 cases of bronchial infiltration by malignant lymphoma as well as the 4 cases of carcinoid tumors and the 2 cases of large cell neuroendocrine carcinomas were negative. These findings were confirmed in the surgical specimens of operatedon cases. We conclude that, in lung carcinoma biopsies showing a small cell pattern, presence of 34betaE12 CK immunoreactivity favors a non-NE carcinoma, whereas its absence supports the diagnosis of SCC. Int J Surg Pathol 8(4):317-322, 2000

Detection of chromogranin A in human gastric adenocarcinomas using a sensitive immunohistochemical technique

Neuroendocrine cells are often disclosed in human gastric adenocarcinomas and may be recognised by their immunoreactivity towards chromogranin A. However, in dedifferentiated neuroendocrine tumour cells, the chromogranin A content may be reduced making it difficult to detect with conventional immunohistochemical methods. We therefore used a sensitive signal amplification technique in order to evaluate chromogranin A immunoreactivity and thus neuroendocrine differentiation in 40 gastric adenocarcinomas. Neuroendocrine cells were visualised by means of a monoclonal chromogranin A antibody and the avidin-biotin peroxidase complex technique, without and with addition of tyramide signal amplification. Double immunohistochemistry towards chromogranin A and Ki-67 were used to disclose proliferation in the neoplastic cells. A marked increase in the number of carcinomas containing chromogranin A-immunoreactive neoplastic cells was noted when applying the tyramide signal amplification technique. In addition, the number of immunoreactive cells within each tumour increased, and in some cases almost all the neoplastic cells became immunoreactive. Chromogranin A-immunoreactive tumour cells showing signs of proliferation were found in the majority of these carcinomas. In conclusion, we have disclosed widespread immunoreactivity towards chromogranin A in a proportion of gastric adenocarcinomas when enhancing the signal with tyramide signal amplification. Neuroendocrine differentiation is thus a common finding in gastric carcinomas when using sensitive methods.

High-density hapten labeling and HRP conjugation of oligonucleotides for use as in situ hybridization probes to detect mRNA targets in cells and tissues

Oligonucleotides that carry a detectable label can be used to probe for mRNA targets in in situ hybridization experiments. Oligonucleotide probes (OPs) have several advantages over cDNA probes and riboprobes. These include the easy synthesis of large quantities of probe, superior penetration of probe into cells and tissues, and the ability to design gene- or allele-specific probes. One significant disadvantage of OPs is poor sensitivity, in part due to the constraints of adding and subsequently detecting multiple labels per oligonucleotide. In this study, we compared OPs labeled with multiple detectable haptens (such as biotin, digoxigenin, or fluorescein) to those directly conjugated with horseradish peroxidase (HRP). We used branching phosphoramidites to add from two to 64 haptens per OP and show that in cells, 16-32 haptens per OP give the best detection sensitivity for mRNA targets. OPs were also made by directly conjugating the same oligonucleotide sequences to HRP. In general, the HRP-conjugated OPs were more sensitive than the multihapten versions of the same sequence. Both probe designs work well both on cells and on formaldehyde-fixed, paraffin-embedded tissues. We also show that a cocktail of OPs further increases sensitivity and that OPs can be designed to detect specific members of a gene family. This work demonstrates that multihapten-labeled and HRP-conjugated OPs are sensitive and specific and can make superior in situ hybridization probes for both research and diagnostic applications.