Detection of gastrin and its messenger RNA in Zollinger-Ellison tumors by non-radioactive in situ hybridization and immunocytochemistry

Production of a bovine IL-12p40 probe and application using in situ hybridization on ruminant fixed tissues

Pro-inflammatory cytokines (particularly IL-12) are important for initiating protective T helper 1 (Th1)-type immune responses and hence vital for combating intracellular infections and tumours. In situ hybridization (ISH) provides a powerful diagnostic tool allowing the identification and localization of cells producing these mediators in fixed tissues. The objective of this work was to produce a bovine IL-12p40 probe that allows detection of IL-12p40 mRNA in fixed tissues from different ruminant species. The RNA probe sequence is 447bp in length and from a region with high cross-species-sequence homology (>97.3% homology) to the ovine, cervine, caprine and bubaline IL-12p40 genes. ISH was carried out on paraformaldehyde fixed tissues collected from cattle, sheep and goats. The probe was efficient in identifying IL-12p40 expressing cells in fixed tissues from all these species. In conclusion, the IL-12p40 probe was efficient in identifying and localizing cells that express IL-12p40, and provides a good immuno-diagnostic technique to characterize immune responses in fixed tissues.

Strong Stromal Hyaluronan Expression Is Associated with PSA Recurrence in Local Prostate Cancer

OBJECTIVE

HA (hyaluronan) is involved in cell migration, differentiation and cell proliferation, which all are essential to tumour growth. In addition, the cell surface receptor of HA, CD44, is important in cancer cell adhesion, cell migration and tumour neovascularisation. We studied the expression of HA and CD44 and their relationship with other prognostic factors and prostate-specific antigen (PSA) recurrence in local prostate cancer (PC).

MATERIALS AND METHODS

77 PC patients treated with radical prostatectomy were followed-up for a mean of 4 years. HA was detected by using a HA specific probe and CD44 expression was analysed by conventional immunohistochemistry.

RESULTS

All specimens expressed HA in tumour stroma and 78% (60/77) of the tumours showed strong stromal expression of HA. The fraction of positively stained specimens for CD44 was 66% (51/77). The strong stromal HA expression was related to perineural infiltration (p = 0.001) and capsule invasion (p = 0.05). No correlation was demonstrated between the stromal HA expression and CD44 expression, preoperative PSA, clinical or pathological T classification, pN status, Gleason grade, seminal vesicle invasion or surgical margin invasion. Reduced CD44 expression was related only to preoperative PSA level (p = 0.008). The PSA recurrence was predicted by strong stromal HA expression, pT classification, seminal vesicle invasion, capsule invasion and surgical margin invasion (p <or= 0.02 for all). pT classification and seminal vesicle infiltration predicted PSA recurrence free survival (RFS). In the multivariate analysis only the seminal vesicle infiltration was an independent predictor of PSA RFS (p = 0.009).

CONCLUSION

The strong stromal HA expression was related to PSA recurrence, perineural infiltration and seminal vesicle invasion. Those are the factors related to unfavourable prognosis, but the follow-up period of this series is too short to make definitive prognostic conclusions.

Signaling pathways mediating gastrin's growth-promoting effects

In addition to its fundamental role in stimulating gastric acid secretion, the peptide hormone gastrin induces growth-promoting effects on diversity of target cells. Various mechanisms, including endocrine, paracrine, and autocrine, have been proposed for gastrin's growth-promoting actions. The mitogenic effects of gastrin are mediated by specific cell surface receptors activated after gastrin binding. The functionally defined receptors for gastrin include cholecystokinin A (CCKA) receptor, which is discriminating for sulfated CCK8; cholecystokinin B (CCKB)/gastrin receptor, which binds gastrin17 sulfated, and nonsulfated CCK8 with nearly equal affinities; cholecystokinin C (CCKC), which is a low-affinity gastrin binding protein; and novel, high-affinity receptors selective for amidated gastrin, processing intermediates of gastrin, or both. The signaling pathways mediating gastrin's stimulation of the CCKB/gastrin receptor have been progressively outlined, and the pathways mediating other receptors have been slowly emerging. Engagement of the gastrin receptor initiates various biochemical and molecular events, including recruitment and activation of tyrosine kinases, activation of the phospholipase C signaling pathway leading to phosphoinositide breakdown, intracellular calcium mobilization and protein kinase C stimulation, activation of the mitogen-activated protein kinase pathway, and induction of early response genes. Current emphasis is on understanding the functional significance of processing intermediate forms of gastrin, and the receptor subtypes and pathways that promote the trophic/mitogenic effects of the different molecular forms of gastrin.

In situ hybridization and its diagnostic applications in pathology

In situ hybridization (ISH) is a technique by which specific nucleotide sequences are identified in cells or tissue sections. These may be endogenous, bacterial or viral, DNA or RNA. On the basis of research applications, the technique is now being translated into diagnostic practice, mainly in the areas of gene expression, infection and interphase cytogenetics. Diagnostic applications are most often based on short nucleotide sequences (oligomers) labelled with non-isotopic reporter molecules, and sites of binding may be localized by histochemical or immunohistochemical methods. The technique can be applied to routinely fixed and processed tissues; with some targets, it is even possible to obtain hybridization in autopsy material. ISH has been used to detect messenger RNA (mRNA) as a marker of gene expression, where levels of protein storage are low; for example, to confirm an endocrine tumour as the source of excess hormone production. Its application in infectious diseases has to date been mainly in viral infections, such as the typing of human papillomavirus (HPV) or the detection of Epstein-Barr virus by the presence of small nuclear RNAs (EBERs). The expression of mRNAs for histone proteins has been used to detect cells in S phase, and related methods may be applied to detect apoptotic cells. Using probes to chromosome-specific sequences, it is possible to detect aneuploidy, and to document changes in specific chromosomes, which may have prognostic significance in some tumours, such as B-cell chronic lymphatic leukaemia. Using sequence-specific probes, translocations can be identified, such as the t(11;12) of Ewing's sarcoma. This review presents an outline of the technique of in situ hybridization and discusses areas of current and potential diagnostic application.

Pancreatic-duodenal homeobox 1 -role in gastric endocrine patterning

The gastrointestinal tract is subdivided into regions with different roles in digestion and absorption. How this patterning is established is unknown. We now report that the pancreatic-duodenal homeobox 1 gene (pdx1) is also expressed in cells of the distal stomach. Positive cells include subpopulations of the three main endocrine (gastrin, somatostatin and serotonin) cell types of this region. Pdx1 deficient mice were virtually devoid of gastrin cells, had normal numbers of somatostatin cells and increased numbers of serotonin cells. Pdx1 is thus important for development of the gastrin cells of the antropyloric mucosa of the stomach and probably acts by controlling the fate of gastrin/serotonin precursor cells.

Coexpression of the gastrin and somatostatin genes in differentiating and neoplastic human cells

Double immunofluorescence and in situ hybridizations performed on adjacent thin sections show that a population of normal antropyloric cells of the human stomach expresses both gastrin and somatostatin mRNA's and the corresponding peptides. Such cells were present in both adult and fetal antropyloric mucosa and were situated in the regenerative (isthmus) region of the antropyloric tubes. It is, hence, likely that these cells represent immature endocrine cells that yet have to be committed to either the gastrin or somatostatin lineage. Cells coexpressing gastrin and somatostatin were also detected in pancreatic endocrine tumours. The presence of gastrin-somatostatin cells during development and in tumours suggests that gastrin and somatostatin cells may differentiate from such multipotent precursor cells.

The LIM-homeodomain protein Isl-1 segregates with somatostatin but not with gastrin expression during differentiation of somatostatin/gastrin precursor cells

The gastric epithelium is renewed from stem cells in the isthmus of the gastric glands. We describe that the two neuroendocrine peptides gastrin and somatostatin are coexpressed by isthmic stem cells. Bromodeoxyuridine labeling indicates that the coexpressing cells divide and differentiate into gastrin and somatostatin cells, which remain in paracrine contact during most of their migration down into the gland. The coexpressing cells display nuclear immunoreactivity for the transcription factors Isl-1 and CREB, which have been implicated in somatostatin gene expression. Differentiated gastrin cells lack Isl-1 reactivity and show variable staining for CREB while differentiated somatostatin cells display Isl-1 and CREB reactivity.

Prevalence of erm gene classes in erythromycin-resistant Staphylococcus aureus strains isolated between 1959 and 1988

The epidemiology of the two common erythromycin resistance methylase (erm) genes ermA and ermC was analyzed by Southern blotting in 428 erythromycin-resistant Staphylococcus aureus strains isolated from blood between 1959 and 1988 in Denmark. ermA and/or ermC was present in 98% of the erythromycin-resistant strains tested. ermA was found only as a chromosomal insert and was solely responsible for erythromycin resistance in these strains until about 1971. ermA was the only erm gene found in 337 strains and was a single insert in 61% of these strains, two inserts were seen in 37%, and three inserts were found in 2%. Thirteen different ermA EcoRI restriction fragment length polymorphisms were identified. ermA was not found in strains of phage type patterns group II and type 95, which are very common today. ermC was found on a plasmid in 77 strains. ermC was first seen in 1971 and spread rapidly in the S. aureus population, with a 5- to 10-fold increase every 5 years, and in 1984 to 1988, it was responsible for erythromycin resistance in 72% of the strains. The predominant plasmid carrying ermC was 2.5 kb, while four plasmids were smaller and three were larger. ermC has been found in all phage type patterns. Eight strains contained combinations of ermA and ermC, and no erm gene was detected in six strains.

Detection of gastrin mRNA in paraffin-embedded samples of normal antral mucosae using polymerase chain reaction technique

Gastrin, a peptide hormone produced by the G cells of the gastric antrum, plays a major role in the regulation of digestive mucosal growth. Although some light has been shed on the peptidic aspects of this hormone's mode of action and the co-regulatory activity in which it is involved along with the other gastrointestinal hormones, little is known at present about the modes of expression of its mRNA at the tissue level. A few attempts have been made so far to detect the transcript, mostly using molecular hybridization techniques. Here it was proposed to detect gastrin mRNA using a RT-PCR technique on a series of paraffin-embedded samples of normal human antrum processed with various fixatives commonly used in histology. The transcript was detectable in all the 7-microns sections of the samples treated with either formalin or Carnoy's solution, whereas Bouin's solution, which is also used as a fixative in histology, was found to have inhibitory effects on the method described here.

Adaptation of a non-radioactive in situ hybridization method to electron microscopy: detection of tenascin mRNAs in mouse cerebellum with digoxigenin-labelled probes and gold-labelled antibodies

In this study we describe a method for the detection of mRNAs at the ultrastructural level using a non-radioactive in situ hybridization method based on digoxigenin-labelled cRNA probes and gold-labelled digoxigenin-specific antibodies. We applied this protocol to an analysis of the expression of the extracellular matrix protein tenascin in the developing cerebellar cortex of the mouse. To gain an impression of the sensitivity attainable with digoxigenin-labelled probes, we first established at the light microscopic level that the hybridization signal obtained with the non-radioactive probe is as sensitive as that obtained with a 35S-labelled probe. The non-radioactive hybridization protocol was then combined with electron microscopic post-embedding and immunogold detection techniques. Tenascin-specific, digoxigenin-labelled cRNA probes were hybridized to ultrathin sections of Lowicryl K4M-embedded tissue and the probe/target mRNA hybrids were detected using gold-labelled antibodies to digoxigenin. In agreement with the observations from in situ hybridization at the light microscopic level, specific labelling was observed in Golgi epithelial cells in the region of the Purkinje cell layer and cells in the internal granular layer, which could be identified as astrocytes by ultrastructural criteria. Labelling was detectable in association with free ribosomes and ribosomes of the rough endoplasmic reticulum. In addition, focal hybridization signals were occasionally found in the nucleus. No signal was observed in Golgi epithelial cells or astrocytes using sense or in any other cerebellar cell type using either sense or anti-sense probes. The described in situ hybridization technique uses ultrastructural criteria to associate the presence of a given mRNA species with a particular cell type. Additionally, it provides information about the target mRNA's subcellular distribution, thus offering the possibility to study intracellular transport of particular mRNAs.

Comparison of 35S- and digoxigenin-labeled RNA and oligonucleotide probes for in situ hybridization. Expression of mRNA of the seminal vesicle secretion protein II and androgen receptor genes in the rat prostate

The sensitivity of radiolabeled and digoxigenin-labeled RNA probes and synthetic oligonucleotide probes for the detection of seminal vesicle secretion protein II (SVS II) and androgen receptor (AR) mRNA was compared by in situ hybridization in paraformaldehyde-fixed cryostat sections of the rat prostate. Both genes are expressed in different amounts in the various prostatic lobes and contiguous glands. SVS II or AR RNA probes were either labeled with digoxigenin-11-UTP or [35S]UTP by in vitro transcription. A synthetic SVS II oligonucleotide probe was 3' end-labeled (tailed) with either digoxigenin-11-dUTP or [35S]dATP. Hybridized 35S-labeled probes were detected by autoradiography and digoxigenin-labeled probes by immunohistochemistry using alkaline phosphatase conjugated anti-digoxigenin antibody or gold-labeled antibody followed by protein A-gold and silver enhancement. Digoxigenin-labeled probes provided the same degree of sensitivity as their 35S-labeled counterparts for the detection by in situ hybridization of weakly and strongly expressed mRNA. Using both labeling methods, the SVS II RNA probes were more sensitive than the oligonucleotide probes and background labelling of the 35S-labeled oligonucleotide probe was high. The digoxigenin method produced less background with all probe types, hybridization signals showed higher resolution and results were obtained faster than with radiolabeled probes. The immunogold silver enhancement system provided the fastest detection of digoxigenin-labeled probes with a sensitivity and resolution similar to that provided by alkaline phosphatase anti-digoxigenin immunohistochemistry. It is concluded that digoxigenin probe labeling and detection provides a sensitive, reliable, and efficient alternative to radiolabeled probes for in situ hybridization of mRNA.