Human pepsinogen C (progastricsin) polymorphism: evidence for a single locus located at 6p21.1-pter

Pepsinogen-II 100 bp ins/del gene polymorphism and its elevated circulating levels are associated with gastric cancer, particularly with Helicobacter pylori infection and intestinal metaplasia

BACKGROUND

Polymorphism in the gene of pepsinogen-II (PG-II) and its serum level are effective biomarkers for terminal differentiation of gastric mucosa into gastritis, intestinal metaplasia (IM), and gastric cancer (GC) in relationship to Helicobacter pylori infection.

METHODS

Genotyping of the PG-II 100 bp insertion/deletion (ins/del) polymorphism was performed in patients with GC (n = 192) and age- and gender-matched H. pylori-associated dyspepsia (n = 180) and healthy subjects (HS, n = 240) by PCR. IgG anti-H. pylori (in all subjects) and serum PG-II levels were estimated in 145 patients each with GC and dyspepsia and in 65 healthy controls (HC) using ELISA (Biohit Oyj, Finland).

RESULTS

Five alleles were amplified by PCR: allele 5 (510 bp), allele 4 (480 bp), allele 3 (450 bp), allele 2 (400 bp), and allele 1 (shorter allele, 310 bp). Allele 1 carriage was infrequent, and serum PG-II level was higher among patients with GC than in HC [OR 0.43 (95 % CI, 0.29-0.85), p < 0.001 and mean ± SD; 17.53 ± 12.60 vs. 12.77 ± 7.53 µg/l, p = 0.005, respectively], particularly in the presence of H. pylori [OR 0.42 (0.25-0.71), p = 0.001 and 18.78 ± 12.63 vs. 13.97 ± 8.14, p = 0.034]. However, allele 1 carriage and PG-II levels were comparable among patients with GC and dyspepsia. Patients with IM also carried allele 1 infrequently and had higher levels of PG-II than those without [OR 0.5 (0.29-0.85), p = 0.011 and 20.07 ± 14.22 vs. 16.61 ± 12.08, p = 0.048].

CONCLUSIONS

Carriage of the shorter allele of the PG-II 100 bp ins/del polymorphism and elevated levels of PG-II are associated with GC, particularly with H. pylori infection and IM.

Potential prognostic, diagnostic and therapeutic markers for human gastric cancer

The high incidence of gastric cancer (GC) and its consequent mortality rate severely threaten human health. GC is frequently not diagnosed until a relatively advanced stage. Surgery is the only potentially curative treatment. Thus, early screening and diagnosis are critical for improving prognoses in patients with GC. Gastroscopy with biopsy is an appropriate method capable of aiding the diagnosis of specific early GC tumor types; however, the stress caused by this method together with it being excessively expensive makes it difficult to use it as a routine method for screening for GC on a population basis. The currently used tumor marker assays for detecting GC are simple and rapid, but their use is limited by their low sensitivity and specificity. In recent years, several markers have been identified and tested for their clinical relevance in the management of GC. Here, we review the serum-based tumor markers for GC and their clinical significance, focusing on discoveries from microarray/proteomics research. We also review tissue-based GC tumor markers and their clinical application, focusing on discoveries from immunohistochemical research. This review provides a brief description of various tumor markers for the purposes of diagnosis, prognosis and therapeutics, and we include markers already in clinical practice and various forthcoming biomarkers.

Impact of pepsinogen C polymorphism on individual susceptibility to gastric cancer and its precancerous conditions in a Northeast Chinese population

PURPOSE

Human pepsinogen C (PGC) is an aspartic protease produced specifically by the gastric mucosa, and is considered as a mature marker of gastric epithelium. This study examined the contributions of PGC polymorphisms and the Helicobacter pylori (H. pylori) infection to the risk of gastric cancer (GC), and its precancerous conditions in a Northeast Chinese population.

METHODS

The PGC insertion/deletion polymorphism was evaluated by polymerase chain reaction analysis, followed by direct DNA sequencing in 564 cases of GC, atrophic gastritis (AG), gastric ulcer (GU) and superficial gastritis (as control). All cases were frequency-matched 1:1 by gender and age (+/-5). H. pylori infection was identified by serum anti-H. pylori IgG measurement through enzyme-linked immunosorbent assay.

RESULTS

Patients with a homozygous PGC allele 1 genotype had a significant risk of AG [adjusted odds ratio (OR) 3.11; 95% confidence interval (CI) 1.44-6.71] or of GC (OR 3.00; 95% CI 1.38-6.51), and a significantly elevated risk of intestinal metaplasia (OR 1.90, 95% CI 1.11-3.27). PGC polymorphism with H. pylori infection increased risk of GU (OR 8.69; 95% CI 1.01-74.69), and AG (OR 11.12; 95% CI 1.37-90.84) or GC (OR 10.61; 95% CI 1.28-87.79) in a super-multiplicative manner. The S value was 5.40, 6.48 and 4.34; and the AP value was 72.09, 7.00 and 69.69%, respectively.

CONCLUSIONS

The PGC gene polymorphism increases an individual's susceptibility to GC and its precancerous conditions. Moreover, the PGC gene polymorphism shows a positive link to H. pylori infection in the development of GC.

An ovarian progastricsin is present in the trout coelomic fluid after ovulation

An up-regulated cDNA fragment was isolated using a differential display polymerase chain reaction between ovulatory and postovulatory brook trout ovarian tissues. Using this fragment as a probe, a full-length cDNA of 1783 base pairs was obtained from an ovarian cDNA library. The cDNA presumably codes for a 383-amino acid protein with strong sequence similarity to an aspartic protease, progastricsin (EC 3.4.23.3), also known as pepsinogen C. On Northern blots of ovarian tissue, the trout progastricsin cDNA hybridized with a 1.8-kilobase transcript that was strongly up-regulated 4-6 days after ovulation. Of all other tissues tested, a transcript was only detected in the stomach. A recombinant trout progastricsin protein was produced and used to raise an antibody. On Western blots of ovarian tissue, the progastricsin antibody recognized a single 39-kDa protein that was present in the ovary only following ovulation. On Western blots of coelomic fluid, the 39-kDa protein was strongly detected 4-10 days after ovulation. The trout progastricsin was immunocytochemically localized to the granulosa cells of postovulatory follicles, suggesting that it is released from this tissue into the coelomic fluid following ovulation. Progastricsin has been found in the stomach, prostate, seminal vesicle, seminal fluid, and pancreas of vertebrates; however, this is the first report of a progastricsin in an animal ovary.

Peptic ulcer inheritance in patients with elevated serum pepsinogen group A levels and without infection of Helicobacter pylori

BACKGROUND

Peptic ulcer has multifactorial aetiology, including genetic factors. We have identified a family with pepsinogen Group A levels higher than normal, with a high prevalence of ulcer disease and a low prevalence of Helicobacter pylori infection.

AIMS

Performing linkage analysis in the identified family

PATIENTS AND METHODS

We examined the segregation of pepsinogens with microsatellite dinucleotide repeat DNA markers along chromosome 11 (D11S480, PYGM) for pepsinogen Group A and along chromosome 6 [D6S105, D6S 1610, TRMI) for pepsinogen Group C.

RESULTS

In markers examined along chromosome 11, linkage analysis provided no evidence for significant causal mutation but, controlling for some risk factors we observed that the probability of falling ill, increases. The linkage analysis along chromosome 6 for pepsinogen Group C did not show a uniform genetic profile.

CONCLUSIONS

This study evaluates the hypothesis of peptic ulcer inheritance at least in a small group of patients without the common risk factors.

Hormonal regulation of the human pepsinogen C gene in breast cancer cells. Identification of a cis-acting element mediating its induction by androgens, glucocorticoids, and progesterone

Pepsinogen C is an aspartic proteinase mainly involved in the digestion of proteins in the stomach, which is also synthesized by certain human breast tumors. To examine the possibility that extragastric production of this proteolytic enzyme could be mediated by hormonal factors, we have analyzed pepsinogen C gene expression in human breast cancer cells subjected to different hormonal treatments. Northern blot analyses revealed the expression of pepsinogen C gene by T-47D breast cancer cells after induction with dihydrotestosterone, dexamethasone, and progesterone but not with estradiol, retinoic acid, or ethanol. Reverse transcription-polymerase chain reaction analysis in a series of breast cancer cell lines confirmed the amplification of pepsinogen C mRNA after induction with dihydrotestosterone, in those cells expressing the androgen receptor mRNA. The promoter region of the pepsinogen C gene was functionally characterized by transient expression of a vector containing the promoter region cloned in front of the chloramphenicol acetyltransferase (CAT) reporter gene. CAT activity in T-47D cells was stimulated in the presence of dihydrotestosterone, dexamethasone, and progesterone but not by estradiol. By further deletion mapping of the pepsinogen C promoter, a minimal region (AGAACTattTGTTCC) was identified as being responsible for glucocorticoid-, androgen-, and progesterone-regulated gene expression.

Genetic heterogeneity of combined gastric and duodenal ulcers detected by pepsinogen C gene polymorphism

It has been reported recently that there was genetic heterogeneity in gastric ulcer disease depending upon the location of the ulcer, and that there was a significant association between the restriction fragment length polymorphism (RFLP) for pepsinogen C (PGC) gene and gastric body ulcer. In the present study, the association of the RFLP for PGC gene with combined gastric and duodenal ulcers was investigated to analyse genetic factors in its aetiology. Eighty unrelated controls and 47 patients with combined gastric and duodenal ulcers were studied. The allele frequencies of the large (3.6 kilobase EcoRI fragment) and the small fragment (3.5 kilobase EcoRI fragment) were, respectively 80.6 and 19.4% in controls, 60.0 and 40.0% in patients with combined gastric body and duodenal ulcers, 69.0 and 31.0% in patients with combined gastric angular and duodenal ulcers, and 81.8 and 18.2% in patients with combined gastric antral and duodenal ulcers. The allele frequency of the small fragment was significantly higher in patients with combined gastric body and duodenal ulcers than in controls. The genotypes that possessed the small fragment were significantly more frequent in patients with combined gastric body and duodenal ulcers (66.7%) than in controls (33.8%) and combined gastric antral and duodenal ulcers (27.3%). These results suggest that there is genetic heterogeneity in combined gastric and duodenal ulcers depending upon the location of gastric ulcer, and that combined gastric body and duodenal ulcers are associated with the small fragment allele of the PGC RFLP in the same way as solitary gastric body ulcers.

Pepsinogens in health and disease

Pepsinogens, precursors of pepsins (potent and abundant digestive enzymes that are the primary products of the gastric chief cells), are members of the family of aspartic proteases. Because of the heterogeneity of pepsinogens, several classifications have appeared in the literature. I describe the recommended classification and nomenclature of the aspartic proteases and discuss their genetics, biochemistry (structure, activation of zymogens, mechanism of proteolytic activity and inhibitors), and physiology. The focus will be on the zymogens of pepsin, the so-called pepsinogens. The measurement of these enzymes in serum is a reliable noninvasive biochemical method for evaluating peptic secretion and obtaining information on the gastric mucosal status. A detailed review of the methods for the measurement of pepsinogens in serum, urine, and gastric mucosa is also provided. Data on pepsinogen levels in healthy subjects are discussed with respect to sex, age, smoking habit, and the presence of a circadian rhythm. The value of pepsinogen measurements in peptic ulcer to determine ulcer outcome and recurrence, in gastric cancer, and in Helicobacter pylori infection is reviewed. Finally, the effects of drugs on peptic secretion are discussed. In light of these data, the measurement of aspartic proteases, and in particular that of pepsinogen A and C, may be regarded as an effective biochemical approach to the evaluation and monitoring of patients with upper gastrointestinal diseases.

Detection of a polymorphism within the pepsinogen C gene with PCR: construction of a linkage map around PGC from 6p11-6p21.3

An insertion/deletion polymorphism between exons 7 and 8 of the pepsinogen C gene (PGC), previously detectable with Southern analysis, was formatted for detection with PCR. Alleles were rapidly typed by UV irradiation of ethidium bromide-stained agarose gels. Whereas Southern analysis revealed two alleles, the smaller fragments generated with PCR allowed the resolution of three alleles that were previously scored as a single allele and increased the heterozygosity of the system from 0.20 to 0.53. After a set of reference families was genotyped with the PCR-based polymorphism, a linkage map around the PGC gene on chromosome 6 was constructed. This included the HLA cluster and the highly informative D6S223 locus. PGC lies 22 cM proximal to HLA-DPB and between D6S5 and D6S4 at distances of 4.5 and 13.1 cM, respectively.

Peptide maps of five human pepsin isoenzymes and other aspartic proteinases

Peptide maps of five individual human pepsins were developed using reversed-phase high-performance liquid chromatography after protein digestion with either Staphylococcus aureus proteinase (V8) or alpha-chymotrypsin. Human pepsins 3a, 3b and 3c produced almost identical peptide maps suggestive of proteins with very similar amino acid sequences. The map for human pepsin 1 was similar to pepsin 3b (the most predominant human pepsin) but less than half the expected amount of each equivalent peptide fragment was generated, indicating that the actual mass of digested protein used was less than the dry weight measurement would suggest, probably as a result of carbohydrate attached to pepsin 1. Comparison of human pepsin 3b maps with other aspartic proteinases confirmed a significant homology with swine pepsin A but not with endothiapepsin. The alpha-chymotrypsin digests compared with V8 gave more complex peptide maps as a result of its broader bond cleavage specificities.

Assignment of the human pancreatic colipase gene to chromosome 6p21.1 to pter

Pancreatic colipase is a 12-kDa polypeptide cofactor for pancreatic lipase (EC 3.1.1.3), an enzyme essential for the absorption of dietary long-chain triglyceride fatty acids. Colipase is thought to anchor lipase noncovalently to the surface of lipid micelles, counteracting the destabilizing influence of intestinal bile salts. Using primers derived from the known amino acid sequence, we have used the polymerase chain reaction to produce a cDNA clone corresponding to the complete coding region of the human procolipase mRNA. Southern blot analysis of genomic DNA from a panel of mouse-human somatic cell hybrids indicated that the colipase gene (CLPS) resides on human chromosome 6. Further analysis of somatic cell hybrids carrying chromosome 6 translocations permitted regional localization of CLPS to the 6p21.1-pter region.