Masashi Matsushima

Clinical Application of Serum Pepsinogen I and II Levels for Mass Screening to Detect Gastric Cancer

A considerable number of gastric cancers derive from stomach mucosa where chronic atrophic gastritis is severe and extensive. Based on the fact that the serum pepsinogen levels provide a precise measure of the extent of chronic atrophic gastritis, we have devised a mass screening method involving serum pepsinogen measurement to identify subjects at high risk of gastric cancer. In 1991, we screened 4,647 workers (male: 4,113, female: 534, mean age: 49.0 years) at a Japanese company using this method. Out of 875 subjects (18.8%) with a serum pepsinogen I level of less than 50 μg/liter and a pepsinogen I/II ratio of less than 3.0, 676 subjects (14.5%) were selected for further investigation by endoscopy. This led to the detection of four subjects (0.086%) with gastric cancer (three in an early stage) and four subjects with adenoma. The cancer detection rate of this new screening method was comparable, and in some respects superior, to that of the traditional barium X‐ray screening. Since the incidence of test‐positive subjects was as low as 10% amongst subjects aged less than 40, this screening method appears to be especially useful for screening of younger generations. The new method is less expensive than the traditional barium X‐ray and subjects experience little discomfort. Further, many serum samples can be quickly measured simultaneously. The results of this study have indicated that serum pepsinogen screening provides a valuable method for detecting gastric cancers.

The Clinical Application of the Serum Pepsinogen I And II Levels as a Mass Screening Method for Gastric Cancer

Gastric cancer, despite a recent decline in the incidence, is still a leading cause of death in Japan. For this reason, much effort has been directed to the early detection of the cancer through mass screening programs throughout the country. In most workplaces in Japan, an indirect X-ray examination, using 10 cm square film, is the conventional first screening step, after which those suspected of having some abnormalities in the gastric mucosa are further investigated either with a higher quality X-ray examination or by endoscopy. However, the sensitivity of the conventional X-ray screening step is by no means high. To improve the effectiveness of gastric cancer screening, we have devised a new screening method that utilizes measurement of serum pepsinogen (pepsinogen I and II) levels. This new screening system is based on the facts that a considerable part of gastric cancers develop in gastric mucosa affected by severe and extensive atrophic gastritis (1) and that serum pepsinogen levels serve as a sensitive marker of chronic atrophic gastritis (2). We report the first application of serum pepsinogen measurement for mass screening of gastric cancer at a certain workplace and compare the results with those of the conventional X-ray screening method.

The nucleotide and deduced amino acid sequences of porcine liver proline-β-naphthylamidase: swEvidence for the identity with carboxylesterase

A cDNA clone for porcine liver proline‐β‐naphthylamidase was isolated and sequenced. The deduced amino acid sequence of 567 residues was highly homologous with those of carboxylesterases (EC 3.1.1.1) previously reported for other species. In addition, proline‐β‐naphthylamidase purified from porcine liver was shown to have strong activity towards p‐nitrophenylacetate, a representative substrate for carboxylesterases. These results suggest that proline‐β‐naphthylamidase is identical with carboxylesterase.

Structural and immunological evidence for the identity of prolyl aminopeptidase with leucyl aminopeptidase

Prolyl aminopeptidase (EC 3.4.11.5) has been assumed to be a unique enzyme catalyzing specifically the removal of unsubstituted NH2-terminal L-prolyl residues from various peptides and to be distinct from leucyl aminopeptidase (EC 3.4.11.1). In the present study, prolyl aminopeptidases were purified to apparent homogeneity from pig small intestine mucosa and human liver and their NH2-terminal amino acid sequences were determined together with that of pig kidney leucyl aminopeptidase. The NH2-terminal 24-residue sequence of pig intestinal prolyl aminopeptidase was shown to be identical with that of pig kidney leucyl aminopeptidase. The NH2-terminal sequence of human liver prolyl aminopeptidase was also shown to be very similar to that of pig kidney leucyl aminopeptidase. Further, pig intestinal prolyl aminopeptidase and pig kidney leucyl aminopeptidase were immunologically indistinguishable. These lines of evidence strongly suggest that prolyl aminopeptidase is identical with leucyl aminopeptidase.

Methylation and Expression of Human Pepsinogen Genes in Normal Tissues and Their Alteration in Stomach Cancer

In normal human tissues, pepsinogen A mRNA was expressed only in the fundic mucosa of the stomach, whereas pepsinogen C mRNA was expressed in all regions of the stomach mucosa and also in the proximal duodenal mucosa. The distributions of these mRNAs were consistent with those of pepsinogens A and C in the gastroduodenal mucosa. Methylation analysis of DNAs from normal tissues with methylation‐sensitive restriction enzymes, Hpa II and Hha I, revealed that pepsinogen A and C genes are hypomethylated in tissues producing pepsinogens A and C, suggesting a role of DNA methylation in the regulation of the differential expression of the genes for the two human pepsinogens during normal differentiation. In stomach cancer tissues and cancer cell lines, the expressions of the pepsinogen genes were decreased or lost, in good accordance with their pepsinogen productions. No gross structural changes of the pepsinogen genes were observed in these cancers, but the methylation patterns of the pepsinogen genes were found to be altered in different ways in different cancers. The functional significance of the altered methylation is unknown; however, these results suggest that considerable heterogeneity of the methylation patterns occurs in human stomach cancers.

Hydrocortisone-induced enhancement of expression and changes in methylation of pepsinogen genes in stomach mucosa of the developing rat.

Administration of hydrocortisone to infant rats caused a precocious increase in levels of mucosal pepsinogen and its mRNA together with morphological maturation of pepsinogen-producing cells. The increase in levels of pepsinogen mRNA was induced rapidly and was associated with increase in levels of its precursors, suggesting transcriptional regulation of pepsinogen genes by hydrocortisone. Methylation analysis with the methylation-sensitive restriction enzymes, HpaII and HhaI, revealed that hydrocortisone also induced sequential demethylation changes of CCGG and GCGC sites in and around pepsinogen genes. Most of these changes occurred after increases in transcription of the genes and did not appear to play a causal role in gene activation. Superficially, the observed demethylations corresponded to the sequential processes of morphological maturation of pepsinogen-producing cells. Thus, these changes in methylation are probably linked to hydrocortisone-induced differentiation of pepsinogen-producing cells and may reflect the mechanism in vivo for the maturation of pepsinogen genes.

Tissue- and Cell-Specific Control of Guinea Pig Cathepsin E Gene Expression

Northern blotting of RNAs from normal guinea pig tissues revealed that the tissue distribution of cathepsin E mRNA was relatively limited and the highest level of the mRNA was observed in the stomach mucosa. Expression of the mRNA was also observed in the spleen, although the level was very low. These results were in good agreement with the distribution of the cathepsin E-producing cells as revealed by immunohistochemistry. In the separated fractions of dispersed mucosal cells prepared from the stomach by centrifugal elutriation, the extent of cathepsin E mRNA expression was closely correlated with the enrichment of the producing cells. In addition, both CCGG and GCGC sites within the gene region were hypomethylated to a greater extent in the producing tissues than elsewhere, reflecting specific hypomethylation in the producing cells. The observed tissue- and cell-specific transcriptional control of cathepsin E gene, which is correlated with a decreased level of methylation in the gene region, suggests that the enzyme is probably involved in specific functions of particular differentiated cells, especially those of the stomach mucosa.

Effects of Omeprazole, a Proton Pump Inhibitor, on Pepsinogen-Producing Cells, with Special Reference to Neonatal Development

Omeprazole, a proton pump inhibitor, exerts its effects by binding covalently to the H+/K+-ATPase that is located in the apical membrane of gastric parietal cells. However, its effects on pepsinogen-producing cells have not been investigated in detail and results of previous relevant studies on pepsinogen secretion are conflicting. Gastric mucosal cells proliferate and differentiate under an acidic environment in the gastric lumen. Thus, it is probable that omeprazole-induced reduced acidity in the gastric lumen has some influences on the proliferation and differentiation of the mucosal cells. As the first step to elucidate the effects of omeprazole on pepsinogen-producing cells, we analyzed the processes from the gene expression to the secretion of pepsinogen in vivo in adult rat glandular stomach. Next, we investigated the effects of omeprazole on the development of rat gastric mucosa biochemically and histologically, with special reference to pepsinogen expression as a marker of terminal differentiation.

Serum Pepsinogen Values as Possible Markers for Evaluating the Possibility of Peptic Ulcer Recurrence under H2-Blocker Half-Dose Maintenance Therapy

The introduction of Hrblockers and proton pump inhibitors has made peptic ulcer a curative disease without surgery. However, prevention of the ulcer recurrence is still a difficult problem. Various maintenance therapies have been set up and tried. But there has been almost no indicator to select a proper therapy for each case. Thus, a marker for predicting ulcer recurrence has been long desired. Serum pepsinogen (PG) values, PG I originating from fundic gland ( I ) and PG II from throughout stomach mucosa and Brunner gland (2), have been reported to reflect morphology and function of the gastroduodenal mucosa (3,4). Some of the previous studies suggested their possible roles as markers for peptic ulcer diseases and recurrence. For the ulcer incidence, a high PG II value and a low PG IIII ratio in gastric ulcer patients and high PG I value in duodenal ulcer patients were reported to be observed against normal control subjects (5). For the ulcer recurrence, high PG I values in recurrent peptic ulcer patients were reported to be observed against no recurrent ones (6). For evaluating the clinical usefulness as a marker of ulcer recurrence,

Effects of Hydrocortisone on the Pepsinogen-Producing Cells in Rat Stomach Mucosa

Pepsinogen is a marker of the terminal differentiation of stomach mucosa. At present, controlling mechanisms of differentiation in stomach mucosa is not fully understood. Previous studies demonstrated that administration of hydrocortisone to developing rats induces a precocious increase in the mucosal pepsinogen level in the stomach (1–3), indicating that glucocorticoids are somehow involved in the differentiation of the stomach mucosa. However, the physiological significance of glucocorticoids in the regulation of pepsinogen gene expression is not well understood. In addition, the effects of glucocorticoids on pepsinogen-producing cells in fully-differentiated stomach mucosa are less clear (4,5). In this study, we examined the effects of hydrocortisone on infant and adult rat stomach mucosa, especially on pepsinogen gene expression and the morphology of pepsinogen-producing cells.