DNA distribution pattern in chronic gastritis. I. DNA ploidy and cell cycle distribution

AKT plays a crucial role in gastric cancer

The AKT protein is involved in the phosphatidylinositol-3 kinase signaling pathway and is a vital regulator of survival, proliferation and differentiation in various types of cells. Helicobacter pylori infection induces epithelial cell proliferation and oxidative stress in chronic gastritis. These alterations lead to telomere shortening, resulting in the activation of telomerase. AKT, in particular, is activated by H. pylori-induced inflammation. AKT then promotes the expression of human telomerase reverse transcriptase, which encodes a catalytic subunit of telomerase, and induces telomerase activity, an essential component of the process of carcinogenesis. AKT activation is increased in gastric mucosa with carcinogenic properties and is associated with the low survival of patients with gastric cancer. The findings of the present study suggest that AKT is pivotal in gastric carcinogenesis and progression.

Genetic alterations in benign lesions: Chronic gastritis and gastric ulcer

AIM: To investigate the occurrence of chromosome 3, 7, 8, 9, and 17 aneuploidies, TP53 gene deletion and p53 protein expression in chronic gastritis, atrophic gastritis and gastric ulcer, and their association with H pylori infection.

METHODS: Gastric biopsies from normal mucosa (NM, n = 10), chronic gastritis (CG, n = 38), atrophic gastritis (CAG, n=13) and gastric ulcer (GU, n = 21) were studied using fluorescence in situ hybridization (FISH) and immunohistochemical assay. A modified Giemsa staining technique and PCR were used to detect H pylori. An association of the gastric pathologies and aneuploidies with H pylori infection was assessed.

RESULTS: Aneuploidies were increasingly found from CG (21%) to CAG (31%) and to GU (62%), involving mainly monosomy and trisomy 7, trisomies 7 and 8, and trisomies 7, 8 and 17, respectively. A significant association was found between H pylori infection and aneuploidies in CAG (P = 0.0143) and GU (P = 0.0498). No TP53 deletion was found in these gastric lesions, but p53-positive immunoreactivity was detected in 45% (5/11) and 12% (2/17) of CG and GU cases, respectively. However, there was no significant association between p53 expression and H pylori infection.

CONCLUSION: The occurrence of aneuploidies in benign lesions evidences chromosomal instability in early stages of gastric carcinogenesis associated with H pylori infection, which may confer proliferative advantage. The increase of p53 protein expression in CG and GU may be due to overproduction of the wild-type protein related to an inflammatory response in mucosa.

DNA analysis and DNA ploidy in gastric cancer and gastric precancerous lesions

Gastric cancer (GCa) is still a common cause of cancer-related deaths worldwide, despite improved diagnostic and therapeutic implications. Hence, early diagnosis has critical importance. Flow cytometry reveals rapid and reproducible quantification of nuclear DNA content of disaggregated tissues and assessment of its significance in various malignant and precancerous lesions. A total of 121 patients with GCa, chronic atrophic gastritis (CAG), gastric polyps, intestinal metaplasia (IM) and gastric dysplasia and 36 healthy controls were enrolled in this study. Flow cytometric measurements of DNA ploidy, total S-phase, G2M-phase and proliferative indexes (PIs) were analysed on fresh gastric biopsy specimens obtained by gastroscopy. DNA aneuploidy was present in 43.75% of the GCas (p < 0.05). We found a DNA aneuploidy rate of 15.38% in CAG, 15.38% in IM and 25% in epithelial dysplasia. One of nine polyps had aneuploidy. None of the normal gastric mucosa samples showed aneuploidy. The controls had lower rates of total S-phase and PIs (p < 0.05). In conclusion, DNA flow cytometry may be offered as an objective diagnostic tool for early detection of malignant transformation in gastric lesions.

Expression of human telomerase catalytic subunit gene in cancerous and precancerous gastric conditions

BACKGROUND AND AIMS

Telomerase activity is thought to be necessary for cellular immortality and carcinogenesis. The mRNA that encodes the telomerase catalytic subunit (hTERT) has recently been identified, and expression of hTERT mRNA is thought to regulate activation of telomerase. To determine at what stage of carcinogenesis cells begin to express hTERT, we analysed hTERT mRNA expression in gastric carcinoma and precancerous conditions, focusing on chronic gastritis with or without intestinal metaplasia.

METHODS

Using reverse transcription-polymerase chain reaction, hTERT gene expression was investigated in 18 gastric cancers and 60 specimens of chronic gastritis. Telomerase activity was evaluated using telomeric repeat amplification protocol.

RESULTS

Sixteen of 18 (89%) gastric carcinomas expressed hTERT mRNA, and this expression was unrelated to histological type or depth of invasion. Telomerase activity was found in seven of eight (88%) gastric cancer tissues, all of which expressed hTERT mRNA. Expression of hTERT mRNA was positive in 14 of 60 (23%) specimens of chronic gastritis, and was most prominent in seven of 15 (47%) specimens of gastric mucosa with intestinal metaplasia. Expression of the hTERT gene was significantly more frequent in chronic gastritis with intestinal metaplasia than in gastritis without intestinal metaplasia (P=0.030). In addition, hTERT gene expression was not correlated with age, sex, biopsy site, histological grade of inflammatory cells, glandular atrophy and lymph follicles, or infection with Helicobacter pylori. None of eight normal gastric mucosa expressed hTERT mRNA.

CONCLUSIONS

Our results indicate that hTERT mRNA is expressed in precancerous conditions as well as in gastric cancer, and that hTERT gene expression is induced at an early stage of gastric carcinogenesis.

Helicobacter pylori attaches to NeuAc alpha 2,3Gal beta 1,4 glycoconjugates produced in the stomach of transgenic mice lacking parietal cells

Helicobacter pylori infection of the human stomach is associated with altered acid secretion, loss of acid-producing parietal cells, and, in some hosts, adenocarcinoma. We have used a transgenic mouse model to study the effects of parietal cell ablation on H. pylori pathogenesis. Ablation results in amplification of the presumptive gastric epithelial stem cell and its immediate committed daughters. The amplified cells produce sialylated oncofetal carbohydrate antigens that function as receptors for H. pylori adhesins. Attachment results in enhanced cellular and humoral immune responses. NeuAc alpha 2,3Gal beta 1,4 glycoconjugates may not only facilitate persistent H. pylori infection in a changing gastric ecosystem, but by promoting interactions with lineage progenitors and/or initiated cells contribute to tumorigenesis in patients with chronic atrophic gastritis.

Expression of human telomerase RNA is an early event of stomach carcinogenesis

Expression of human telomerase RNA (hTR) and telomerase activity in gastric cancer and corresponding non-cancerous mucosa were studied. Telomerase activity was detected in 23 (88%) of 26 carcinoma tissues. Although all tumor specimens and non-cancerous mucosa expressed various levels of hTR, 21 (81%) of 26 cases expressed hTR at a higher level in the tumor than that in the corresponding mucosa. All 8 gastric carcinoma cell lines also expressed hTR at high levels. Nine (35%) of 26 non-cancerous mucosa showed telomerase activity and all of them contained intestinal metaplasia. The incidence of telomerase-positive mucosa in grade 2 intestinal metaplasia was significantly higher than that in grade 0 or grade 1 intestinal metaplasia, whereas hTR overexpression was found in grade 0 or grade 1 intestinal metaplasia as well as grade 2 intestinal metaplasia. The degree of Helicobacter pylori infection increased in parallel with the level of hTR expression and telomerase positivity. These results overall suggest that Helicobacter pylori infection may be a strong trigger for hTR overexpression in intestinal metaplasia, and this may lead to telomerase reactivation.

Gastric epithelial dysplasia. How clinicopathologic background relates to management

BACKGROUND

Gastric epithelial dysplasia (GED) in metaplastic mucosa is considered the most advanced preinvasive lesion in the multistep morphogenesis of intestinal-type gastric cancer (GC). The rate of GED's evolution into GC is still under debate and probably is related to pathologic and clinical parameters other than the dysplasia itself. The aim of this study was to evaluate whether clinical aspects (sex and age) and/or morphologic variables (GED grade, coexisting atrophic gastritis) are relevant to the outcome of dysplasia, with a view toward initiating the establishment of a rational follow-up protocol for practical GED management.

METHODS

Ninety-three patients harboring GED (G1: 56, G2:34, G3:18) were followed for more than 12 months according to a previously-agreed protocol. Regression, progression, or evolution into GC were detected for each grade of GED. Multivariate analysis was used to check the independence of clinical and pathologic variables in the progression of GED into more severe dysplastic lesions and/or as risk factors for evolution into GC.

RESULTS

Age, male sex, GED grade and grade of coexisting atrophic gastritis proved independent risk factors for GED progression, with no significant interactions. Only GED grade (G2 and G3) was significantly associated with carcinomatous evolution. In G1-GED, age and the grade of coexisting atrophy proved to be independent risk factors for carcinomatous evolution.

CONCLUSIONS

In G1-GED, more stringent follow-up should be recommended for older patients with coexisting high grade atrophic gastritis; stringent follow-up is always mandatory for G2-GED; and a surgical approach is justified in G3-GED.

Cytophotometric and flow cytometric DNA content of isolated glands in gastric neoplasia

The gland isolation method was applied to various gastric lesions to measure DNA content by cytophotometry and flow cytometry for the first time. By incubating and agitating fresh specimens from surgically resected stomachs in calcium-magnesium free Hanks's balanced salt solution (CMFH) containing EDTA, many neoplastic glandular epithelial cells were successfully isolated from the stroma, and their characteristic three dimensional features were seen morphologically. The DNA content of pure nuclear suspensions of isolated glands was obtained by cytophotometry and flow cytometry staining with 4',6-diamino-2-phenylindole dihydrochloride (DAPI) and propidium iodide, respectively. Compared with histological grading, the frequency of the DNA aneuploidy of cancer with moderate or poor differentiation by cytophotometry (75%) was significantly higher than that of well differentiated cancer (25%), but the histological typing of gastric cancer DNA frequency were not correlated. This method allowed us to detect small aneuploid peaks by flow cytometry, which were previously masked by contaminating interstitial cells. The frequency of DNA aneuploidy detected by flow cytometry (87.5%) was higher than detected by cytophotometry (58.3%). The results of these studies shows the feasibility of this technique for analysing the DNA content of various lesions of the stomach.

Gastric epithelial dysplasia in the natural history of gastric cancer: a multicenter prospective follow-up study. Interdisciplinary Group on Gastric Epithelial Dysplasia

BACKGROUND/AIMS

Because the precancerous significance of gastric epithelial dysplasia (GED) is still under debate, this study attempts to ascertain whether a prospective follow-up of GED can contribute to clarifying its clinical and pathological relationships with gastric cancer (GC).

METHODS

One hundred twelve patients with mild (G1), moderate (G2), and severe (G3) GED or diagnosed as indefinite for dysplasia were prospectively followed up with a standardized endoscopic and bioptic protocol.

RESULTS

Evaluation of GED outcome refers only to 93 patients with a follow-up period longer than 12 months. Regression of dysplasia was documented in 36%, 27%, and 0% of G1, G2, and G3 GED cases, respectively. Progression to more severe dysplasia or evolution into GC was detected in 21%, 33%, and 57% of G1, G2, and G3 GED cases, respectively. Evolution into GC was documented for all grades of dysplasia and correlated significantly with high-grade atrophic gastritis. A high prevalence of early GC (86.9%) was also observed.

CONCLUSIONS

GED is a pre-invasive lesion, and carcinomatous evolution increases proportionally with its histological grade. Bioptical follow-up is mandatory for all histological grades of GED and significantly increases the likelihood of GC being detected in its early stages.