Detection of H. pylori DNA in gastric epithelial cells by in situ hybridization

ARK5 expression in colorectal cancer and its implications for tumor progression

A novel member of the human AMPK family, ARK5, was recently discovered to be a key molecule in mediating cancer cell migration activity in human pancreas cancer cell line PANC-1, and its activation was found to be induced by Akt-dependent phosphorylation at Ser 600. DNA array analysis with 241 paired cDNAs from 13 different types of tumors and corresponding normal tissues derived from cancer patients revealed ARK5 overexpression in the samples of colorectal cancer. ARK5 expression was measured and an in vitro invasion assay was performed in six human colorectal cancer cell lines, WiDr, HCT-15, DLD-1, SW620, LoVo, and SW480, and since high invasion activity was concordant with higher ARK5 expression, ARK5 expression was examined in relation to tumor progression and metastatic activity in clinical samples. In 56 clinical samples of primary colorectal cancers and their liver metastases, higher ARK5 expression was observed in the samples from more advanced cases, and much higher expression was observed in the liver metastases. In situ hybridization analysis showed ARK5 overexpression in tumor cells. Based on these findings, we propose that ARK5 overexpression is involved in tumor progression of colon cancer clinically.

Construction of expression systems for flaA and flaB genes of Helicobacter pylori and determination of immunoreactivity and antigenicity of recombinant proteins

AIM: To clone flagellin genes A (flaA) and B (flaB) from a clinical strain of Helicobacter pylori (H pylori) and to construct prokaryotic expression systems of the genes and identify immunity of the fusion proteins.

METHODS: The flaA and flaB genes from a clinical H pylori isolate Y06 were amplified by high fidelity PCR. The nucleotide sequences of target DNA amplification fragments from the two genes were sequenced after T-A cloning. The recombinant expression vector pET32a inserted with flaA and flaB genes was constructed, respectively. The expressions of FlaA and FlaB fusion proteins in E. coli BL21DE3 induced by isopropylthio-β-D-galactoside (IPTG) at different concentrations were examined by SDS-PAGE. Western blot using commercial antibodies against whole cell of H pylori and immunodiffusion assay using self-prepared rabbit antiserum against FlaA (rFlaA) or FlaB (rFlaB) recombinant proteins were applied to the determination of the fusion proteins immunity. ELISA was used to detect the antibodies against rFlaA and rFlaB in sera of 125 H pylori infected patients and to examine rFlaA and rFlaB expression in 98 clinical isolates of H pylori, respectively.

RESULTS: In comparison with the reported corresponding sequences, the nucleotide sequence homologies of the cloned flaA and flaB genes were from 96.28%-97.13% and 96.31%-97.73%, and their putative amino acid sequence homologies were 99.61%-99.80% and 99.41%-100% for the two genes, respectively. The output of rFlaA and rFlaB expressed by pET32a-flaA-BL21DE3 and pET32a-flaB-BL21DE3 systems was as high as 40%-50% of the total bacterial proteins. Both rFlaA and rFlaB were able to combine with the commercial antibodies against whole cell of H pylori and to induce rabbits to produce specific antibodies with the same 1:2 immunodiffusion titers after the animals were immunized with the two recombinant proteins. Ninety-eight and zero point 4 and 92.80% of the serum samples from 125 patients infected with H pylori were positive for rFlaA and rFlaB antibodies, respectively. One hundred percent and 98.98% of the 98 tested isolates of H pylori were detectable for rFlaA and rFlaB epitopes, respectively.

CONCLUSION: Two prokaryotic expression systems with high efficiency of H pylori flaA and flaB genes were successfully established. The expressed rFlaA and rFlaB showed satisfactory immunoreactivity and antigenicity. High frequencies of FlaA and FlaB expression in different H pylori clinical strains and the general existence of specific antibodies against FlaA and FlaB in H pylori infected patients strongly indicate that FlaA and FlaB are excellent antigen candidates for developing H pylori vaccine.

Construction of hpaA gene from a clinical isolate of Helicobacter pylori and identification of fusion protein

AIM: To clone hpaA gene from a clinical strain of Helicobacter pylori and to construct the expression vector of the gene and to identify immunity of the fusion protein.

METHODS: The hpaA gene from a clinical isolate Y06 of H. pylori was amplified by high fidelity PCR. The nucleotide sequence of the target DNA amplification fragment was sequenced after T-A cloning. The recombinant expression vector inserted with hpaA gene was constructed. The expression of HpaA fusion protein in E.coli BL21(DE3) induced by IPTG at different dosages was examined by SDS-PAGE. Western blot with commercial antibody against whole cell of H. pylori as well as immunodiffusion assay with self-prepared rabbit antiserum against HpaA fusion protein were applied to determine immunity of the fusion protein. ELISA was used to detect the antibody against HpaA in sera of 125 patients infected with H. pylori and to examine HpaA expression of 109 clinical isolates of H. pylori.

RESULTS: In comparison with the reported corresponding sequences, the homologies of nucleotide and putative amino acid sequences of the cloned hpaA gene were from 94.25%-97.32% and 95.38%-98.46%, respectively. The output of HpaA fusion protein in its expression system of pET32a-hpaA-BL21(DE3) was approximately 40% of the total bacterial proteins. HpaA fusion protein was able to combine with the commercial antibody against whole cell of H. pylori and to induce rabbit producing specific antiserum with 1:4 immunodiffusion titer after the animal was immunized with the fusion protein. 81.6% of the serum samples from 125 patients infected with H. pylori (102/125) were positive for HpaA antibody and all of the tested isolates of H. pylori (109/109) were detectable for HpaA.

CONCLUSION: A prokaryotic expression system with high efficiency of H. pylorihpaA gene was successfully established. The HpaA expressing fusion protein showed satisfactory immunoreactivity and antigenicity. High frequencies of HpaA expression in different H. pylori clinical strains and specific antibody production in H. pylori infected patients indicate that HpaA is an excellent and ideal antigen for developing H. pylori vaccine.

Clinicopathologic study of mucosa-associated lymphoid tissue lymphoma in gastroscopic biopsy

AIM: To explore and discuss the clinicopathologic characteristics of mucosa-associated lymphoid tissue (MALT) lymphoma in gastroscopic biopsy specimen.

METHODS: A retrospective study of 26 cases of lymphoma diagnosed by gastroscopic biopsy during 1999 to 2001 from gastroscopy files of Xijing Hospital was made. The diagnostic criteria were adopted according to the new classification of non-Hodgkin's lymphoma.

RESULTS: Twenty-six cases of primary gastric lymphoma consisting of 15 men and 11 women, aged between 23 to 76 years were recruited from 6225 cases who received gastroscopy. All of them were diagnosed by both endoscopic findings and histological examinations. Histologically, 23 cases were MALToma (low grade) and 3 cases lymphoblastic lymphoma (high grade). Immunohistochemically, all cases were CD20 positive, while CK and EMA were negative.

CONCLUSION: The majority of the cases of primary low-grade gastric lymphoma have morphologic and clinical features that justify their inclusion in the category of low-grade lymphoma of mucosa associated lymphoid tissue.

Virulence of water-induced coccoid Helicobacter pylori and its experimental infection in mice

AIM: To explore the virulence and the infectivity of coccoid Helicobacter pylori (H. pylori) transformed from spiral form by exposure to sterile tap water.

METHODS: Three strains of H. pylori, isolated from gastric biopsy specimens of confirmed peptic ulcer, were converted from spiral into coccoid form by exposure to sterile tap water. Both spiral and coccoid forms of H. pylori were tested for the urease activity, and the adherence to Hep-2 cells. The presence of flagella was examined under electron microscopy. In the experimental animal infection, the spiral and coccoid forms of H. pylori originated from the same strain F49 were inoculated intragastrically into BALB/c mice respectively four times at a 3-day interval. Half of the mice from each group were sacrificed at Day 21 and Day 28 after the last inoculation. Histology and H.pylori colonization were detected by urease test of gastric mucosa, cultures of H.pylori, and electron microscopy and so on.

RESULTS: The urease activity and the ability of adherence to Hep-2 cells were found to be lower in coccoid H.pylori than that in its spiral form. For example, the transformation in strain F₄₄ led to a significant decrease of the adherence rate and adherence index from 70.0% ± 5.3% to 30.2% ± 3.5% (P < 0.01), and from 2.6 ± 0.4 to 0.86 ± 0.3 (P < 0.01), respectively. The flagella of coccoid H. pylori were observed under electron microscope. In the experimental infection in mice, the positive rate of gastric mucosa urease test was 93.8% (15/16) in the group infected by spiral H.pylori and 50% (8/16) in the group infected by coccoid H.pylori, and the estimated coccoid H.pylori colony number was 1.75 vs 0.56. The positive rates of H.pylori culture were 87.5% (14/16) in spiral H. pylori group and 68.8% (11/16) in coccoid H. pylori group. There was no significant difference in either urease test or bacterial culture rate between the groups examined at Day 21 and Day 28 after inoculation. Electron microscopic examination of the samples taken from both groups showed the adherence of H.pylori in spiral, bacillary and coccoid shapes to the epithelial cells of gastric wall. Histological examination showed the occurrence of gastric mucosal injury as indicated by various degrees of erosion, ulcer, and inflammatory cell infiltration. Mucosal injury was slighter in the mice infected by coccoid H.pylori. No positive result was obtained in the control group that received intragastrical administration of sterile tap water.

CONCLUSION: Although the virulence of coccoid H.pylori induced by water decrease, coccoid H.pylori still remains a considerable urease activity and the adhering ability to epithelial cells. Furthermore, the flagella, an important component responsible for bacterial movement and infection, were still observed as a cellular structure of coccoid H.pylori under electron microscope. The coccoid H.pylori induced by water is capable of colonizing in gastric mucosa and causing gastrititis in mice.

Expression of gastric cancer-associated MG7 antigen in gastric cancer, precancerous lesions and H. pylori-associated gastric diseases

AIM: To investigate the relationship between the antigen MG7 antigen expression and gastric cancer as well as precancerous condition; to study the relationship between the MG7 antigen expression and H. pylori infection in benign gastric lesions in order to find out the effect of H. pylori infection on the process of gastric cancer development.

METHODS: The level of MG7 antigen expression was determined by immunohistochemical method in 383 gastric biopsied materials. The intestinal metaplasia was determined by histochemistry method. The H. pylori infection was determined by HE stain, PCR and ELISA in 291 specimens, among which only 34 cases of H. pylori-associated gastric lesions were followed up.

RESULTS: The positive rate of MG7 expression in normal gastric mucosa, intestinal metaplasia, dysplasia and gastric cancer increased gradually in ascending order (P < 0.01). The positive rate of MG7 antigen expression in type III intestinal metaplasia of gastric mucosa was higher than that of type I and II intestinal metaplasia, being highly significant (P < 0.05). The positive rate of MG7 antigen expression in superficial gastritis, atrophic gastritis and gastric cancer increased gradually (11.9%, 64.8%, 91.2%, P < 0.01). There was no significant difference between H .pylori-negative and H. pylori-positive intestinal metaplasia, atrophic gastritis and dysplasia of gastric epithelium in the positive rate of MG7 antigen expression. There was no expression of MG7 antigen in H. pylori-negative superficial gastritis. The positive rate of MG7 expression in H. pylori-positive superficial gastritis was 20.5%, and the difference between them was significant (P < 0.05). During following up, one of the three H. pylori negative cases turned positive again, and its MG7 antigen expression turned to be stronger correspondingly. 3 of 31 H. pylori positive cases were detected as early gastric cancer, among which one with “+++” MG7 antigen expression was diminished after H. pylori eradication.

CONCLUSION: MG7 antigen expression is highly specific in gastric cancer and can be used as a good marker for screening of gastric cancer; type III intestinal metaplasia, atrophic gastritis and dysplasia should be followed up and MG7 antigen expression has high clinical value in the dynamic follow-up study; although the positive -MG7 in positive - H. pylori superficial gastritis show benign morphology in features, there is still the potential risk of developing into gastric cancer, hence special attention should be paid to those showing increasing MG7 antigen expression.