Expression of CD10, CD75 and CD43 in MALT lymphoma and their usefulness in discriminating MALT lymphoma from follicular lymphoma and chronic gastritis.

AIMS: While it may be difficult to discriminate between chronic gastritis, MALT lymphoma and a gastric location of a nodal lymphoma using histology of small endoscopic biopsies alone, additional markers like CD10, CD75 and CD43 and proliferative activity may be of value. We assessed the expression of these antigens in MALT lymphoma and their usefulness in discriminating MALT lymphoma from follicular lymphoma and from gastritis. METHODS AND RESULTS: Tissue samples of 38 patients with gastric MALT lymphoma were immunohistochemically stained for expression of CD10, CD75 and/or CD43. Proliferation index was scored using MIB-1 staining. Ten cases of nodal follicle centre B-cell lymphomas (n = 11) and 18 cases of high-grade MALT lymphoma (n = 22) showed moderate to high CD75 expression (25-100% positive cells). All tested low-grade MALT lymphomas (n = 9) and chronic gastritis (n = 6) were negative (0-25%) for CD75. All MALT lymphomas (n = 25) were negative for CD10. High-grade lymphomas show significantly higher proliferation indices (67% vs. 16%) than low-grade lymphomas. Only four of 26 MALT lymphomas were slightly positive for CD43. All gastritis biopsies (n = 4) were negative for CD43. CONCLUSIONS: These data suggest that combining both CD10 and CD75 may be useful in discriminating between low-grade MALT, high-grade MALT lymphoma and extranodal location of follicular lymphoma. However, CD43 expression cannot in the majority of cases be used to distinguish between low-grade MALT lymphoma and gastritis.     

The role of Helicobacter pylori in primary gastric MALT lymphoma

AIMS: Helicobacter pylori has been claimed to be an important aetiological factor which raises the risk of mucosa-associated tissue lymphoid (MALT) lymphoma. However, some studies on gastric MALT lymphoma revealed a low rate of H. pylori infection suggesting that not all gastric lymphomas are related to H. pylori infection. The aim of this study was to verify the H. pylori infection frequency in a series of patients with primary gastric MALT lymphomas and to examine the relationship between H. pylori and the pathological features of those lymphomas. METHODS AND RESULTS: Thirty-one cases of resected gastric lymphoma were analysed: 10 cases (32%) were low-grade MALT lymphomas and 21 cases (68%) were high-grade MALT lymphomas. Helicobacter pylori was found in only 18 of 31 (58%) cases. Helicobacter pylori infection was significantly correlated with the grade and depth of invasion of MALT lymphoma since 63% of superficial low-grade MALT lymphomas were positive for H. pylori compared with 38% of advanced high-grade MALT lymphomas (P = 0.02). CONCLUSION: We confirmed the relationship between H. pylori infection and a subset of gastric MALT lymphoma. Our results also showed that not all low- and high-grade gastric MALT lymphomas are H. pylori-dependent. This suggests that H. pylori infection may play a promoter role in the development of MALT lymphoma, but its presence is not mandatory for the progression of the lymphoma in view of its low frequency in advanced high-grade MALT lymphoma.     

Helicobacter mustelae-associated gastric MALT lymphoma in ferrets.

Gastric lymphoma resembling gastric mucosa-associated lymphoid tissue (MALT) lymphoma linked with Helicobacter pylori infection in humans was observed in ferrets infected with H. mustelae. Four ferrets with ante- or postmortem evidence of primary gastric lymphoma were described. Lymphoma was diagnosed in the wall of the lesser curvature of the pyloric antrum, corresponding to the predominant focus of H. mustelae induced gastritis in ferrets. Two ferrets had low-grade small-cell lymphoma and two ferrets had high-grade large-cell lymphoma. Gastric lymphomas demonstrated characteristic lymphoepithelial lesions, and the lymphoid cells were IgG+ in all ferrets. Lymphoma was confirmed by light chain restriction, which contrasted with the 1.2:1 kappa lambda ratio observed in H. mustelae-associated chronic gastritis. H. mustelae infection in ferrets has been used as a model for gastritis, ulcerogenesis, and carcinogenesis. The ferret may provide an attractive model to study pathogenesis and treatment of gastric MALT lymphoma in humans.     

Mucosal humoral immune response to CagA shows a high prevalence in patients with gastric MALT-type lymphoma

In the pathogenesis of gastric mucosa-associated lymphoid tissue (MALT)-type lymphoma, CagA-positive Helicobacter pylori strains have been suspected of making a significant contribution. To investigate this hypothesis in more detail, the mucosal humoral immune response of 15 patients with gastric MALT-type lymphoma was examined in the tumor and in the tumor-free gastritis of the same patient. Mononuclear cells from different sites (antrum, corpus, lymphoma) were cultured. Culture supernatant and serum of the same patient were used for immunodetection of CagA. All patients displayed an immune response to CagA in the tissue-culture supernatants. Although the humoral immune response in the tumor was restricted to a very few H. pylori antigens, antibodies directed against CagA protein were found in most patients. The immune response to CagA in nearly all lymphoma patients – not only in the serum, but also in the mucosa, including the tumor site – support the hypothesis that CagA is involved in the pathogenesis of gastric MALT-type lymphoma. Received: 16 April 1999 / Accepted: 30 August 1999     

HELICOBACTER PYLORI-SPECIFIC TUMOUR-INFILTRATING T CELLS PROVIDE CONTACT DEPENDENT HELP FOR THE GROWTH OF MALIGNANT B CELLS IN LOW-GRADE GASTRIC LYMPHOMA OF MUCOSA-ASSOCIATED LYMPHOID TISSUE

Previous studies have shown that tumour cells from low-grade B-cell gastric lymphomas of mucosa-associated lymphoid tissue (MALT) type proliferate in vitro in response to heat-killed whole cell preparations of Helicobacter pylori , but only in the presence of tumour-infiltrating T cells. This response is strain-specific in that the tumours studied responded optimally to different strains of H. pylori . It was unclear from these studies, however, whether the ability to recognize the specific stimulating strains of H. pylori was a property of the tumour cells or the tumour-infiltrating T cells. This study shows that whereas the tumour cells do not respond to H. pylori , both freshly isolated tumour-infiltrating T cells and a T cell line derived from these cells proliferate in response to stimulating strains of H. pylori . T cells from the spleen of one of the patients do not share this property. These results suggest that B-cell proliferation in cases of low-grade gastric lymphoma of MALT type in vitro in response to H. pylori is due to recognition of H. pylori by tumour-infiltrating T cells, which in turn provide help for tumour cell proliferation. The observations provide an explanation for properties of gastric MALT-type lymphoma, such as regression following eradication of H. pylori and the tendency of the tumour to remain localized to the primary site.     

Gastric low-grade mucosa-associated lymphoid tissue lymphomas: Their histogenesis and high-grade transformation

Gastric low-grade mucosa-associated lymphoid tissue (MALT) lymphoma is a unique disease. A vast majority of lymphoma cells are centrocyte-like cells or resemble monocytold B cells, and occasionally show plasmacytic differentiation. Immunophenotypical and immunogeno-typical examinations have indicated that they are in the differentiation stage of memory B cells, whose normal counterparts are marginal zone lymphocytes or monocytoid B cells In the lymphoid tissues. It arises from chronic gastritis closely associated with Helicobacter pylori (H. pylori ) infection. Mucosa-associated lymphoid tissue lymphomas of other organs are also based on acquired MALT associated with chronic inflammation or autoimmune diseases. Interestingly, the majority of gastric low-grade MALT lymphomas regress by the eradication of H. pylori . The lymphoma cells, however, are not derived from B cells reacting with H. pylori itself but from autoreactive B cells. Although the mechanism of their oncogenesis has not been clarified, previous data suggest that autoreactive B cells proliferate in response to H. pylori-specific T cells, presumably with some cytoklnes. The genetic Instability of such B cells then induces chromosomal abnormalities including trisomy 3 and/or other genetic changes. These B cells have the ability of autonomic proliferation and, even so, they might be sensitive to T cell stimuli. Low-grade gastric lymphomas occasionally progress to high-grade malignancy. The high-grade component of MALT lymphomas are composed of large-sized lymphoma cells that are morphologically indistinguishable from nodal large B cell lymphomas. This high-grade transformation is associated with p53 abnormalities or Bcl-6 overexpresslon. Gastric MALT lymphoma may provide a useful model in understanding multistep lymphomagenesls.     

Antigen-dependent progression of mucosa-associated lymphoid tissue (MALT)-type lymphoma in the stomach. Effects of antimicrobial therapy on gastric MALT lymphoma in mice.

In humans, low-grade B-cell mucosa-associated lymphoid tissue (MALT) lymphomas of the stomach regress when Helicobacter pylori infection is cured by antimicrobial therapy. Using an animal model of human gastric MALT lymphoma, we observed the effects of Helicobacter felis eradication and the relationship between infection and disease progression. Antimicrobial therapy was given to one-half of the BALB/c mice infected with H. felis for 20 months. Groups of antibiotic-treated and untreated mice were killed 2, 3, and 4 months after antimicrobial therapy (ie, 22, 23, and 24 months after infection). The numbers of mice with MALT decreased after H. felis eradication with no lymphoid follicles seen 4 months after treatment. MALT lymphoma was present in a total of 23% (11/48) of antibiotic-treated infected mice compared with 75% (27/36) in untreated infected mice. These lymphomas were further graded into low-, intermediate-, and high-grade lymphoma. In the untreated mice, lymphoma development was more advanced with 36% low-grade (13/36), 39% intermediate-grade (14/36), and 6% high-grade (large B-cell) lymphoma (2/36) whereas in the treated mice the incidence was 21% (10/48), 6% (3/48), and 0% (0/48), respectively. These observations suggest that antigenic stimulation by H. felis sustained growth and progression of low-grade MALT lymphoma and that primary high-grade gastric lymphomas can evolve from the transformation of these tumors. Eradication of the organism caused low-grade tumors to regress, with inhibition or slowing down of lymphoma development toward high-grade lymphoma. The H. felis mouse model of gastric MALT lymphoma presents an opportunity to address the issues arising from antimicrobial treatment of these tumors in humans.     

Serum Antibody Responses to Helicobacter pylori and the cagA Marker in Patients with Mucosa-Associated Lymphoid Tissue Lymphoma

The lymphoma of the mucosa-associated lymphoid tissue (MALT) of the stomach has been linked to Helicobacter pylori infection, but the mechanisms involved in B-cell proliferation remain elusive. In a search for putative H. pylori-specific monoclonal immunoglobulin production, an H. pylori strain was isolated from 10 patients with MALT lymphoma and used to detect the specific serum antibody response to the homologous strain by immunoblotting. Moreover, the antigenicity of the different strains was compared by using each of the 10 sera. We found that the different strains induced highly variable patterns of systemic immunoglobulin G antibody response, although several bacterial antigens, such as the 60-kDa urease B, were often recognized by the different sera. The cagA marker was detected in the strains by PCR with specific primers and by dot blot analysis, and the CagA protein was found in the sera of 4 of the 10 patients by immunoblotting. In conclusion, MALT lymphoma patients, like other patients with H. pylori gastritis, exhibit a polymorphic systemic antibody response, despite an apparently similar antigenic profile. The CagA marker of pathogenicity is not associated with this disease.     

c-myc GENE ABNORMALITIES IN MUCOSA-ASSOCIATED LYMPHOID TISSUE (MALT) LYMPHOMAS

c-myc gene abnormalities associated with lymphomagenesis, including rearrangements and mutations in the regulatory region between exon I and intron I, have been studied in 54 MALT lymphomas (43 low and 11 high grade) and 36 nodal lymphomas (27 low and 9 high grade). By Southern blot analysis, none of the 54 MALT lymphomas but 2 of 36 nodal lymphomas had c-myc gene rearrangements. Defined tumour cell populations from all MALT lymphoma cases were isolated by microdissection from frozen tissue sections and analysed by polymerase chain reaction–single-strand conformational polymorphism (PCR–SSCP) and direct sequencing for somatic mutations in the exon I/intron I region of the gene. Point mutations in this region were identified in nine cases of MALT lymphoma (7/43=16·2 per cent of low grade; 2/11=18·1 per cent of high grade). These mutations were located at either the exon I/intron I border of myc intron factor (MIF) binding sites, which are critical in the negative regulation of c-myc expression. Of the nodal lymphomas, only the two cases (5·6 per cent) with c-myc gene rearrangement showed scattered or clustered mutations. These results suggest that c-myc mutations in MALT lymphomas are unlikely to be associated with chromosome translocation, which is the main cause of somatic mutations observed in other types of lymphoma. The mutations involving the c-myc regulatory regions may play a pathogenetic role in at least a proportion of MALT lymphomas. © 1997 by John Wiley & Sons, Ltd.     

Mutational analysis of the 5' noncoding region of the bcl-6 gene in primary gastric lymphomas.

Bcl-6 mRNA and protein are frequently expressed in the transformed counterparts of the germinal center B-cells, diffuse large B-cell lymphoma and follicular lymphoma, irrespective of the gene rearrangements. Most of the primary gastric lymphomas are thought to be of mucosa-associated lymphoid tissue (MALT) origin, and neither bcl-6 gene rearrangement nor protein expression is found in low-grade gastric lymphomas of the MALT type as in normal marginal zone cells. However, bcl-6 protein expression was identified in high-grade gastric lymphomas, suggesting its role in high-grade transformation. In this study, polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis for bcl-6 primer was performed in order to ascertain the molecular mechanisms of bcl-6 protein expression in primary gastric lymphomas. A total 31 cases of gastric lymphoma were classified into low-grade gastric lymphomas of MALT type (n = 13), high-grade gastric lymphomas of MALT type (n = 6) and gastric diffuse large B-cell lymphomas (n = 12). Bcl-6 mutations were observed in 11 of 13 (84.6%) low-grade gastric lymphomas of the MALT type and in 8 of 12 (66.7%) diffuse large B-cell gastric lymphomas. In 6 cases of the high-grade gastric lymphomas of the MALT type, both the low- and high-grade components demonstrated the same frequency (3/6, 50%) of mutations. The tissue obtained from the marginal zone of Peyer's patch by microdissection technique revealed no bcl-6 mutations by the PCR-SSCP analysis. These findings suggest that the acquisition process of bcl-6 mutations by the marginal zone cells may be involved in the lymphomagenesis of the stomach, but our data does not explain the reason why bcl-6 protein is expressed only in high-grade gastric lymphomas.     

Deregulation of a distinct set of microRNAs is associated with transformation of gastritis into MALT lymphoma

The mechanisms underlying the transformation from chronic Helicobacter pylori gastritis to gastric extranodal marginal zone lymphoma (MALT lymphoma) are poorly understood. This study aims to identify microRNAs that might be involved in the process of neoplastic transformation. We generated microRNA signatures by RT-PCR in 68 gastric biopsy samples representing normal mucosa, gastritis, suspicious lymphoid infiltrates, and overt MALT lymphoma according to Wotherspoon criteria. Analyses revealed a total of 41 microRNAs that were significantly upregulated (n = 33) or downregulated (n = 8) in succession from normal mucosa to gastritis and to MALT lymphoma. While some of these merely reflect the presence of lymphocytes (e.g. miR-566 and miR-212) or H. pylori infection (e.g. miR-155 and let7f), a distinct set of five microRNAs (miR-150, miR-550, miR-124a, miR-518b and miR-539) was shown to be differentially expressed in gastritis as opposed to MALT lymphoma. This differential expression might therefore indicate a central role of these microRNAs in the process of malignant transformation.     

THE SIGNIFICANCE OF B-CELL CLONALITY IN GASTRIC LYMPHOID INFILTRATES

The significance of the demonstration of a clonal B-cell population in gastric lymphoid infiltrates was investigated by analysis of immunoglobulin heavy chain (IgH) gene rearrangements using sensitive polymerase chain reactions, employing fluorescently labelled primers to target the FR3 and FR1 regions. Tissue blocks were studied showing different histological features (high-grade lymphoma, low-grade lymphoma, and chronic gastritis) from 12 gastrectomies for primary gastric lymphoma, together with blocks showing chronic gastritis from 13 cases of gastric adenocarcinoma and biopsies from 33 patients with active Helicobacter -associated chronic gastritis. Clonal IgH gene rearrangements were detected in lymphoma samples from eight of the gastrectomies for lymphoma (67 per cent). In four of these eight specimens, clonal rearrangements were also detectable in the samples showing only chronic gastritis. Three of 28 (11 per cent) informative biopsies showing active Helicobacter -associated chronic gastritis had detectable clonal populations. Clonal rearrangements were also demonstrated in two of eight (25 per cent) informative blocks showing chronic gastritis from eight gastrectomies for adenocarcinoma. It is concluded that the detection of a clonal population in a suspicious lymphoid infiltrate does not confirm the diagnosis of lymphoma, nor does the absence of such a population imply benignity.     

Biased VH family usage in primary gastric B cell lymphoma of mucosa-associated lymphoid tissue-type and the selected Vβ expression of T cells infiltrating into the lymphoma cells

Seven cases of primary gastric low-grade B cell lymphoma of mucosa-assoclated lymphoid tissue (MALT) type, two cases of high-grade B cell lymphoma with a low-grade component and three cases of pure high-grade lymphoma were selected for the current study. The Ig VH gene use of lymphoma cells and the Vβ repertoires of infiltrating T cells were Investigated. The VH gene analysis showed multiple VH family usage In 12 cases, but the MALT-type lymphoma cell usage was found to be biased for the families that have a low number of VH genes (VHIV and V). Another analysis of lymphoma-lnfiltrating T cells showed restricted expressions of the Vβ repertoire in all seven low-grade cases and three high-grade cases. In those 10 cases, a considerable number of CD4-postttve T cells Infiltrated Into lymphoma cells and RAG-1 was also prominently expressed. Based on these findings, It was thus assumed that the normal counterpart of gastric B cell lymphoma of MALT type is different from the conventional B cell lymphoma, and the restricted expression of Vβ repertoires Is therefore considered to be a characteristic finding in low-grade B cell lymphomas of MALT type as well as in a proportion of high-grade lymphomas (the so called 'high-grade lymphoma of MALT type').     

Management of Suspicious Mucosa-Associated Lymphoid Tissue Lymphoma in Gastric Biopsy Specimens Obtained during Screening Endoscopy

It is often difficult to differentiate gastric mucosa-associated lymphoid tissue (MALT) lymphoma from Helicobacter pylori-associated follicular gastritis, and thus, it becomes unclear how to manage these diseases. This study aimed to explore the management strategy for and the long-term outcomes of suspicious gastric MALT lymphoma detected by forceps biopsy during screening upper endoscopy. Between October 2003 and May 2013, consecutive subjects who were diagnosed with suspicious gastric MALT lymphomas by screening endoscopy in a health checkup program in Korea were retrospectively enrolled. Suspicious MALT lymphoma was defined as a Wotherspoon score of 3 or 4 upon pathological evaluation of the biopsy specimen. Of 105,164 subjects who underwent screening endoscopies, 49 patients with suspicious MALT lymphomas who underwent subsequent endoscopy were enrolled. Eight patients received a subsequent endoscopy without H. pylori eradication (subsequent endoscopy only group), and 41 patients received H. pylori eradication first followed by endoscopy (eradication first group). MALT lymphoma development was significantly lower in the eradication first group (2/41, 4.9%) than in the subsequent endoscopy only group (3/8, 37.5%, P = 0.026). Notably, among 35 patients with successful H. pylori eradication, there was only one MALT lymphoma patient (2.9%) in whom complete remission was achieved, and there was no recurrence during a median 45 months of endoscopic follow-up. H. pylori eradication with subsequent endoscopy would be a practical management option for suspicious MALT lymphoma detected in a forceps biopsy specimen obtained during screening upper endoscopy.     

Activation of Infiltrating Cytotoxic T Lymphocytes and Lymphoma Cell Apoptotic Rates in Gastric MALT Lymphomas : Differences between High-Grade and Low-Grade Cases

In this study, we have characterized infiltrating T lymphocytes from 13 low-grade and 17 high-grade primary gastric MALT lymphomas by immunohistochemistry, with particular regard to the presence, activation, and topographic distribution of cytotoxic effectors. Although the prevalence of CD4+ and CD8+ cells was similar in low- and high-grade lymphomas, higher numbers of TIA-1+ cytotoxic effectors were found in this latter group of cases (11.6 versus 7. 8%; P = 0.004). Activation of CD8+ cytotoxic T lymphocytes (CTLs) was significantly more pronounced in high- than in low-grade lymphomas, as shown by immunostaining for perforin (8.7 versus 4.0%; P = 0.001) and granzyme-B (GrB) (8.7% versus 3.0%; P < 0.0001). Of note, CD20/GrB double labeling showed that high-grade lymphomas carried a markedly higher content (about ninefold) of activated CTLs relative to the number of CD20+ lymphoma B cells (0.081 +/- 0.076 versus 0.009 +/- 0.011; P < 0.0001). Moreover, high-grade lymphomas showed significantly increased apoptotic rates compared to low-grade cases (5.3 and 1.1% of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells, respectively; P < 0.0001). In the whole series, the percentage of GrB+ cells and the GrB+/CD20+ ratio showed a strong linear correlation with the number of TUNEL-labeled cells. These findings, together with the frequent colocalization of CTLs and TUNEL+ neoplastic cells, suggested that apoptotic death of lymphoma cells may be due at least in part to the killing by cytotoxic effectors. Our results are consistent with the occurrence of host antitumor cell-mediated immune responses in gastric MALT lymphomas. Moreover, the finding of stronger cytotoxic responses in high- than in low-grade cases is of potential usefulness in the design of more effective therapeutic strategies for the management of these disorders.     

Clinicopathologic study of primary gastric lymphoma of B cell phenotype with special reference to low-grade B cell lymphoma of mucosa-associated lymphoid tissue among the Japanese

Resection specimens from 83 patients with primary gastric lymphoma (PGL) of B cell phenotype at stage I_E and at stage II_E, according to the Ann Arbor classification were investigated. Histologically, these lymphomas could be divided into four types: Type I lesions (n=24) were entirely made up of MALT lymphoma; Type II lesions (n=13) were predominantly MALT lymphoma containing one to a few foci of high-grade B cell lymphoma; Type III lesions (n=22) consisted largely of high-grade lymphoma with small areas of low-grade MALT lymphoma; and Type IV lesions (n=24) were pure high-grade B cell lymphoma, mostly of the large cefi type. All patients had undergone primary gastric resection, and 14 received additional chemotherapy (n=12), or both chemotherapy and radiotherapy (n=2). The survival probability was significantly higher for Types I and II lymphomas than for Types III and IV tumors (P < 0.05 by the generalized Wilcoxon test). According to The General Rules for the Gastric Cancer Study by the Japanese Research Society for Gastric Cancer, the stage of disease showed a clear distinction between each of them (P < 0.01 by the generalized Wilcoxon test). This staging method seemed to serve well as a prognostic indicator. The histological typing of the PGL of the present series also seemed to correlate with the gross appearance, pathologic stage and prognosis. Furthermore, the expression of cyclin D1, bcl-2 and p53 protein, and PCNA was immunohistochemically investigated in 42 cases of the present series. Most of the low-grade PGL (Types I and II) had less than 60% PCNA-positive cells, whereas the high-grade PGL (Types III and IV) had more than 60% positive cells. In a study for cyclin D1 protein, no cases showed the nuclear staining pattern characteristic for mantle cell lymphoma, and the cytoplasmic staining frequently observed in the node-based large B cell lymphoma was seldom identified in the PGL. This discrepancy might suggest a lineage difference among the morphologically similar, but site-dierent, lymphomas. On the other hand, bcl-2 protein overexpression was almost equal in frequency between the gastric and node-based high-grade B cell lymphomas. This is in contrast to the reports from Western countries, in which the majority of high-grade gastric tumors were bcl-2 negative.     

p53 OVEREXPRESSION AND HUMAN PAPILLOMAVIRUS INFECTION IN TRANSITIONAL CELL CARCINOMA OF THE URINARY BLADDER: CORRELATION WITH HISTOLOGICAL PARAMETERS

Seventy-nine transitional cell carcinomas (TCCs) of the urinary bladder (25 grade 1, 22 grade 2, and 32 grade 3 tumours) were examined for p53 overexpression by immunohistochemistry with a monoclonal antibody and for human papillomavirus (HPV) infection by the polymerase chain reaction (PCR). Positive immunostaining for p53 was detected in 40·5 per cent of the cases; the percentage of positive cases was significantly lower in low-grade (G1 and G2) TCCs than in high-grade (G3) tumours (10·6 per cent vs. 84·4 per cent; P <0·0001). The overall rate of HPV infection was 32·9 per cent; 20·3 per cent of the cases were positive for HPV 16, 3·8 per cent for HPV 18, and 8·9 per cent for both. Consensus primers as well as type-specific primers for HPV types 6, 11, and 33 failed to detect any additional case with HPV infection. The prevalence of HPV 16 and/or HPV 18 infection was significantly higher in low-grade than in high-grade tumours (44·7 per cent vs. 15·6 per cent; P =0·0061). p53-positive cases were more common among papillary, deeply infiltrating tumours, and HPV-positive cases among papillary, non-infiltrating lesions. According to these data, p53 overexpression and HPV 16/18 infection are common findings in bladder TCC and there appears to be an inverse correlation of p53 overexpression and of HPV infection with tumour aggressiveness. The possibility of different molecular pathways in superficial low-grade and in invasive high-grade tumours is suggested.     

Helicobacter pylori infection and gastric cancer

Helicobacter pylori infection has an association with histological gastritis, gastric atrophy, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma in the stomach. Gastric cancer occurs in only a minority of infected individuals, however. Such clinical diversities are caused by variations of H. pylori pathogenicity, host susceptibility, environmental factors, and interactions of these factors. By three prospective epidemiological studies, the International Agency for Research on Cancer, World Health Organization (IARC/WHO) concluded in 1994 that H. pylori had a causal linkage to gastric carcinogenesis and is a definite carcinogen in humans. In addition, the Mongolian gerbil model with or without low-dose chemical carcinogens demonstrated that H. pylori infection could develop into gastric cancer. The experimental studies have elucidated that virulence factors of H. pylori have an interaction with gastric epithelial cell signaling related to carcinogenesis. The cag pathogenicity island (cagPAI) is a major virulence gene cluster and codes the type IV secretion machinery system, forming a cylinder-like structure. The CagA protein is translocated into target cells via this secretion system and induces a hummingbird morphology, growth factor-like effect. The other gene products are probably translocated into target cells and accelerate cellular proliferation and apoptosis. Understanding the molecular mechanism of the interaction between H. pylori and gastric epithelial cells will provide us with a new strategy for effective prevention of the development of gastric cancer induced by H. pylori infection.     

Expression of adhesion molecules in primary B-cell gastric lymphoma and lymphoid follicles

To determine whether primary B-cell gastric lymphoma (GL) is one entity, we examined the expression of three adhesion molecules in the microvasculature of lymphomas. Stromal cells, including vascular endothelial cells, within lymphoid follicles of the gastric mucosa were also investigated. Twenty-two surgical specimens of GL were classified into low-grade malignant lymphoma arising from mucosa-associated lymphoid tissue (low-grade lymphoma, n=9), and high-grade malignant lymphoma with (secondary high-grade lymphoma, n=6) or without (primary high-grade lymphoma, n=7) a low-grade component. The proportion of venules positive for ELAM-1 or VCAM-1 was significantly higher (P<0.001) in primary high-grade lymphoma than in low-grade and secondary high-grade lymphomas. In gastric lymphoid follicles, the stromal cells of the germinal centre (GC) were positive for ICAM-1, ELAM-1, and VCAM-1, but the stromal cells of the marginal zone (MZ) were positive only for ICAM-1. We found two patterns of adhesion molecule expression in gastric lymphoid follicles, the MZ pattern and the GC pattern. Low-grade and secondary high-grade lymphomas, which had the MZ pattern, might be of MZ-cell lineage, but most primary high-grade lymphomas, which had the GC pattern, might be of follicular centre cell lineage.     

Differing degree and distribution of gastritis in Helicobacter pylori-associated diseases

Infection with Helicobacter pylori (H. pylori) causes gastritis, and may be associated with gastric and duodenal ulcers and also with such malignant diseases as MALT lymphoma and gastric carcinoma. In order to determine whether there are differences in the degree and distribution of gastritis, each patient with H. pylori gastritis only (n = 50) was matched for sex and age with four patients, one each with H. pylori-associated duodenal ulcer, gastric ulcer, gastric carcinoma or MALT lymphoma. From each patient, two biopsies were taken from the antrum and two from the corpus for histopathological examination of H. pylori gastritis. The median summed gastritis score decreases in the following order: antrum: gastric ulcer > duodenal ulcer > gastritis alone > carcinoma > MALT lymphoma, and corpus: gastric ulcer > carcinoma > MALT lymphoma > gastritis alone and duodenal ulcer. We conclude that the degree and distribution of H. pylori gastritis differs significantly among H. pylori-associated diseases. These differences may explain some of the underlying pathomechanisms associated with H. pylori infection.