Detection of the Helicobacter pylori CagA protein in gastric mucosa-associated lymphoid tissue lymphoma cells: clinical and biological significance. Blood Cancer J. 2013;3:e125. [PMID: 23852160 PMCID: PMC3730200 DOI: 10.1038/bcj.2013.22]

Cooperative participation of CagA and NFATc1 in the pathogenesis of antibiotics-responsive gastric MALT lymphoma

BACKGROUND

This study aimed to explore whether cytotoxin-associated gene A (CagA) can inhibit cell cycle progression by activating nuclear factor of activated T cells (NFAT) in lymphoma B cells and contribute to Helicobacter pylori eradication (HPE) responsiveness (complete remission [CR] after HPE) in gastric mucosa-associated lymphoid tissue (MALT) lymphoma.

MATERIALS AND METHODS

We co-cultured three B-lymphoma cell lines (MA-1, OCI-Ly3, and OCI-Ly7) with HP strains (derived from HPE-responsive gastric MALT lymphoma) and evaluated the expression patterns of CagA, phosphorylated (p)-CagA (CagAP-Tyr), and CagA-signaling molecules, cell-cycle inhibitors, p-NFATc1 (Ser172), and NFATc1 using western blotting. Furthermore, we evaluated the association between nuclear NFATc1 expression in the tumor cells of 91 patients who received first-line HPE (59 patients with HPE responsiveness and 32 without HPE responsiveness) and HPE responsiveness and CagA expression in tumor cells.

RESULTS

In HP strains co-cultured with B cell lymphoma cell lines, CagA was translocated to the nucleus through tyrosine phosphorylation (CagAP-Tyr) and simultaneously dephosphorylated NFATc1, subsequently causing nuclear NFATc1 translocation and stimulating the expression of p-SHP-2/p-ERK/Bcl-xL. Activated NFATc1 causes G1 cell cycle retardation in both MA-1 and OCI-Ly3 cells by triggering p21 and p27 production. Nuclear NFATc1 localization was significantly associated with the presence of CagA in gastric MALT lymphomas (80% [41/51] vs. 33% [13/40]; p < 0.001) and with HPE responsiveness (73% [43/59] vs. 25% [8/32]; p < 0.001). Patients exhibiting both the presence of CagA and nuclear NFATc1 localization responded more rapidly to HPE than those without (median interval to CR, 4.00 vs. 6.00 months, p = 0.003).

CONCLUSIONS

Our findings indicated that CagA and NFATc1 cooperatively participate in the lymphomagenesis of HPE-responsive gastric MALT lymphoma.

Insights into the molecular mechanisms of H. pylori-associated B-cell lymphoma

Cancer research has extensively explored various factors contributing to cancer development, including chemicals, drugs, smoking, and obesity. However, the role of bacterial infections in cancer induction remains underexplored. In particular, the mechanisms underlying H. pylori-induced B-cell lymphoma, a potential consequence of bacterial infection, have received little attention. In recent years, there has been speculation about contagious agents causing persistent inflammation and encouraging B-lymphocyte transition along with lymphomagenesis. MALT lymphoma associated with chronic H. pylori infection, apart from two other central associated lymphomas - Burkitt's Lymphoma and DLBCL, is well studied. Owing to the increasing colonization of H. pylori in the host gut and its possible action in the development of B-cell lymphoma, this review aims to summarize the existing reports on different B-cell lymphomas' probable association with H. pylori infections; also emphasizing the function of the organism in lymphomagenesis; including its interaction with the host, pathogen and host-specific factors, and tumor microenvironment.

Gastric Non-Hodgkin Lymphoma in a Helicobacter pylori-Infected Patient

Primary gastric diffuse large B-cell lymphoma (PG-DLBCL) is a rare gastric malignant neoplasm. While the association between Heliobacter pylori infection and gastric mucosa-assisted lymphoid tissue lymphoma is well established, data supporting its association with DLBCL are less robust. Here we present a rare case of PG-DLBCL diagnosed with H. pylori. An 82-year-old man presented to clinic with complaints of worsening epigastric pain. He underwent an endoscopy which revealed 1 large nonbleeding gastric ulcer. Histopathological and immunohistochemical analysis confirmed PG-DLBCL. He was started on H. pylori eradication (HPE) and subsequently completed 6 cycles of R-mini-CHOP chemotherapy. Since then, the patient maintained clinical and radiological remission for more than a year without recurrence. PG-DLBCL is an aggressive Non-hodgkin lymphoma (NHL) that usually presents late. It has been shown that HPE without chemotherapy in DLBCL codiagnosed with H. pylori is not an effective strategy. Thus, the standard of care for patients would be HPE and chemotherapy as in our patient. More research is needed to better understand association between H. pylori and DLBCL.

Helicobacter pylori CagA promotes immune evasion of gastric cancer by upregulating PD-L1 level in exosomes

Cytotoxin-associated gene A (CagA) of Helicobacter pylori (Hp) may promote immune evasion of Hp-infected gastric cancer (GC), but potential mechanisms are still under explored. In this study, the positive rates of CagA and PD-L1 protein in tumor tissues and the high level of exosomal PD-L1 protein in plasma exosomes were significantly associated with the elevated stages of tumor node metastasis (TNM) in Hp-infected GC. Moreover, the positive rate of CagA was positively correlated with the positive rate of PD-L1 in tumor tissues and the level of PD-L1 protein in plasma exosomes, and high level of exosomal PD-L1 might indicate poor prognosis of Hp-infected GC. Mechanically, CagA increased PD-L1 level in exosomes derived from GC cells by inhibiting p53 and miRNA-34a, suppressing proliferation and anticancer effect of CD8+ T cells. This study provides sights for understanding immune evasion mediated by PD-L1. Targeting CagA and exosomal PD-L1 may improve immunotherapy efficacy of Hp-infected GC.

Outcome and patterns of relapse in primary gastric diffuse large B cell lymphoma treated with RCHOP

OBJECTIVES

Patterns and predictors of relapse in primary gastric diffuse large B cell lymphoma (DLBCL) were variably reported. Our study aims to evaluate the patterns and predictors of relapse in early-stage gastric DLBCL treated with Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, and Prednisolone (RCHOP).

METHODS

From 2005 to 2019, the medical records of 72 patients with stage I or stage II gastric DLBCL treated with six cycles of RCHOP without radiotherapy were reviewed. Different variables were correlated with progression free survival (PFS), overall survival (OS), and local relapse free survival (LRFS).

RESULTS

64 (88.1%) patients achieved a complete response (CR), while 8 (11.9%) had refractory disease. After CR, 9 (14%) patients relapsed; 7 (78%) relapses were loco-regional. Abnormal LDH (p = 0.028), H. pylori negative (p = 0.032) and, stage adjusted international prognostic index (sa-IPI) > 1 (p = 0.013) correlated with loco-regional failure. The 5-year PFS, OS, and LRFS were 74.8%, 75.3%, and 87.5%, respectively, after a median follow-up of 58 (range: 6-185) months. The median time to progression or relapse was 9 months (range: 5-54 months). In multivariate analysis, a sa-IPI >1 (HR: 3.56, CI: 1.35-8.8, p = 0.01) was associated with PFS while low albumin (HR: 8.85, CI: 1.09-71.4, p = 0.041) was associated with worse OS. None of the variables were associated with LRFS.

CONCLUSION

Treatment of primary gastric DLBCL with RCHOP results in a high CR rate. The majority of treatment failures were loco-regional. Sa-IPI and H. pylori status may be used to identify patients who may benefit from combined modality treatment.

Diversification and deleterious role of microbiome in gastric cancer

Gut microbiota dictates the fate of several diseases, including cancer. Most gastric cancers (GC) belong to gastric adenocarcinomas (GAC). Helicobacter pylori colonizes the gastric epithelium and is the causative agent of 75% of all stomach malignancies globally. This bacterium has several virulence factors, including cytotoxin-associated gene A (CagA), vacuolating cytotoxin (VacA), and outer membrane proteins (OMPs), all of which have been linked to the development of gastric cancer. In addition, bacteria such as Escherichia coli, Streptococcus, Clostridium, Haemophilus, Veillonella, Staphylococcus, and Lactobacillus play an important role in the development of gastric cancer. Besides, lactic acid bacteria (LAB) such as Bifidobacterium, Lactobacillus, Lactococcus, and Streptococcus were found in greater abundance in GAC patients. To identify potential diagnostic and therapeutic interventions for GC, it is essential to understand the mechanistic role of H. pylori and other bacteria that contribute to gastric carcinogenesis. Furthermore, understanding bacteria-host interactions and bacteria-induced inflammatory pathways in the host is critical for developing treatment targets for gastric cancer.

Helicobacter pylori cagA status and gastric mucosa-associated lymphoid tissue lymphoma: a systematic review and meta-analysis

Background

Recent studies have investigated the role of Helicobacter pylori infection in the development of gastric mucosa-associated lymphoid tissue (MALT) lymphoma. It is estimated that approximately 0.1% of people infected with H. pylori develop gastric MALT lymphoma. However, the role of the CagA antigen, the highest causative agent of H. pylori, in increasing the risk of gastric MALT lymphoma remains unclear and controversial. A systematic review and meta-analysis were conducted to evaluate the effect of cagA status on the development of gastric MALT lymphoma.

Methods

All articles evaluating the status of the cagA gene in the development of gastric MALT lymphoma were collected using systematic searches in online databases, including PubMed, Scopus, Embase, and Google Scholar, regardless of publication date. The association between cagA and gastric MALT lymphoma was assessed using the odds ratio (OR) summary. In addition, a random-effects model was used in cases with significant heterogeneity.

Results

A total of 10 studies met our inclusion criteria, among which 1860 patients participated. No association between cagA status and the development of MALT lymphoma (extranodal marginal zone B-cell lymphoma) was found in this study (OR 1.30; 0.906–1.866 with 95% CIs; I²: 45.83; Q-value: 12.92). Surprisingly, a meaningful association was observed between cagA status and diffuse large B-cell lymphoma (OR 6.43; 2.45–16.84 with 95% CIs). We also observed an inverse association between vacA and gastric MALT lymphoma risk (OR 0.92; 0.57–1.50 with 95% CIs).

Conclusions

It seems that the infection with cagA-positive H. pylori strains does not have a meaningful effect on the gastric MALT lymphoma formation, while translocated CagA antigen into the B cells plays a crucial role in the development of diffuse large B-cell lymphoma.

Bacterial Infection and Non-Hodgkin B-Cell Lymphoma: Interactions between Pathogen, Host and the Tumor Environment

Non-Hodgkin B-cell lymphomas (NHL) are a heterogeneous group of lymphoid neoplasms with complex etiopathology, rich symptomatology, and a variety of clinical courses, therefore requiring different therapeutic approaches. The hypothesis that an infectious agent may initiate chronic inflammation and facilitate B lymphocyte transformation and lymphogenesis has been raised in recent years. Viruses, like EBV, HTLV-1, HIV, HCV and parasites, like Plasmodium falciparum, have been linked to the development of lymphomas. The association of chronic Helicobacter pylori (H. pylori) infection with mucosa-associated lymphoid tissue (MALT) lymphoma, Borrelia burgdorferi with cutaneous MALT lymphoma and Chlamydophila psittaci with ocular adnexal MALT lymphoma is well documented. Recent studies have indicated that other infectious agents may also be relevant in B-cell lymphogenesis such as Coxiella burnettii, Campylobacter jejuni, Achromobacter xylosoxidans, and Escherichia coli. The aim of the present review is to provide a summary of the current literature on infectious bacterial agents associated with B-cell NHL and to discuss its role in lymphogenesis, taking into account the interaction between infectious agents, host factors, and the tumor environment.

PTEN Loss and Cyclin A2 Upregulation Define a PI3K/AKT Pathway Activation in Helicobacter pylori-induced MALT and DLBCL Gastric Lymphoma With Features of MALT

Helicobacter pylori infection is strongly associated with primary gastric diseases, such as extranodal mucosa-associated lymphoid tissue (MALT) lymphoma, diffuse large B-cell lymphoma (DLBCL) with histologic evidence of MALT origin, and gastric carcinoma. The cytotoxin-associated gene A (CagA) protein behaves as a bacterial oncoprotein, promoting tumorigenesis via dysregulation of the phosphatidylinositol 3-kinase/AKT pathway (PI3K/AKT). We investigated the molecular mechanisms of PI3K/AKT pathway dysregulation in H. pylori-induced MALT and DLBCL gastric lymphoma. Immunohistochemical assays for CagA, phospho(p)-S473-AKT, PTEN, SHIP, and cyclin A2 proteins were performed on samples from 23 patients with H. pylori-positive MALT lymphoma and 16 patients with H. pylori-positive gastric DLBCL. We showed that CagA localization is correlated with the activation of the AKT pathway in both MALT and DLBCL lymphoma cells. Interestingly, we found a close association between the loss of PTEN, the overexpression of cyclin A2, and the phosphorylation of AKT in gastric MALT and DLBCL tumor cells.

Helicobacter pylori Virulence Factor Cytotoxin-Associated Gene A (CagA)-Mediated Gastric Pathogenicity

Helicobacter pylori causes persistent infection in the gastric epithelium of more than half of the world’s population, leading to the development of severe complications such as peptic ulcer diseases, gastric cancer, and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Several virulence factors, including cytotoxin-associated gene A (CagA), which is translocated into the gastric epithelium via the type 4 secretory system (T4SS), have been indicated to play a vital role in disease development. Although infection with strains harboring the East Asian type of CagA possessing the EPIYA-A, -B, and -D sequences has been found to potentiate cell proliferation and disease pathogenicity, the exact mechanism of CagA involvement in disease severity still remains to be elucidated. Therefore, we discuss the possible role of CagA in gastric pathogenicity.

Dissecting the Helicobacter pylori-regulated transcriptome of B cells

Persistent infections with the bacterial group-I carcinogen Helicobacter pylori (H. pylori) have been associated with a broad range of gastric disorders, including gastritis, ulceration, gastric cancer or mucosa-associated lymphoid tissue (MALT) lymphoma. Pathogenesis of H. pylori requires a balance between immune tolerance and defense. Although H. pylori induces inflammatory responses, the immune system cannot eliminate the pathogen. The detailed molecular mechanisms of how H. pylori interferes with cells of the immune system, in particular infiltrated B cells, are not well investigated. Previously, it was shown that the bacterial effector and oncoprotein cytotoxin-associated gene A (CagA) is delivered into B cells followed by its tyrosine-phosphorylation. To investigate the functional consequences in B cells colonized by CagA-positive H. pylori, we analyzed the global transcriptome of H. pylori-infected Mec-1 cells by RNA sequencing. We found 889 differentially expressed genes (DEGs) and validated JUN, FOSL2, HSPA1B, SRC, CXCR3, TLR-4, TNF-α, CXCL8, CCL2, CCL4, MHC class I and MHC class II molecules by qPCR, western blot, flow cytometry and ELISA assays. The H. pylori-specific mRNA expression signature reveals a downregulation of inflammation- and migration-associated genes, whereas central signal transduction regulators of cell survival and death are upregulated.

Prognostic significance of helicobacter pylori-infection in gastric diffuse large B-cell lymphoma

Background

Helicobacter pylori (H. pylori) is thought to have an oncogenic effect on the development of gastric malignancies. However, the effect of H. pylori status on the prognosis of gastric diffuse large B-cell lymphoma (DLBCL) remains unconfirmed. This study aimed to identify the prognostic importance of H. pylori infection in de novo gastric DLBCL.

Methods

One hundred and twenty-nine patients diagnosed with primary de novo gastric DLBCL at the West China Hospital of Sichuan University from 1st January 2009 to 31st May 2016 were included. The clinical features of the patients were documented. H. pylori status was assessed via urease breath tests and histologic examinations. The prognostic value of H. pylori was verified via univariate and multivariate analyses.

Results

Over a median follow-up of 52.2 months (range 4–116), the 5-year overall survival (OS) for all patients was 78.7%. Patients with H. pylori infections had significantly better 5-year PFS and OS than did the H. pylori-negative subgroup (5-year PFS, 89.3% vs. 74.1%, P = 0.040; 5-year OS, 89.7% vs. 71.8%, P = 0.033). Negative H. pylori status and poor ECOG performance were independent negative prognostic indicators for both PFS and OS (PFS, P = 0.045 and P = 0.001, respectively; OS, P = 0.021 and P < 0.001, respectively).

Conclusions

H. pylori status in de novo gastric DLBCL can be a promising predictor of disease outcome, and patients with negative H. pylori status require careful follow-up since they tend to have a worse outlook.

Novel Insights of Lymphomagenesis of Helicobacter pylori-Dependent Gastric Mucosa-Associated Lymphoid Tissue Lymphoma

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is the most common subtype of gastric lymphoma. Most gastric MALT lymphomas are characterized by their association with the Helicobacter pylori (HP) infection and are cured by first-line HP eradication therapy (HPE). Several studies have been conducted to investigate why most gastric MALT lymphomas remain localized, are dependent on HP infection, and show HP-specific intratumoral T-cells (e.g., CD40-mediated signaling, T-helper-2 (Th2)-type cytokines, chemokines, costimulatory molecules, and FOXP3+ regulatory T-cells) and their communication with B-cells. Furthermore, the reason why the antigen stimuli of these intratumoral T-cells with tonic B-cell receptor signaling promote lymphomagenesis of gastric MALT lymphoma has also been investigated. In addition to the aforementioned mechanisms, it has been demonstrated that the translocated HP cytotoxin-associated gene A (CagA) can promote B-cell proliferation through the activation of Src homology-2 domain-containing phosphatase (SHP-2) phosphorylation-dependent signaling, extracellular-signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), B-cell lymphoma (Bcl)-2, and Bcl-xL. Furthermore, the expression of CagA and these CagA-signaling molecules is closely associated with the HP-dependence of gastric MALT lymphomas (completely respond to first-line HPE). In this article, we summarize evidence of the classical theory of HP-reactive T-cells and the new paradigm of direct interaction between HP and B-cells that contributes to the HP-dependent lymphomagenesis of gastric MALT lymphomas. Although the role of first-line HPE in the treatment of HP-negative gastric MALT lymphoma remains uncertain, several case series suggest that a proportion of HP-negative gastric MALT lymphomas remains antibiotic-responsive and is cured by HPE. Considering the complicated interaction between microbiomes and the genome/epigenome, further studies on the precise mechanisms of HP- and other bacteria-directed lymphomagenesis in antibiotic-responsive gastric MALT lymphomas are warranted.

MALT Lymphoma as a Model of Chronic Inflammation-Induced Gastric Tumor Development

Mucosa-associated lymphoid tissue (MALT) lymphoma, or extranodal marginal zone lymphoma of MALT, is an indolent B-cell non-Hodgkin lymphoma linked with preexisting chronic inflammation. The stomach is the most commonly affected organ and the MALT lymphoma pathogenesis is clearly associated with Helicobacter pylori gastroduodenitis. Inflammation induces the lymphoid infiltrates in extranodal sites, where the lymphoma then subsequently develops. Genetic aberrations arise through the release of reactive oxygen species (ROS), H. pylori-induced endonucleases, and other effects. The involvement of nuclear factor kappa B (NF-κB) pathway activation, a critical regulator of pro-inflammatory responses, further highlights the role of inflammation in gastric MALT lymphoma. The NF-κB pathway regulates key elements of normal lymphocyte function, including the transcription of proliferation-promoting and anti-apoptotic genes. Aberrant constitutive activation of NF-κB signaling can lead to autoimmunity and malignancy. NF-κB pathway activation can happen through both the canonical and non-canonical pathways and can be caused by multiple genetic aberrations such as t(11;18)(q12;q21), t(1;14)(p22;q32), and t(14;18)(q32;q21) translocations, chronic inflammation and even directly by H. pylori-associated mechanisms. Gastric MALT lymphoma is considered one of the best models of how inflammation initiates genetic events that lead to oncogenesis, determines tumor biology, dictates clinical behavior and leads to viable therapeutic targets. The purpose of this review is to present gastric MALT lymphoma as an outstanding example of the close pathogenetic link between chronic inflammation and tumor development and to describe how this information can be integrated into daily clinical practice.

Gastric microbiota: An emerging player in Helicobacter pylori-induced gastric malignancies

The complex diversity of nonpathogenic microbes that colonize the human body, known as microbiota, exert considerable effects on physiological homeostasis, and immune regulation. Helicobacter pylori (H. pylori) is a bacterium that frequently colonizes human stomach and is a major pathogenic agent for peptic ulcer diseases, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma. Due to its acidic pH and peristaltic movements, the stomach has been considered a hostile environment for most microorganisms, however various commensal microorganisms are capable of colonizing the stomach to form a stomach niche. Recent pieces of evidence indicate that commensal gastric microbes or their metabolites influence the capability of H. pylori to colonize the stomach and directly modulate its pathogenicity and carcinogenic potential. In this article, we present an overview of recent advances in the understanding of H. pylori-commensal interactions in the pathogenesis and clinical evolution of H. pylori-associated gastric malignancies.

First-line antibiotic therapy in Helicobacter pylori-negative low-grade gastric mucosa-associated lymphoid tissue lymphoma

First-line antibiotic treatment for eradicating Helicobacter pylori (HP) infection is effective in HP-positive low-grade gastric mucosa-associated lymphoid tissue lymphoma (MALToma), but its role in HP-negative cases is uncertain. In this exploratory retrospective study, we assessed the outcome and potential predictive biomarkers for 25 patients with HP-negative localized gastric MALToma who received first-line HP eradication (HPE) therapy. An HP-negative status was defined as negative results on histology, rapid urease test, ¹³C urea breath test, and serology. We observed an antibiotic response (complete remission [CR], number = 8; partial remission, number = 1) in 9 (36.0%) out of 25 patients. A t(11;18)(q21;q21) translocation was detected in 7 (43.8%) of 16 antibiotic-unresponsive cases, but in none of the 9 antibiotic-responsive cases (P = 0.027). Nuclear BCL10 expression was significantly higher in antibiotic-unresponsive tumors than in antibiotic-responsive tumors (14/16 [87.5%] vs. 1/9 [11.1%]; P = 0.001). Nuclear NF-κB expression was also significantly higher in antibiotic-unresponsive tumors than in antibiotic-responsive tumors (12/16 [75.0%] vs. 1/9 [11.1%]; P = 0.004). A substantial portion of patients with HP-negative gastric MALToma responded to first-line HPE. In addition to t(11;18)(q21;q21), BCL10 and NF-κB are useful immunohistochemical biomarkers to predict antibiotic-unresponsive status in this group of tumors.

Helicobacter pylori Strains and Gastric MALT Lymphoma

This article summarizes the main findings concerning Helicobacter pylori associated with gastric MALT lymphoma (GML). Considered together, GML strains based on their virulence factor profile appear to be less virulent than those associated with peptic ulcers or gastric adenocarcinoma. A particular Lewis antigen profile has been identified in GML strains and could represent an alternative adaptive mechanism to escape the host immune response thereby allowing continuous antigenic stimulation of infiltrating lymphocytes.

The B-cell-activating factor signalling pathway is associated with Helicobacter pylori independence in gastric mucosa-associated lymphoid tissue lymphoma without t(11;18)(q21;q21)

We previously reported that activation of the B-cell-activating factor (BAFF) pathway upregulates nuclear factor-κB (NF-κB) and induces BCL3 and BCL10 nuclear translocation in Helicobacter pylori (HP)-independent gastric diffuse large B-cell lymphoma (DLBCL) tumours with evidence of mucosa-associated lymphoid tissue (MALT). However, the significance of BAFF expression in HP independence of gastric low-grade MALT lymphomas without t(11;18)(q21;q21) remains unexplored. Sixty-four patients who underwent successful HP eradication for localized HP-positive gastric MALT lymphomas without t(11;18)(q21;q21) were studied. BAFF expression was significantly higher in the HP-independent group than in the HP-dependent group [22/26 (84.6%) versus 8/38 (21.1%); p < 0.001]. Similarly, BAFF receptor (BAFF-R) expression (p = 0.004) and nuclear BCL3 (p = 0.004), BCL10 (p < 0.001), NF-κB (p65) (p = 0.001) and NF-κB (p52) (p = 0.005) expression were closely correlated with the HP independence of these tumours. Moreover, BAFF overexpression was significantly associated with BAFF-R expression and nuclear BCL3, BCL10, NF-κB (p65) and NF-κB (p52) expression. These findings were further validated in an independent cohort, including 40 HP-dependent cases and 18 HP-independent cases of gastric MALT lymphoma without t(11;18)(q21;q21). The biological significance of BAFF signalling in t(11;18)(q21;q21)-negative lymphoma cells was further studied in two types of lymphoma B cell: OCI-Ly3 [non-germinal centre B-cell origin DLBCL without t(11;18)(q21;q21) cell line] and MA-1 [t(14;18)(q32;q21)/IGH-MALT1-positive DLBCL cell line]. In both cell lines, we found that BAFF activated the canonical NF-κB and AKT pathways, and induced the formation of BCL10-BCL3 complexes, which translocated to the nucleus. BCL10 and BCL3 nuclear translocation and NF-κB (p65) transactivation were inhibited by either LY294002 or by silencing BCL3 or BCL10 with small interfering RNA. BAFF also activated non-canonical NF-κB pathways (p52) through tumour necrosis factor receptor-associated factor 3 degradation, NF-κB-inducing kinase accumulation, inhibitor of κB kinase (IKK) α/β phosphorylation and NF-κB p100 processing in both cell lines. Our data indicate that the autocrine BAFF signal transduction pathway contributes to HP independence in gastric MALT lymphomas without the t(11;18)(q21;q21) translocation. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Expressions of the CagA protein and CagA-signaling molecules predict Helicobacter pylori dependence of early-stage gastric DLBCL

Expression of CagA and CagA-signaling molecules p-SHP2 and p-ERK is associated with HP dependence of gastric DLBCL. CagA is associated with the direct lymphomagenic effect of HP on B cells of HP-dependent gastric DLBCL.

Structure and function of Helicobacter pylori CagA, the first-identified bacterial protein involved in human cancer

Chronic infection with Helicobacter pylori cagA-positive strains is the strongest risk factor of gastric cancer. The cagA gene-encoded CagA protein is delivered into gastric epithelial cells via bacterial type IV secretion, where it undergoes tyrosine phosphorylation at the Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs. Delivered CagA then acts as a non-physiological scaffold/hub protein by interacting with multiple host signaling molecules, most notably the pro-oncogenic phosphatase SHP2 and the polarity-regulating kinase PAR1/MARK, in both tyrosine phosphorylation-dependent and -independent manners. CagA-mediated manipulation of intracellular signaling promotes neoplastic transformation of gastric epithelial cells. Transgenic expression of CagA in experimental animals has confirmed the oncogenic potential of the bacterial protein. Structural polymorphism of CagA influences its scaffold function, which may underlie the geographic difference in the incidence of gastric cancer. Since CagA is no longer required for the maintenance of established gastric cancer cells, studying the role of CagA during neoplastic transformation will provide an excellent opportunity to understand molecular processes underlying "Hit-and-Run" carcinogenesis.

Differences in amino acid frequency in CagA and VacA sequences of Helicobacter pylori distinguish gastric cancer from gastric MALT lymphoma

Background

Helicobacter pylori is a pathogenic bacterium that causes various gastrointestinal diseases. The most common gastric malignancies associated with H. pylori are gastric cancer and lymphoma of mucosa associated lymphoid tissue (MALT). Helicobacter pylori virulence genes, namely cagA and vacA, are known to be associated with malignancy development. Conventionally, cagA and vacA were classified by looking at partial sequences of the genes. However, such genotyping has hardly proven useful predicting different risks for gastric cancer or MALT lymphoma. In search of new loci that distinguish these diseases, we investigated the full sequences of cagA and vacA.

Results

We compared cagA and vacA sequences of 18 and 12 H. pylori strains obtained, respectively, from patients with gastric cancer and MALT lymphoma in Oita, Japan. Conventional genotyping of cagA and vacA showed no significant difference between the two diseases. We further investigated the full protein sequences of CagA and VacA to identify loci where allele frequency was significantly different between the diseases. We found four such loci on CagA, and three such loci on VacA. We also inspected the corresponding loci on the genes of 22 gastritis strains that potentially lead to gastric cancer or MALT lymphoma in the long run. Significant differences were observed at one CagA locus between gastritis and MALT lymphoma strains, and at one VacA locus between gastritis and gastric cancer strains.

Conclusions

We found novel candidate loci in H. pylori virulence genes in association with two different types of gastric malignancies that could not be differentiated by conventional genotyping. Biological connotations of the amino acid polymorphisms merit further study.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-016-0137-x) contains supplementary material, which is available to authorized users.

Epidemiology and environmental aspects of marginal zone lymphomas

Marginal zone lymphomas (MZLs) account for between 5% and 17% of all non-Hodgkin's lymphomas. MZLs consist of 3 different subtypes with extranodal being the most commonly reported, representing 50-70% of MZL, followed by splenic (20%) and nodal (10%). Median age at presentation varies between these lymphoma sub-types, ranging between 50 and 69 years, with an overall greater incidence noted in males compared to females. Given the rarity of these lymphomas, epidemiologic data has been sparse, although it has been suggested the aetiology is multi-factorial including ethnicity and geographical factors. Other reported associations include autoimmune disease and infection, with Helicobacter pylori and Campylobacter psittaci, being the most commonly reported pathogens. Larger population studies are required to investigate the role of these environmental factors further as these can direct the future management of these lymphomas, through the use of more effective targeted treatments.

CagA Phosphorylation in Helicobacter pylori-Infected B Cells Is Mediated by the Nonreceptor Tyrosine Kinases of the Src and Abl Families

CagA is one of the most important virulence factors of the human pathogen Helicobacter pylori. CagA expression can be associated with the induction of severe gastric disorders such as gastritis, ulceration, gastric cancer, or mucosa-associated lymphoid tissue (MALT) lymphoma. After translocation through a type IV secretion system into epithelial cells, CagA is tyrosine phosphorylated by kinases of the Src and Abl families, leading to drastic cell elongation and motility. While the functional role of CagA in epithelial cells is well investigated, knowledge about CagA phosphorylation and its associated signal transduction pathways in B cells is only marginal. Here, we established the B cell line MEC1 derived from a B cell chronic lymphocytic leukemia (B-CLL) patient as a new infection model to study the signal transduction in B cells controlled by H. pylori. We observed that CagA was rapidly injected, strongly tyrosine phosphorylated, and cleaved into a 100-kDa N-terminal and a 40-kDa C-terminal fragment. To identify upstream signal transduction pathways of CagA phosphorylation in MEC1 cells, pharmacological inhibitors were employed to specifically target Src and Abl kinases. We observed that CagA phosphorylation was strongly inhibited upon treatment with an Src inhibitor and slightly diminished when the Abl kinase inhibitor imatinib mesylate (Gleevec) was applied. The addition of dasatinib to block c-Abl and Src kinases led to a complete loss of CagA phosphorylation. In conclusion, these results demonstrate an important role for Src and Abl tyrosine kinases in CagA phosphorylation in B cells, which represent druggable targets in H. pylori-mediated gastric MALT lymphoma.

Host SHP1 phosphatase antagonizes Helicobacter pylori CagA and can be downregulated by Epstein-Barr virus

Most if not all gastric cancers are associated with chronic infection of the stomach mucosa with Helicobacter pylori cagA-positive strains(1-4). Approximately 10% of gastric cancers also harbour Epstein-Barr virus (EBV) in the cancer cells(5,6). Following delivery into gastric epithelial cells via type IV secretion(7,8), the cagA-encoded CagA protein undergoes tyrosine phosphorylation on the Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs initially by Src family kinases (SFKs) and then by c-Abl(9,10). Tyrosine-phosphorylated CagA binds to the pro-oncogenic protein tyrosine phosphatase SHP2 and thereby deregulates the phosphatase activity(11,12), which has been considered to play an important role in gastric carcinogenesis(13). Here we show that the SHP2 homologue SHP1 interacts with CagA independently of the EPIYA motif. The interaction potentiates the phosphatase activity of SHP1 that dampens the oncogenic action of CagA by dephosphorylating the CagA EPIYA motifs. In vitro infection of gastric epithelial cells with EBV induces SHP1 promoter hypermethylation, which strengthens phosphorylation-dependent CagA action via epigenetic downregulation of SHP1 expression. Clinical specimens of EBV-positive gastric cancers also exhibit SHP1 hypermethylation with reduced SHP1 expression. The results reveal that SHP1 is the long-sought phosphatase that can antagonize CagA. Augmented H. pylori CagA activity, via SHP1 inhibition, might also contribute to the development of EBV-positive gastric cancer.

Infectious Aetiology of Marginal Zone Lymphoma and Role of Anti-Infective Therapy

Marginal zone lymphomas have been associated with several infectious agents covering both viral and bacterial pathogens and in some cases a clear aetiological role has been established. Pathogenetic mechanisms are currently not completely understood. However, the role of chronic stimulation of the host immune response with persistent lymphocyte activation represents the most convincing explanation for lymphoproliferation. Gastric MALT lymphoma is strictly associated with Helicobacter pylori infection and various eradicating protocols, developed due to increasing antibiotic resistance, represent the first line therapy for gastric MALT. The response rate to eradication is good with 80% of response at 1 year; this finding is also noteworthy because it recapitulates cancer cured only by the antibacterial approach and it satisfies the Koch postulates of causation, establishing a causative relationship between Hp and gastric MALT lymphoma. Patients with chronic HCV infection have 5 times higher risk to develop MZL, in particular, an association with splenic and nodal MZL has been shown in several studies. Moreover, there is evidence of lymphoma regression after antiviral therapy with interferon+ribavirin, thus raising hope that newly available drugs, extremely efficient against HCV replication, could improve outcome also in HCV-driven lymphomas. Another case-study are represented by those rare cases of MZL localized to orbital fat and eye conjunctivas that have been associated with Chlamydophila psittaci infection carried by birds. Efficacy of antibacterial therapy against C. psittaci are conflicting and generally poorer than gastric MALT. Finally, some case reports will cover the relationship between primary cutaneous B-cell Lymphomas and Borrelia Burgdorferi.

The origin and targeting of mucosa-associated lymphoid tissue lymphomas

PURPOSE OF REVIEW

Extranodal mucosa-associated lymphoid tissue (MALT lymphoma) is a distinct clinical-pathological entity that can be distinguished from other lymphomas by a number of unique features, including their location in various extranodal sites, being preceded by chronic inflammatory or infection processes; a characteristic histopathological picture; and the presence of exclusive chromosomal translocations which increase MALT1 proteolytic activity to promote constitutive NF-κB signaling and eventually drive lymphomagenesis.

RECENT FINDINGS

This review explores the major molecular and cellular events that participate in MALT lymphoma pathogenesis, focusing on gastric MALT lymphoma as a model of chronic inflammation-induced tumor development. In addition, the pivotal roles of activated MALT1 protease, its substrate TNFAIP3/A20, and the MyD88 adaptor protein in abnormally triggering downstream NF-κB pathway are overviewed. These new insights provide a mechanistic basis for using novel therapies targeting MALT1 protease or IRAK4 kinase activities. Finally, the putative cellular origin of MALT lymphomas is also discussed.

SUMMARY

Over the last decade, unraveling the biological complexity of MALT lymphomas has shed light on the fundamental cellular and molecular aspects of the disease that are to be translated into clinical diagnostics and therapy.

Helicobacter pylori eradication in gastric diffuse large B cell lymphoma

Diffuse large B cell lymphoma (DLBCL) of the stomach is a heterogenous disease. There are tumors without histological evidence of mucosa-associated lymphoid tissue (MALT) lymphoma, which are classified as pure or de novo DLBCL and those with evidence of MALT, which are classified as DLBCL (MALT). The association between Helicobacter pylori (H. pylori) and gastric MALT lymphoma and remission with H. pylori eradication was shown in the 1990s. In recent years, scientists from Taiwan and others have shown that high-grade gastric lymphomas may be dependent on H. pylori and eradication of this microorganism is effective in these cases. This entity is biologically distinct from H. pylori (-) cases and has a better clinical outcome. There are sufficient data about the complete remission in some of these cases with brief treatment with antibiotics. With this strategy, it is possible to save some of these cases from the harmful effects of standard chemotherapy. It is time to treat these cases with H. pylori eradication. However, strict histopathological follow-up is crucial and histopathological response must be evaluated according to the scoring system proposed by Groupe d’Etude des Lymphomes de l’Adulte. If there is no sufficient response, chemotherapy must be given immediately. These results suggest that H. pylori dependency and high-grade transformation in gastric MALT lymphomas are distinct events.

Dual phosphoinositide 3-kinase/mammalian target of rapamycin inhibitor is an effective radiosensitizer for colorectal cancer

The present study was aimed to investigate whether combination of molecular targeting therapy, a dual PI3K/mTOR inhibitor (BEZ235), with radiation can enhance the radiosensitivity of colorectal cancer cells (CRC). K-RAS mutant CRC cells (HCT 116 and SW 620) and wild type CRC cells (HT 29) were irradiated with different dose of radiation (0-6 Gy). The synergistic effects of combining radiation with different concentration of BEZ235 (0-10 nM) pretreatment were demonstrated by cell survival assay. When comparing with radiation alone and BEZ235 alone, the combination of BEZ235 pretreatment and radiation resulted in an increased percentage of sub-G1 phase cells, and an increased number of γ-H2AX/cell (DNA double strand breaks). Radiation up-regulated AKT/mTOR signaling pathway, including the activation of phospho (p)-AKT, p-mTOR, p-eIF4E, and p-rpS6; and this activated AKT/mTOR signaling pathway was attenuated by BEZ235 pretreatment. In addition, BEZ235 blocked double strand break repair induced by radiation through attenuating the activation of ATM and DNA-PKcs and sensitized CRC cells to radiation. In vivo model, the tumor size and the expression pattern of p-mTOR, p-eIF4E, and p-rpS6 were significantly decreased in combined group than radiation alone or BEZ235 alone. Our findings indicate that the administration of BEZ235 before radiation enhances the radiotherapeutic effect of CRC cells both in vitro and in vivo.

Occurrence of Helicobacter pylori and Epstein-Barr virus infection in endoscopic and gastric cancer patients from Northern Brazil

BACKGROUND

Helicobacter pylori (HP) and Epstein-Barr virus (EBV) have been associated with cancer development. We evaluated the prevalence of HP, HP CagA+ and EBV infection in gastric cancer (GC) samples from adults and in gastric tissues from patients who underwent upper endoscopy (UE).

METHODS

Samples from UE and GC were collected to investigate the presence of HP infection and the HP virulence factor CagA by a urease test and PCR. The presence of EBV was detected by Eber-1 in situ hybridization.

RESULTS

In UE, 85.5% of juvenile patients showed some degree of gastritis (45.3% of patients with mild gastritis and 54.7% with moderate/severe gastritis) and patients with mild gastritis were younger than patients with moderate/severe gastritis. Among adults, 48.7% presented mild gastritis and 51.3% moderate/severe gastritis. HP infection was detected in 0% of normal mucosa, 58.5% of juvenile gastritis patients, 69.2% of adult gastritis patients and 88% of GC patients. In these same groups, HP CagA+ was detected in 0%, 37.7%, 61.5% and 67.2% of tissue samples, respectively. In juvenile patients, HP infection was more common in those with gastritis than in normal samples (p = 0.004). The patients with either HP or HP CagA+ were older than patients without these pathogens (p < 0.05). In juvenile patients, HP infection was more frequent in cases of moderate/severe gastritis than in cases of mild gastritis (p = 0.026). Moreover, in patients with GC, HP infection was more frequent in males than in females (p = 0.023). GC patients with HP CagA+ were older than patients with HP CagA- (p = 0.027). HP CagA+ was more common in intestinal-type than diffuse-type GC (p = 0.012). HP CagA+ was also associated with lymph-node (p = 0.024) and distal (p = 0.005) metastasis. No association between EBV infection and HP infection or any clinicopathological variable was detected.

CONCLUSIONS

Our results suggest that HP is involved in the pathophysiology of severe gastric lesions and in the development of GC, particularly when CagA+ is present. EBV was not the primary pathogenic factor in our samples.

Beyond the stomach: An updated view of Helicobacter pylori pathogenesis, diagnosis, and treatment

Helicobacter pylori (H. pylori) is an extremely common, yet underappreciated, pathogen that is able to alter host physiology and subvert the host immune response, allowing it to persist for the life of the host. H. pylori is the primary cause of peptic ulcers and gastric cancer. In the United States, the annual cost associated with peptic ulcer disease is estimated to be $6 billion and gastric cancer kills over 700000 people per year globally. The prevalence of H. pylori infection remains high (> 50%) in much of the world, although the infection rates are dropping in some developed nations. The drop in H. pylori prevalence could be a double-edged sword, reducing the incidence of gastric diseases while increasing the risk of allergies and esophageal diseases. The list of diseases potentially caused by H. pylori continues to grow; however, mechanistic explanations of how H. pylori could contribute to extragastric diseases lag far behind clinical studies. A number of host factors and H. pylori virulence factors act in concert to determine which individuals are at the highest risk of disease. These include bacterial cytotoxins and polymorphisms in host genes responsible for directing the immune response. This review discusses the latest advances in H. pylori pathogenesis, diagnosis, and treatment. Up-to-date information on correlations between H. pylori and extragastric diseases is also provided.

Inhibition of ZEB1 by miR-200 characterizes Helicobacter pylori-positive gastric diffuse large B-cell lymphoma with a less aggressive behavior

Primary gastric diffuse large B-cell lymphomas may or may not have a concurrent component of mucosa-associated lymphoid tissue lymphoma. Diffuse large B-cell lymphoma/mucosa-associated lymphoid tissue lymphomas are often associated with Helicobacter pylori (H. pylori) infection, suggesting that the large cells are transformed from mucosa-associated lymphoid tissue lymphomas. In contrast, only limited data are available on the clinical and molecular features of pure gastric diffuse large B-cell lymphomas. In 102 pure gastric diffuse large B-cell lymphomas, we found H. pylori infection in 53% of the cases. H. pylori-positive gastric diffuse large B-cell lymphomas were more likely to present at an earlier stage (73% vs 52% at stage I/II, P=0.03), to achieve complete remission (75% vs 43%, P=0.001), and had a better 5-year disease-free survival rate (73% vs 29%, P<0.001) than H. pylori-negative gastric diffuse large B-cell lymphomas. Through genome-wide expression profiles of both miRNAs and mRNAs in nine H. pylori-positive and nine H. pylori-negative gastric diffuse large B-cell lymphomas, we identified inhibition of ZEB1 (zinc-finger E-box-binding homeobox 1) by miR-200 in H. pylori-positive gastric diffuse large B-cell lymphomas. ZEB1, a transcription factor for marginal zone B cells, can suppress BCL6, the master transcription factor for germinal center B cells. In 30 H. pylori-positive and 30 H. pylori-negative gastric diffuse large B-cell lymphomas, we confirmed that H. pylori-positive gastric diffuse large B-cell lymphomas had higher levels of miR-200 by qRT-PCR, and lower levels of ZEB1 and higher levels of BCL6 using immunohistochemistry. As BCL6 is a known predictor of a better prognosis in gastric diffuse large B-cell lymphomas, our data demonstrate that inhibition of ZEB1 by miR-200, with secondary increase in BCL6, is a molecular event that characterizes H. pylori-positive gastric diffuse large B-cell lymphomas with a less aggressive behavior.

Interactions between pork consumption, CagA status and IL-1B-31 genotypes in gastric cancer

AIM: To explore potential interactions among Helicobacter pylori (H. pylori), CagA status, interleukin (IL)-1B-31 genotypes, and non-cardiac gastric cancer (GC) risk.

METHODS: A case-control study of non-cardia GC was performed at 3 hospitals located in Xi’an, China, between September 2008 and July 2010. We included 171 patients with histologically diagnosed primary non-cardia GC and 367 population based controls (matched by sex, age and city of residence). A standardized questionnaire was used to obtain information regarding potential risk factors, including pork consumption. H. pylori CagA status was assessed by enzyme-linked immunosorbent assay, and IL-1B-31 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism. Multivariate unconditional logistic regression was used to explore potential interactions among the factors.

RESULTS: The CagA appeared to confer an increased risk of GC (OR = 1.81, 95%CI: 1.25-2.61). The main associations with IL-1B-31C allele here were 0.98 (95%CI: 0.59-1.63) for CC vs TT and 0.99 (95%CI: 0.64-1.51) for C Carriers vs TT. However, no associations were observed for CagA or IL-1B-31 genotype status among subjects who reported low pork consumption (P for interaction = 0.11). In contrast, high pork consumption and IL-1B-31C genotypes appeared to synergistically increase GC risk (P for interaction = 0.048) after adjusting for confounding factors, particularly among subjects with CagA (OR = 3.07, 95%CI: 1.17-10.79). We did not observe effect modification of pork consumption by H. pylori CagA status, or between H. pylori CagA status and IL-1B-31 genotypes after adjustment for pork consumption and other factors.

CONCLUSION: These interaction relationships among CagA, IL-1B-31 and pork consumption may have implications for development of the preventive strategies for the early detection of non-cardiac GC.

Helicobacter pylori-related diffuse large B-cell lymphoma of the stomach: a distinct entity with lower aggressiveness and higher chemosensitivity

We recently showed that Helicobacter pylori (HP)-positive gastric ‘pure' diffuse large B-cell lymphoma (DLBCL) may respond to HP eradication therapy. However, whether these HP-related ‘pure' DLBCL of the stomach may differ fundamentally from those unrelated to HP remains unclear. In this study, we compared the clinicopathologic features of these two groups of patients who had been uniformly treated by conventional chemotherapy. Forty-six patients were designated HP-positive and 49 were HP-negative by conventional criteria. HP-positive patients had a lower International Prognostic Index score (0–1, 65% vs 43%, P=0.029), a lower clinical stage (I-IIE1, 70% vs 39%, P=0.003), a better tumor response to chemotherapy (complete pathologic response, 76% vs 47%, P=0.004) and significantly superior 5-year event-free survival (EFS) (71.7% vs 31.8%, P<0.001) and overall survival (OS) (76.1% vs 39.8%, P<0.001). To draw a closer biologic link with HP, HP-positive tumors were further examined for CagA expression in lymphoma cells. Compared with CagA-negative cases (n=16), CagA-positive cases (n=27) were associated with high phosphorylated SHP-2 expression (P=0.016), and even better 5-year EFS (85.2% vs 46.3%, P=0.002) and OS (88.9% vs 52.9%, P=0.003). HP-related gastric ‘pure' DLBCL may be a distinct tumor entity, which is less aggressive, and responds better to conventional chemotherapy.

Gastric MALT lymphoma: old and new insights

The stomach is the most frequent site of extranodal lymphoma. Gastric lymphoma originating from mucosa-associated lymphoid tissue (MALT) is typically a low-grade, B-cell neoplasia strongly associated with Helicobacter pylori (H. pylori) infection. Only certain H. pylori strains in some predisposed patients determine lymphoma development in the stomach, according to a strain-host-organ specific process. The clinical presentation is poorly specific, symptoms ranging from vague dyspepsia to alarm symptoms. Similarly, different endoscopy patterns have been described for gastric lymphoma. H. pylori eradication is advised as first-line therapy in early stage disease, and complete lymphoma remission is achieved in 75% of cases. Neoplasia stage, depth of infiltration in the gastric wall, presence of the API2-MALT1 translocation, localization in the stomach, and patient ethnicity have been identified as predictors of remission. Recent data suggests that H. pylori eradication therapy may be successful for gastric lymphoma treatment also in a small subgroup (15%) of H. pylori-negative patients. The overall 5-year survival and disease-free survival rates are as high as 90% and 75%, respectively. Management of patients who failed to achieve lymphoma remission following H. pylori eradication include radiotherapy, chemotherapy and, in selected cases, surgery.

Role of Helicobacter pylori virulence factor cytotoxin-associated gene A in gastric mucosa-associated lymphoid tissue lymphoma

Helicobacter pylori (H. pylori) infection might initiate and contribute to the progression of lymphoma from gastric mucosa-associated lymphoid tissue (MALT). Increasing evidence shows that eradication of H. pylori with antibiotic therapy can lead to regression of gastric MALT lymphoma and can result in a 10-year sustained remission. The eradication of H. pylori is the standard care for patients with gastric MALT lymphoma. Cytotoxin-associated gene A (CagA) protein, one of the most extensively studied H. pylori virulence factors, is strongly associated with the gastric MALT lymphoma. CagA possesses polymorphisms according to its C-terminal structure and displays different functions among areas and races. After being translocated into B lymphocytes via type IV secretion system, CagA deregulates intracellular signaling pathways in both tyrosine phosphorylation-dependent and -independent manners and/or some other pathways, and thereby promotes lymphomagenesis. A variety of proteins including p53 and protein tyrosine phosphatases-2 are involved in the malignant transformation induced by CagA. Mucosal inflammation is the foundational mechanism underlying the occurrence and development of gastric MALT lymphoma.

Helicobacter pylori and mucosa-associated lymphoid tissue: what's new

Low-grade mucosa-associated lymphoid tissue (MALT) lymphoma of the stomach, gastric MALT lymphoma, is associated with Helicobacter pylori infection. The eradication of H pylori using antibiotics is successful in 60% to 80% of affected patients. In contrast to the previous paradigm, we and other investigators have shown that a certain proportion of patients with H pylori-positive early-stage diffuse large B-cell lymphoma (DLBCL) of the stomach with histological evidence of MALT lymphoma, including high-grade transformed gastric MALT lymphoma and gastric DLBCL(MALT), achieved long-term complete pathological remission (pCR) after first-line H pylori eradication therapy, indicating that the loss of H pylori dependence and high-grade transformation are separate events in the progression of gastric lymphoma. In addition, patients with H pylori-positive gastric DLBCL without histological evidence of MALT (gastric pure DLBCL) may also respond to H pylori eradication therapy. A long-term follow-up study showed that patients who achieved pCR remained lymphoma free. Gastric MALT lymphoma is indirectly influenced by H pylori infection through T-cell stimulation, and recent studies have shown that H pylori-triggering chemokines and their receptors, H pylori-associated epigenetic changes, H pylori-regulated miRNA expression, and tumor infiltration by CD4+CD25+ regulatory T cells contribute to lymphomagenesis of gastric MALT lymphoma. Recent studies have also demonstrated that the translocation of CagA into B lymphocytes inhibits apoptosis through p53 accumulation, BAD phosphorylation, and the up-regulation of Bcl-2 and Bcl-XL expression. In gastric MALT lymphoma, CagA may stimulate lymphomagenesis directly, through the regulation of signal transduction, and intracellular CagA is associated with H pylori dependence. These findings represent a substantial paradigm shift compared with the classical theory of H pylori-reactive T cells contributing indirectly to the development of MALT lymphoma. In conclusion, a wide range of H pylori-related gastric lymphomas have been identified. The use of antibiotics as the sole first-line therapy for early-stage gastric pure DLBCL requires validation in a prospective study. The clinical and biological significance of the CagA oncoprotein in the lymphomagenesis of gastric MALT lymphoma warrants further study.