Role of activated host T cells in the promotion of MALT lymphoma growth

Role of non-Helicobacter pylori gastric Helicobacters in helicobacter pylori-negative gastric mucosa-associated lymphoid tissue lymphoma

Marginal zone lymphomas rank as the third most prevalent form of non-Hodgkin B-cell lymphoma, trailing behind diffuse large B-cell lymphoma and follicular lymphoma. Gastric mucosa-associated lymphoid tissue lymphoma (GML) is a low-grade B-cell neoplasia frequently correlated with Helicobacter pylori (H. pylori)-induced chronic gastritis. On the other hand, a specific subset of individuals diagnosed with GML does not exhibit H. pylori infection. In contrast to its H. pylori-positive counterpart, it was previously believed that H. pylori-negative GML was less likely to respond to antimicrobial therapy. Despite this, surprisingly, in-creasing evidence supports that a considerable proportion of patients with H. pylori-negative GML show complete histopathological remission after bacterial eradication therapy. Nonetheless, the precise mechanisms underlying this treatment responsiveness are not yet fully comprehended. In recent years, there has been growing interest in investigating the role of non-H. pylori gastric helicobacters (NHPHs) in the pathogenesis of H. pylori-negative GML. However, additional research is required to establish the causal relationship between NHPHs and GML. In this minireview, we examined the current understanding and proposed prospects on the involvement of NHPHs in H. pylori-negative GML, as well as their potential response to bacterial eradication therapy.

Helicobacter pylori Deregulates T and B Cell Signaling to Trigger Immune Evasion

Helicobacter pylori is a prevalent human pathogen that successfully establishes chronic infection, which leads to clinically significant gastric diseases including chronic gastritis, peptic ulcer disease (PUD), and gastric cancer (GC). H. pylori is able to produce a persistent infection due in large part to its ability to hijack the host immune response. The host adaptive immune response is activated to strategically and specifically attack pathogens and normally clears them from the infected host. Since B and T lymphocytes are central mediators of adaptive immunity, in this chapter we review their development and the fundamental mechanisms regulating their activation in order to understand how some of the normal processes are subverted by H. pylori. In this review, we place particular emphasis on the CD4⁺ T cell responses, their subtypes, and regulatory mechanisms because of the expanding literature in this area related to H. pylori. T lymphocyte differentiation and function are finely orchestrated through a series of cell-cell interactions, which include immune checkpoint receptors. Among the immune checkpoint receptor family, there are some with inhibitory properties that are exploited by tumor cells to facilitate their immune evasion. Gastric epithelial cells (GECs), which act as antigen-presenting cells (APCs) in the gastric mucosa, are induced by H. pylori to express immune checkpoint receptors known to sway T lymphocyte function and thus circumvent effective T effector lymphocyte responses. This chapter reviews these and other mechanisms used by H. pylori to interfere with host immunity in order to persist.

Omeprazole Induces Apoptosis in Jurkat Cells

We report for the first time a potent apoptotic effect of omeprazole (OM). Apoptosis was induced in Jurkat cells in a time and concentration-dependent mode. Caspase 3 and PARP were rapidly cleaved in response to OM, but apoptosis was only partially inhibited by the caspase 3 inhibitor DEVD-CHO. OM also induced an early lysosomal destabilization which increased progressively and was correlated with a parallel increase in apoptotic cells. The cysteine protease inhibitor E64d gave strong protection against apoptosis thus proving the involvement of lysosomal enzymes in OM-induced apoptosis whereas, it did not impede the caspase 3 cleavage. Instead ZVAD-fmk, a general caspase inhibitor, also able to inhibit cathepsin activity, protected cells completely from OM-induced apoptosis. It therefore seems that both caspases and cysteine cathepsins are involved in the execution stage of OM-induced apoptosis.

Toll-Like Receptors and Cancer: MYD88 Mutation and Inflammation

Pattern recognition receptors (PRRs) expressed on immune cells are crucial for the early detection of invading pathogens, in initiating early innate immune response and in orchestrating the adaptive immune response. PRRs are activated by specific pathogen-associated molecular patterns that are present in pathogenic microbes or nucleic acids of viruses or bacteria. However, inappropriate activation of these PRRs, such as the Toll-like receptors (TLRs), due to genetic lesions or chronic inflammation has been demonstrated to be a major cause of many hematological malignancies. Gain-of-function mutations in the TLR adaptor protein MYD88 found in 39% of the activated B cell type of diffuse large B cell lymphomas and almost 100% of Waldenström’s macroglobulinemia further highlight the involvement of TLRs in these malignancies. MYD88 mutations result in the chronic activation of TLR signaling pathways, thus the constitutive activation of the transcription factor NFκB to promote cell survival and proliferation. These recent insights into TLR pathway driven malignancies warrant the need for a better understanding of TLRs in cancers and the development of novel anti-cancer therapies targeting TLRs. This review focuses on TLR function and signaling in normal or inflammatory conditions, and how mutations can hijack the TLR signaling pathways to give rise to cancer. Finally, we discuss how potential therapeutic agents could be used to restore normal responses to TLRs and have long lasting anti-tumor effects.

Review of the molecular profile and modern prognostic markers for gastric lymphoma: how do they affect clinical practice?

Primary gastric lymphoma is a rare cancer of the stomach with an indeterminate prognosis. Recently, a series of molecular prognostic markers has been introduced to better describe this clinical entity. This review describes the clinical importance of several oncogenes, apoptotic genes and chromosomal mutations in the initiation and progress of primary non-Hodgkin gastric lymphoma and their effect on patient survival. We also outline the prognostic clinical importance of certain cellular adhesion molecules, such as ICAM and PECAM-1, in patients with gastric lymphoma, and we analyze the correlation of these molecules with apoptosis, angiogenesis, tumour growth and metastatic potential. We also focus on the host-immune response and the impact of Helicobacter pylori infection on gastric lymphoma development and progression. Finally, we explore the therapeutic methods currently available for gastric lymphoma, comparing the traditional invasive approach with more recent conservative options, and we stress the importance of the application of novel molecular markers in clinical practice.

Long-term follow-up of gastrectomized patients with mucosa-associated lymphoid tissue lymphoma: need for a revisit of surgical treatment

BACKGROUND

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is characterized by multifocality of the tumors, which often scatter over the mucosa of the stomach and adjacent upper gastrointestinal tract, and is therefore theoretically not curable by surgical resection.

METHODS

We conducted a long-term follow-up study of 14 patients who received surgical treatment for gastric MALT lymphoma. Tissues from the surgical margins of the resected stomach were analyzed by polymerase chain reaction-based amplification of the complementarity-determining region 3 of the IgH gene for the presence of residual tumors. T (11;18)(q21;q21), a marker of Helicobacter pylori-independent MALT lymphoma, was analyzed by reverse transcription polymerase chain reaction. All living patients were restaged, and rebiopsied if suspicious lesions were identified.

RESULTS

At a median follow-up of 11.5 years, only 1 patient had evidence of tumor recurrence. Three patients with molecularly proven residual tumors in the surgical margin remained disease-free at 9.6 to 11.6 years. Five patients with t(11;18)(q21;q21) in the tumor cells were disease-free at 9.2 to 12.6 years.

CONCLUSION

Our results indicate that surgical resection is a highly curative treatment for gastric MALT lymphoma, even for patients with residual tumor cells in the surgical margins, and for patients with H. pylori-independent tumors. A revisit of surgical treatment for gastric MALT lymphoma is mandatory.

Association of T-cell regulatory gene polymorphisms with susceptibility to gastric mucosa-associated lymphoid tissue lymphoma

PURPOSE

Helicobacter pylori infection and host susceptibility interact to develop gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and activation of specific T cells might play a crucial role in this process. Recent investigations show that the CTLA4, CD28, and ICOS genes are located on chromosome 2q33 and their polymorphisms confer susceptibility to infectious and immune diseases through deregulation of T-cell stimulation. We aimed to determine the role of CTLA4, CD28, and ICOS polymorphisms in gastric MALT lymphoma.

PATIENTS AND METHODS

Genotyping for CTLA4 (49 A/G, -318 C/T, and CT60 A/G), CD28 (IVS3+ 17T/C), and ICOS (c.602 A/C and c.1624C/T) was performed for 62 patients with gastric MALT lymphoma and compared with 250 unrelated healthy controls.

RESULTS

H pylori infection was significantly higher in patients with gastric MALT lymphoma (90.3%) compared with controls (66.4%; P < .001). The CTLA4 -318 C/T genotype was associated with a lower risk of developing gastric MALT lymphoma (odds ratio [OR] = 0.3; P = .022), whereas CTLA4 49 G/G genotype was linked to a higher risk (OR = 4.1; P = .044). In patients with H pylori infection, CTLA4 49 G/G genotype was associated with an even higher risk (OR = 6.4; P = .047). Carriage of the tightly linked -318C -49G haplotype conferred a four-fold higher susceptibility to MALT lymphoma (OR = 4.2; P = .042). Complete remission after H pylori eradication was related to tumor stage but not to genotypes or haplotypes.

CONCLUSION

These results indicate a genetic link of CTLA4 gene polymorphisms to development of gastric MALT lymphoma and indirectly support the crucial role of host activated T cells in the MALT lymphomagenesis.

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Expression of CD86 and increased infiltration of NK cells are associated with Helicobacter pylori-dependent state of early stage high-grade gastric MALT lymphoma

AIM

A high percentage of early-stage high-grade gastric mucosa-associated lymphoid tissue (MALT) lymphomas remain Helicobacter pylori (H pylori)-dependent. However, unlike their low-grade counterparts, high-grade gastric MALT lymphomas may progress rapidly if unresponsive to H pylori eradication. It is mandatory to identify markers that may predict the H pylori-dependent status of these tumors. Proliferation of MALT lymphoma cells depends on cognate help and cell-to-cell contact of H pylori-specific intratumoral T-cells. To examine whether the expression of co-stimulatory marker CD86 (B7.2) and the infiltration of CD56 (+) natural killer (NK) cells can be useful markers to predict H pylori-dependent status of high-grade gastric MALT lymphoma.

METHODS

Lymphoma biopsies from 26 patients who had participated in a prospective study of H pylori-eradication for stage I(E) high-grade gastric MALT lymphomas were evaluated. Tumors that resolved to Wotherspoon grade II or less after H pylori eradication were classified as H pylori-dependent; others were classified as H pylori-independent. The infiltration of NK cells and the expression of CD86 in pre-treatment paraffin-embedded lymphoma tissues were determined by immunohistochemistry.

RESULTS

There were 16 H pylori-dependent and 10 H pylori-independent cases. CD86 expression was detected in 11 (68.8%) of 16 H pylori-dependent cases but in none of 10 H pylori-independent cases (P = 0.001). H pylori-dependent high-grade gastric MALT lymphomas contained significantly higher numbers of CD56 (+) NK cells than H pylori-independent cases (2.8+/-1.4% vs 1.1+/-0.8%; P = 0.003). CD86 positive MALT lymphomas also showed significantly increased infiltration of CD56 (+) NK cells compared to CD86-negative cases (2.9+/-1.1% vs 1.4+/-1.3%; P = 0.005).

CONCLUSION

These results suggest that the expression of co-stimulatory marker CD86 and the increased infiltration of NK cells are associated with H pylori-dependent state of early-stage high-grade gastric MALT lymphomas.