**8. Discussion**

We and other investigators have demonstrated that a large proportion of localized (stage IE to IIE1) gastric DLBCLs, including DLBCL(MALT) and "pure" DLBCL remain *Hp*-dependent and can possibly be treated by first-line HPE [21–28], indicating that DLBCL transformation is not associated with the loss of *Hp* dependence. We first discovered that most patients with *Hp*-dependent gastric DLBCL(MALT), in whom with DLBCL and MALT lymphoma showed the same clonality using laser capture microdissection and *IgH* CDR3 rearrangement analyses [67]. Starostik et al. compared the genetic aberrations of t(11;18)(q21;q21)-negative MALT lymphoma and DLBCL of the stomach [132]. They demonstrated that both lymphomas share allelic imbalances, such as 3q26.2–27 amplification [132]. Furthermore, Barth et al. found a high pathogenetic similarity between MALT lymphoma and small-cell components of DLBCL(MALT) and between DLBCL and large-cell components of DLBCL(MALT) of the stomach, through expression profile analysis [133]. These findings suggest that some of the large-cell components in patients with gastric DLBCL may be transformed from *Hp*–related MALT lymphoma [133]. Whether *Hp*-related gastric "pure" DLBCLs share biological, immunological, and molecular features of *Hp*-related gastric MALT lymphoma and DLBCL(MALT) is worth investigating in the future.

Although first-line antibiotic HPE has saved approximately 60% of early stage gastric DLBCL patients from the risks of systemic chemotherapy, approximately 40% of early stage and most patients with advanced, gastric DLBCL still receive immunochemotherapy as the primary treatment. To avoid delaying the administration of immunochemotherapy for these *Hp*-independent patients, the identification of molecular markers predicting antibiotic unresponsiveness has become an emergent issue. Previously, we discovered that canonical and noncanonical NF-κB signalings contribute to *Hp*-independent tumor growth of gastric lymphoma, including MALT lymphoma, DLBCL(MALT), and "pure" DLBCL of the stomach, and their respective determinant molecular markers, nuclear BCL10, nuclear NF-κB(p65), and B-cell-activating factor of TNF family (BAFF), closely correlated with *Hp* independence of these tumors [41, 134–136]. The incorporation of *Hp*-independent molecular markers with clinicopathological features into further personalized treatment for *Hp*-positive early stage gastric DLBCL patients is warranted. Our ongoing prospective trial (ClinicalTrials.gov, NCT02388581) is the first study to evaluate the efficacy of first-line antibiotic HPE, as determined by the CR rate and time to tumor progression, in patients with *Hp*-positive localized (stage IE and IIE1) gastric "pure" DLBCL. This trial will also validate the accuracy (sensitivity and specificity) of molecular markers, including CagA, BCL10, NF-κB(p65), and BAFF, in predicting antibiotic responsiveness. This ongoing phase II study hopes to answer the question of "whether not just MALT lymphoma," "pure" DLBCL of the stomach is still responsive to antibiotic treatment".

However, genetic abnormalities found so far in gastric MALT lymphoma, such as t(11;18)(q21;q21), are far from providing a complete understanding of the molecular mechanisms of *Hp*-related gastric DLBCL [93, 137]. *Hp* infection perturbs or changes the epigenetic status, including the methylation profiles, DNA methyltransferase, cytokines, and the inflammatory responses, and causes aberrant hypermethylation [138–140]; these *Hp*-regulated epigenetic and genetic changes are worth exploring as to their relationship with lymphomagenesis of *Hp*-related gastric lymphoma.

Although we and other investigators have demonstrated that CagA-signaling and tumor-infiltrating T-cells co-participate in the molecular mechanisms of *Hp*-related gastric lymphoma [94], *Hp* in the gastric microenvironment may alter immune responses [141–144]. In a murine model of *H. felis*-induced gastric MALT lymphoma, Craig et al. showed that the development of MALT lymphoma requires B-cell receptor signaling through the poly-reactivation of tumor immunoglobulin with certain antigens and tumor-infiltrating T-cells [145]. Most of the tumor-infiltrating CD4+ cells in gastric MALT lymphoma were shown to be Foxp3+ CD4+ CD25+ regulatory T-cells (Tregs), and these Tregs were recruited by tumor cells through the chemokines, CCL17 and CCL22, secreted by Foxp3+ Tregs [145]. In addition, the systemic depletion of Foxp3+ Tregs *in vivo* efficiently resulted in the regression of MALT lymphoma [145]. Two recent *in vivo* studies examined the possible mechanisms of Tregs involvement in the immunomodulation of gastric MALT lymphoma and showed that the presence of Foxp3+ expression was significantly higher in patients who achieved CR after HPE than in those without CR, suggesting that Tregs-mediated signaling contributes to *Hp*-dependent lymphomagenesis of gastric MALT lymphoma [146, 147]. Whether *Hp*-regulated chemokines, IL-22, CCL17, and CCL12, and Tregs and *Hp*-altering immune responses also contribute to the *Hp*-dependent lymphomagenesis of gastric DLBCL remains uncertain, and these clues from MALT lymphoma would push us to comprehensively explore the mechanisms by which *Hp*-related immune responses participate in the lymphomagenesis of *Hp*-related gastric DLBCL.
