Despite the unquestionable success achieved by rituximab-based regimens in the management of diffuse large B-cell lymphoma (DLBCL), the high incidence of relapsed/refractory disease still remains a challenge. The widespread clinical use of chemo-immunotherapy demonstrated that it invariably leads to the induction of resistance; however, the molecular mechanisms underlying this phenomenon remain unclear. Rituximab-mediated therapeutic effect primarily relies on complement-dependent cytotoxicity and antibody-dependent cell cytotoxicity, and their outcome is often compromised following the development of resistance. Factors involved include inherent genetic characteristics and rituximab-induced changes in effectors cells, the role of ligand/receptor interactions between target and effector cells, and the tumor microenvironment. This review focuses on summarizing the emerging advances in the understanding of the molecular basis responsible for the resistance induced by various forms of immunotherapy used in DLBCL. We outline available models of resistance and delineate solutions that may improve the efficacy of standard therapeutic protocols, which might be essential for the rational design of novel therapeutic regimens.

Immunotherapy revolutionized cancer treatment in the last decade. Both NK cells and T cells are key components of host immunity against malignant cells that are being extensively investigated in the field of cancer immunotherapy. While approaches have been developed to improve the antitumor activity of NK and T cells, the tumor microenvironment remains an obstacle to effective NK and T-cell–based therapies. Here, we demonstrated that cancer-conditioned medium suppresses the antitumor activity of NK cells. Ammonia, a by-product of cancer cell metabolism, accumulated in cancer-conditioned medium and in the tumor microenvironment, and impaired the cytotoxicity of NK cells as well as the efficacy of antibody-based and chimeric antigen receptor (CAR) NK and CAR T-cell–based therapies in vitro. Ammonia induced NK and T-cell dysfunction by decreasing the amount of mature perforin in secretory lysosomes, which was dependent on its lysosomotropic features and ability to increase pH in acidic compartments. These findings demonstrate that, in addition to its previously described role in promoting tumor growth as a source of nitrogen for tumor biomass, ammonia promotes tumor immune escape by inhibiting both NK and CAR T-cell cytotoxicity. Significance: Ammonia is elevated in the tumor microenvironment and functions as an immunoinhibitory metabolite in cancer by reducing perforin levels, inhibiting NK and T-cell–mediated immunity and limiting the efficacy of immunotherapies.

Despite the high incidence of diffuse large B-cell lymphoma (DLBCL), its management constitutes an ongoing challenge. The most common DLBCL variants include activated B-cell (ABC) and germinal center B-cell-like (GCB) subtypes including DLBCL with MYC and BCL2/BCL6 rearrangements which vary among each other with sensitivity to standard rituximab (RTX)-based chemoimmunotherapy regimens and lead to distinct clinical outcomes. However, as first line therapies lead to resistance/relapse (r/r) in about half of treated patients, there is an unmet clinical need to identify novel therapeutic strategies tailored for these patients. In particular, immunotherapy constitutes an attractive option largely explored in preclinical and clinical studies. Patient-derived cell lines that model primary tumor are indispensable tools that facilitate preclinical research. The current review provides an overview of available DLBCL cell line models and their utility in designing novel immunotherapeutic strategies.

Despite the introduction of a plethora of different anti-neoplastic approaches including standard chemotherapy, molecularly targeted small-molecule inhibitors, monoclonal antibodies, and finally hematopoietic stem cell transplantation (HSCT), there is still a need for novel therapeutic options with the potential to cure hematological malignancies. Although nowadays HSCT already offers a curative effect, its implementation is largely limited by the age and frailty of the patient. Moreover, its efficacy in combating the malignancy with graft-versus-tumor effect frequently coexists with undesirable graft-versus-host disease (GvHD). Therefore, it seems that cell-based adoptive immunotherapies may constitute optimal strategies to be successfully incorporated into the standard therapeutic protocols. Thus, modern cell-based immunotherapy may finally represent the long-awaited “magic bullet” against cancer. However, enhancing the safety and efficacy of this treatment regimen still presents many challenges. In this review, we summarize the up-to-date state of the art concerning the use of CAR-T cells and NK-cell-based immunotherapies in hemato-oncology, identify possible obstacles, and delineate further perspectives.

Supplementary Fig. 8 shows effects of ammonia on perforin gene expression at the transcriptional level

Supplementary Fig. 11 shows that ammonia increases the number of LAMP1+ vesicles but decreases their volume and LAMP1 level