Regulation of B-Cell Receptor Signaling and Its Therapeutic Relevance in Aggressive B-Cell Lymphomas

B-cell non-Hodgkin lymphoma; B-cell receptor; AcalabrutinibLinfoma no Hodgkin de células B; Receptor de células B; AcalabrutinibLimfoma no Hodgkin de cèl·lules B; Receptor de cèl·lules B; AcalabrutinibThe proliferation and survival signals emanating from the B-cell receptor (BCR) constitute a crucial aspect of mature lymphocyte’s life. Dysregulated BCR signaling is considered a potent contributor to tumor survival in different subtypes of B-cell non-Hodgkin lymphomas (B-NHLs). In the last decade, the emergence of BCR-associated kinases as rational therapeutic targets has led to the development and approval of several small molecule inhibitors targeting either Bruton’s tyrosine kinase (BTK), spleen tyrosine kinase (SYK), or phosphatidylinositol 3 kinase (PI3K), offering alternative treatment options to standard chemoimmunotherapy, and making some of these drugs valuable assets in the anti-lymphoma armamentarium. Despite their initial effectiveness, these precision medicine strategies are limited by primary resistance in aggressive B-cell lymphoma such as diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL), especially in the case of first generation BTK inhibitors. In these patients, BCR-targeting drugs often fail to produce durable responses, and nearly all cases eventually progress with a dismal outcome, due to secondary resistance. This review will discuss our current understanding of the role of antigen-dependent and antigen-independent BCR signaling in DLBCL and MCL and will cover both approved inhibitors and investigational molecules being evaluated in early preclinical studies. We will discuss how the mechanisms of action of these molecules, and their off/on-target effects can influence their effectiveness and lead to toxicity, and how our actual knowledge supports the development of more specific inhibitors and new, rationally based, combination therapies, for the management of MCL and DLBCL patients.G.R. acknowledges supports from Fondo de Investigación Sanitaria PI18/01383, Spanish Ministry of Science and Innovation, European Regional Development Fund (ERDF) “Una manera de hacer Europa”. J.C.S. holds a Sara Borrell research contract from Instituto de Salud Carlos III, Spanish Ministry of Science and Innovation (CD19/00228)

Immune-Checkpoint Inhibitors in B-Cell Lymphoma

For years, immunotherapy has been considered a viable and attractive treatment option for patients with cancer. Among the immunotherapy arsenal, the targeting of intratumoral immune cells by immune-checkpoint inhibitory agents has recently revolutionised the treatment of several subtypes of tumours. These approaches, aimed at restoring an effective antitumour immunity, rapidly reached the market thanks to the simultaneous identification of inhibitory signals that dampen an effective antitumor response in a large variety of neoplastic cells and the clinical development of monoclonal antibodies targeting checkpoint receptors. Leading therapies in solid tumours are mainly focused on the cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed death 1 (PD-1) pathways. These approaches have found a promising testing ground in both Hodgkin lymphoma and non-Hodgkin lymphoma, mainly because, in these diseases, the malignant cells interact with the immune system and commonly provide signals that regulate immune function. Although several trials have already demonstrated evidence of therapeutic activity with some checkpoint inhibitors in lymphoma, many of the immunologic lessons learned from solid tumours may not directly translate to lymphoid malignancies. In this sense, the mechanisms of effective antitumor responses are different between the different lymphoma subtypes, while the reasons for this substantial difference remain partially unknown. This review will discuss the current advances of immune-checkpoint blockade therapies in B-cell lymphoma and build a projection of how the field may evolve in the near future. In particular, we will analyse the current strategies being evaluated both preclinically and clinically, with the aim of fostering the use of immune-checkpoint inhibitors in lymphoma, including combination approaches with chemotherapeutics, biological agents and/or different immunologic therapies

Constitutive Activation of p62/Sequestosome-1-Mediated Proteaphagy Regulates Proteolysis and Impairs Cell Death in Bortezomib-Resistant Mantle Cell Lymphoma

Apoptosis; Autophagy; Proteasome inhibitorApoptosis; Autofagia; Inhibidor del proteasomaApoptosi; Autofàgia; Inhibidor del proteasomaProtein ubiquitylation coordinates crucial cellular events in physiological and pathological conditions. A comparative analysis of the ubiquitin proteome from bortezomib (BTZ)-sensitive and BTZ-resistant mantle cell lymphoma (MCL) revealed an enrichment of the autophagy–lysosome system (ALS) in BTZ-resistant cells. Pharmacological inhibition of autophagy at the level of lysosome-fusion revealed a constitutive activation of proteaphagy and accumulation of proteasome subunits within autophagosomes in different MCL cell lines with acquired or natural resistance to BTZ. Inhibition of the autophagy receptor p62/SQSTM1 upon verteporfin (VTP) treatment disrupted proteaphagosome assembly, reduced co-localization of proteasome subunits with autophagy markers and negatively impacted proteasome activity. Finally, the silencing or pharmacological inhibition of p62 restored the apoptosis threshold at physiological levels in BTZ-resistant cells both in vitro and in vivo. In total, these results demonstrate for the first time a proteolytic switch from the ubiquitin–proteasome system (UPS) to ALS in B-cell lymphoma refractory to proteasome inhibition, pointing out a crucial role for proteaphagy in this phenomenon and paving the way for the design of alternative therapeutic venues in treatment-resistant tumors.This work was supported at early stages by Spanish MINECO, CTQ2011–27874 grant. M.G.-S. is a fellow of the UbiCODE project funded by the EU’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 765445. M.S.R. and L.C. were also funded by the Institut National du Cancer, France (PLBIO16-251), CONACyT-SRE (Mexico) grant 0280365 and the REPERE program of Occitanie. O.C. is funded by “La Ligue contre le cancer du Gard”. ICFO authors were supported by funding from the Spanish MINECO “Severo Ochoa” program for Centres of Excellence in R&D (CEX2019-000910-S [MCIN/ AEI/10.13039/501100011033]), from Fundació Privada Cellex, Fundación Mig-Puig, from Generalitat de Catalunya CERCA program and from LASERLAB Europe (grant agreement No 871124;). G.R. was financially supported by Fondo de Investigación Sanitaria PI15/00102 and PI18/01383, European Regional Development Fund (ERDF) ‘Una manera de hacer Europa’. G.R. and D.R.G. are members of the Spanish Network of Excellence UBIRed funded by the Spanish Ministry Science, Innovation and Universities (SAF2017-90900-REDT)

Role of ZEB factors in B cell activation and malignant progression

[eng] ZEB1 and ZEB2 are two transcription factors best known for their role driving a dedifferentiation process, commonly referred as epithelial to mesenchymal transition (EMT). This process is carried out either in multiple physiological and pathological conditions, such as normal development and tumor progression. More recently their role in T cell development and T cell leukemias have been studied but their role in B-cell activation and B cell malignant progression remains still poorly understood. In this PhD dissertation, it was found that both ZEB1 and ZEB2 factors are expressed during the differentiation of the B cell lineage and specifically in the Germinal Center (GC) B cells. ZEB1 is required for GC formation and to prepare a correct T-dependent response in front of a specific antigen. Due to different chromosomal alterations and mutations, the GC B cells can undergo malignant transformation and give rise to different subtypes of B cell lymphoma, being diffuse large B cell lymphoma (DLBCL) the most common. It was found that ZEB1 and ZEB2 are involved in the progression of DLBCL as they regulate the DLBCL proliferation and cell metabolism, being ZEB1 a marker of poorer prognosis and associated to higher proliferation rate of tumoral cells and ZEB2 having an inversed pattern. These reversed expression patterns of ZEB1 and ZEB2 was also found in multiple myeloma (MM), where ZEB2 acts as an anti-tumoral marker and is associated with a pre-malignant stage, the monoclonal gammopathy of undetermined significance (MGUS). ZEB1 acts as a pro-tumoral gene, associated with the malignization of the disease and is associated with different hallmarks: poorer treatment response, cell migration, and in the bone formation. The results set ZEB1 and ZEB2 as potent prognosis markers in lymphomas and highlight that their potential as therapeutic targets needs to be assessed in the future.[cat] ZEB1 i ZEB2 són dos factors de transcripció descrits pel seu paper en dur a terme un procés de desdiferenciació, conegut com la transició epiteli-mesènquima. Aquest procés es duu a terme tant en condicions fisiològiques com patològiques, com pot ser durant el desenvolupament o en la progressió tumoral i metàstasi. Recentment s’ha descrit el seu paper en el desenvolupament de cèl·lules T i en leucèmies de cèl·lula T, però el seu rol durant el desenvolupament i activament de les cèl·lules B i en la progressió de tumors hematològics de cèl·lula B encara no és del tot conegut. En aquesta tesis, s’ha trobat que els dos factors, ZEB1 i ZEB2, s’expressen durant la diferenciació del llinatge de cèl·lules B i específicament en les cèl·lules B del Centre Germinal. Per la formació de centres germinals i per donar a lloc una bona resposta humoral enfront un antigen específic és necessària la intervenció de ZEB1. En limfomes difusos de cèl·lula gran, ZEB1 i ZEB2 estan implicats en la progressió de la malaltia, ja que en regulen la seva proliferació i metabolisme cel·lular. En aquest cas, ZEB1 està associat a un pitjor prognàtic i ZEB2 té una funció inversa, associant-se a un millor pronòstic. Aquest patró també es pot observar en el cas de mieloma múltiple, en què ZEB2 està associat a un estadi premaligne de la malaltia i ZEB1 actua com un gen protumoral, associat a diferents marcadors com podria ser una pitjor resposta al tractament, migració cel·lular i formació d’osteoclasts. Aquests resultats situen ZEB1 i ZEB2 com marcadors de prognosi en limfomes, sent considerat ZEB1 com un gen promotor de la tumorigènesi i marcador de mal pronòstic i ZEB2 sent un marcador de bon pronòstic. També suggereixen ZEB1 com una potencial diana terapèutica en limfomes

RHOA Therapeutic Targeting in Hematological Cancers

Primarily identified as an important regulator of cytoskeletal dynamics, the small GTPase Ras homolog gene family member A (RHOA) has been implicated in the transduction of signals regulating a broad range of cellular functions such as cell survival, migration, adhesion and proliferation. Deregulated activity of RHOA has been linked to the growth, progression and metastasis of various cancer types. Recent cancer genome-wide sequencing studies have unveiled both RHOA gain and loss-of-function mutations in primary leukemia/lymphoma, suggesting that this GTPase may exert tumor-promoting or tumor-suppressive functions depending on the cellular context. Based on these observations, RHOA signaling represents an attractive therapeutic target for the development of selective anticancer strategies. In this review, we will summarize the molecular mechanisms underlying RHOA GTPase functions in immune regulation and in the development of hematological neoplasms and will discuss the current strategies aimed at modulating RHOA functions in these diseases

RHOA Therapeutic Targeting in Hematological Cancers

Primarily identified as an important regulator of cytoskeletal dynamics, the small GTPase Ras homolog gene family member A (RHOA) has been implicated in the transduction of signals regulating a broad range of cellular functions such as cell survival, migration, adhesion and proliferation. Deregulated activity of RHOA has been linked to the growth, progression and metastasis of various cancer types. Recent cancer genome-wide sequencing studies have unveiled both RHOA gain and loss-of-function mutations in primary leukemia/lymphoma, suggesting that this GTPase may exert tumor-promoting or tumor-suppressive functions depending on the cellular context. Based on these observations, RHOA signaling represents an attractive therapeutic target for the development of selective anticancer strategies. In this review, we will summarize the molecular mechanisms underlying RHOA GTPase functions in immune regulation and in the development of hematological neoplasms and will discuss the current strategies aimed at modulating RHOA functions in these diseases

Antitumor Activity of Simvastatin in Preclinical Models of Mantle Cell Lymphoma

Background: Mantle cell lymphoma (MCL) is a rare and aggressive subtype of B-cell non-Hodgkin lymphoma that remains incurable with standard therapy. Statins are well-tolerated, inexpensive, and widely prescribed as cholesterol-lowering agents to treat hyperlipidemia and to prevent cardiovascular diseases through the blockage of the mevalonate metabolic pathway. These drugs have also shown promising anti-cancer activity through pleiotropic effects including the induction of lymphoma cell death. However, their potential use as anti-MCL agents has not been evaluated so far. Aim: The present study aimed to investigate the activity of simvastatin on MCL cells. Methods: We evaluated the cytotoxicity of simvastatin in MCL cell lines by CellTiter-Glo and lactate dehydrogenase (LDH) release assays. Cell proliferation and mitotic index were assessed by direct cell recounting and histone H3-pSer10 immunostaining. Apoptosis induction and reactive oxygen species (ROS) generation were evaluated by flow cytometry. Cell migration and invasion properties were determined by transwell assay. The antitumoral effect of simvastatin in vivo was evaluated in a chick embryo chorioallantoic membrane (CAM) MCL xenograft model. Results: We show that treatment with simvastatin induced a 2 to 6-fold LDH release, inhibited more than 50% of cell proliferation, and enhanced the caspase-independent ROS-mediated death of MCL cells. The effective impairment of MCL cell survival was accompanied by the inhibition of AKT and mTOR phosphorylation. Moreover, simvastatin strongly decreased MCL cell migration and invasion ability, leading to a 55% tumor growth inhibition and a consistent diminution of bone marrow and spleen metastasis in vivo. Conclusion: Altogether, these data provide the first preclinical insight into the effect of simvastatin against MCL cells, suggesting that this agent might be considered for repurpose as a precise MCL therapy

Immune-checkpoint inhibitors in B-cell lymphoma

Altres ajuts: G.R. acknowledges supports from Fondo de Investigación Sanitaria PI18/01383, European Regional Development Fund (ERDF) "Una manera de hacer Europa". J.C.S. holds a Sara Borrell research contract from Instituto de Salud Carlos III.For years, immunotherapy has been considered a viable and attractive treatment option for patients with cancer. Among the immunotherapy arsenal, the targeting of intratumoral immune cells by immune-checkpoint inhibitory agents has recently revolutionised the treatment of several subtypes of tumours. These approaches, aimed at restoring an effective antitumour immunity, rapidly reached the market thanks to the simultaneous identification of inhibitory signals that dampen an effective antitumor response in a large variety of neoplastic cells and the clinical development of monoclonal antibodies targeting checkpoint receptors. Leading therapies in solid tumours are mainly focused on the cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed death 1 (PD-1) pathways. These approaches have found a promising testing ground in both Hodgkin lymphoma and non-Hodgkin lymphoma, mainly because, in these diseases, the malignant cells interact with the immune system and commonly provide signals that regulate immune function. Although several trials have already demonstrated evidence of therapeutic activity with some checkpoint inhibitors in lymphoma, many of the immunologic lessons learned from solid tumours may not directly translate to lymphoid malignancies. In this sense, the mechanisms of effective antitumor responses are different between the different lymphoma subtypes, while the reasons for this substantial difference remain partially unknown. This review will discuss the current advances of immune-checkpoint blockade therapies in B-cell lymphoma and build a projection of how the field may evolve in the near future. In particular, we will analyse the current strategies being evaluated both preclinically and clinically, with the aim of fostering the use of immune-checkpoint inhibitors in lymphoma, including combination approaches with chemotherapeutics, biological agents and/or different immunologic therapies

Exportin 1-mediated nuclear/cytoplasmic trafficking controls drug sensitivity of classical Hodgkin's lymphoma

Exportin 1 (XPO1) is the main nuclear export receptor that controls the subcellular trafficking and the functions of major regulatory proteins. XPO1 is overexpressed in various cancers and small inhibitors of nuclear export (SINEs) have been developed to inhibit XPO1. In primary mediastinal B-cell lymphoma (PMBL) and classical Hodgkin's lymphoma (cHL), the XPO1 gene may be mutated on one nucleotide and encodes the mutant XPO1. To understand the impact of mutation on protein function, we studied the response of PMBL and cHL cells to selinexor, a SINE, and ibrutinib, an inhibitor of Bruton tyrosine kinase. XPO1 mutation renders lymphoma cells more sensitive to selinexor due to a faster degradation of mutant XPO1 compared to the wild-type. We further showed that a mistrafficking of p65 (RELA) and p52 (NFκB2) transcription factors between the nuclear and cytoplasmic compartments accounts for the response toward ibrutinib. XPO1 mutation may be envisaged as a biomarker of the response of PMBL and cHL cells and other B-cell hemopathies to SINEs and drugs that target even indirectly the NFκB signaling pathway

G protein-coupled receptor 183 mediates the sensitization of Burkitt lymphoma tumors to CD47 immune checkpoint blockade by anti-CD20/PI3Kδi dual therapy

Altres ajuts: CERCA Programme/Generalitat de Catalunya ; PROTEOblood, a project co-financed by the European Regional Development Fund (ERDF) through the Interreg V-A Spain-France-Andorra (POCTEFA) program (EFA360/19)Immunotherapy-based regimens have considerably improved the survival rate of B-cell non-Hodgkin lymphoma (B-NHL) patients in the last decades; however, most disease subtypes remain almost incurable. TG-1801, a bispecific antibody that targets CD47 selectively on CD19+ B-cells, is under clinical evaluation in relapsed/refractory (R/R) B-NHL patients either as a single-agent or in combination with ublituximab, a new generation CD20 antibody. A set of eight B-NHL cell lines and primary samples were cultured in vitro in the presence of bone marrow-derived stromal cells, M2-polarized primary macrophages, and primary circulating PBMCs as a source of effector cells. Cell response to TG-1801 alone or combined with the U2 regimen associating ublituximab to the PI3Kδ inhibitor umbralisib, was analyzed by proliferation assay, western blot, transcriptomic analysis (qPCR array and RNA sequencing followed by gene set enrichment analysis) and/or quantification of antibody-dependent cell death (ADCC) and antibody-dependent cell phagocytosis (ADCP). CRISPR-Cas9 gene edition was used to selectively abrogate GPR183 gene expression in B-NHL cells. In vivo, drug efficacy was determined in immunodeficient (NSG mice) or immune-competent (chicken embryo chorioallantoic membrane (CAM)) B-NHL xenograft models. Using a panel of B-NHL co-cultures, we show that TG-1801, by disrupting the CD47-SIRPα axis, potentiates anti-CD20-mediated ADCC and ADCP. This led to a remarkable and durable antitumor effect of the triplet therapy composed by TG-1801 and U2 regimen, in vitro, as well as in mice and CAM xenograft models of B-NHL. Transcriptomic analysis also uncovered the upregulation of the G protein-coupled and inflammatory receptor, GPR183, as a crucial event associated with the efficacy of the triplet combination. Genetic depletion and pharmacological inhibition of GPR183 impaired ADCP initiation, cytoskeleton remodeling and cell migration in 2D and 3D spheroid B-NHL co-cultures, and disrupted macrophage-mediated control of tumor growth in B-NHL CAM xenografts. Altogether, our results support a crucial role for GPR183 in the recognition and elimination of malignant B cells upon concomitant targeting of CD20, CD47 and PI3Kδ, and warrant further clinical evaluation of this triplet regimen in B-NHL