Characterization of metabolic alterations of chronic lymphocytic leukemia in the lymph node microenvironment

BNT162b2 mRNA vaccination affects the gut microbiome composition of patients with follicular lymphoma and chronic lymphocytic leukemia

BACKGROUND

In both chronic lymphatic leukemia (CLL) and follicular lymphoma (FL) immunotherapy determines B-depletion that leads to temporary suppression of humoral immunity, which is clinically relevant especially during the COVID-19 pandemic, when most patients in the first wave received the BNT162b2 vaccine during anti-neoplastic treatment.

METHODS

To capture changes in the immunome and microbiome composition in CLL and FL patients upon mRNA-based vaccination, we designed a prospective, longitudinal study to profile both the humoral and the cellular response after exposure to the BNT162b2 COVID-19 vaccine.

RESULTS

In both CLL patients and FL patients, the second and third administrations of the BNT162b2 vaccine increased the titer of specific antibodies against SARS-CoV-2. In FL patients, vaccination induced expansion of central memory CD8 + CD57dim CD279 + T cells and reduction of the neutrophil subset myeloid 1 (CD14-CD15+CD16dimCD64+CD33-CD38+PDL1+HLA-DR-); in both cohorts, CD45RA + CD27 + CD279 + NK cells were expanded after a full cycle of vaccination. After vaccination, the genera Collinsella, Gemmiger, Lachnospiraceae, Blautia, Ruminococcus and Lactobacillus increased in both CLL patients and FL patients, whereas Faecalibacterium, Enterobacteriacae, and Enterococcus decreased. Multivariate analysis failed to identify factors associated with changes in microbiome communities among the CLL and FL cohorts, considering age, sex, exposure to anti-CD20 therapy and disease activity. Only in FL patients, alpha diversity was negatively correlated with neutrophil subsets myeloid 1 e 5 at baseline and positively correlated with neutrophil subset 6 after vaccination. PICRUSt2 analysis showed how microbiome can also affect the host health promoting chronic inflammation. The L-lysine biosynthesis pathway was more represented in CLL patients, whereas the L-valine degradation pathway and the anaerobic degradation of purine nucleobases were overrepresented in the FL cohort.

CONCLUSIONS

Taken together, our findings reveal the effect of the BNT162b2 vaccine in shaping the microbiome composition in CLL and FL patients, despite receiving treatment for their underlying active disease, and highlight the importance of a comprehensive analysis of the immunome and microbiome profiling to understand immune function in these cohorts of patients.

The multi-faceted roles of MYC in the prognosis of chronic lymphocytic leukemia

In this review, we focus on the pro-oncogene MYC, the modes of deregulation in mouse and human B-cells, its undisputable importance in the evaluation of biological prognostication of patients, but also how it impacts on response to modern therapeutics, and how it should be targeted to improve the overall survival of chronic lymphocytic lymphoma (CLL) patients. After an overview of the current understanding of the molecular dysregulation of c-MYC, we will show how CLL, both in its indolent and transformed phases, has developed among other B-cell lymphomas a tight regulation of its expression through the chronic activation of B-Cell Receptors (among others). This is particularly important if one desires to understand the mechanisms at stake in the over-expression of c-MYC especially in the lymph nodes compartment. So doing, we will show how this oncogene orchestrates pivotal cellular functions such as metabolism, drug resistance, proliferation and histologic transformation (Richter syndrome).

Metabolic reprogramming, malignant transformation and metastasis: Lessons from chronic lymphocytic leukaemia and prostate cancer

Metabolic reprogramming is a hallmark of cancer, crucial for malignant transformation and metastasis. Chronic lymphocytic leukaemia (CLL) and prostate cancer exhibit similar metabolic adaptations, particularly in glucose and lipid metabolism. Understanding this metabolic plasticity is crucial for identifying mechanisms contributing to metastasis. This review considers glucose and lipid metabolism in CLL and prostate cancer, exploring their roles in healthy and malignant states and during disease progression. In CLL, lipid metabolism supports cell survival and migration, with aggressive disease characterised by increased fatty acid oxidation and altered sphingolipids. Richter's transformation and aggressive lymphoma, however, exhibit a metabolic shift towards increased glycolysis. Similarly, prostate cell metabolism is unique, relying on citrate production in the healthy state and undergoing metabolic reprogramming during malignant transformation. Early-stage prostate cancer cells increase lipid synthesis and uptake, and decrease glycolysis, whereas metastatic cells re-adopt glucose metabolism, likely driven by interactions with the tumour microenvironment. Genetic drivers including TP53 and ATM mutations connect metabolic alterations to disease severity in these two malignancies. The bone microenvironment supports the metabolic demands of these malignancies, serving as an initiation niche for CLL and a homing site for prostate cancer metastases. By comparing these malignancies, this review underscores the importance of metabolic plasticity in cancer progression and highlights how CLL and prostate cancer may be models of circulating and solid tumours more broadly. The metabolic phenotypes throughout cancer cell transformation and metastasis, and the microenvironment in which these processes occur, present opportunities for interventions that could disrupt metastatic processes and improve patient outcomes.

Aberrant BCAT1 expression augments MTOR activity and accelerates disease progression in chronic lymphocytic leukemia

We performed gene expression profiling of mRNA/cDNA isolated from N = 117 flow sorted CLL. We detected aberrant expression of the metabolic enzyme branched chain amino acid transferase (BCAT1) in CLL with del17p/TP53mut. Through extensive validation, we confirmed the highly preferential expression of BCAT1 in CLL with del17p/TP53mut (66%) or trisomy 12 (77%). BCAT1 was not expressed in B cells isolated from normal human lymph nodes. The products of the bidirectional BCAT1 reaction, including leucine, acetyl-CoA, and alpha-ketoglutarate are known activators of MTOR. We measured an ~two-fold higher MTOR activity via normalized p-S6K levels in primary CLL with BCAT1 high versus absent expression before and after sIgM crosslinking. Through steady state metabolomics and heavy isotope metabolic tracing in primary CLL cells, we demonstrate that CLL cells are avid consumers of branched chain amino acids (BCAAs) and that BCAT1 in CLL engages in bidirectional substrate reactions. Of additional interest, CLL with aberrant BCAT1 expression were less sensitive to Venetoclax-induced apoptosis. Biologically, three CLL-derived cell lines with disruption of BCAT1 had substantially reduced growth ex vivo. Clinically, the expression of any detectable BCAT1 protein in CLL independently associated with shorter median survival (125 months versus 296 months; p < 0.0001), even after exclusion of del17p/TP53mut cases.

The survival grip-how cell adhesion promotes tumor maintenance within the microenvironment

Cell adhesion is warranted by proteins that are crucial for the maintenance of tissue integrity and homeostasis. Most of these proteins behave as receptors to link adhesion to the control of cell survival and their expression or regulation are often altered in cancers. B-cell malignancies do not evade this principle as they are sustained in relapsed niches by interacting with the microenvironment that includes cells and their secreted factors. Focusing on chronic lymphocytic leukemia and mantle cell lymphoma, this Review delves with the molecules involved in the dialog between the adhesion platforms and signaling pathways known to regulate both cell adhesion and survival. Current therapeutic strategies disrupt adhesive structures and compromise the microenvironment support to tumor cells, rendering them sensitive to immune recognition. The development of organ-on-chip and 3D culture systems, such as spheroids, have revealed the importance of mechanical cues in regulating signaling pathways to organize cell adhesion and survival. All these elements contribute to the elaboration of the crosstalk of lymphoma cells with the microenvironment and the education processes that allow the establishment of the supportive niche.

Prospective investigation of amino acid transport and PSMA-targeted positron emission tomography for metastatic lobular breast carcinoma

PURPOSE

To explore the feasibility of imaging amino-acid transport and PSMA molecular pathways in the detection of metastatic breast invasive lobular carcinoma (ILC) and if there is superior detection compared to standard-of-care imaging [computed tomography (CT)/bone scan, or 18F-FDG positron-emission-tomography (PET)-CT].

METHODS

20 women with de-novo or suspected metastatic ILC underwent two PET-CT scans with 18F-fluciclovine and 68Ga-PSMA-11 on separate days. Uptake per patient and in 3 regions per patient - ipsilateral axillary lymph node (LN), extra-axillary LN (ipsilateral supraclavicular or internal mammary), or distant sites of disease - was compared to standard-of-care imaging (CT/bone scan in 13 patients and 18F-FDG PET-CT in 7 patients). Results were correlated to a composite standard of truth. Confirmed detection rate (cDR) was compared using McNemar's test. Mean SUVmax of 18F-fluciclovine and 68Ga-PSMA-11 in the most avid lesion for each true positive metastatic region and intact primary lesion were compared by t-test.

RESULTS

The cDR for standard-of-care imaging was 5/20 patients in 5/60 regions. 68Ga-PSMA-11 PET-CT detected metastasis in 7/20 patients in 7/60 regions. 18F-fluciclovine PET-CT detected metastasis in 9/20 patients in 12/60 regions. The cDR for 18F-fluciclovine PET-CT was significantly higher versus standard-of-care imaging on the patient and combined region levels, while there were no significant differences between 68Ga-PSMA-11 and standard-of care imaging. 18F-fluciclovine cDR was also significantly higher than 68Ga-PSMA-11 on the combined region level. Mean SUVmax for true positive metastatic and primary lesions with 18F-fluciclovine (n = 18) was significantly greater than for 68Ga-PSMA-11 (n = 11) [5.5 ± 1.8 versus 3.5 ± 2.7 respectively, p = 0.021].

CONCLUSION

In this exploratory trial, 18F-fluciclovine PET-CT has a significantly higher cDR for ILC metastases compared to standard-of-care imaging and to 68Ga-PSMA-11. Mean SUVmax for true positive malignancy was significantly higher with 18F-fluciclovine than for 68Ga-PSMA-11. Exploratory data from this trial suggests that molecular imaging of amino acid metabolism in patients with ILC deserves further study.

CLINICAL TRIAL REGISTRATION

Early phase (I-II) clinical trial (NCT04750473) funded by the National Institutes of Health (R21CA256280).

Metabolic regulation of the immune system in health and diseases: mechanisms and interventions

Metabolism, including glycolysis, oxidative phosphorylation, fatty acid oxidation, and other metabolic pathways, impacts the phenotypes and functions of immune cells. The metabolic regulation of the immune system is important in the pathogenesis and progression of numerous diseases, such as cancers, autoimmune diseases and metabolic diseases. The concept of immunometabolism was introduced over a decade ago to elucidate the intricate interplay between metabolism and immunity. The definition of immunometabolism has expanded from chronic low-grade inflammation in metabolic diseases to metabolic reprogramming of immune cells in various diseases. With immunometabolism being proposed and developed, the metabolic regulation of the immune system can be gradually summarized and becomes more and more clearer. In the context of many diseases including cancer, autoimmune diseases, metabolic diseases, and many other disease, metabolic reprogramming occurs in immune cells inducing proinflammatory or anti-inflammatory effects. The phenotypic and functional changes of immune cells caused by metabolic regulation further affect and development of diseases. Based on experimental results, targeting cellular metabolism of immune cells becomes a promising therapy. In this review, we focus on immune cells to introduce their metabolic pathways and metabolic reprogramming, and summarize how these metabolic pathways affect immune effects in the context of diseases. We thoroughly explore targets and treatments based on immunometabolism in existing studies. The challenges of translating experimental results into clinical applications in the field of immunometabolism are also summarized. We believe that a better understanding of immune regulation in health and diseases will improve the management of most diseases.

Glucose metabolism in B cell malignancies: a focus on glycolysis branching pathways

Glucose catabolism, one of the essential pathways sustaining cellular bioenergetics, has been widely studied in the context of tumors. Nevertheless, the function of various branches of glucose metabolism that stem from 'classical' glycolysis have only been partially explored. This review focuses on discussing general mechanisms and pathological implications of glycolysis and its branching pathways in the biology of B cell malignancies. We summarize here what is known regarding pentose phosphate, hexosamine, serine biosynthesis, and glycogen synthesis pathways in this group of tumors. Despite most findings have been based on malignant B cells themselves, we also discuss the role of glucose metabolism in the tumor microenvironment, with a focus on T cells. Understanding the contribution of glycolysis branching pathways and how they are hijacked in B cell malignancies will help to dissect the role they have in sustaining the dissemination and proliferation of tumor B cells and regulating immune responses within these tumors. Ultimately, this should lead to deciphering associated vulnerabilities and improve current therapeutic schedules.

Metabolic reprogramming in the CLL TME; potential for new therapeutic targets

Chronic lymphocytic leukemia (CLL) cells circulate between peripheral (PB) blood and lymph node (LN) compartments, and strictly depend on microenvironmental factors for proliferation, survival and drug resistance. All cancer cells display metabolic reprogramming and CLL is no exception - though the inert status of the PB CLL cells has hampered detailed insight into these processes. We summarize previous work on reactive oxygen species (ROS), oxidative stress, and hypoxia, as well as the important roles of Myc, and PI3K/Akt/mTor pathways. In vitro co-culture systems and gene expression analyses have provided a partial picture of CLL LN metabolism. New broad omics techniques allow to obtain molecular and also single-cell level understanding of CLL plasticity and metabolic reprogramming. We summarize recent developments and describe the new concept of glutamine addiction for CLL, which may hold therapeutic promise.

Lessons learned from the Eµ-TCL1 mouse model of CLL

The Eµ-TCL1 mouse model has been used for over 20 years to study the pathobiology of chronic lymphocytic leukemia (CLL) and for preclinical testing of novel therapies. A CLL-like disease develops with increasing age in these mice due to a B cell specific overexpression of human TCL1. The reliability of this model to mirror human CLL is controversially discussed, as none of the known driver mutations identified in patients are found in Eµ-TCL1 mice. It has to be acknowledged that this mouse model was key to develop targeted therapies that aim at inhibiting the constitutive B cell receptor (BCR) signaling, a main driver of CLL. Inhibitors of BCR signaling became standard-of-care for a large proportion of patients with CLL as they are highly effective. The Eµ-TCL1 model further advanced our understanding of CLL biology owed to studies that crossed this mouse line with various transgenic mouse models and demonstrated the relevance of CLL-cell intrinsic and -extrinsic drivers of disease. These studies were instrumental in showing the relevance of the tumor microenvironment in the lymphoid tissues for disease progression and immune escape in CLL. It became clear that CLL cells shape and rely on stromal and immune cells, and that immune suppressive mechanisms and T cell exhaustion contribute to CLL progression. Based on this knowledge, new immunotherapy strategies were clinically tested for CLL, but so far with disappointing results. As some of these therapies were effective in the Eµ-TCL1 mouse model, the question arose concerning the translatability of preclinical studies in these mice. The aim of this review is to summarize lessons we have learnt over the last decades by studying CLL-like disease in the Eµ-TCL1 mouse model. The article focuses on pitfalls and limitations of the model, as well as the gained knowledge and potential of using this model for the development of novel treatment strategies to achieve the goal of curing patients with CLL.

The complexities of T-cell dysfunction in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy characterized by profound alterations and defects in the T-cell compartment. This observation has gained renewed interest as T-cell treatment strategies, which are successfully applied in more aggressive B-cell malignancies, have yielded disappointing results in CLL. Despite ongoing efforts to understand and address the observed T-cell defects, the exact mechanisms and nature underlying this dysfunction remain largely unknown. In this review, we examine the supporting signals from T cells to CLL cells in the lymph node niche, summarize key findings on T-cell functional defects, delve into potential underlying causes, and explore novel strategies for reversing these deficiencies. Our goal is to identify strategies aimed at resolving CLL-induced T-cell dysfunction which, in the future, will enhance the efficacy of autologous T-cell-based therapies for CLL patients.

Role of the tumor microenvironment in CLL pathogenesis

Chronic lymphocytic leukemia (CLL) cells extensively interact with and depend on their surrounding tumor microenvironment (TME). The TME encompasses a heterogeneous array of cell types, soluble signals, and extracellular vesicles, which contribute significantly to CLL pathogenesis. CLL cells and the TME cooperatively generate a chronic inflammatory milieu, which reciprocally reprograms the TME and activates a signaling network within CLL cells, promoting their survival and proliferation. Additionally, the inflammatory milieu exerts chemotactic effects, attracting CLL cells and other immune cells to the lymphoid tissues. The intricate CLL-TME interactions also facilitate immune evasion and compromise leukemic cell surveillance. We also review recent advances that have shed light on additional aspects that are substantially influenced by the CLL-TME interplay.

Metabolic signature and response to glutamine deprivation are independent of p53 status in B cell malignancies

The tumor suppressor p53 has been described to control various aspects of metabolic reprogramming in solid tumors, but in B cell malignancies that role is as yet unknown. We generated pairs of p53 functional and knockout (KO) clones from distinct B cell malignancies (acute lymphoblastic leukemia, chronic lymphocytic leukemia, diffuse large B cell lymphoma, and multiple myeloma). Metabolomics and isotope tracing showed that p53 loss did not drive a common metabolic signature. Instead, cell lines segregated according to cell of origin. Next, we focused on glutamine as a crucial energy source in the B cell tumor microenvironment. In both TP53 wild-type and KO cells, glutamine deprivation induced cell death through the integrated stress response, via CHOP/ATF4. Lastly, combining BH3 mimetic drugs with glutamine starvation emerged as a possibility to target resistant clones. In conclusion, our analyses do not support a common metabolic signature of p53 deficiency in B cell malignancies and suggest therapeutic options for exploration based on glutamine dependency.

Improved Photodynamic Therapy Based on Glutaminase Blockage via Tumor Membrane Coated CB-839/IR-780 Nanoparticles

Photodynamic therapy (PDT) has promising applications. However, the lethal function of reactive oxygen species (ROS) produced during PDT is typically limited. This restriction is induced by oxygen shortage in the tumor microenvironment due to tumor cell hypermetabolism and reductive chemicals overexpression in tumor tissues. Glutamine (Gln) metabolism is crucial for malignancy development and is closely associated with redox. Herein, a novel nanoparticle (NP) named IRCB@M is constructed to boost PDT through dual effects. This NP simultaneously blocks aerobic respiration and inhibits cellular reduced substances by blocking the Gln metabolic pathway. Within the nanocomplex, a photosensitizer (IR-780) and a glutaminase inhibitor (CB-839) are self-assembled and then encapsulated by cancer cell membranes for homologous targeting. The Gln metabolism intervention relieves hypoxia and decreases the levels of nicotinamide adenine dinucleotide phosphate (NADPH) as well as reduced glutathione (GSH) in vitro and in vivo, which are the dual amplification effects on the IR-780-mediated lethal PDT. The antitumor effects against gastric cancer are ultimately evoked in vivo, thus offering a novel concept for enhancing PDT and other ROS-dependent therapeutic approaches.

ACOX1-mediated peroxisomal fatty acid oxidation contributes to metabolic reprogramming and survival in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is still an incurable disease, with many patients developing resistance to conventional and targeted therapies. To better understand the physiology of CLL and facilitate the development of innovative treatment options, we examined specific metabolic features in the tumor CLL B-lymphocytes. We observed metabolic reprogramming, characterized by a high level of mitochondrial oxidative phosphorylation activity, a low glycolytic rate, and the presence of C2- to C6-carnitine end-products revealing an unexpected, essential role for peroxisomal fatty acid beta-oxidation (pFAO). Accordingly, downmodulation of ACOX1 (a rate-limiting pFAO enzyme overexpressed in CLL cells) was enough to shift the CLL cells' metabolism from lipids to a carbon- and amino-acid-based phenotype. Complete blockade of ACOX1 resulted in lipid droplet accumulation and caspase-dependent death in CLL cells, including those from individuals with poor cytogenetic and clinical prognostic factors. In a therapeutic translational approach, ACOX1 inhibition spared non-tumor blood cells from CLL patients but led to the death of circulating, BCR-stimulated CLL B-lymphocytes and CLL B-cells receiving pro-survival stromal signals. Furthermore, a combination of ACOX1 and BTK inhibitors had a synergistic killing effect. Overall, our results highlight a less-studied but essential metabolic pathway in CLL and pave the way towards the development of new, metabolism-based treatment options.

Power out chronic lymphocytic leukemia: unplugging OXPHOS/mTOR pathways to overcome venetoclax resistance

Not available.

Electron transport chain and mTOR inhibition synergistically decrease CD40 signaling and counteract venetoclax resistance in chronic lymphocytic leukemia

CD40 signaling upregulates BCL-XL and MCL-1 expression in the chronic lymphocytic leukemia (CLL) lymph node microenvironment, affording resistance to the BCL-2 inhibitor, venetoclax. Venetoclax resistance in the therapeutic setting and after long-term laboratory selection has been linked to metabolic alterations, but the underlying mechanism(s) are unknown. We aimed here to discover how CD40 stimulation as a model for tumor microenvironment-mediated metabolic changes, affects venetoclax sensitivity/resistance. CD40 stimulation increased oxidative phosphorylation and glycolysis, but only inhibition of oxidative phosphorylation countered venetoclax resistance. Furthermore, blocking mitochondrial import of pyruvate, glutamine or fatty acids affected CLL metabolism, but did not prevent CD40-mediated resistance to venetoclax. In contrast, inhibition of the electron transport chain (ETC) at complex I, III or V attenuated CLL activation and ATP production, and downregulated MCL-1 and BCL-XL, correlating with reduced CD40 surface expression. Moreover, ETC inhibition equaled mTOR1/2 but not mTOR1 inhibition alone for venetoclax resistance, and all three pathways were linked to control of general protein translation. In line with this, ETC plus mTOR inhibition synergistically counteracted venetoclax resistance. These findings link oxidative CLL metabolism to CD40 expression and cellular signaling, and may hold clinical potential.

Untargeted metabolomics identifies metabolic dysregulation of sphingolipids associated with aggressive chronic lymphocytic leukaemia and poor survival

BACKGROUND

Metabolic dependencies of chronic lymphocytic leukaemia (CLL) cells may represent new personalized treatment approaches in patients harbouring unfavourable features.

METHODS

Here, we used untargeted metabolomics and lipidomics analyses to isolate metabolomic features associated with aggressive CLL and poor survival outcomes. We initially focused on profiles associated with overexpression of the adverse metabolic marker glycosyltransferase (UGT2B17) associated with poor survival and drug resistance.

RESULTS

Leukaemic B-cell metabolomes indicated a significant perturbation in lipids, predominantly bio-active sphingolipids. Expression of numerous enzyme-encoding genes of sphingolipid biosynthesis pathways was significantly associated with shorter patient survival. Targeted metabolomics further exposed higher circulating levels of glucosylceramides (C16:0 GluCer) in CLL patients relative to healthy donors and an aggressive cancer biology. In multivariate analyses, C16:0 GluCer and sphinganine were independent prognostic markers and were inversely linked to treatment-free survival. These two sphingolipid species function as antagonistic mediators, with sphinganine being pro-apoptotic and GluCer being pro-proliferative, tested in leukemic B-CLL cell models. Blocking GluCer synthesis using ceramide glucosyltransferase inhibitors induced cell death and reduced the proliferative phenotype, which further sensitized a leukaemic B-cell model to the anti-leukaemics fludarabine and ibrutinib in vitro.

CONCLUSIONS

Specific sphingolipids may serve as prognostic markers in CLL, and inhibiting enzymatic pathways involved in their biosynthesis has potential as a therapaeutic approach.

Inhibition of MYC translation through targeting of the newly identified PHB-eIF4F complex as a therapeutic strategy in CLL

Dysregulation of messenger RNA (mRNA) translation, including preferential translation of mRNA with complex 5' untranslated regions such as the MYC oncogene, is recognized as an important mechanism in cancer. Here, we show that both human and murine chronic lymphocytic leukemia (CLL) cells display a high translation rate, which is inhibited by the synthetic flavagline FL3, a prohibitin (PHB)-binding drug. A multiomics analysis performed in samples from patients with CLL and cell lines treated with FL3 revealed the decreased translation of the MYC oncogene and of proteins involved in cell cycle and metabolism. Furthermore, inhibiting translation induced a proliferation arrest and a rewiring of MYC-driven metabolism. Interestingly, contrary to other models, the RAS-RAF-(PHBs)-MAPK pathway is neither impaired by FL3 nor implicated in translation regulation in CLL cells. Here, we rather show that PHBs are directly associated with the eukaryotic initiation factor (eIF)4F translation complex and are targeted by FL3. Knockdown of PHBs resembled FL3 treatment. Importantly, inhibition of translation controlled CLL development in vivo, either alone or combined with immunotherapy. Finally, high expression of translation initiation-related genes and PHBs genes correlated with poor survival and unfavorable clinical parameters in patients with CLL. Overall, we demonstrated that translation inhibition is a valuable strategy to control CLL development by blocking the translation of several oncogenic pathways including MYC. We also unraveled a new and direct role of PHBs in translation initiation, thus creating new therapeutic opportunities for patients with CLL.

Ibrutinib sensitizes CLL cells to venetoclax by interrupting TLR9-induced CD40 upregulation and protein translation

Chronic lymphocytic leukemia (CLL) cells upregulate Bcl-2 proteins within the lymph node (LN) microenvironment. Signaling via B-cell receptor, Toll-like receptors and CD40 collectively reduce sensitivity to the BCL-2 inhibitor venetoclax. Time-limited treatment with venetoclax plus the BTK-inhibitor ibrutinib results in deep remissions, but how this combination affects LN-related signaling is not yet completely clear. Therefore, samples obtained from the HOVON141/VISION phase 2 clinical trial were used to analyze this. Two cycles of lead-in ibrutinib monotherapy resulted in decreased protein expression of Bcl-2 proteins in circulating CLL cells. Strikingly, at this timepoint CD40-induced venetoclax resistance was strongly attenuated, as was expression of CD40. Since CD40 signaling occurs within the CLL LN, we tested various LN-related signals that could affect CD40 signaling. While BCR stimulation had only a minor effect, TLR9 stimulation via CpG led to significantly increased CD40 expression and importantly, reverted the effects of ibrutinib treatment on venetoclax sensitivity by inducing overall protein translation. Together, these findings identify a novel effect of ibrutinib: interruption of TLR9-induced CD40 upregulation and translation of pro-survival proteins. This mechanism may potentially further inhibit priming of CLL cells in the LN microenvironment for venetoclax resistance.

Extracellular Vesicles in Chronic Lymphocytic Leukemia: Tumor Microenvironment Messengers as a Basis for New Targeted Therapies?

In addition to intrinsic genomic and nongenomic alterations, tumor progression is also dependent on the tumor microenvironment (TME, mainly composed of the extracellular matrix (ECM), secreted factors, and bystander immune and stromal cells). In chronic lymphocytic leukemia (CLL), B cells have a defect in cell death; contact with the TME in secondary lymphoid organs dramatically increases the B cells' survival via the activation of various molecular pathways, including the B cell receptor and CD40 signaling. Conversely, CLL cells increase the permissiveness of the TME by inducing changes in the ECM, secreted factors, and bystander cells. Recently, the extracellular vesicles (EVs) released into the TME have emerged as key arbiters of cross-talk with tumor cells. The EVs' cargo can contain various bioactive substances (including metabolites, proteins, RNA, and DNA); upon delivery to target cells, these substances can induce intracellular signaling and drive tumor progression. Here, we review recent research on the biology of EVs in CLL. EVs have diagnostic/prognostic significance and clearly influence the clinical outcome of CLL; hence, from the perspective of blocking CLL-TME interactions, EVs are therapeutic targets. The identification of novel EV inhibitors might pave the way to the development of novel combination treatments for CLL and the optimization of currently available treatments (including immunotherapy).

Emerging Therapies in CLL in the Era of Precision Medicine

Over the past decade, the treatment landscape of CLL has vastly changed from the conventional FC (fludarabine and cyclophosphamide) and FCR (FC with rituximab) chemotherapies to targeted therapies, including inhibitors of Bruton tyrosine kinase (BTK) and phosphatidylinositol 3-kinase (PI3K) as well as inhibitors of BCL2. These treatment options dramatically improved clinical outcomes; however, not all patients respond well to these therapies, especially high-risk patients. Clinical trials of immune checkpoint inhibitors (PD-1, CTLA4) and chimeric antigen receptor T (CAR T) or NK (CAR NK) cell treatment have shown some efficacy; still, long-term outcomes and safety issues have yet to be determined. CLL remains an incurable disease. Thus, there are unmet needs to discover new molecular pathways with targeted or combination therapies to cure the disease. Large-scale genome-wide whole-exome and whole-genome sequencing studies have discovered genetic alterations associated with disease progression, refined the prognostic markers in CLL, identified mutations underlying drug resistance, and pointed out critical targets to treat the disease. More recently, transcriptome and proteome landscape characterization further stratified the disease and revealed novel therapeutic targets in CLL. In this review, we briefly summarize the past and present available single or combination therapies, focusing on potential emerging therapies to address the unmet clinical needs in CLL.

Discovery of orally active 1,4,5,6,8-pentaazaacenaphthylens as novel, selective, and potent covalent BTK inhibitors for the treatment of rheumatoid arthritis

Bruton's tyrosine kinase (BTK) plays a crucial role in adaptive and immune responses by modulating B-cell, Fc, toll-like, and chemokine receptor signaling pathways. BTK inhibition is a promising therapeutic approach for the treatment of inflammatory and autoimmune diseases. The development of novel, highly selective, and less toxic BTK inhibitors may be beneficial for the treatment of autoimmune diseases with unmet medical needs. In this study, structure-based drug design was used to discover a series of novel, potent, and selective covalent BTK inhibitors with a 1,4,5,6,8-pentaazaacenaphthylen scaffold. Among them, compound 36R exhibited high kinase selectivity, long target occupancy time, appropriate pharmacokinetic properties, and dose-dependent efficacy in a rat model of collagen-induced arthritis. Therefore, 36R is a novel BTK inhibitor requiring further development for the treatment of autoimmune diseases.

Current Status of Novel Agents for the Treatment of B Cell Malignancies: What's Coming Next?

Resistance to death is one of the hallmarks of human B cell malignancies and often contributes to the lack of a lasting response to today's commonly used treatments. Drug discovery approaches designed to activate the death machinery have generated a large number of inhibitors of anti-apoptotic proteins from the B-cell lymphoma/leukemia 2 family and the B-cell receptor (BCR) signaling pathway. Orally administered small-molecule inhibitors of Bcl-2 protein and BCR partners (e.g., Bruton's tyrosine kinase and phosphatidylinositol-3 kinase) have already been included (as monotherapies or combination therapies) in the standard of care for selected B cell malignancies. Agonistic monoclonal antibodies and their derivatives (antibody-drug conjugates, antibody-radioisotope conjugates, bispecific T cell engagers, and chimeric antigen receptor-modified T cells) targeting tumor-associated antigens (TAAs, such as CD19, CD20, CD22, and CD38) are indicated for treatment (as monotherapies or combination therapies) of patients with B cell tumors. However, given that some patients are either refractory to current therapies or relapse after treatment, novel therapeutic strategies are needed. Here, we review current strategies for managing B cell malignancies, with a focus on the ongoing clinical development of more effective, selective drugs targeting these molecules, as well as other TAAs and signaling proteins. The observed impact of metabolic reprogramming on B cell pathophysiology highlights the promise of targeting metabolic checkpoints in the treatment of these disorders.

Advances in Understanding of Metabolism of B-Cell Lymphoma: Implications for Therapy

There have been significant recent advances in the understanding of the role of metabolism in normal and malignant B-cell biology. Previous research has focused on the role of MYC and mammalian target of rapamycin (mTOR) and how these interact with B-cell receptor signaling and hypoxia to regulate glycolysis, glutaminolysis, oxidative phosphorylation (OXPHOS) and related metabolic pathways in germinal centers. Many of the commonest forms of lymphoma arise from germinal center B-cells, reflecting the physiological attenuation of normal DNA damage checkpoints to facilitate somatic hypermutation of the immunoglobulin genes. As a result, these lymphomas can inherit the metabolic state of their cell-of-origin. There is increasing interest in the potential of targeting metabolic pathways for anti-cancer therapy. Some metabolic inhibitors such as methotrexate have been used to treat lymphoma for decades, with several new agents being recently licensed such as inhibitors of phosphoinositide-3-kinase. Several other inhibitors are in development including those blocking mTOR, glutaminase, OXPHOS and monocarboxylate transporters. In addition, recent work has highlighted the importance of the interaction between diet and cancer, with particular focus on dietary modifications that restrict carbohydrates and specific amino acids. This article will review the current state of this field and discuss future developments.

Tipping the balance: toward rational combination therapies to overcome venetoclax resistance in mantle cell lymphoma

Mantle cell lymphoma (MCL), an aggressive, but incurable B-cell lymphoma, is genetically characterized by the t(11;14) translocation, resulting in the overexpression of Cyclin D1. In addition, deregulation of the B-cell lymphoma-2 (BCL-2) family proteins BCL-2, B-cell lymphoma-extra large (BCL-XL), and myeloid cell leukemia-1 (MCL-1) is highly common in MCL. This renders these BCL-2 family members attractive targets for therapy; indeed, the BCL-2 inhibitor venetoclax (ABT-199), which already received FDA approval for the treatment of chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML), shows promising results in early clinical trials for MCL. However, a significant subset of patients show primary resistance or will develop resistance upon prolonged treatment. Here, we describe the underlying mechanisms of venetoclax resistance in MCL, such as upregulation of BCL-XL or MCL-1, and the recent (clinical) progress in the development of inhibitors for these BCL-2 family members, followed by the transcriptional and (post-)translational (dys)regulation of the BCL-2 family proteins, including the role of the lymphoid organ microenvironment. Based upon these insights, we discuss how rational combinations of venetoclax with other therapies can be exploited to prevent or overcome venetoclax resistance and improve MCL patient outcome.