The lymph node microenvironment promotes B-cell receptor signaling, NF-kappaB activation, and tumor proliferation in chronic lymphocytic leukemia

"Accelerated" chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL): unraveling the biological gray zone of CLL/SLL in the era of novel therapies

Accelerated chronic lymphocytic leukemia/small lymphocytic lymphoma (A-CLL/SLL) is a histologically aggressive subtype of CLL/SLL that lies in between conventional CLL/SLL (C-CLL/SLL) and Richter transformation (RT) on the biological spectrum. Although the histologic criteria for A-CLL/SLL were defined 14 years ago, the clinical and genetic characteristics and survival outcomes of these patients have yet to be studied in the era of novel therapies. We retrospectively analyzed the clinicopathologic, genetic, and survival characteristics of 34 patients with confirmed tissue diagnosis of A-CLL/SLL and compared them with 120 patients with C-CLL/SLL. Patients with A-CLL/SLL had significantly higher frequencies of B-symptoms, anemia and thrombocytopenia, splenomegaly, higher LDH, and more advanced Rai stages. A-CLL/SLL showed a significantly higher frequency of TP53 mutations (55.0% vs. 11.5%;p < 0.0001) and deletions (38.2% vs. 8.3%;p < 0.0001), lower isolated del(13q) (5.8% vs. 27.5%;p < 0.0001), and increased incidence of RT (11.76% vs. 0.83%;p = 0.0025). The overall survival of patients with A-CLL/SLL was significantly lower than C-CLL/SLL (median survival: 6.17 years vs. not reached; 2 and 5-year survival rates: 75.5% vs. 94.7% and 53.3% vs. 93.7%, respectively; p < 0.0001); however, novel agents have improved the outcomes dramatically compared to the previously published data in the pre-BTKi era. Our results support the categorization of A-CLL/SLL as a distinct biologically aggressive subtype of CLL/SLL and highlight the need to revise the diagnostic criteria utilizing a multifaceted approach that integrates the overall pathobiological profile of the disease, in addition to the histology.

Molecular Mechanisms in the Transformation from Indolent to Aggressive B Cell Malignancies

Histological transformation (HT) into aggressive lymphoma is a turning point in a significant fraction of patients affected by indolent lymphoproliferative neoplasms, namely, chronic lymphocytic leukemia (CLL), follicular lymphoma (FL), marginal zone lymphomas (MZLs), and lymphoplasmacytic lymphoma (LPL) [...].

Targeting Tumor Microenvironment Interactions in Chronic Lymphocytic Leukemia Using Leukotriene Inhibitors

Chronic lymphocytic leukemia (CLL) cells depend on microenvironment niches for proliferation and survival. The adhesion of tumor cells to stromal cells in such niches triggers the activation of signaling pathways crucial for their survival, including B-cell receptor (BCR) signaling. While inhibitors of Bruton's tyrosine kinase (BTKi) have shown efficacy in patients with CLL by disrupting these interactions, acquired resistance and toxicity remain a challenge during long-term therapy. Thus, identifying additional therapeutic modalities is important. Previously, we demonstrated that 5-lipoxygenase (5-LOX) pathway inhibitors reduced mantle cell lymphoma (MCL) cell adhesion to stromal cells, motivating us to investigate their potential in the context of CLL. We employed an ex vivo co-culture model to study CLL cell adhesion to stromal cells in the absence and presence of 5-LOX pathway inhibitors (zileuton and MK886) as well as the BTKi ibrutinib that was included for comparative purposes. Our findings demonstrated that different CLL samples adhere to stromal cells differentially. We observed a variable decrease in CLL cell adhesion to stromal cells following the inhibition of the 5-LOX pathway across a spectrum of patient samples that was distinct to the spectrum for ibrutinib. Positive and negative correlations were shown between the clinical and genetic features of the CLL samples and their level of adherence to stromal cells in both the absence and presence of the tested inhibitors. These results suggest the 5-LOX pathway as a candidate for assessment as a new therapeutic target in CLL.

From development to clinical success: the journey of established and next-generation BTK inhibitors

Over the past decade, Bruton's tyrosine kinase (BTK) has emerged as a pivotal therapeutic target for B-cell malignancies and autoimmune diseases, given its essential role in B-cell development and function. Dysregulation of BTK signalling is implicated in a range of hematologic cancers, including Waldenström's macroglobulinaemia (WM), mantle cell lymphoma (MCL), and chronic lymphocytic leukaemia (CLL). The development of BTK inhibitors (BTKIs), starting with ibrutinib, has revolutionized the treatment of these malignancies by inhibiting B-cell receptor (BCR) signalling and inducing apoptosis in malignant B-cells. Despite the impressive clinical efficacy of ibrutinib, challenges such as resistance mutations and off-target effects remain. To address these issues, next-generation BTKIs, including acalabrutinib, orelabrutinib, zanubrutinib, and pirtobrutinib, have been developed, offering improved specificity and reduced toxicity profiles. This review highlights the therapeutic potential of BTK-targeted therapies in treating B-cell malignancies, discusses recent advancements with FDA-approved BTKIs, and explores the latest clinical outcomes from ongoing trials of novel inhibitors.

G-protein coupled receptor kinase-2 regulates the migration of chronic lymphocytic leukaemia cells to sphingosine-1 phosphate in vitro and their trafficking in vivo

Disease progression and drug resistance in patients with chronic lymphocytic leukaemia (CLL) depend on signals from the tumour microenvironment in lymphoid sites. GRK2 inhibits the egress of normal B cells from lymphoid tissues by inducing the downregulation of the S1P-receptor 1 (S1PR1). In this study we investigated the role of GRK2 in the context of CLL using in vitro and in vivo murine models, and also primary samples from CLL patients. We found that pharmacological inhibition of GRK2 enhanced the migration of leukemic cells from CLL patients towards S1P and impaired the S1P-induced downregulation of S1PR1. Likewise, CRISPR/Cas9-mediated GRK2 deletion in a murine leukemic cell line derived from the Eµ-TCL1 mouse model of CLL also increased migratory capacity toward S1P in vitro. Furthermore, when injected into mice, GRK2-deficient murine leukemic cells exhibited an altered in vivo localization, with a higher presence in the blood and spleen compared to the bone marrow. Within the spleen, these cells displayed reduced localization to the follicles compared to control murine leukemic cells. Deletion of GRK2 on murine leukemic cells did not affect their in vitro proliferation, but notably, conferred a growth disadvantage in vivo. These findings underscore GRK2 as a critical regulator of the localization of CLL cells in vivo and suggest its potential as a therapeutic target to disrupt survival niches in CLL.

Normal Residual Lymphoid Cell Populations in Blood as Surrogate Biomarker of the Leukemia Cell Kinetics in CLL BinetA/Rai 0

BACKGROUND/OBJECTIVES

Despite the current international prognostic index for chronic lymphocytic leukemia (CLL) being widely accepted and broadly used, it does not consider the kinetics of the B-cell clone over time. Here, we investigated the potential association between distinct features of leukemic cells and other immune cells in blood and the kinetics of clonal B-cells in CLL stage Binet A/Rai 0 (A/0) patients; Methods: Based on the leukemia cell kinetics, 69 CLL A/0 cases followed for a median of 105 months were classified as carrying stable (n = 53) vs. rapidly increasing in size (n = 16) CLL clones; Results: Patients with increasing CLL clones had a significantly higher risk of disease progression and shortened time to first therapy vs. those carrying stable B-cell clones (p ≤ 0.001). Strikingly, the distribution of various immune-cell populations in blood at diagnosis also differed significantly between the two groups, with lower Tαβ CD4+CD8lo cell counts (p = 0.03), a greater switched/unswitched memory B-cell ratio (p = 0.01), and higher plasma cell counts (p = 0.05) in CLL with increasing vs. stable clones. Multivariate analysis revealed that the number of circulating clonal B-cells (≥15 × 109/L) and Tαβ CD4+CD8lo cells (≤35 cells/µL), together with an IGHV unmutated gene status at diagnosis, were independent predictors of an increasing CLL clone; Conclusions: Altogether, these data suggest that the expansion of the CLL clone in stage A/0 patients may depend on both the intrinsic characteristics of CLL cells and the surrounding immune microenvironment.

JNK1 inhibitors target distal B cell receptor signaling and overcome BTK-inhibitor resistance in CLL

Inhibition of the proximal B cell receptor (BCR) signaling pathway by BTK inhibitors is highly effective in the treatment of CLL, but drug resistance or intolerance occurs. Here, we investigated c-Jun N-terminal protein kinase 1 (JNK1) as an alternative drug target in the distal BCR pathway. JNK1 was preferentially overexpressed and activated in poor prognostic CLL with unmutated IGHV. Proximal BCR inhibition (BTK, PI3K, or SYK inhibitors) or SYK knockdown efficiently dephosphorylated JNK1, identifying JNK1 as a critical BCR downstream kinase in CLL. JNK1 inhibition induced apoptosis in primary CLL cells, resulting in the downregulation of BCL2, MCL1, and c-JUN. JNK1 inhibition in patient-derived CLL xenografted mice and Eµ-TCL1-tg mice prevented CLL progression, reduced splenic infiltration, and restored T cell function and normal hematopoiesis. JNK1 inhibitors even remained effective in ibrutinib refractory CLL. In conclusion, our study revealed JNK1 as a promising drug target in CLL downstream of the BCR, overcoming ibrutinib resistance, blocking the protective microenvironment, and improving CLL-specific immunosuppressive mechanisms.

In Vitro 3D Models of Haematological Malignancies: Current Trends and the Road Ahead?

Haematological malignancies comprise a diverse group of life-threatening systemic diseases, including leukaemia, lymphoma, and multiple myeloma. Currently available therapies, including chemotherapy, immunotherapy, and CAR-T cells, are often associated with important side effects and with the development of drug resistance and, consequently, disease relapse. In the last decades, it was largely demonstrated that the tumor microenvironment significantly affects cancer cell proliferation and tumor response to treatment. The development of biomimetic, in vitro models may promote the investigation of the interactions between cancer cells and the tumor microenvironment and may help to better understand the mechanisms leading to drug resistance. Although advanced in vitro models have been largely explored in the field of solid tumors, due to the complex nature of the blood cancer tumor microenvironment, the mimicking of haematological malignancies mostly relies on simpler systems, often limited to two-dimensional cell culture, which intrinsically excludes the microenvironmental niche, or to ethically debated animal models. This review aims at reporting an updated overview of state-of-the-art hematological malignancies 3D in vitro models, emphasizing the key features and limitations of existing systems to inspire further research in this underexplored field.

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.

Research progress on the mechanism of common inflammatory pathways in the pathogenesis and development of lymphoma

In recent years, the incidence and mortality rates of lymphoma have gradually increased worldwide. Tumorigenesis and drug resistance are closely related to intracellular inflammatory pathways in lymphoma. Therefore, understanding the biological role of inflammatory pathways and their abnormal activation in relation to the development of lymphoma and their selective modulation may open new avenues for targeted therapy of lymphoma. The biological functions of inflammatory pathways are extensive, and they are central hubs for regulating inflammatory responses, immune responses, and the tumour immune microenvironment. However, limited studies have investigated the role of inflammatory pathways in lymphoma development. This review summarizes the relationship between abnormal activation of common inflammatory pathways and lymphoma development to identify precise and efficient targeted therapeutic options for patients with advanced, drug-resistant lymphoma.

CD38/NAD+ glycohydrolase and associated antigens in chronic lymphocytic leukaemia: From interconnected signalling pathways to therapeutic strategies

Chronic lymphocytic leukaemia (CLL) is a heterogenous disease characterized by the accumulation of neoplastic CD5+/CD19+ B lymphocytes. The spreading of the leukaemia relies on the CLL cell's ability to survive in the blood and migrate to and proliferate within the bone marrow and lymphoid tissues. Some patients with CLL are either refractory to the currently available therapies or relapse after treatment; this emphasizes the need for novel therapeutic strategies that improving clinical responses and overcome drug resistance. CD38 is a marker of a poor prognosis and governs a set of survival, proliferation and migration signals that contribute to the pathophysiology of CLL. The literature data evidence a spatiotemporal association between the cell surface expression of CD38 and that of other CLL antigens, such as the B-cell receptor (BCR), CD19, CD26, CD44, the integrin very late antigen 4 (VLA4), the chemokine receptor CXCR4, the vascular endothelial growth factor receptor-2 (VEGF-R2), and the neutrophil gelatinase-associated lipocalin receptor (NGAL-R). Most of these proteins contribute to CLL cell survival, proliferation and trafficking, and cooperate with CD38 in multilayered signal transduction processes. In general, these antigens have already been validated as therapeutic targets in cancer, and a broad repertoire of specific monoclonal antibodies and derivatives are available. Here, we review the state of the art in this field and examine the therapeutic opportunities for cotargeting CD38 and its partners in CLL, e.g. by designing novel bi-/trispecific antibodies.

Proliferating CLL cells express high levels of CXCR4 and CD5

Chronic lymphocytic leukemia (CLL) is an incurable progressive malignancy of CD5+ B cells with a birth rate between 0.1% and 1% of the entire clone per day. However, the phenotype and functional characteristics of proliferating CLL cells remain incompletely understood. Here, we stained peripheral blood CLL cells for ki67 and DNA content and found that CLL cells in G1-phase have a CXCR4loCD5hi phenotype, while CLL cells in S/G2/M-phase express high levels of both CXCR4 and CD5. Induction of proliferation in vitro using CD40L stimulation results in high ki67 levels in CXCR4loCD5hi cells with CXCR4 expression increasing as CLL cells progress through S and G2/M-phases, while CXCR4hiCD5lo CLL cells remained quiescent. Dye dilution experiments revealed an accumulation of Ki67hi-divided cells in the CXCR4hiCD5hi fraction. In Eµ-TCL1 transgenic mice, the CXCR4hiCD5hi fraction expressed high levels of ki67 and was expanded in enlarged spleens of diseased animals. Human peripheral blood CXCR4hiCD5hi CLL cells express increased levels of IgM and the chemokine receptors CCR7 and CXCR5 and migrate efficiently toward CCL21. We found higher levels of CXCR4 in patients with progressive disease and the CXCR4hiCD5hi fraction was expanded upon clinical relapse. Thus, this study defines the phenotype and functional characteristics of dividing CLL cells identifying a novel subclonal population that underlies CLL pathogenesis and may drive clinical outcomes.

Highly sensitive electrochemical multimodal immunosensor for cluster of differentiation 5 (CD5) detection in human blood serum for early stage cancer detection based on laser-processed Ti/Au electrodes

In the rapidly evolving field of medical diagnostics, biomarkers play a pivotal role, particularly in the early detection of cancer. Cluster of differentiation 5 (CD5), a cell surface glycoprotein found on T cells and B-1a lymphocytes, is instrumental in immune regulation and is associated with both autoimmune diseases and malignancies. Despite its significant diagnostic and therapeutic potential, CD5 detection has been limited by modern methods in the pg/ml range. This study presents a novel multimodal electrochemical immunosensor that employs laser-processed Ti/Au electrodes for the ultra-sensitive detection of CD5 in human blood serum. The "multimodal" approach combines different analytical techniques - differential pulse volctammetry (DPV) and electrochemical impedance spectroscopy (EIS) - to ensure comprehensive analysis, enhancing both the accuracy and reliability of the sensor. This novel sensor significantly outperforms existing commercial ELISA kits, achieving a limit of detection (LOD) of 1.1 ± 0.2 fg/mL with DPV and 3.9 ± 0.5 fg/mL with EIS in phosphate-buffered saline (PBS) and 6.6 ± 3.1 fg/mL and 15.6 ± 3.1 fg/mL in human serum (HS), respectively. These results highlight the immunosensor's potential for improving early-stage cancer diagnosis and broader medical applications.

Overview on Immunopathology of Chronic Lymphocytic Leukemia and Tumor-Associated Antigens with Therapeutic Applications

Chronic Lymphocytic Leukemia (CLL) is a clinically and biologically heterogeneous disease with a variable clinical course. The induction of a generalized state of immuno-suppression, leading to susceptibility to infections and the failure of anti-tumor immune responses, is a key feature of the clinical course of CLL. In addition to B-cell receptor (BCR) signaling in CLL, several receptor tyrosine kinases (RTKs) have been reported to be constitutively active in leukemic B cells, resulting in promoted survival and resistance to apoptosis induced by chemotherapy. Several treatment options are available for CLL, including a watch-and-wait strategy, chemotherapy, targeted therapies, immunotherapies such as adoptive cellular therapy (CAR T-Cell Therapy), stem cell transplantation (allogeneic transplantation), radiation therapy and surgery. The identification of Tumor-Associated Antigens (TAAs) is the bottleneck of tumor immunology and immunotherapy, serving as promising targets for precise diagnosis, monitoring, or therapeutic approaches. Numerous TAAs have been identified, and their application in immunotherapy holds promise for the treatment of CLL. Furthermore, extensive ongoing research aims to identify new cancer TAAs. In this review, our objective is to provide a comprehensive overview of CLL immunology and recent findings regarding advances in TAAs with therapeutic applications in CLL.

Targeted protein degradation in hematologic malignancies: clinical progression towards novel therapeutics

Targeted therapies, such as small molecule kinase inhibitors, have made significant progress in the treatment of hematologic malignancies by directly modulating protein activity. However, issues such as drug toxicity, drug resistance due to target mutations, and the absence of key active sites limit the therapeutic efficacy of these drugs. Targeted protein degradation (TPD) presents an emergent and rapidly evolving therapeutic approach that selectively targets proteins of interest (POI) based on endogenous degradation processes. With an event-driven pharmacology of action, TPD achieves efficacy with catalytic amounts, avoiding drug-related toxicity. Furthermore, TPD has the unique mode of degrading the entire POI, such that resistance derived from mutations in the targeted protein has less impact on its degradation function. Proteolysis-targeting chimeras (PROTACs) and molecular glue degraders (MGDs) are the most maturely developed TPD techniques. In this review, we focus on both preclinical experiments and clinical trials to provide a comprehensive summary of the safety and clinical effectiveness of PROTACs and MGDs in hematologic malignancies over the past two decades. In addition, we also delineate the challenges and opportunities associated with these burgeoning degradation techniques. TPD, as an approach to the precise degradation of specific proteins, provides an important impetus for its future application in the treatment of patients with hematologic malignancies.

Stromal cells engineered to express T cell factors induce robust CLL cell proliferation in vitro and in PDX co-transplantations allowing the identification of RAF inhibitors as anti-proliferative drugs

Several in vitro models have been developed to mimic chronic lymphocytic leukemia (CLL) proliferation in immune niches; however, they typically do not induce robust proliferation. We prepared a novel model based on mimicking T-cell signals in vitro and in patient-derived xenografts (PDXs). Six supportive cell lines were prepared by engineering HS5 stromal cells with stable expression of human CD40L, IL4, IL21, and their combinations. Co-culture with HS5 expressing CD40L and IL4 in combination led to mild CLL cell proliferation (median 7% at day 7), while the HS5 expressing CD40L, IL4, and IL21 led to unprecedented proliferation rate (median 44%). The co-cultures mimicked the gene expression fingerprint of lymph node CLL cells (MYC, NFκB, and E2F signatures) and revealed novel vulnerabilities in CLL-T-cell-induced proliferation. Drug testing in co-cultures revealed for the first time that pan-RAF inhibitors fully block CLL proliferation. The co-culture model can be downscaled to five microliter volume for large drug screening purposes or upscaled to CLL PDXs by HS5-CD40L-IL4 ± IL21 co-transplantation. Co-transplanting NSG mice with purified CLL cells and HS5-CD40L-IL4 or HS5-CD40L-IL4-IL21 cells on collagen-based scaffold led to 47% or 82% engraftment efficacy, respectively, with ~20% of PDXs being clonally related to CLL, potentially overcoming the need to co-transplant autologous T-cells in PDXs.

MD-1 downregulation is associated with reduced cell surface CD180 expression in CLL

CD180 is a toll-like receptor that is highly expressed in complex with the MD-1 satellite molecule on the surface of B cells. In chronic lymphocytic leukaemia (CLL) however, the expression of CD180 is highly variable and overall, significantly reduced when compared to normal B cells. We have recently shown that reduced CD180 expression in CLL lymph nodes is associated with inferior overall survival. It was therefore important to better understand the causes of this downregulation through investigation of CD180 at the transcriptional and protein expression levels. Unexpectedly, we found CD180 RNA levels in CLL cells (n = 26) were comparable to those of normal B cells (n = 13), despite heterogeneously low expression of CD180 on the cell surface. We confirmed that CD180 RNA is translated into CD180 protein since cell surface CD180-negative cases presented with high levels of intracellular CD180 expression. Levels of MD-1 RNA were, however, significantly downregulated in CLL compared to normal controls. Together, these data suggest that changes in CD180 cell surface expression in CLL are not due to transcriptional downregulation, but defective post-translational stabilisation of the receptor due to MD-1 downregulation.

B cell receptor signaling proteins as biomarkers for progression of CLL requiring first-line therapy

The molecular landscape of chronic lymphocytic leukemia (CLL) has been extensively characterized, and various potent prognostic biomarkers were discovered. The genetic composition of the B-cell receptor (BCR) immunoglobulin (IG) was shown to be especially powerful for discerning indolent from aggressive disease at diagnosis. Classification based on the IG heavy chain variable gene (IGHV) somatic hypermutation status is routinely applied. Additionally, BCR IGH stereotypy has been implicated to improve risk stratification, through characterization of subsets with consistent clinical profiles. Despite these advances, it remains challenging to predict when CLL progresses to requiring first-line therapy, thus emphasizing the need for further refinement of prognostic indicators. Signaling pathways downstream of the BCR are essential in CLL pathogenesis, and dysregulated components within these pathways impact disease progression. Considering not only genomics but the entirety of factors shaping BCR signaling activity, this review offers insights in the disease for better prognostic assessment of CLL.

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.

The malignant transformation potential of the oncogene STYK1/NOK at early lymphocyte development in transgenic mice

B-cell Chronic Lymphocytic Leukemia (B-CLL) is a malignancy caused by the clonal expansion of mature B lymphocytes bearing a CD5+CD19+ (B1) phenotype. However, the origin of B-CLL remains controversial. We showed previously that STYK1/NOK transgenic mice develop a CLL-like disease. Using this model system in this study, we attempt to define the stage of CLL initiation. Here, we show that the phenotype of STYK1/NOK-induced B-CLL is heterogeneous. The expanded B1 lymphocyte pool was detected within peripheral lymphoid organs and was frequently associated with the expansions of memory B cells. Despite this immunophenotypic heterogeneity, suppression of B cell development at an early stage consistently occurred within the bone marrow (BM) of STYK1/NOK-tg mice. Overall, we suggest that enforced expression of STYK1/NOK in transgenic mice might significantly predispose BM hematopoietic stem cells (HSCs) towards the development of B-CLL.

Long-term follow up of the combination of ofatumumab, high-dose methylprednisolone, and lenalidomide for untreated chronic lymphocytic leukemia with biomarker analysis

BACKGROUND

Advancements in frontline therapy and chemotherapy-sparing treatments in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) have altered the treatment algorithms of this disease. We present a frontline alternative for treatment- naïve (TN) CLL/SLL patients.

METHODS

This was a single-center, phase 2 study of high-dose methylprednisolone (HDMP) and ofatumumab with lenalidomide and ofatumumab consolidative therapy for all comers with TN CLL/SLL. Treatment was continued until disease progression or intolerable side effects. Patients were assessed for response per iwCLL 2008 criteria after completing cycles 3 and 12.

RESULTS

Forty-five patients were enrolled (median age, 62.6 years). High-risk features included del17p (18%), Del11q (22%), and unmutated IGHV gene (76%). Median treatment duration was 32·2 (2·7-75·9) months. Thirty-six patients discontinued treatment due to disease progression (22%), adverse events (40%), allogeneic hematopoietic cell transplantation (allo-HCT) (7%), consent withdrawal (4%), and secondary malignancies (7%). The best overall and complete response rates were 96& and 29% respectively. At median follow-up of 61·7 (5·6-84·9) months, 9 patients remained on treatment. Median progression-free survival was 54·4 (2·9-77·6) months. Three patients underwent allo-HCT after a median of 3 (3-4) treatment cycles. Treatment was well tolerated, with a grade 3/4 infusion reaction in one patient. The most common grade 3/4 hematological adverse event was neutropenia (69%). Four patients had grade 3/4 infections. No grade 3/4 tumor flares, tumor lysis syndrome, or thrombosis were observed.

CONCLUSION

The combination of ofatumumab, HDMP, and lenalidomide was effective and relatively well tolerated in treatment-naive CLL/SLL. Its role in the frontline setting remains unclear given the current available and effective treatment options.

FUNDING

The funders had no role in the study.

IκBε deficiency accelerates disease development in chronic lymphocytic leukemia

The NFKBIE gene, which encodes the NF-κB inhibitor IκBε, is mutated in 3-7% of patients with chronic lymphocytic leukemia (CLL). The most recurrent alteration is a 4-bp frameshift deletion associated with NF-κB activation in leukemic B cells and poor clinical outcome. To study the functional consequences of NFKBIE gene inactivation, both in vitro and in vivo, we engineered CLL B cells and CLL-prone mice to stably down-regulate NFKBIE expression and investigated its role in controlling NF-κB activity and disease expansion. We found that IκBε loss leads to NF-κB pathway activation and promotes both migration and proliferation of CLL cells in a dose-dependent manner. Importantly, NFKBIE inactivation was sufficient to induce a more rapid expansion of the CLL clone in lymphoid organs and contributed to the development of an aggressive disease with a shortened survival in both xenografts and genetically modified mice. IκBε deficiency was associated with an alteration of the MAPK pathway, also confirmed by RNA-sequencing in NFKBIE-mutated patient samples, and resistance to the BTK inhibitor ibrutinib. In summary, our work underscores the multimodal relevance of the NF-κB pathway in CLL and paves the way to translate these findings into novel therapeutic options.

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.

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.

Novel Spirocyclic Dimer, SpiD3, Targets Chronic Lymphocytic Leukemia Survival Pathways with Potent Preclinical Effects

Chronic lymphocytic leukemia (CLL) cell survival and growth is fueled by the induction of B-cell receptor (BCR) signaling within the tumor microenvironment (TME) driving activation of NFκB signaling and the unfolded protein response (UPR). Malignant cells have higher basal levels of UPR posing a unique therapeutic window to combat CLL cell growth using pharmacologic agents that induce accumulation of misfolded proteins. Frontline CLL therapeutics that directly target BCR signaling such as Bruton tyrosine kinase (BTK) inhibitors (e.g., ibrutinib) have enhanced patient survival. However, resistance mechanisms wherein tumor cells bypass BTK inhibition through acquired BTK mutations, and/or activation of alternative survival mechanisms have rendered ibrutinib ineffective, imposing the need for novel therapeutics. We evaluated SpiD3, a novel spirocyclic dimer, in CLL cell lines, patient-derived CLL samples, ibrutinib-resistant CLL cells, and in the Eµ-TCL1 mouse model. Our integrated multi-omics and functional analyses revealed BCR signaling, NFκB signaling, and endoplasmic reticulum stress among the top pathways modulated by SpiD3. This was accompanied by marked upregulation of the UPR and inhibition of global protein synthesis in CLL cell lines and patient-derived CLL cells. In ibrutinib-resistant CLL cells, SpiD3 retained its antileukemic effects, mirrored in reduced activation of key proliferative pathways (e.g., PRAS, ERK, MYC). Translationally, we observed reduced tumor burden in SpiD3-treated Eµ-TCL1 mice. Our findings reveal that SpiD3 exploits critical vulnerabilities in CLL cells including NFκB signaling and the UPR, culminating in profound antitumor properties independent of TME stimuli.

SIGNIFICANCE

SpiD3 demonstrates cytotoxicity in CLL partially through inhibition of NFκB signaling independent of tumor-supportive stimuli. By inducing the accumulation of unfolded proteins, SpiD3 activates the UPR and hinders protein synthesis in CLL cells. Overall, SpiD3 exploits critical CLL vulnerabilities (i.e., the NFκB pathway and UPR) highlighting its use in drug-resistant CLL.

Profiling the activity of the para-caspase MALT1 in B-cell acute lymphoblastic leukemia for potential targeted therapeutic application

B-cell acute lymphoblastic leukemia (B-ALL) remains a hard-to-treat disease with a poor prognosis in adults. Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a para-caspase required for B-cell receptor (BCR)-mediated NF-κB activation. Inhibition of MALT1 in preclinical models has proven efficacious in many B-cell malignancies including chronic lymphocytic leukemia, mantle cell lymphoma and diffuse large B-cell lymphoma. We sought to examine the role of MALT1 in B-ALL and determine the biological consequences of its inhibition. Targeting MALT1 with both Z-VRPR-fmk and MI-2 efficiently kills B-ALL cells independent of the cell-of-origin (pro, pre, mature) or the presence of the Philadelphia chromosome, and spares normal B cells. The mechanism of cell death was through apoptotic induction, mostly in cycling cells. The proteolytic activity of MALT1 can be studied by measuring its ability to cleave its substrates. Surprisingly, with the exception of mature B-ALL, we did not detect cleavage of MALT1 substrates at baseline, nor after proteasomal inhibition or following activation of pre-BCR. To explore the possibility of a distinct role for MALT1 in B-ALL, independent of signaling through BCR, we studied the changes in gene expression profiling following a 24-hour treatment with MI-2 in 12 B-ALL cell lines. Our transcriptome analysis revealed a strong inhibitory effect on MYC-regulated gene signatures, further confirmed by Myc protein downregulation, concomitant with an increase in the Myc degrader FBXW7. In conclusion, our evidence suggests a novel role for MALT1 in B-ALL through Myc regulation and provides support for clinical testing of MALT1 inhibitors in B-ALL.

Potential New Therapies "ROS-Based" in CLL: An Innovative Paradigm in the Induction of Tumor Cell Apoptosis

Chronic lymphocytic leukemia, in spite of recent advancements, is still an incurable disease; the majority of patients eventually acquire resistance to treatment through relapses. In all subtypes of chronic lymphocytic leukemia, the disruption of normal B-cell homeostasis is thought to be mostly caused by the absence of apoptosis. Consequently, apoptosis induction is crucial to the management of this illness. Damaged biological components can accumulate as a result of the oxidation of intracellular lipids, proteins, and DNA by reactive oxygen species. It is possible that cancer cells are more susceptible to apoptosis because of their increased production of reactive oxygen species. An excess of reactive oxygen species can lead to oxidative stress, which can harm biological elements like DNA and trigger apoptotic pathways that cause planned cell death. In order to upset the balance of oxidative stress in cells, recent therapeutic treatments in chronic lymphocytic leukemia have focused on either producing reactive oxygen species or inhibiting it. Examples include targets created in the field of nanomedicine, natural extracts and nutraceuticals, tailored therapy using biomarkers, and metabolic targets. Current developments in the complex connection between apoptosis, particularly ferroptosis and its involvement in epigenomics and alterations, have created a new paradigm.

B cell receptor signaling and associated pathways in the pathogenesis of chronic lymphocytic leukemia

B cell antigen receptor (BCR) signaling is a key driver of growth and survival in both normal and malignant B cells. Several lines of evidence support an important pathogenic role of the BCR in chronic lymphocytic leukemia (CLL). The significant improvement of CLL patients' survival with the use of various BCR pathway targeting inhibitors, supports a crucial involvement of BCR signaling in the pathogenesis of CLL. Although the treatment landscape of CLL has significantly evolved in recent years, no agent has clearly demonstrated efficacy in patients with treatment-refractory CLL in the long run. To identify new drug targets and mechanisms of drug action in neoplastic B cells, a detailed understanding of the molecular mechanisms of leukemic transformation as well as CLL cell survival is required. In the last decades, studies of genetically modified CLL mouse models in line with CLL patient studies provided a variety of exciting data about BCR and BCR-associated kinases in their role in CLL pathogenesis as well as disease progression. BCR surface expression was identified as a particularly important factor regulating CLL cell survival. Also, BCR-associated kinases were shown to provide a crosstalk of the CLL cells with their tumor microenvironment, which highlights the significance of the cells' milieu in the assessment of disease progression and treatment. In this review, we summarize the major findings of recent CLL mouse as well as patient studies in regard to the BCR signalosome and discuss its relevance in the clinics.

miR-17-92 cluster-BTG2 axis regulates B-cell receptor signaling in mantle cell lymphoma

B-cell receptor (BCR) signaling is critically activated and stable for mantle cell lymphoma (MCL), but the underlying mechanism of the activated BCR signaling pathway is not clear. The pathogenic basis of miR-17-92 cluster remains unclear although the oncogenic microRNA (miRNA) miR-17-92 cluster is highly expressed in patients with MCL. We revealed that miR-17-92 cluster overexpression is partly dependent on SOX11 expression and chromatin acetylation of MIR17HG enhancer regions. Moreover, miR-17-92 cluster regulates not only cell proliferation but BCR signaling activation in MCL cell lines. To comprehensively identify miR-17-92 cluster target genes, we performed pulldown-seq, where target RNA of miRNA was captured using the biotinylated miRNA mimics and magnetic bead-coated streptavidin, and quantified using next-generation sequencing. The pulldown-seq identified novel miRNA target genes, including tumor suppressors such as BTG2 (miR-19b), CDKN2A (miR-17), SYNE1 (miR-20a), TET2 (miR-18, miR-19b, and miR-92a), TNFRSF10A (miR-92a), and TRAF3 (miR-17). Notably, the gene expression profile data of patients with MCL revealed that BTG2 expression was negatively associated with that of BCR signature genes, and low BTG2 expression was associated with poor overall survival. Moreover, BTG2 silencing in MCL cell lines significantly induced BCR signaling overactivation and cell proliferation. Our results suggest an oncogenic role of miR-17-92 cluster-activating BCR signaling throughout BTG2 deregulation in MCL. Furthermore, this may contribute to the prediction of the therapeutic efficacy and improved outcomes of MCL.

Treatment of Double-Refractory Chronic Lymphocytic Leukemia-An Unmet Clinical Need

Recent years have seen significant improvement in chronic lymphocytic leukemia (CLL) management. Targeting B-cell lymphoma (BCL-2) and Bruton's kinase (BTK) have become the main strategies to restrain CLL activity. These agents are generally well tolerated, but the discontinuation of these therapies happens due to resistance, adverse effects, and Richter's transformation. A growing population of patients who have previously used both BTK inhibitors and BCL2 suffer from the constriction of the following regimens. This review explores the resistance mechanisms for both ibrutinib and venetoclax. Moreover, we present innovative approaches evaluated for treating double-refractory CLL.

Screening and Characterization of Allosteric Small Molecules Targeting Bruton's Tyrosine Kinase

Bruton's Tyrosine Kinase (BTK) is a nonreceptor tyrosine kinase that belongs to the TEC family. Mutations in the BTK gene cause X-linked agammaglobulinemia (XLA) leading to an arrest in B-cell development. BTK is also a drug target for B-cell lymphomas that rely on an intact B-cell receptor signaling cascade for survival. All FDA approved drugs for BTK target the ATP binding site of the catalytic kinase domain, leading to potential adverse events due to off-target inhibition. In addition, acquired resistance mutations occur in a subset of patients, rendering available BTK inhibitors ineffective. Therefore, allosteric sites on BTK should be explored for drug development to target BTK more specifically and in combination with active site inhibitors. Virtual screening against nonactive site pockets and in vitro experiments resulted in a series of small molecules that bind to BTK outside of the active site. We characterized these compounds using biochemical and biophysical techniques and narrowed our focus to compound "C2". C2 activates full-length BTK and smaller multidomain BTK fragments but not the isolated kinase domain, consistent with an allosteric mode of action. Kinetic experiments reveal a C2-mediated decrease in Km and an increase in kcat leading to an overall increase in the catalytic efficiency of BTK. C2 is also capable of activating the BTK XLA mutants. These proof-of-principle data reveal that BTK can be targeted allosterically with small molecules, providing an alternative to active site BTK inhibitors.

Can Galectin-3 Be a Novel Biomarker in Chronic Lymphocytic Leukemia?

Galectin-3's (Gal-3) effect on the pathogenesis of chronic lymphocytic leukemia (CLL) has not yet been extensively studied. The present study aims to analyze the potential role of Gal-3 as a prognostic biomarker in CLL patients. The Gal-3 expression was evaluated in CLL cells with RT-qPCR and flow cytometry. Due to the unclear clinical significance of soluble Gal-3 in CLL, our goal was also to assess the prognostic value of Gal-3 plasma level. Because cell survival is significantly affected by the interaction between Gal-3 and proteins such as Bcl-2, the results of Gal-3 expression analysis were also compared with the expression of Bcl-2. The results were analyzed for known prognostic factors, clinical data, and endpoints such as time to first treatment and overall survival time. Our research confirmed that Gal-3 is detected in and on CLL cells. However, using Gal-3 as a potential biomarker in CLL is challenging due to the significant heterogeneity in its expression in CLL cells. Moreover, our results revealed that Gal-3 mRNA expression in leukemic B cells is associated with the expression of proliferation markers (Ki-67 and PCNA) as well as anti-apoptotic protein Bcl-2 and can play an important role in supporting CLL cells.

Single-cell functional genomics reveals determinants of sensitivity and resistance to natural killer cells in blood cancers

Cancer cells can evade natural killer (NK) cell activity, thereby limiting anti-tumor immunity. To reveal genetic determinants of susceptibility to NK cell activity, we examined interacting NK cells and blood cancer cells using single-cell and genome-scale functional genomics screens. Interaction of NK and cancer cells induced distinct activation and type I interferon (IFN) states in both cell types depending on the cancer cell lineage and molecular phenotype, ranging from more sensitive myeloid to less sensitive B-lymphoid cancers. CRISPR screens in cancer cells uncovered genes regulating sensitivity and resistance to NK cell-mediated killing, including adhesion-related glycoproteins, protein fucosylation genes, and transcriptional regulators, in addition to confirming the importance of antigen presentation and death receptor signaling pathways. CRISPR screens with a single-cell transcriptomic readout provided insight into underlying mechanisms, including regulation of IFN-γ signaling in cancer cells and NK cell activation states. Our findings highlight the diversity of mechanisms influencing NK cell susceptibility across different cancers and provide a resource for NK cell-based therapies.

mTORC1-selective activation of translation elongation promotes disease progression in chronic lymphocytic leukemia

Targeted deletion of Raptor, a component of mechanistic target of rapamycin complex 1 (mTORC1), reveals an essential role for mTORC1 in initiation/maintenance of leukemia in a CLL model, resulting from a failure for haemopoietic stem/progenitor cells (HSPCs) to commit to the B cell lineage. Induction of Raptor-deficiency in NSG mice transplanted with Mx1-Raptor CLL progenitor cells (PKCα-KR-transduced HSPCs) after disease establishment revealed a reduction in CLL-like disease load and a significant increase in survival in the mice. Interestingly in an aggressive CLL-like disease model, rapamycin treatment reduced disease burden more effectively than AZD2014 (dual mTORC1/2 inhibitor), indicating a skew towards mTORC1 sensitivity with more aggressive disease. Rapamycin, but not ibrutinib, efficiently targeted the eEF2/eEF2K translation elongation regulatory axis, downstream of mTORC1, resulting in eEF2 inactivation through induction of eEF2T56 phosphorylation. mTOR inhibitor treatment of primary patient CLL cells halted proliferation, at least in part through modulation of eEF2K/eEF2 phosphorylation and expression, reduced protein synthesis and inhibited expression of MCL1, Cyclin A and Cyclin D2. Our studies highlight the importance of translation elongation as a driver of disease progression and identify inactivation of eEF2 activity as a novel therapeutic target for blocking CLL progression.

EGR1-mediated metabolic reprogramming to oxidative phosphorylation contributes to ibrutinib resistance in B-cell lymphoma

The use of Bruton tyrosine kinase inhibitors, such as ibrutinib, to block B-cell receptor signaling has achieved a remarkable clinical response in several B-cell malignancies, including mantle cell lymphoma (MCL) and diffuse large B-cell lymphoma (DLBCL). Acquired drug resistance, however, is significant and affects the long-term survival of these patients. Here, we demonstrate that the transcription factor early growth response gene 1 (EGR1) is involved in ibrutinib resistance. We found that EGR1 expression is elevated in ibrutinib-resistant activated B-cell-like subtype DLBCL and MCL cells and can be further upregulated upon ibrutinib treatment. Genetic and pharmacological analyses revealed that overexpressed EGR1 mediates ibrutinib resistance. Mechanistically, TCF4 and EGR1 self-regulation induce EGR1 overexpression that mediates metabolic reprogramming to oxidative phosphorylation (OXPHOS) through the transcriptional activation of PDP1, a phosphatase that dephosphorylates and activates the E1 component of the large pyruvate dehydrogenase complex. Therefore, EGR1-mediated PDP1 activation increases intracellular adenosine triphosphate production, leading to sufficient energy to enhance the proliferation and survival of ibrutinib-resistant lymphoma cells. Finally, we demonstrate that targeting OXPHOS with metformin or IM156, a newly developed OXPHOS inhibitor, inhibits the growth of ibrutinib-resistant lymphoma cells both in vitro and in a patient-derived xenograft mouse model. These findings suggest that targeting EGR1-mediated metabolic reprogramming to OXPHOS with metformin or IM156 provides a potential therapeutic strategy to overcome ibrutinib resistance in relapsed/refractory DLBCL or MCL.

Factors associated with long-term outcomes of CD19 CAR T-cell therapy for relapsed/refractory CLL

High response rates have been reported after CD19-targeted chimeric antigen receptor-modified (CD19 CAR) T-cell therapy for relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL), yet the factors associated with duration of response in this setting are poorly characterized. We analyzed long-term outcomes in 47 patients with R/R CLL and/or Richter transformation treated on our phase 1/2 clinical trial of CD19 CAR T-cell therapy with an updated median follow-up of 79.6 months. Median progression-free survival (PFS) was 8.9 months, and the 6-year PFS was 17.8%. Maximum standardized uptake value (hazard ratio [HR], 1.15; 95% confidence interval [CI], 1.07-1.23; P < .001) and bulky disease (≥5 cm; HR, 2.12; 95% CI, 1.06-4.26; P = .034) before lymphodepletion were associated with shorter PFS. Day +28 complete response by positron emission tomography-computed tomography (HR, 0.13; 95% CI, 0.04-0.40; P < .001), day +28 measurable residual disease (MRD) negativity by multiparameter flow cytometry (HR, 0.08; 95% CI, 0.03-0.22; P < .001), day +28 MRD negativity by next-generation sequencing (HR, 0.21; 95% CI, 0.08-0.51; P < .001), higher peak CD8+ CAR T-cell expansion (HR, 0.49; 95% CI; 0.36-0.68; P < .001), higher peak CD4+ CAR T-cell expansion (HR, 0.47; 95% CI; 0.33-0.69; P < .001), and longer CAR T-cell persistence (HR, 0.56; 95% CI, 0.44-0.72; P < .001) were associated with longer PFS. The 6-year duration of response and overall survival were 26.4% and 31.2%, respectively. CD19 CAR T-cell therapy achieved durable responses with curative potential in a subset of patients with R/R CLL. This trial was registered at www.clinicaltrials.gov as #NCT01865617.

Prognostic Potential of Galectin-9 mRNA Expression in Chronic Lymphocytic Leukemia

Galectin-9 (Gal-9), very poorly characterized in chronic lymphocytic leukemia (CLL), was chosen in our study to examine its potential role as a CLL biomarker. The relation of Gal-9 expression in malignant B-cells and other routinely measured CLL markers, as well as its clinical relevance are poorly understood. Gal-9 mRNA expression was quantified with RT-qPCR in purified CD19+ B-cells of 100 CLL patients and analyzed in the context of existing clinical data. Our results revealed the upregulation of Gal-9 mRNA in CLL cells. High Gal-9 mRNA expression was closely associated with unfavorable prognostic markers. In addition, Gal-9 expression in leukemic cells was significantly elevated in CLL patients who did not respond to the first-line therapy compared to those who did respond. This suggests its potential predictive value. Importantly, Gal-9 was an independent predictor for the time to treatment parameters. Thus, we can suggest an adverse role of Gal-9 expression in CLL. Interestingly, it is possible that Gal-9 expression is induced in B-cells by EBV infection, so we determined the patients' EBV status. Our suggestion is that EBV coinfection could worsen prognosis in CLL, partly due to Gal-9 expression upregulation caused by EBV.

Negative feedback regulation of MAPK signaling is an important driver of chronic lymphocytic leukemia progression

Despite available targeted treatments for the disease, drug-resistant chronic lymphocytic leukemia (CLL) poses a clinical challenge. The objective of this study is to examine whether the dual-specific phosphatases DUSP1 and DUSP6 are required to negatively regulate mitogen-activated protein kinases (MAPKs) and thus counterbalance excessive MAPK activity. We show that high expression of DUSP6 in CLL correlates with poor clinical prognosis. Importantly, genetic deletion of the inhibitory phosphatase DUSP1 or DUSP6 and blocking DUSP1/6 function using a small-molecule inhibitor reduces CLL cell survival in vitro and in vivo. Using global phospho-proteome approaches, we observe acute activation of MAPK signaling by DUSP1/6 inhibition. This promotes accumulation of mitochondrial reactive oxygen species and, thereby, DNA damage and apoptotic cell death in CLL cells. Finally, we observe that DUSP1/6 inhibition is particularly effective against treatment-resistant CLL and therefore suggest transient DUSP1/6 inhibition as a promising treatment concept to eliminate drug-resistant CLL cells.

Anti-tumor activity of selinexor in combination with antineoplastic agents in chronic lymphocytic leukemia

Despite recent relevant therapeutic progresses, chronic lymphocytic leukemia (CLL) remains an incurable disease. Selinexor, an oral inhibitor of the nuclear export protein XPO1, is active as single agent in different hematologic malignancies, including CLL. The purpose of this study was to evaluate the anti-tumor effects of selinexor, used in combination with chemotherapy drugs (i.e. fludarabine and bendamustine) or with the PI3Kδ inhibitor idelalisib in CLL. Our results showed a significant decrease in CLL cell viability after treatment with selinexor-containing drug combinations compared to each single compound, with demonstration of synergistic cytotoxic effects. Interestingly, this drug synergism was exerted also in the presence of the protective effect of stromal cells. From the molecular standpoint, the synergistic cytotoxic activity of selinexor plus idelalisib was associated with increased regulatory effects of this drug combination on the tumor suppressors FOXO3A and IkBα compared to each single compound. Finally, selinexor was also effective in potentiating the in vivo anti-tumor effects of the PI3Kδ inhibitor in mice treated with the drug combination compared to single agents. Our data provide preclinical evidence of the synergism and potential efficacy of a combination treatment targeting XPO1 and PI3Kδ in CLL.

MALAT1 expression is associated with aggressive behavior in indolent B-cell neoplasms

MALAT1 long non-coding RNA has oncogenic roles but has been poorly studied in indolent B-cell neoplasms. Here, MALAT1 expression was analyzed using RNA-seq, microarrays or qRT-PCR in primary samples from clinico-biological subtypes of chronic lymphocytic leukemia (CLL, n = 266), paired Richter transformation (RT, n = 6) and follicular lymphoma (FL, n = 61). In peripheral blood (PB) CLL samples, high MALAT1 expression was associated with a significantly shorter time to treatment independently from other known prognostic factors. Coding genes expressed in association with MALAT1 in CLL were predominantly related to oncogenic pathways stimulated in the lymph node (LN) microenvironment. In RT paired samples, MALAT1 levels were lower, concordant with their acquired increased independency of external signals. Moreover, MALAT1 levels in paired PB/LN CLLs were similar, suggesting that the prognostic value of MALAT1 expression in PB is mirroring expression differences already present in LN. Similarly, high MALAT1 expression in FL predicted for a shorter progression-free survival, in association with expression pathways promoting FL pathogenesis. In summary, MALAT1 expression is related to pathophysiology and more aggressive clinical behavior of indolent B-cell neoplasms. Particularly in CLL, its levels could be a surrogate marker of the microenvironment stimulation and may contribute to refine the clinical management of these patients.

Prognostic value and therapeutic targeting of XPO1 in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a subtype of B-cell malignancy with high heterogeneity. XPO1 is highly expressed in many hematological malignancies, which predicts poor prognosis. In the study, we aimed to explore the prognostic role of XPO1 and the therapeutic effect of Selinexor, a selective inhibitor of nuclear export, which targets XPO1. We collected 200 CLL samples in our center to confirm XPO1 mRNA expression and analyzed the correlation between XPO1 expression and prognosis. Then, we decreased XPO1 expression with Selinexor to explore the effect of proliferation inhibition, cell cycle arrest, and apoptosis in CLL cell lines. RNA-Seq was performed to explore potential mechanisms. We analyzed XPO1 expression in a cohort of 150 treatment naive patients and another cohort of 50 relapsed and refractory (R/R) patients and found that XPO1 expression was upregulated in 76% of CLL patients compared with healthy donors. Survival analysis suggested that patients with increased XPO1 expression had inferior treatment-free survival (P = 0.022) and overall survival (P = 0.032). The inhibitor of XPO1, Selinexor, induced apoptosis in primary CLL cells. We showed the effects of Selinexor on proliferation inhibition, cell cycle arrest, and apoptosis in CLL cell lines with JVM3, MEC1, and ibrutinib-resistant (MR) cells via nuclear retention of cargo proteins of IκBα, p65, p50, and FOXO3a. Moreover, downregulation of the NF-κB and FOXO pathways was a common feature of the three CLL cell lines responding to Selinexor, indicating the potential application of XPO1 inhibitor even in the high-risk CLL cells. We identified XPO1 as an unfavorable prognostic factor for CLL patients and provided a rationale for further investigation of the clinically XPO1 targeted therapeutic strategy against CLL.

Nucleosome repositioning in chronic lymphocytic leukemia

The location of nucleosomes in the human genome determines the primary chromatin structure and regulates access to regulatory regions. However, genome-wide information on deregulated nucleosome occupancy and its implications in primary cancer cells is scarce. Here, we conducted a genome-wide comparison of high-resolution nucleosome maps in peripheral blood B cells from patients with chronic lymphocytic leukemia (CLL) and healthy individuals at single-base-pair resolution. Our investigation uncovered significant changes of nucleosome positioning in CLL. Globally, the spacing between nucleosomes-the nucleosome repeat length (NRL)-is shortened in CLL. This effect is stronger in the more aggressive IGHV-unmutated CLL subtype than in the IGHV-mutated CLL subtype. Changes in nucleosome occupancy at specific sites are linked to active chromatin remodeling and reduced DNA methylation. Nucleosomes lost or gained in CLL marks differential binding of 3D chromatin organizers such as CTCF as well as immune response-related transcription factors and delineated mechanisms of epigenetic deregulation. The principal component analysis of nucleosome occupancy in cancer-specific regions allowed the classification of samples between cancer subtypes and normal controls. Furthermore, patients could be better assigned to CLL subtypes according to differential nucleosome occupancy than based on DNA methylation or gene expression. Thus, nucleosome positioning constitutes a novel readout to dissect molecular mechanisms of disease progression and to stratify patients. Furthermore, we anticipate that the global nucleosome repositioning detected in our study, such as changes in the NRL, can be exploited for liquid biopsy applications based on cell-free DNA to stratify patients and monitor disease progression.

Chronic Lymphocytic Leukemia: Disease Biology

BACKGROUND

B-cell receptor (BCR) signaling is crucial for normal B-cell development and adaptive immunity. In chronic lymphocytic leukemia (CLL), the malignant B cells display many features of normal mature B lymphocytes, including the expression of functional B-cell receptors (BCRs). Cross talk between CLL cells and the microenvironment in secondary lymphatic organs results in BCR signaling and BCR-driven proliferation of the CLL cells. This critical pathomechanism can be targeted by blocking BCR-related kinases (BTK, PI3K, spleen tyrosine kinase) using small-molecule inhibitors. Among these targets, Bruton tyrosine kinase (BTK) inhibitors have the highest therapeutic efficacy; they effectively block leukemia cell proliferation and generally induce durable remissions in CLL patients, even in patients with high-risk disease. By disrupting tissue homing receptor (i.e., chemokine receptor and adhesion molecule) signaling, these kinase inhibitors also mobilize CLL cells from the lymphatic tissues into the peripheral blood (PB), causing a transient redistribution lymphocytosis, thereby depriving CLL cells from nurturing factors within the tissue niches.

SUMMARY

The clinical success of the BTK inhibitors in CLL underscores the central importance of the BCR in CLL pathogenesis. Here, we review CLL pathogenesis with a focus on the role of the BCR and other microenvironment cues.

KEY MESSAGES

(i) CLL cells rely on signals from their microenvironment for proliferation and survival. (ii) These signals are mediated by the BCR as well as chemokine and integrin receptors and their respective ligands. (iii) Targeting the CLL/microenvironment interaction with small-molecule inhibitors provides a highly effective treatment strategy, even in high-risk patients.

Severe Fatal Mucormycosis in a Patient with Chronic Lymphocytic Leukaemia Treated with Zanubrutinib: A Case Report and Review of the Literature

Severe mucormycosis is a fatal disease rarely complicating chronic lymphoproliferative disorders. We present a fulminant and fatal case of a 74-year-old Caucasian woman suffering from CLL treated with second-generation BTK inhibitor zanubrutinib. After a first septic episode a month prior, originating from the lung with later systemic involvement by an unidentified agent and treated with large-spectrum antibiotics and fluconazonle, a slow-onset enlarging tender warm and erythematous nodular swollen cutaneous lesion appeared in her lower limbs and spread subsequently to her upper limbs, progressing towards central ulceration with a necrotic core. Suspecting a mycotic dissemination from an unknown agent, a skin punch biopsy was performed, and intraconazole was started. Due to spread of the skin lesions, the patient was hospitalized and intravenous liposomal ampthotericin B was started. Histopathology showed an atypical sporangium-rich mycotic angioinvasion of the small vessels. Only the increase of BDG and GM could corroborate the hypothesis of mycotic infection. However, long-term CLL, immunosuppressive therapies, neutropenia, and prior use of azoles and other antimycotic agents were risk factors for mucormycosis; BTK inhibitor could also be added as another novel risk factor. Despite all therapeutic efforts, the patient died. Post-mortem molecular exams confirmed the diagnosis of disseminated mucormycosis.

Accelerated Chronic Lymphocytic Leukemia and Richter Transformation in the Era of Novel Agents

BACKGROUND

Tremendous developments in the field of chronic lymphocytic leukemia (CLL) in recent years have led to a revolutionary change in the treatment approach, which today is based on targeted treatments with a good response and optimal prognosis. Nevertheless, CLL can present or progress to "accelerated CLL" (A-CLL) or to "Richter transformation" (RT) and these two entities have a more aggressive course and are still characterized by challenges in the fields of diagnosis and therapy. In the current review, we summarized the latest knowledge in terms of diagnostic approaches to A-CLL, available treatments and clinical trials, for both A-CLL and RT which still pose an unmet need and require additional basic and clinical investigations.

SUMMARY

A-CLL is a rare and underdiagnosed entity that probably stands in the "gray zone" between CLL and RT, generally holding an intermediate prognosis. Its diagnosis is mainly based on histological findings including expanded proliferation centers, increased mitotic activity, and/or high Ki-67 index. Due to its rarity, its treatment approach has still not been defined, but it seems that novel agents, especially Bruton tyrosine kinase inhibitors (BTKi), are effective. As for RT, the standard therapy still consists of chemo-immunotherapy followed by stem-cell transplantation for fit responders with a dismal prognosis. New approaches are recently adopted including B-cell inhibition via novel agents (BTKi, venetoclax), T-cell engagers (checkpoint inhibitors, bispecific antibodies [BiTe] or the chimeric antigen receptor [CAR] technology), antibody-drug conjugates, or drug combinations. Although both CAR-T and BiTe seem promising, especially when combined with BTKi, evidence is still insufficient, and patients should generally be recruited in clinical trials.

KEY MESSAGES

The field of CLL has been a subject of major advances in recent years, but A-CLL and RT remain topics of "unmet need" and require further studies to identify the best diagnostic approach and a more effective treatment.

In Vitro 3D Spheroid Culture System Displays Sustained T Cell-dependent CLL Proliferation and Survival

Chronic lymphocytic leukemia (CLL) cells are highly dependent on microenvironmental cells and signals. The lymph node (LN) is the critical site of in vivo CLL proliferation and development of resistance to both chemotherapy and targeted agents. We present a new model that incorporates key aspects of the CLL LN, which enables investigation of CLL cells in the context of a protective niche. We describe a three-dimensional (3D) in vitro culture system using ultra-low attachment plates to create spheroids of CLL cells derived from peripheral blood. Starting from CLL:T cell ratios as observed in LN samples, CLL activation was induced by either direct stimulation and/or indirectly via T cells. Compared with two-dimensional cultures, 3D cultures promoted CLL proliferation in a T cell-dependent manner, and enabled expansion for up to 7 weeks, including the formation of follicle-like structures after several weeks of culture. This model enables high-throughput drug screening, of which we describe response to Btk inhibition, venetoclax resistance, and T cell-mediated cytotoxicity as examples. In summary, we present the first LN-mimicking in vitro 3D culture for primary CLL, which enables readouts such as real-time drug screens, kinetic growth assays, and spatial localization. This is the first in vitro CLL system that allows testing of response and resistance to venetoclax and Bruton's tyrosine kinase inhibitors in the context of the tumor microenvironment, thereby opening up new possibilities for clinically useful applications.

Lymph node metastasis and tumor-educated immune tolerance: Potential therapeutic targets against distant metastasis

Lymph node metastasis has been shown to positively associated with the prognosis of many cancers. However, in clinical treatment, lymphadenectomy is not always successful, suggesting that immune cells in the tumor and sentinel lymph nodes still play a pivotal role in tumor immunosuppression. Recent studies had shown that tumors can tolerate immune cells through multiple strategies, including tumor-induced macrophage reprogramming, T cells inactivation, production of B cells pathogenic antibodies and activation of regulatory T cells to promote tumor colonization, growth, and metastasis in lymph nodes. We reviewed the bidirectional effect of immune cells on anti-tumor or promotion of cancer cell metastasis during lymph node metastasis, and the mechanisms by which malignant cancer cells modify immune cells to create a more favorable environment for the growth and survival of cancer cells. Research and treatment strategies focusing on the immune system in lymph nodes and potential immune targets in lymph node metastasis were also be discussed.

GSK-J4 Inhibition of KDM6B Histone Demethylase Blocks Adhesion of Mantle Cell Lymphoma Cells to Stromal Cells by Modulating NF-κB Signaling

Multiple signaling pathways facilitate the survival and drug resistance of malignant B-cells by regulating their migration and adhesion to microenvironmental niches. NF-κB pathways are commonly dysregulated in mantle cell lymphoma (MCL), but the exact underlying mechanisms are not well understood. Here, using a co-culture model system, we show that the adhesion of MCL cells to stromal cells is associated with elevated levels of KDM6B histone demethylase mRNA in adherent cells. The inhibition of KDM6B activity, using either a selective inhibitor (GSK-J4) or siRNA-mediated knockdown, reduces MCL adhesion to stromal cells. We showed that KDM6B is required both for the removal of repressive chromatin marks (H3K27me3) at the promoter region of NF-κB encoding genes and for inducing the expression of NF-κB genes in adherent MCL cells. GSK-J4 reduced protein levels of the RELA NF-κB subunit and impaired its nuclear localization. We further demonstrated that some adhesion-induced target genes require both induced NF-κB and KDM6B activity for their induction (e.g., IL-10 cytokine gene), while others require induction of NF-κB but not KDM6B (e.g., CCR7 chemokine gene). In conclusion, KDM6B induces the NF-κB pathway at different levels in MCL, thereby facilitating MCL cell adhesion, survival, and drug resistance. KDM6B represents a novel potential therapeutic target for MCL.