PCI-32765: a novel Bruton's tyrosine kinase inhibitor for the treatment of lymphoid malignancies

Molecular Classification and Treatment of Diffuse Large B-Cell Lymphoma and Primary Mediastinal B-Cell Lymphoma

Diffuse large B-cell lymphoma (DLBCL) encompasses a group of aggressive B-cell non-Hodgkin lymphomas with striking genetic heterogeneity and variable clinical presentations. Among these is primary mediastinal B-cell lymphoma (PMBL), which has unique clinical and molecular features resembling Hodgkin lymphoma. Treatment of DLBCL is usually curative, but identifiable subsets at highest risk for treatment failure may benefit from intensified chemotherapy regimens and/or targeted agents added to frontline therapy. Recent comprehensive genomic analyses have identified distinct genetic subtypes of DLBCL with characteristic genetic drivers and signaling pathways that are targetable. Immune therapy with chimeric antigen receptor T cells and checkpoint inhibitors has revolutionized the treatment of relapsed or refractory disease, and antibody drug conjugates have weaponized otherwise intolerable cytotoxic agents. Ongoing clinical trials are further refining the specificity of these approaches in different genetic subtypes and moving them from the setting of recurrent disease to frontline treatment in high-risk patient populations.

Systemic Approach to Recurrent Primary CNS Lymphoma: Perspective on Current and Emerging Treatment Strategies

There is no uniform standard of care for the treatment of refractory or recurrent primary central nervous lymphoma (r/r PCNSL). Many different systemic treatment regimens have been studied, but available data are based on small prospective or retrospective reports. There have been no randomized controlled trials in r/r PCNSL to date. Here, we provide an overview of published systemic regimens for the treatment of r/r PCNSL, as well as therapies that are under investigation. In addition, based on available data, we propose strategies of how to approach choice of therapy for different groups of patients in this disease setting. Patients can be mainly divided into three groups: 1) patients suitable for a re-challenge with high-dose methotrexate (HD-MTX)-based regimens and that may or may not be candidates for consolidation with high-dose chemotherapy with autologous stem cell transplant, 2) patients refractory to HD-MTX or that had early relapse, but suitable for an aggressive treatment strategy with re-induction with non-MTX-based therapy, possibly followed by high-dose chemotherapy with autologous transplant, and 3) patients not suitable for re-treatment with HD-MTX and that are not candidates for aggressive therapy. As PCNSL is a rare disease and as there is urgent need for better outcomes in r/r PCNSL, clinical trial participation is encouraged, especially in elderly or frail patients who are not candidates for high-dose chemotherapy and transplant.

B-cell receptor-mediated NFATc1 activation induces IL-10/STAT3/PD-L1 signaling in diffuse large B-cell lymphoma

Knowledge of programmed death ligand 1 (PD-L1) expression and its regulation in B-cell lymphoma cells is limited. Investigating mechanisms that control PD-L1 expression in B-cell lymphoma cells might identify biomarkers that predict the efficacy of immunotherapy with anti-programmed death-1/PD-L1 antibodies. In addition, identification of mechanisms that regulate PD-L1 may identify molecules that can be targeted to improve the clinical efficacy of immune checkpoint inhibitors. In this study, we used proteomic approaches and patient-derived B-cell lymphoma cell lines to investigate mechanisms that regulate PD-L1 expression. We found that PD-L1 expression, particularly in nongerminal center B cell-derived diffuse large B-cell lymphoma (DLBCL), is controlled and regulated by several interactive signaling pathways, including the B-cell receptor (BCR) and JAK2/STAT3 signaling pathways. We found that that BCR-mediated NFATc1 activation upregulates IL-10 chemokine expression in PD-L1⁺ B-cell lymphoma cells. Released IL-10 activates the JAK2/STAT3 pathway, leading to STAT3-induced PD-L1 expression. IL-10 antagonist antibody abrogates IL-10/STAT3 signaling and PD-L1 protein expression. We also found that BCR pathway inhibition by BTK inhibitors (ibrutinib, acalabrutinib, and BGB-3111) blocks NFATc1 and STAT3 activation, thereby inhibiting IL-10 and PD-L1 expression. Finally, we validated the PD-L1 signaling network in 2 primary DLBCL cohorts consisting of 428 and 350 cases and showed significant correlations among IL-10, STAT3, and PD-L1. Thus, our findings reveal a complex signaling network regulating PD-L1 expression in B-cell lymphoma cells and suggest that PD-L1 expression can be modulated by small molecule inhibitors to potentiate immunotherapies.

Efficacy and Safety of Ibrutinib in Indian Patients with Relapsed or Refractory Chronic Lymphocytic Leukemia and Mantle Cell Lymphoma: Cases from a Named Patient Program

Context:

This named patient program evaluated the safety and efficacy of ibrutinib, a selective inhibitor of Bruton's tyrosine kinase in Indian patients with relapsed/refractory chronic lymphocytic leukemia (CLL, with/without chromosome 17 deletion [del17p]) and mantle cell lymphoma (MCL).

Subjects and Methods:

The eight enrolled patients (relapsed/refractory CLL: n = 6 [4/6 patients with del17p] and relapsed/refractory MCL: n = 2) had median age of 55 years (range, 52–60) and had received a median of 3 (CLL patients) and 4 (MCL patients) prior therapies. Patients received once-daily dose of ibrutinib (420 mg: CLL, 560 mg: MCL).

Results:

In CLL patients, the median time to response was 3 months (range, 0.5–7) and five of six patients had partial response (PR) whereas one achieved complete response (CR). Median time on treatment was 11.5 months (range, 8–14); five patients continued treatment and one was recommended stem cell transplantation (SCT). Of the two MCL patients, one achieved PR and one showed CR and advanced to SCT. In CLL patients, the median (range) hemoglobin level improved from 9.8 g/dL (7.2–11) at baseline to 12.0 g/dL (9.5–13.2) and median (range) platelet count improved from 150,000 cells/μL (21,000–195,000) at baseline to 190,350 cells/μL (130,000–394,000) at the time of analysis (July 2016). Most adverse events (AEs) reported were infections (n = 2). No Grade 3-4 or serious AEs, dose reductions, or treatment discontinuation due to AEs were reported.

Conclusions:

In this first real-world experience in Indian patients, ibrutinib demonstrated therapeutic efficacy in relapsed/refractory CLL (with/without del17p) and MCL. Safety results were consistent with the current known profile of ibrutinib.

Proteome-wide Map of Targets of T790M-EGFR-Directed Covalent Inhibitors

Patients with non-small cell lung cancers that have kinase-activating epidermal growth factor receptor (EGFR) mutations are highly responsive to first- and second-generation EGFR inhibitors. However, these patients often relapse due to a secondary, drug-resistant mutation in EGFR whereby the gatekeeper threonine is converted to methionine (T790M). Several third-generation EGFR inhibitors have been developed that irreversibly inactivate T790M-EGFR while sparing wild-type EGFR, thus reducing epithelium-based toxicities. Using chemical proteomics, we show here that individual T790M-EGFR inhibitors exhibit strikingly distinct off-target profiles in human cells. The FDA-approved drug osimertinib (AZD9291), in particular, was found to covalently modify cathepsins in cell and animal models, which correlated with lysosomal accumulation of the drug. Our findings thus show how chemical proteomics can be used to differentiate covalent kinase inhibitors based on global selectivity profiles in living systems and identify specific off-targets of these inhibitors that may affect drug activity and safety.

Inhibition of the Bruton Tyrosine Kinase Pathway in B-Cell Lymphoproliferative Disorders

Activation of the Bruton tyrosine kinase (BTK) pathway plays an important role in the pathophysiology of a number of B-cell lymphoproliferative disorders (LPDs). A number of preclinical studies support inhibiting BTK as a mechanism to treat LPDs. Clinically, BTK inhibitors, specifically ibrutinib, have shown to be safe and effective on treating patients with indolent B-cell lymphomas and chronic lymphocytic leukemia (CLL). Ibrutinib has recently gained approval for the treatment of patients with mantle cell lymphoma, Waldenström macroglobulinemia, and CLL. Ongoing clinical trials are investigating ibrutinib and other BTK inhibitors alone or in combination for the treatment of mantle cell lymphoma, Waldenström macroglobulinemia, CLL, activated B-cell-type diffuse large B-cell lymphoma, and follicular lymphoma, among others. The objective of this review is to succinctly summarize the current body of evidence on BTK inhibition in patients with B-cell LPDs.

Bioanalysis of ibrutinib and its active metabolite in human plasma: selectivity issue, impact assessment and resolution

Ronald de Vries graduated in Organic and Analytical Chemistry at the Free University of Amsterdam, The Netherlands. After working in a Contract Laboratory (CRO) for 7 years, he joined Janssen R&D in 1998. At Janssen R&D, Belgium, Ronald worked in the bioanalytical department that supports both clinical and nonclinical bioanalysis. In this department he had several roles, such as providing the bioanalytical support for various drug development programs and leading the method establishment group. He has done numerous global assay transfers to/from Janssen from/to other laboratories and plays an important role in the introduction and application of new technologies and applied innovation in the department. In 2014 he started in the drug metabolism and pharmacokinetics department of Janssen R&D, where his main tasks are in vivo and in vitro metabolite identification using high resolution MS and Radiodetection.

Rational combination therapies targeting survival signaling in aggressive B-cell leukemia/lymphoma

PURPOSE OF REVIEW

The identification of oncogenic 'driver' mutations and activated survival pathways in selected aggressive B-cell malignancies directs the development of novel adjunctive therapies using targeted small molecule inhibitors. With a focus on diffuse large B-cell lymphoma 'not otherwise specified', Hodgkin lymphoma and childhood B-cell precursor acute lymphoblastic leukemia, this review will provide an up-to-date account of the current literature on the development of new molecularly targeted treatment modalities for aggressive B-cell malignancies.

RECENT FINDINGS

Subclassification of B-cell malignancies depending on their particular genetic 'driver' lesions and transcriptional and/or signaling signatures has led to the development of targeted therapeutic approaches using small molecule inhibitors to amend current combination chemotherapy.

SUMMARY

Treatment outcome with current combination chemotherapy is still poor for subsets of aggressive B-cell malignancies, and demands development of targeted therapeutic approaches. Advanced gene expression profiling and genomic sequencing have revealed a more detailed landscape of recurrent alterations, allowing a better subclassification of B-cell lymphomas and leukemias. Many alterations directly or indirectly lead to activation of survival signaling pathways and expression of key oncoproteins and prosurvival molecules, including Janus kinase-signal transducer and activator of transcription (JAK-STAT), phosphatidylinositol-3 kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR), avian myelocytomatosis viral oncogene homolog (MYC) and B-cell lymphoma 2 (BCLl-2). Small molecule inhibitors targeting these proteins and pathways are currently being tested in clinical trials and preclinically to improve chemotherapeutic regimes and treatment outcomes.

Role of Bruton's tyrosine kinase inhibitors in HIV-1-infected cells

Many cellular cofactors have been documented to be critical for various stages of viral replication. Using high-throughput proteomic assays, we have previously identified Bruton's tyrosine kinase (BTK) as a host protein that was uniquely upregulated in the plasma membrane of human immunodeficiency virus (HIV-1)-infected T cells. Here, we have further characterized the BTK expression in HIV-1 infection and show that this cellular factor is specifically expressed in infected myeloid cells. Significant upregulation of the phosphorylated form of BTK was observed in infected cells. Using size exclusion chromatography, we found BTK to be virtually absent in the uninfected U937 cells; however, new BTK protein complexes were identified and distributed in both high molecular weight (∼600 kDa) and a small molecular weight complex (∼60-120 kDa) in the infected U1 cells. BTK levels were highest in cells either chronically expressing virus or induced/infected myeloid cells and that BTK translocated to the membrane following induction of the infected cells. BTK knockdown in HIV-1-infected cells using small interfering RNA (siRNA) resulted in selective death of infected, but not uninfected, cells. Using BTK-specific antibody and small-molecule inhibitors including LFM-A13 and a FDA-approved compound, ibrutinib (PCI-32765), we have found that HIV-1-infected cells are sensitive to apoptotic cell death and result in a decrease in virus production. Overall, our data suggests that HIV-1-infected cells are sensitive to treatments targeting BTK expressed in infected cells.

Targeting Btk/Etk of prostate cancer cells by a novel dual inhibitor

Btk and Etk/BMX are Tec-family non-receptor tyrosine kinases. Btk has previously been reported to be expressed primarily in B cells and has an important role in immune responses and B-cell malignancies. Etk has been shown previously to provide a strong survival and metastasis signal in human prostate cancer cells, and to confer androgen independence and drug resistance. While the role of Etk in prostate carcinogenesis is well established, the functions of Btk in prostate cancer have never been investigated, likely due to the perception that Btk is a hematopoietic, but not epithelial, kinase. Herein, we found that Btk is overexpressed in prostate cancer tissues and prostate cancer cells. The level of Btk in prostate cancer tissues correlates with cancer grades. Knockdown of Btk expression selectively inhibits the growth of prostate cancer cells, but not that of the normal prostate epithelial cells, which express very little Btk. Dual inhibition of Btk and Etk has an additive inhibitory effect on prostate cancer cell growth. To explore Btk and Etk as targets for prostate cancer, we developed a small molecule dual inhibitor of Btk and Etk, CTN06. Treatment of PC3 and other prostate cancer cells, but not immortalized prostate epithelial cells with CTN06 resulted in effective cell killing, accompanied by the attenuation of Btk/Etk signals. The killing effect of CTN06 is more potent than that of commonly used inhibitors against Src, Raf/VEGFR and EGFR. CTN06 induces apoptosis as well as autophagy in human prostate cancer cells, and is a chemo-sensitizer for docetaxel (DTX), a standard of care for metastatic prostate cancer patients. CTN06 also impeded the migration of human prostate cancer cells based on a ‘wound healing' assay. The anti-cancer effect of CTN06 was further validated in vivo in a PC3 xenograft mouse model.

Bruton tyrosine kinase mediates TLR9-dependent human dendritic cell activation

BACKGROUND

Bruton tyrosine kinase (BTK) plays an essential role in various biologic functions of different cell types. Mutations in BTK lead to X-linked agammaglobulinemia (XLA) in humans. BTK was recently linked to the innate immune system, in particular, the Toll-like receptor (TLR) pathway; however, the TLR9 pathway has never been studied in dendritic cells (DCs) of patients with XLA.

OBJECTIVE

The aim of this study was to investigate the role of BTK in human DC activation upon TLR9 stimulation.

METHODS

DCs of patients with XLA and healthy donors were stimulated via TLR4/9 and evaluated for cell activation and cytokine production.

RESULTS

We showed that BTK plays an essential role in DC responses to unmethylated CpG oligodeoxynucleotide: although responses to lipopolysaccaride/TLR4 induce normal DC activation in terms of upregulation of specific markers (CD86, CD83, CD80, HLA-DR), the CpG/TLR9 pathway is completely impaired in patients with XLA. Furthermore, cytokine production upon TLR9 activation in patients with XLA is radically impaired in terms of IL-6, IL-12, TNF-α, and IL-10 production. Interestingly, BTK mediated STAT1/3 upregulation in a TLR9-dependent manner. The important role of BTK in human DC activation was confirmed after incubation of healthy DCs with ibrutinib, the specific BTK inhibitor, which resulted in impairment of TLR9 responses as seen in patients with XLA.

CONCLUSION

Analysis of these data suggests that BTK regulates human DC responses upon TLR9 engagement in terms of activation, cytokine production, and STAT1/3 upregulation. These findings may be of important significance for better understanding and managing different clinical conditions, such as agammaglobulinemia and lymphoid malignancies.

Diffuse large B-cell lymphoma-treatment approaches in the molecular era

Diffuse large B-cell lymphoma (DLBCL) is an aggressive B-cell non-Hodgkin lymphoma that affects patients of all ages with a wide range of clinical presentations. Although DLBCL is curable even in advanced stages, up to one-third of patients will not achieve cure with initial therapy. In the modern era of rituximab-based therapy as the first-line treatment, the prognoses of patients who require salvage therapy are poor and most will eventually succumb to their disease. Insight into the complex molecular circuitry of DLBCL reveals a diverse range of somatic mutations and aberrant intracellular signalling pathways that characterize distinct molecular subsets of the disease. The next major breakthrough in DLBCL therapy during this 'molecular era' of disease definition will be the identification of combinations of novel agents that target the oncogenic drivers of these subsets. Well-conducted clinical trials, with translational molecular investigations, will be essential to achieve the goal of precision medicine and expand the number of patients with DLBCL who achieve a cure.

The promising impact of ibrutinib, a Bruton's tyrosine kinase inhibitor, for the management of lymphoid malignancies

Lymphoid malignancies comprise a heterogeneous group of disorders originating from clonal proliferation of B or T lymphocytes. Treatment of lymphoid neoplasms has traditionally been pursued with cytotoxic chemotherapy. To improve efficacy and ameliorate the adverse effects associated with classic chemotherapy, molecularly targeted therapy has been developed. At the forefront of clinical development is ibrutinib, an inhibitor of Bruton's tyrosine kinase (Btk). Btk is a protein tyrosine kinase that plays an important role in regulating B-cell signaling. Dysregulated Btk results in uncontrolled B-lymphocyte proliferation, differentiation, and survival. Ibrutinib is currently being studied in numerous malignancies of lymphoid origin including chronic lymphocytic leukemia, mantle cell lymphoma, non-Hodgkin lymphoma, follicular lymphoma, and multiple myeloma. Thus far, ibrutinib has demonstrated very promising results in treatment-naive patients as well as those with relapsed or refractory disease with an acceptable safety profile. In this article, we describe the pharmacology, efficacy, and toxicity profile of ibrutinib and depict the potential role that ibrutinib will play in the treatment paradigm of lymphoid neoplasms.

PI3K-δ and PI3K-γ inhibition by IPI-145 abrogates immune responses and suppresses activity in autoimmune and inflammatory disease models

Phosphoinositide-3 kinase (PI3K)-δ and PI3K-γ are preferentially expressed in immune cells, and inhibitors targeting these isoforms are hypothesized to have anti-inflammatory activity by affecting the adaptive and innate immune response. We report on a potent oral PI3K-δ and PI3K-γ inhibitor (IPI-145) and characterize this compound in biochemical, cellular, and in vivo assays. These studies demonstrate that IPI-145 exerts profound effects on adaptive and innate immunity by inhibiting B and T cell proliferation, blocking neutrophil migration, and inhibiting basophil activation. We explored the therapeutic value of combined PI3K-δ and PI3K-γ blockade, and IPI-145 showed potent activity in collagen-induced arthritis, ovalbumin-induced asthma, and systemic lupus erythematosus rodent models. These findings support the hypothesis that inhibition of immune function can be achieved through PI3K-δ and PI3K-γ blockade, potentially leading to significant therapeutic effects in multiple inflammatory, autoimmune, and hematologic diseases.

A novel isoform of the B cell tyrosine kinase BTK protects breast cancer cells from apoptosis

Tyrosine kinases orchestrate key cellular signaling pathways and their dysregulation is often associated with cellular transformation. Several recent cases in which inhibitors of tyrosine kinases have been successfully used as anticancer agents have underscored the importance of this class of proteins in the development of targeted cancer therapies. We have carried out a large-scale loss-of-function analysis of the human tyrosine kinases using RNA interference to identify novel survival factors for breast cancer cells. In addition to kinases with known roles in breast and other cancers, we identified several kinases that were previously unknown to be required for breast cancer cell survival. The most surprising of these was the cytosolic, nonreceptor tyrosine kinase, Bruton's tyrosine kinase (BTK), which has been extensively studied in B cell development. Down regulation of this protein with RNAi or inhibition with pharmacological inhibitors causes apoptosis; overexpression inhibits apoptosis induced by Doxorubicin in breast cancer cells. Our results surprisingly show that BTK is expressed in several breast cancer cell lines and tumors. The predominant form of BTK found in tumor cells is transcribed from an alternative promoter and results in a protein with an amino-terminal extension. This alternate form of BTK is expressed at significantly higher levels in tumorigenic breast cells than in normal breast cells. Since this protein is a survival factor for these cells, it represents both a potential marker and novel therapeutic target for breast cancer.

Ibrutinib: an evidence-based review of its potential in the treatment of advanced chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a heterogeneous disease with a variable course, and remains an incurable disease. Frequent relapses and eventual resistance to fludarabine characterize symptomatic CLL and portends a dismal prognosis for patients. Growing evidence has shown that signaling pathways such as the B cell receptor and NFkB are implicated in the survival and proliferation of the CLL cells which are ultimately associated with persistence of the disease. The Bruton's tyrosine kinase pathway regulates downstream activation of the B cell receptor and has emerged as an attractive target. Ibrutinib inhibits the Bruton's tyrosine kinase pathway, and consequently induces apoptosis of B cells. Phase I and II studies have shown impressive response rates with an excellent safety profile in patients with refractory/relapsed CLL and elderly treatment-naïve CLL patients. This paper reviews the preclinical and clinical data for ibrutinib when used in the treatment of CLL. Recent studies showing the benefit of combination therapy using ibrutinib, monoclonal antibodies, and chemoimmunotherapy are also discussed.

BCR signaling in chronic lymphocytic leukemia and related inhibitors currently in clinical studies

Normal B lymphocytes receive signals from B-cell antigen receptor (BCR) that are triggered by binding of the BCR to an external antigen. Tonic signaling through the BCR provides growth and signals to chronic lymphocytic leukemia (CLL) cells, and plays an important role in the pathogenesis and progression of the disease. Antigen engagement of BCR is followed by intracellular recruitment and activation of BCR-associated kinases including spleen tyrosine kinase (Syk), Bruton's tyrosine kinase (Btk) and phosphatidylinositol 3-kinases (PI3K). Inhibition of signaling pathways downstream of the BCR induces disruption of chemokine-mediated CLL cell migration and cell killing. BCR signal transduction inhibitors represent a promising new strategy for targeted CLL treatment. A number of therapeutic agents have recently been developed with significant activity in CLL. The compounds that are currently investigated in patients with CLL include ibrutinib -inhibitor of Btk, fostamatinib-inhibitor of Syk and idelalisib (GS-1101) -a specific isoform of the PI3K (PI3K) inhibitor. The clinical activity of ibrutinib, GS-1101 and fostamatinib in patients with CLL is associated with marked lymphocytosis due to release of tumor cells from the lymph nodes into the peripheral blood. Further studies are ongoing with single agents and their combinations with other targeted and conventional therapies. This article will review the preclinical rationale of BCR signaling inhibitors in the treatment of CLL, and the clinical evidence supporting the use of these agents in CLL patients.

Chronic lymphocytic leukaemia--the role of the microenvironment pathogenesis and therapy

Chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL) is one of the more common forms of B cell malignancy. Although the condition has a variable clinical course, the trend is towards eventual relapse and the disease is considered incurable. Whilst the majority of the circulating CD5-positive neoplastic B cells are arrested in the G0 phase of the cell cycle, those in the bone marrow and lymphoid tissues proliferate at a rate of 0·1-1% of the entire clone per day. This proliferation is supported by the tissue microenvironment, which has been shown to induce upregulation of anti-apoptotic proteins and enhance the survival of the neoplastic cells. Microenvironmental factors are also thought to be important in tumour relapse and resistance to therapy. This review outlines the main signalling pathways involved in these tumour cell-stromal interactions, and includes potential therapeutic strategies based on the manipulation of key components within the CLL microenvironment.

MicroRNAs and Glucocorticoid-Induced Apoptosis in Lymphoid Malignancies

The initial response of lymphoid malignancies to glucocorticoids (GCs) is a critical parameter predicting successful treatment. Although being known as a strong inducer of apoptosis in lymphoid cells for almost a century, the signaling pathways regulating the susceptibility of the cells to GCs are only partly revealed. There is still a need to develop clinical tests that can predict the outcome of GC therapy. In this paper, I discuss important parameters modulating the pro-apoptotic effects of GCs, with a specific emphasis on the microRNA world comprised of small players with big impacts. The journey through the multifaceted complexity of GC-induced apoptosis brings forth explanations for the differential treatment response and raises potential strategies for overcoming drug resistance.

Spontaneous regression of chronic lymphocytic leukemia to a monoclonal B-lymphocytosis or to a normal phenotype

Spontaneous remission of chronic lymphocytic leukemia (CLL) is an unusual and poorly characterized event. We performed a search for spontaneous remission in patients with CLL. Cases must have had a pathological diagnosis of CLL with disease duration > 6 months. Spontaneous remission was defined as absence of lymphadenopathy or splenomegaly with lymphocyte counts < 5 × 10(9)/L for > 9 months without therapy. We identified 20 cases and included one additional case from our institution. Fourteen cases (67%) showed remission into monoclonal B lymphocytosis (MBL) and seven (33%) into a normal phenotype. There was no difference in age distribution, lymphocyte count or stage between groups. There was a significant difference in the median duration of CLL prior to remission, 13 years in the MBL versus 3 years in the normal phenotype group (p = 0.03). This difference in the duration of CLL prior to remission could be due to a possible distinct pathophysiology for these events.

Diffuse large B-cell lymphoma: current strategies and future directions

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is the most common histology of non-Hodgkin lymphoma, representing 25% to 35% of new cases annually. The incidence of DLBCL has doubled in the past decades, highlighting the need for more effective treatment regimens.

METHODS

This article reviews the current protocols applicable to this aggressive lymphoma and discusses ongoing research that is focusing on molecular diagnostics, prognostic factors have also been defined for DLBCL.

RESULTS

Patients with DLBCL vary in clinical presentation, prognosis, and response to current therapies. While current therapy in the rituximab era has led to improved outcomes with reduced toxicity, novel treatment approaches for localized, advanced, and relapsed/refractory DLBCL are being pursued in clinical trials. Several studies have shown promise, such as trials involving proteasome inhibitors, lenalidomide, and antibody drug conjugates.

CONCLUSIONS

Recent discoveries in the spectrum of care for patients with DLBCL have prompted a renaissance for personalized cancer medicine and molecularly targeted therapy. Potential targets and novel drug combinations are undergoing continued study in the hope of achieving successful and personalized care of this disease.

B-cell receptor triggers drug sensitivity of primary CLL cells by controlling glucosylation of ceramides

Survival of chronic lymphocytic leukemia (CLL) cells is triggered by several stimuli, such as the B-cell receptor (BCR), CD40 ligand (CD40L), or interleukin-4 (IL-4). We identified that these stimuli regulate apoptosis resistance by modulating sphingolipid metabolism. Applying liquid chromatography electrospray ionization tandem mass spectrometry, we revealed a significant decrease of proapoptotic ceramide in BCR/IL-4/CD40L–stimulated primary CLL cells compared with untreated controls. Antiapoptotic glucosylceramide levels were significantly increased after BCR cross-linking. We identified BCR engagement to catalyze the crucial modification of ceramide to glucosylceramide via UDP-glucose ceramide glucosyltransferase (UGCG). Besides specific UGCG inhibitors, our data demonstrate that IgM-mediated UGCG expression was inhibited by the novel and highly effective PI3Kδ and BTK inhibitors CAL-101 and PCI-32765, which reverted IgM-induced resistance toward apoptosis of CLL cells. Sphingolipids were recently shown to be crucial for mediation of apoptosis via mitochondria. Our data reveal ABT-737, a mitochondria-targeting drug, as interesting candidate partner for PI3Kδ and BTK inhibition, resulting in synergistic apoptosis, even under protection by the BCR. In summary, we identified the mode of action of novel kinase inhibitors CAL-101 and PCI-32765 by controlling the UGCG-mediated ceramide/glucosylceramide equilibrium as a downstream molecular switch of BCR signaling, also providing novel targeted treatment options beyond current chemotherapy-based regimens.

Akt and mTOR in B Cell Activation and Differentiation

Activation of phosphoinositide 3-kinase (PI3K) is required for B cell proliferation and survival. PI3K signaling also controls key aspects of B cell differentiation. Upon engagement of the B cell receptor (BCR), PI3K activation promotes Ca²⁺ mobilization and activation of NFκB-dependent transcription, events which are essential for B cell proliferation. PI3K also initiates a distinct signaling pathway involving the Akt and mTOR serine/threonine kinases. It has been generally assumed that activation of Akt and mTOR downstream of PI3K is essential for B cell function. However, Akt and mTOR have complex roles in B cell fate decisions and suppression of this pathway can enhance certain B cell responses while repressing others. In this review we will discuss genetic and pharmacological studies of Akt and mTOR function in normal B cells, and in malignancies of B cell origin.