The biology behind PI3K inhibition in chronic lymphocytic leukaemia

Enhanced CD19 activity in B cells contributes to immunodeficiency in mice deficient in the ICF syndrome gene Zbtb24

Immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome is a rare autosomal recessive disorder characterized by DNA hypomethylation and antibody deficiency. It is caused by mutations in DNMT3B, ZBTB24, CDCA7, or HELLS. While progress has been made in elucidating the roles of these genes in regulating DNA methylation, little is known about the pathogenesis of the life-threatening hypogammaglobulinemia phenotype. Here, we show that mice deficient in Zbtb24 in the hematopoietic lineage recapitulate the major clinical features of patients with ICF syndrome. Specifically, Vav-Cre-mediated ablation of Zbtb24 does not affect lymphocyte development but results in reduced plasma cells and low levels of IgM, IgG1, and IgA. Zbtb24-deficient mice are hyper and hypo-responsive to T-dependent and T-independent type 2 antigens, respectively, and marginal zone B-cell activation is impaired. Mechanistically, Zbtb24-deficient B cells show severe loss of DNA methylation in the promoter region of Il5ra (interleukin-5 receptor subunit alpha), and Il5ra derepression leads to elevated CD19 phosphorylation. Heterozygous disruption of Cd19 can revert the hypogammaglobulinemia phenotype of Zbtb24-deficient mice. Our results suggest the potential role of enhanced CD19 activity in immunodeficiency in ICF syndrome.

Functional Testing to Characterize and Stratify PI3K Inhibitor Responses in Chronic Lymphocytic Leukemia

PURPOSE

PI3K inhibitors (PI3Ki) are approved for relapsed chronic lymphocytic leukemia (CLL). Although patients may show an initial response to these therapies, development of treatment intolerance or resistance remain clinical challenges. To overcome these, prediction of individual treatment responses based on actionable biomarkers is needed. Here, we characterized the activity and cellular effects of 10 PI3Ki and investigated whether functional analyses can identify treatment vulnerabilities in PI3Ki-refractory/intolerant CLL and stratify responders to PI3Ki.

EXPERIMENTAL DESIGN

Peripheral blood mononuclear cell samples (n = 51 in total) from treatment-naïve and PI3Ki-treated patients with CLL were studied. Cells were profiled against 10 PI3Ki and the Bcl-2 antagonist venetoclax. Cell signaling and immune phenotypes were analyzed by flow cytometry. Cell viability was monitored by detection of cleaved caspase-3 and the CellTiter-Glo assay.

RESULTS

pan-PI3Kis were most effective at inhibiting PI3K signaling and cell viability, and showed activity in CLL cells from both treatment-naïve and idelalisib-refractory/intolerant patients. CLL cells from idelalisib-refractory/intolerant patients showed overall reduced protein phosphorylation levels. The pan-PI3Ki copanlisib, but not the p110δ inhibitor idelalisib, inhibited PI3K signaling in CD4+ and CD8+ T cells in addition to CD19+ B cells, but did not significantly affect T-cell numbers. Combination treatment with a PI3Ki and venetoclax resulted in synergistic induction of apoptosis. Analysis of drug sensitivities to 73 drug combinations and profiling of 31 proteins stratified responders to idelalisib and umbralisib, respectively.

CONCLUSIONS

Our findings suggest novel treatment vulnerabilities in idelalisib-refractory/intolerant CLL, and indicate that ex vivo functional profiling may stratify PI3Ki responders.

Real-world management of targeted therapies in chronic lymphocytic leukemia

The advent of novel targeted therapies, including B-cell receptor (BCR) pathway and B-cell lymphoma 2 (BCL2) inhibitors, has substantially changed the treatment paradigm for chronic lymphocytic leukemia (CLL). Although targeted therapies have improved outcomes compared to traditional chemoimmunotherapy in the front-line and relapsed or refractory settings, they are associated with resistance mutations and suboptimal outcomes in certain high-risk patients. Additionally, targeted therapies are associated with drug interactions and unique adverse effect profiles which can be challenging for patients and clinicians to manage. Ongoing studies continue to address questions regarding optimal sequencing of therapies, the role of treatment combinations, and the efficacy of next-generation novel agents. This review provides a comprehensive overview regarding the clinical management of targeted therapies for CLL and applies current literature to clinical practice.

The future of antibody therapy in chronic lymphocytic leukemia

INTRODUCTION

Outcomes in chronic lymphocytic leukemia (CLL) have been dramatically improved with the addition of anti-CD20 antibodies to chemotherapy, defining a new standard of care for many years. More recently, therapies targeting fundamental signaling and anti-apoptotic pathways within the CLL cell have demonstrated dramatic clinical responses, including in patients with high-risk prognostic markers, thus emerging as preferred therapy for many patients. While the addition of anti-CD20 antibodies to traditional chemotherapy resulted in significant improvements in outcomes, the role of monoclonal antibodies in the era of targeted agents remains an active area of investigation. Furthermore, since the advent of next-generation anti-CD20 antibodies, the role of specific anti-CD20 antibodies remains an open question.

AREAS COVERED

In this review, we highlight the important role that anti-CD20 antibody therapy has had in the field of CLL, both when used with chemotherapy and in combination with targeted therapy, as well as the current studies that are further exploring this treatment paradigm in the modern era.

EXPERT OPINION

While anti-CD20 antibodies have played a pivotal role in the treatment of CLL, additional studies will be required to determine the optimal application of these therapies in combination with targeted therapy.

ENDOG Impacts on Tumor Cell Proliferation and Tumor Prognosis in the Context of PI3K/PTEN Pathway Status

EndoG influences mitochondrial DNA replication and is involved in somatic cell proliferation. Here, we investigated the effect of ENDOG/Endog expression on proliferation in different tumor models. Noteworthy, ENDOG deficiency reduced proliferation of endometrial tumor cells expressing low PTEN/high p-AKT levels, and Endog deletion blunted the growth of PTEN-deficient 3D endometrial cultures. Furthermore, ENDOG silencing reduced proliferation of follicular thyroid carcinoma and glioblastoma cell lines with high p-AKT expression. High ENDOG expression was associated with a short time to treatment in a cohort of patients with chronic lymphocytic leukemia (CLL), a B-cell lymphoid neoplasm with activation of PI3K/AKT. This clinical impact was observed in the less aggressive CLL subtype with mutated IGHV in which high ENDOG and low PTEN levels were associated with worse outcome. In summary, our results show that reducing ENDOG expression hinders growth of some tumors characterized by low PTEN activity and high p-AKT expression and that ENDOG has prognostic value for some cancer types.

Proteomics and Drug Repurposing in CLL towards Precision Medicine

Simple Summary

Despite continued efforts, the current status of knowledge in CLL molecular pathobiology, diagnosis, prognosis and treatment remains elusive and imprecise. Proteomics approaches combined with advanced bioinformatics and drug repurposing promise to shed light on the complex proteome heterogeneity of CLL patients and mitigate, improve, or even eliminate the knowledge stagnation. In relation to this concept, this review presents a brief overview of all the available proteomics and drug repurposing studies in CLL and suggests the way such studies can be exploited to find effective therapeutic options combined with drug repurposing strategies to adopt and accost a more “precision medicine” spectrum.

Abstract

CLL is a hematological malignancy considered as the most frequent lymphoproliferative disease in the western world. It is characterized by high molecular heterogeneity and despite the available therapeutic options, there are many patient subgroups showing the insufficient effectiveness of disease treatment. The challenge is to investigate the individual molecular characteristics and heterogeneity of these patients. Proteomics analysis is a powerful approach that monitors the constant state of flux operators of genetic information and can unravel the proteome heterogeneity and rewiring into protein pathways in CLL patients. This review essences all the available proteomics studies in CLL and suggests the way these studies can be exploited to find effective therapeutic options combined with drug repurposing approaches. Drug repurposing utilizes all the existing knowledge of the safety and efficacy of FDA-approved or investigational drugs and anticipates drug alignment to crucial CLL therapeutic targets, leading to a better disease outcome. The drug repurposing studies in CLL are also discussed in this review. The next goal involves the integration of proteomics-based drug repurposing in precision medicine, as well as the application of this procedure into clinical practice to predict the most appropriate drugs combination that could ensure therapy and the long-term survival of each CLL patient.

Migration and Adhesion of B-Lymphocytes to Specific Microenvironments in Mantle Cell Lymphoma: Interplay between Signaling Pathways and the Epigenetic Landscape

Lymphocyte migration to and sequestration in specific microenvironments plays a crucial role in their differentiation and survival. Lymphocyte trafficking and homing are tightly regulated by signaling pathways and is mediated by cytokines, chemokines, cytokine/chemokine receptors and adhesion molecules. The production of cytokines and chemokines is largely controlled by transcription factors in the context of a specific epigenetic landscape. These regulatory factors are strongly interconnected, and they influence the gene expression pattern in lymphocytes, promoting processes such as cell survival. The epigenetic status of the genome plays a key role in regulating gene expression during many key biological processes, and it is becoming more evident that dysregulation of epigenetic mechanisms contributes to cancer initiation, progression and drug resistance. Here, we review the signaling pathways that regulate lymphoma cell migration and adhesion with a focus on Mantle cell lymphoma and highlight the fundamental role of epigenetic mechanisms in integrating signals at the level of gene expression throughout the genome.

Efficacy and safety of idelalisib for the treatment of indolent B-cell malignancies

INTRODUCTION

The outcome of patients with lymphoid malignancies has markedly improved in recent years due to the implementation of new therapeutic options. Chronic lymphocytic leukemia (CLL) and indolent B-cell non-Hodgkin lymphomas (NHL) are characterized by the activation of the phosphatidylinositol 3-kinase (PI3 K) pathway via B-cell receptor signaling. The PI3 K delta (PI3 Kδ) p110δ isoform inhibitor, idelalisib, showed high anti-tumor activity in this group of tumors. It was the first agent from a new class of isoform-specific inhibitors to receive regulatory approvals for the treatment of refractory/relapsed CLL, as well as small lymphocytic lymphoma and follicular lymphoma.

AREAS COVERED

In this paper, the authors provide a comprehensive overview of the activity and safety profile of idelalisib and other, newly developed PI3 K inhibitors in patients with indolent B-cell malignancies.

EXPERT OPINION

Idelalisib is a very potent anti-lymphoma agent in CLL and other NHL. However, there are some limitations of its broad clinical use according to some important side effects observed during treatment. Consequently, the development of new PI3 K inhibitors, which will be highly active and possess better safety profiles are warranted.

Mechanism for IL-15-Driven B Cell Chronic Lymphocytic Leukemia Cycling: Roles for AKT and STAT5 in Modulating Cyclin D2 and DNA Damage Response Proteins

Clonal expansion of B cell chronic lymphocytic leukemia (B-CLL) occurs within lymphoid tissue pseudofollicles. IL-15, a stromal cell-associated cytokine found within spleens and lymph nodes of B-CLL patients, significantly boosts in vitro cycling of blood-derived B-CLL cells following CpG DNA priming. Both IL-15 and CpG DNA are elevated in microbe-draining lymphatic tissues, and unraveling the basis for IL-15-driven B-CLL growth could illuminate new therapeutic targets. Using CpG DNA-primed human B-CLL clones and approaches involving both immunofluorescent staining and pharmacologic inhibitors, we show that both PI3K/AKT and JAK/STAT5 pathways are activated and functionally important for IL-15→CD122/ɣc signaling in ODN-primed cells expressing activated pSTAT3. Furthermore, STAT5 activity must be sustained for continued cycling of CFSE-labeled B-CLL cells. Quantitative RT-PCR experiments with inhibitors of PI3K and STAT5 show that both contribute to IL-15-driven upregulation of mRNA for cyclin D2 and suppression of mRNA for DNA damage response mediators ATM, 53BP1, and MDC1. Furthermore, protein levels of these DNA damage response molecules are reduced by IL-15, as indicated by Western blotting and immunofluorescent staining. Bioinformatics analysis of ENCODE chromatin immunoprecipitation sequencing data from cell lines provides insight into possible mechanisms for STAT5-mediated repression. Finally, pharmacologic inhibitors of JAKs and STAT5 significantly curtailed B-CLL cycling when added either early or late in a growth response. We discuss how the IL-15-induced changes in gene expression lead to rapid cycling and possibly enhanced mutagenesis. STAT5 inhibitors might be an effective modality for blocking B-CLL growth in patients.