Targeting Brutons Tyrosine Kinase in Chronic Lymphocytic Leukemia at the Crossroad between Intrinsic and Extrinsic Pro-survival Signals

Chemo immunotherapies for chronic lymphocytic leukemia (CLL) showed a positive impact on clinical outcome, but many patients relapsed or become refractory to the available treatments. The main goal of the researchers in CLL is the identification of specific targets in order to develop new therapeutic strategies to cure the disease. The B cell receptor-signalling pathway is necessary for survival of malignant B cells and its related molecules recently become new targets for therapy. Moreover, leukemic microenvironment delivers survival signals to neoplastic cells also overcoming the apoptotic effect induced by traditional drugs. In this context, the investigation of Bruton\u2019s tyrosine kinase (Btk) is useful in: i) dissecting CLL pathogenesis; ii) finding new therapeutic approaches striking simultaneously intrinsic as well as extrinsic pro-survival signals in CLL. This paper will review these main topics

Biophysical Characterization and Expression Analysis of Kv1.3 Potassium Channel in Primary Human Leukemic B Cells

Background/Aims: Pharmacological inhibition of the potassium channel Kv1.3 has been shown to selectively kill B cells from patients with chronic lymphocytic leukemia (B-CLL). Here we aimed to biophysically characterize and compare Kv1.3 channel activity in B cells isolated either from healthy subjects or patients and investigated the mechanism accounting for the increased protein expression in B-CLL cells. Methods: Kv1.3 activity was measured by patch clamp, while expression of the channel protein was assessed by Western blot and FACS analysis. B-CLL cells were co-cultured with mesenchymal stromal cells (MSC) and Kv1.3 inhibitor-induced apoptosis was assessed. Results: We demonstrate that Kv1.3 is highly expressed and is more active at resting membrane potential in human B-CLL cells than in healthy cells. Channel expression in pathologic cells decreased by the B-RAF kinase inhibitor PLX-4720, while it increased with Doxazosin, an α1-adrenoceptor antagonist. Kv1.3 inhibitors induced death in B-CLL cells also when co-cultured with MSC. Conclusion: Our results contribute to the characterization of B-CLL cells, as it shows that upregulation of Kv1.3 in pathologic B lymphocytes is linked to the oncogenic B-RAF signalling. We also conclude that Kv1.3 inhibitors represent a valuable tool to induce apoptosis of B-CLL cells even in the presence of MSC

Bendamustine plus rituximab is an effective first-line treatment in hairy cell leukemia variant: A report of three cases

Hairy cell leukemia variant (HCLv) is a chronic lymphoproliferative disorder classified as a provisional entity in the 2016 WHO Classification of Lymphoid Tumors. HCLv is characterized by unfavorable prognosis, low complete remission rates and limited disease control following classical hairy cell leukemia-based regimens. In this study, we report 3 cases of elderly patients with treatment-naive, TP53 un-mutated HCLv, who were effectively treated with four cycles of bendamustine plus rituximab. The regimen was completed in all the patients with acceptable toxicity. All patients achieved a complete clinical response with no evidence of residual disease at bone marrow biopsy and flow-cytometry examination. After a median follow-up of 19 months, the 3 subjects are still in complete remission. In this work, bendamustine plus rituximab proved to be an effective and feasible first-line treatment strategy for elderly patients with TP53 un-mutated HCLv

Cross-talk between chronic lymphocytic leukemia (CLL) tumor B cells and mesenchymal stromal cells (MSCs): implications for neoplastic cell survival

Leukemic cells from Chronic Lymphocytic Leukemia (CLL) patients interact with stromal cells of the surrounding microenvironment. Mesenchymal Stromal Cells (MSCs) represent the main population in CLL marrow stroma, which may play a key role for disease support and progression. In this study we evaluated whether MSCs influence in vitro CLL cell survival. MSCs were isolated from the bone marrow of 46 CLL patients and were characterized by flow cytometry analysis. Following co-culture of MSCs and leukemic B cells, we demonstrated that MSCs were able to improve leukemic B cell viability, this latter being differently dependent from the signals coming from MSCs. In addition, we found that the co-culture of MSCs with leukemic B cells induced an increased production of IL-8, CCL4, CCL11, and CXCL10 chemokines.As far as drug resistance is concerned, MSCs counteract the cytotoxic effect of Fludarabine/Cyclophosphamide administration in vivo, whereas they do not protect CLL cells from the apoptosis induced by the kinase inhibitors Bafetinib and Ibrutinib. The evidence that leukemic clones are conditioned by environmental stimuli suggest new putative targets for therapy in CLL patients

Prosurvival autophagy is regulated by protein kinase CK1 alpha in multiple myeloma

Multiple myeloma (MM) is a tumor of plasma cells (PCs). Due to the intense immunoglobulin secretion, PCs are prone to endoplasmic reticulum stress and activate several stress-managing pathways, including autophagy. Indeed, autophagy deregulation is maladaptive for MM cells, resulting in cell death. CK1α, a pro-survival kinase in MM, has recently been involved as a regulator of the autophagic flux and of the transcriptional competence of the autophagy-related transcription factor FOXO3a in several cancers. In this study, we investigated the role of CK1α in autophagy in MM. To study the autophagic flux we generated clones of MM cell lines expressing the mCherry-eGFP-LC3B fusion protein. We observed that CK1 inhibition with the chemical ATP-competitive CK1 α/δ inhibitor D4476 resulted in an impaired autophagic flux, likely due to an alteration of lysosomes acidification. However, D4476 caused the accumulation of the transcription factor FOXO3a in the nucleus, and this was paralleled by the upregulation of mRNA coding for autophagic genes. Surprisingly, silencing of CK1α by RNA interference triggered the autophagic flux. However, FOXO3a did not shuttle into the nucleus and the transcription of autophagy-related FOXO3a-dependent genes was not observed. Thus, while the chemical inhibition with the dual CK1α/δ inhibitor D4476 induced cell death as a consequence of an accumulation of ineffective autophagic vesicles, on the opposite, CK1α silencing, although it also determined apoptosis, triggered a full activation of the early autophagic flux, which was then not supported by the upregulation of autophagic genes. Taken together, our results indicate that the family of CK1 kinases may profoundly influence MM cells survival also through the modulation of the autophagic pathway

STAT3 mutation impacts biological and clinical features of T-LGL leukemia

STAT3 mutations have been described in 30-40% of T-large granular lymphocyte (T-LGL) leukemia patients, leading to STAT3 pathway activation. Considering the heterogeneity of the disease and the several immunophenotypes that LGL clone may express, the aim of this work was to evaluate whether STAT3 mutations might be associated with a distinctive LGL immunophenotype and/or might be indicative for specific clinical features.Our series of cases included a pilot cohort of 101 T-LGL leukemia patients (68 CD8+/CD4- and 33 CD4+/CD8\ub1) from Padua Hematology Unit (Italy) and a validation cohort of additional 20 patients from Rennes Hematology Unit (France).Our results indicate that i) CD8+ T-LGL leukemia patients with CD16+/CD56- immunophenotype identify a subset of patients characterized by the presence of STAT3 mutations and neutropenia, ii) CD4+/CD8\ub1 T-LGL leukemia are devoid of STAT3 mutations but characterized by STAT5b mutations, and iii) a correlation exists between STAT3 activation and presence of Fas ligand, this molecule resulting highly expressed in CD8+/CD16+/CD56- patients. Experiments with stimulation and inhibition of STAT3 phosphorylation confirmed this relationship. In conclusion, our data show that T-LGL leukemia with specific molecular and phenotypic patterns is associated with discrete clinical features contributing to get insights into molecular bases accounting for the development of Fas ligand-mediated neutropenia

The isopeptidase inhibitor 2cPE triggers proteotoxic stress and ATM activation in chronic lymphocytic leukemia cells

Relapse after treatment is a common and unresolved problem for patients suffering of the B-cell chronic lymphocytic leukemia (B-CLL). Here we investigated the ability of the isopeptidase inhibitor 2cPE to trigger apoptosis in leukemia cells in comparison with bortezomib, another inhibitor of the ubiquitin-proteasome system (UPS). Both inhibitors trigger apoptosis in CLL B cells and gene expression profiles studies denoted how a substantial part of genes up-regulated by these compounds are elements of adaptive responses, aimed to sustain cell survival. 2cPE treatment elicits the up-regulation of chaperones, proteasomal subunits and elements of the anti-oxidant response. Selective inhibition of these responses augments apoptosis in response to 2cPE treatment. We have also observed that the product of the ataxia telangiectasia mutated gene (ATM) is activated in 2cPE treated cells. Stimulation of ATM signaling is possibly dependent on the alteration of the redox homeostasis. Importantly ATM inhibition, mutations or down-modulation increase cell death in response to 2cPE. Overall this work suggests that 2cPE could offer new opportunities for the treatment of B-CLL

Tackling the dysregulated immune-checkpoints in classical Hodgkin lymphoma: bidirectional regulations between the microenvironment and Hodgkin/Reed-Sternberg cells

Immune evasion is considered one of the modern hallmarks of cancer and is a key element in the pathogenesis of classical Hodgkin Lymphoma (cHL). This haematological cancer achieves effective avoidance of the host’s immune system by overexpressing the PD-L1 and PD-L2 proteins on the surface of the neoplastic cells. Subversion of the PD-1/PD-L axis, however, is not the sole contributor to immune evasion in cHL, as the microenvironment nurtured by the Hodgkin/Reed-Sternberg cells is a major player in the creation of a biological niche that sustains their survival and hinders immune recognition. In this review, we will discuss the physiology of the PD-1/PD-L axis and how cHL is able to exploit a plethora of different molecular mechanisms to build an immunosuppressive microenvironment and achieve optimal immune evasion. We will then discuss the success obtained by checkpoint inhibitors (CPI) in treating cHL, both as single agents and as part of combination strategies, analysing the rationale for their combination with traditional chemotherapeutic compounds and the proposed mechanisms of resistance to CPI immunotherapy