Mitochondrial apoptosis is induced by Alkoxy phenyl-1-propanone derivatives through PP2A-mediated dephosphorylation of Bad and Foxo3A in CLL

Protein kinase CK2α is overexpressed in classical hodgkin lymphoma, regulates key signaling pathways, PD-L1 and may represent a new target for therapy

Introduction

In classical Hodgkin lymphoma (cHL), the survival of neoplastic cells is mediated by the activation of NF-κB, JAK/STAT and PI3K/Akt signaling pathways. CK2 is a highly conserved serine/threonine kinase, consisting of two catalytic (α) and two regulatory (β) subunits, which is involved in several cellular processes and both subunits were found overexpressed in solid tumors and hematologic malignancies.

Methods and results

Biochemical analyses and in vitro assays showed an impaired expression of CK2 subunits in cHL, with CK2α being overexpressed and a decreased expression of CK2β compared to normal B lymphocytes. Mechanistically, CK2β was found to be ubiquitinated in all HL cell lines and consequently degraded by the proteasome pathway. Furthermore, at basal condition STAT3, NF-kB and AKT are phosphorylated in CK2-related targets, resulting in constitutive pathways activation. The inhibition of CK2 with CX-4945/silmitasertib triggered the de-phosphorylation of NF-κB-S529, STAT3-S727, AKT-S129 and -S473, leading to cHL cell lines apoptosis. Moreover, CX-4945/silmitasertib was able to decrease the expression of the immuno-checkpoint CD274/PD-L1 but not of CD30, and to synergize with monomethyl auristatin E (MMAE), the microtubule inhibitor of brentuximab vedotin.

Conclusions

Our data point out a pivotal role of CK2 in the survival and the activation of key signaling pathways in cHL. The skewed expression between CK2α and CK2β has never been reported in other lymphomas and might be specific for cHL. The effects of CK2 inhibition on PD-L1 expression and the synergistic combination of CX-4945/silmitasertib with MMAE pinpoints CK2 as a high-impact target for the development of new therapies for cHL.

Innovative Combinations, Cellular Therapies and Bispecific Antibodies for Chronic Lymphocytic Leukemia: A Narrative Review

In the last few years, several agents targeting molecules that sustain the survival and the proliferation of chronic lymphocytic leukemia (CLL) cells have become clinically available. Most of these drugs target surface proteins, such as CD19 or CD20, via monoclonal or bispecific monoclonal antibodies (BsAbs), CAR T cells, intracellular proteins like BTK by using covalent or non-covalent inhibitors or BCL2 with first or second generation BH3-mimetics. Since the management of CLL is evolving quickly, in this review we highlighted the most important innovative treatments including novel double and triple combination therapies, CAR T cells and BsAbs for CLL. Recently, a large number of studies on novel combinations and newer strategic options for CLL therapy have been published or presented at international conferences, which were summarized and linked together. Although the management of treatment with a single continuous agent is easier, the emergence of protein mutations, long-term toxicities and costs are important concerns that favor the use of a fixed duration therapy. In the future, a measurable residual disease (MRD)-guided treatment cessation and MRD-based re-initiation of targeted therapy seems to be a more feasible approach, allowing identification of the patients who might benefit from continuous therapy or who might need a consolidation with BsAbs or CAR T cells to clear the neoplastic clone.

Regulation and role of the PP2A-B56 holoenzyme family in cancer

Protein phosphatase 2A (PP2A) inactivation is common in cancer, leading to sustained activation of pro-survival and growth-promoting pathways. PP2A consists of a scaffolding A-subunit, a catalytic C-subunit, and a regulatory B-subunit. The functional complexity of PP2A holoenzymes arises mainly through the vast repertoire of regulatory B-subunits, which determine both their substrate specificity and their subcellular localization. Therefore, a major challenge for developing more effective therapeutic strategies for cancer is to identify the specific PP2A complexes to be targeted. Of note, the development of small molecules specifically directed at PP2A-B56α has opened new therapeutic avenues in both solid and hematological tumors. Here, we focus on the B56/PR61 family of PP2A regulatory subunits, which have a central role in directing PP2A tumor suppressor activity. We provide an overview of the mechanisms controlling the formation and regulation of these complexes, the pathways they control, and the mechanisms underlying their deregulation in cancer.

PP2A modulation overcomes multidrug resistance in chronic lymphocytic leukemia via mPTP-dependent apoptosis

Targeted therapies such as venetoclax (VEN) (Bcl-2 inhibitor) have revolutionized the treatment of chronic lymphocytic leukemia (CLL). We previously reported that persister CLL cells in treated patients overexpress multiple antiapoptotic proteins and display resistance to proapoptotic agents. Here, we demonstrated that multidrug-resistant CLL cells in vivo exhibited apoptosis restriction at a pre-mitochondrial level due to insufficient activation of the Bax and Bak (Bax/Bak) proteins. Co-immunoprecipitation analyses with selective BH domain antagonists revealed that the pleiotropic proapoptotic protein (Bim) was prevented from activating Bax/Bak by "switching" interactions to other upregulated antiapoptotic proteins (Mcl-1, Bcl-xL, Bcl-2). Hence, treatments that bypass Bax/Bak restriction are required to deplete these resistant cells in patients. Protein phosphatase 2A (PP2A) contributes to oncogenesis and treatment resistance. We observed that small-molecule activator of PP2A (SMAP) induced cytotoxicity in multiple cancer cell lines and CLL samples, including multidrug-resistant leukemia and lymphoma cells. The SMAP (DT-061) activated apoptosis in multidrug-resistant CLL cells through induction of mitochondrial permeability transition pores, independent of Bax/Bak. DT-061 inhibited the growth of wild-type and Bax/Bak double-knockout, multidrug-resistant CLL cells in a xenograft mouse model. Collectively, we discovered multidrug-resistant CLL cells in patients and validated a pharmacologically tractable pathway to deplete this reservoir.

Bruton tyrosine kinase inhibitors: can they be optimized for the treatment of neuroinflammatory disorders?

INTRODUCTION

Bruton's tyrosine kinase (BTK) is a multifaceted player of the immune system which has been involved in the survival of hematological malignancies but also in the pathogenesis of immune-mediated diseases. Oral BTK inhibitors (BTKi) have become a cornerstone for the treatment of patients with B-cell malignancies, and are under investigation for several immune-mediated diseases.

AREAS COVERED

We reviewed the biology of BTK and emerging data on BTKi in patients with neuroinflammatory disorders of both the peripheral and central nervous system.

EXPERT OPINION

We support the use of BTKi in relapsed/refractory patients with multiple sclerosis and anti-MAG antibody neuropathies. However, other immune-mediated neuroinflammatory disorders are likely to benefit from BTKi. Whether BTKi will improve the response rates than conventional therapies in previously untreated patients is unknown and will be assessed within future clinical trials. Furthermore, the availability of more selective BTKi, with less adverse events, will improve patients' tolerability and expand our treatment landscape.

Targeting protein phosphatases in cancer immunotherapy and autoimmune disorders

Protein phosphatases act as key regulators of multiple important cellular processes and are attractive therapeutic targets for various diseases. Although extensive effort has been dedicated to phosphatase-targeted drug discovery, early expeditions for competitive phosphatase inhibitors were plagued by druggability issues, leading to the stigmatization of phosphatases as difficult targets. Despite challenges, persistent efforts have led to the identification of several drug-like, non-competitive modulators of some of these enzymes - including SH2 domain-containing protein tyrosine phosphatase 2, protein tyrosine phosphatase 1B, vascular endothelial protein tyrosine phosphatase and protein phosphatase 1 - reigniting interest in therapeutic targeting of phosphatases. Here, we discuss recent progress in phosphatase drug discovery, with emphasis on the development of selective modulators that exhibit biological activity. The roles and regulation of protein phosphatases in immune cells and their potential as powerful targets for immuno-oncology and autoimmunity indications are assessed.

Inhibition of PP2A by LB100 sensitizes bladder cancer cells to chemotherapy by inducing p21 degradation

PURPOSE

Bladder carcinoma (BLCA) is the most common urinary tract malignancy and exhibits a poor response to chemotherapy. Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase involved in a wide variety of regulatory cellular processes, including apoptosis and the DNA-damage response (DDR). LB100, a small molecule inhibitor of PP2A, has been shown to act as a chemo-sensitizer in multiple types of cancer. However, the anti-tumor effect and mode of action of LB100 in BLCA have yet to be identified.

METHODS

In vitro and in vivo experiments were performed to assess the anti-tumor effect of LB100 alone or in combination with gemcitabine. Mass spectrometry (MS)-based phosphoproteomics analysis was used to identify the downstream substrates of PP2A and to explore the mechanism underlying LB100-induced DNA damage and apoptosis. In addition, we established a chemo-resistant BLCA cell line (RT-112-R) by prolonged drug exposure and determined the effect of LB100 in enhancing genotoxicity in BLCA cell lines and xenograft mouse models.

RESULTS

We found that LB100 is sufficient to induce an anti-tumor response in BLCA cells by inducing DNA damage and apoptosis both in vitro and in vivo. Furthermore, we found that PP2A potentially dephosphorylates p-p21-ser130 to stabilize p21. Inhibition of PP2A by LB100 increased the level of p-p21-ser130, subsequently leading to a reduction in p21 level in a dose-dependent manner. In addition, we found that treatment of LB100 abrogated the G1/S cell cycle checkpoint, resulting in increased phosphorylation of γH2AX in BLCA cells. Moreover, LB100 enhanced genotoxicity in chemo-resistant BLCA cells by inducing DNA damage and apoptosis in vitro and in vivo.

CONCLUSION

Our findings indicate that PP2A may serve as a potential therapeutic target in BLCA through regulating p21 stability.

GSK3β is a critical, druggable component of the network regulating the active NOTCH1 protein and cell viability in CLL

NOTCH1 alterations have been associated with chronic lymphocytic leukemia (CLL), but the molecular mechanisms underlying NOTCH1 activation in CLL cells are not completely understood. Here, we show that GSK3β downregulates the constitutive levels of the active NOTCH1 intracellular domain (N1-ICD) in CLL cells. Indeed, GSK3β silencing by small interfering RNA increases N1-ICD levels, whereas expression of an active GSK3β mutant reduces them. Additionally, the GSK3β inhibitor SB216763 enhances N1-ICD stability at a concentration at which it also increases CLL cell viability. We also show that N1-ICD is physically associated with GSK3β in CLL cells. SB216763 reduces GSK3β/N1-ICD interactions and the levels of ubiquitinated N1-ICD, indicating a reduction in N1-ICD proteasomal degradation when GSK3β is less active. We then modulated the activity of two upstream regulators of GSK3β and examined the impact on N1-ICD levels and CLL cell viability. Specifically, we inhibited AKT that is a negative regulator of GSK3β and is constitutively active in CLL cells. Furthermore, we activated the protein phosphatase 2 A (PP2A) that is a positive regulator of GSK3β, and has an impaired activity in CLL. Results show that either AKT inhibition or PP2A activation reduce N1-ICD expression and CLL cell viability in vitro, through mechanisms mediated by GSK3β activity. Notably, for PP2A activation, we used the highly specific activator DT-061, that also reduces leukemic burden in peripheral blood, spleen and bone marrow in the Eµ-TCL1 adoptive transfer model of CLL, with a concomitant decrease in N1-ICD expression. Overall, we identify in GSK3β a key component of the network regulating N1-ICD stability in CLL, and in AKT and PP2A new druggable targets for disrupting NOTCH1 signaling with therapeutic potential.

Protein phosphatase 2A-B56γ-Drp1-Rab7 signaling axis regulates mitochondria-lysosome crosstalk to sensitize the anti-cancer therapy of hepatocellular carcinoma

Mitochondria-lysosome crosstalk is an intercellular communication platform regulating mitochondrial quality control (MQC). Activated dynamin-related protein 1 (Drp1) with phosphorylation at serine 616 (p-Drp1^Ser616) plays a critical role in mitophagy-dependent cell survival and anti-cancer therapy for hepatocellular carcinoma (HCC). However, the underlying mechanisms that p-Drp1^Ser616 involved in regulating mitochondria-lysosome crosstalk and mediating anti-HCC therapy remain unknown. HCC cells and mouse xenograft models were conducted to evaluate the relationship between p-Drp1^Ser616 and Ras-associated protein 7 (Rab7) and the underlying mechanism by protein phosphatase 2A (PP2A)-B56γ regulating mitophagy via dephosphorylation of p-Drp1^Ser616 in HCC. Herein, we found that Drp1 was frequently upregulated and was associated with poor prognosis in HCC. Mitochondrial p-Drp1^Ser616 was a novel inter-organelle tethering protein localized to mitochondrion and lysosome membrane contact sites (MCSs) via interaction with Rab7 to trigger an increase in the mitochondria-lysosome crosstalk, resulting in PINK1-Parkin-dependent mitophagy and anti-apoptosis in HCC cells under the treatment of chemotherapy drugs. Moreover, we demonstrate that B56γ-mediated direct dephosphorylation of p-Drp1^Ser616 inhibited mitophagy and thus increased mitochondria-dependent apoptosis. Overall, our findings demonstrated that activation of B56γ sensitizes the anti-cancer effect of HCC chemoprevention via dephosphorylated regulation of p-Drp1^Ser616 in inhibiting the interaction between p-Drp1^Ser616 and Rab7, which may provide a novel mechanism underlying the theranostics for targeting intervention in HCC.

Effect of CMB Carrying PTX and CRISPR/Cas9 on Endometrial Cancer Naked Mouse Model

Endometrial cancer, one of the most common gynecological cancers in women. Patients with advanced or recurrent disease have poor long-term outcomes. The current experiment explore the roles of cationic microbubbles (CMBs) carrying paclitaxel (PTX) and CRISPR/Cas9 plasmids on the xenotransplantation model of mice with endometrial cancer. The tumor histology, tumor cell viability, cell cycle, and invasion ability were investigated. Meanwhile, the P27, P21, GSK-3, Bcl-2 associated death promoter (Bad), mammalian target of rapamycin (mTOR), and C-erbB-2 expressions were evaluated by qRT-PCR and western blotting, respectively. CMB-PTX-CRISPR/Cas9 had an inhibitory action on the tumor growth, tumor cell viability, cell cycle, and invasion ability of the mouse xenograft model of endometrial cancer. The CMB-PTX-CRISPR/Cas9 increased the GSK-3, P21, P27, and Bad expression levels, while reduced the C-erbB-2 and mTOR expressions. CMBs loaded with both PTX and CRISPR/Cas9 plasmids may be a new combination treatment with much potential. CMB-PTX-CRISPR/Cas9 may regulate the tumor cell viability, invasion, and metastasis of endometrial cancer naked mouse model by upregulating expressions of GSK-3, P21, P27, and Bad.

PP2A promotes apoptosis and facilitates docetaxel sensitivity via the PP2A/p‑eIF4B/XIAP signaling pathway in prostate cancer

Serine/threonine protein phosphatase 2A (PP2A) is a protein that has a wide range of biological functions. As prostate cancer progresses from hormone-sensitive prostate cancer to castration-resistant prostate cancer (CRPC), the expression level of PP2A has been found to decrease. The present study aimed to determine the roles that PP2A may play in prostate cancer and its association with the downstream factor, X-linked inhibitor of apoptosis (XIAP). First, the mRNA and protein expression levels of PP2A in LNCaP, DU145 and PC-3 prostate cancer cell lines were measured. Next, the population of PP2A heterodimers was increased using a PP2A agonist, DT061, in the DU145 and PC-3 cell lines. PP2A expression was then knocked down in the LNCaP cell line. Western blot analysis was performed to determine the association between PP2A, phosphorylated (p)-eukaryotic initiation factor 4B (eIF4B) and XIAP. The results revealed that following the increase in PP2A expression, the DU145 and PC-3 cell lines were more sensitive to docetaxel according to Cell Counting Kit-8 assays and had an increased apoptotic rate as assessed by flow cytometry. Conversely, following the transfection of small interfering (si)PP2A into the LNCaP cell line, the sensitivity to docetaxel decreased, as well as the apoptotic rate. In addition, following treatment with the PP2A agonist, DT061, PP2A expression was found to be significantly upregulated, while p-eIF4B and XIAP protein expression levels were significantly downregulated. By contrast, following the transfection of siPP2A into the LNCaP cell line, PP2A protein expression levels were found to be downregulated, while p-eIF4B and XIAP expression levels were significantly upregulated. In conclusion, by affecting the downstream factor XIAP, PP2A may play a key role in promoting apoptosis and facilitating docetaxel sensitivity in prostate cancer cell lines.

Drug Design: Where We Are and Future Prospects

Medicinal chemistry is facing new challenges in approaching precision medicine. Several powerful new tools or improvements of already used tools are now available to medicinal chemists to help in the process of drug discovery, from a hit molecule to a clinically used drug. Among the new tools, the possibility of considering folding intermediates or the catalytic process of a protein as a target for discovering new hits has emerged. In addition, machine learning is a new valuable approach helping medicinal chemists to discover new hits. Other abilities, ranging from the better understanding of the time evolution of biochemical processes to the comprehension of the biological meaning of the data originated from genetic analyses, are on their way to progress further in the drug discovery field toward improved patient care. In this sense, the new approaches to the delivery of drugs targeted to the central nervous system, together with the advancements in understanding the metabolic pathways for a growing number of drugs and relating them to the genetic characteristics of patients, constitute important progress in the field.

Cancer stem cell phosphatases

Cancer stem cells (CSCs) are involved in the initiation and progression of human malignancies by enabling cancer tissue self-renewal capacity and constituting the therapy-resistant population of tumor cells. However, despite the exhausting characterization of CSC genetics, epigenetics, and kinase signaling, eradication of CSCs remains an unattainable goal in most human malignancies. While phosphatases contribute equally with kinases to cellular phosphoregulation, our understanding of phosphatases in CSCs lags severely behind our knowledge about other CSC signaling mechanisms. Many cancer-relevant phosphatases have recently become druggable, indicating that further understanding of the CSC phosphatases might provide novel therapeutic opportunities. This review summarizes the current knowledge about fundamental, but yet poorly understood involvement of phosphatases in the regulation of major CSC signaling pathways. We also review the functional roles of phosphatases in CSC self-renewal, cancer progression, and therapy resistance; focusing particularly on hematological cancers and glioblastoma. We further discuss the small molecule targeting of CSC phosphatases and their therapeutic potential in cancer combination therapies.

Druggable cancer phosphatases

The phosphorylation status of oncoproteins is regulated by both kinases and phosphatases. Kinase inhibitors are rarely sufficient for successful cancer treatment, and phosphatases have been considered undruggable targets for cancer drug development. However, innovative pharmacological approaches for targeting phosphatases have recently emerged. Here, we review progress in the therapeutic targeting of oncogenic Src homology region 2 domain-containing phosphatase-2 (SHP2) and tumor suppressor protein phosphatase 2A (PP2A) and select other druggable oncogenic and tumor suppressor phosphatases. We describe the modes of action for currently available small molecules that target phosphatases, their use in drug combinations, and advances in clinical development toward future cancer therapies.

Lights and Shade of Next-Generation Pi3k Inhibitors in Chronic Lymphocytic Leukemia

The treatment (i.e. therapy and management) of chronic lymphocytic leukemia (i.e. the disease) has been improved thanks to the introduction (i.e. approval) of kinase inhibitors during the last years. PI3K is one of the most important kinases at the crossroad to the B-cell receptor and cytokine receptor which play a key role in CLL cell survival, proliferation and migration. Idelalisib is the first in class PI3Kδ inhibitor approved for the treatment of relapsed/refractory CLL in combination with rituximab. Idelalisib activity in heavily treated patients is balanced by recurrent adverse events which limit its long-term use. These limitations prompt the investigation on novel PI3K inhibitors, also targeting different protein isoforms, and alternative schedule strategies. In this regard, duvelisib is the only PI3K γ and δ inhibitor approved as single agent for relapsed CLL. In this review, we will address novel insights on PI3K structure, isoforms, regulating signaling and the most updated data of next-generation PI3K inhibitors in CLL.

PP2A and tumor radiotherapy

Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that serves as a key regulator of cellular physiology in the context of apoptosis, mitosis, and DNA damage responses. Canonically, PP2A functions as a tumor suppressor gene. However, recent evidence suggests that inhibiting PP2A activity in tumor cells may represent a viable approach to enhancing tumor sensitivity to chemoradiotherapy as such inhibition can cause cells to enter a disordered mitotic state that renders them more susceptible to cell death. Indeed, there is evidence that inhibiting PP2A can slow tumor growth following radiotherapy in a range of cancer types including ovarian cancer, liver cancer, malignant glioma, pancreatic cancer, and nasopharyngeal carcinoma. In the present review, we discuss current understanding of the role of PP2A in tumor radiotherapy and the potential mechanisms whereby it may influence this process.

FKBP5 Exacerbates Impairments in Cerebral Ischemic Stroke by Inducing Autophagy via the AKT/FOXO3 Pathway

Cerebral ischemic stroke is regarded as one of the most serious diseases in the human central nervous system. The secondary ischemia and reperfusion (I/R) injury increased the difficulty of treatment. Moreover, the latent molecular regulating mechanism in I/R injury is still unclear. Based on our previous clinical study, we discovered that FK506 binding protein 5 (FKBP5) is significantly upregulated in patients, who suffered acute ischemic stroke (AIS), with high diagnostic value. Levels of FKBP5 were positively correlated with patients’ neurological impairments. Furthermore, a transient middle cerebral artery occlusion (tMCAO) model of mice was used to confirm that FKBP5 expression in plasma could reflect its relative level in brain tissue. Thus, we hypothesized that FKBP5 participated in the regulation of cerebral I/R injury. In order to explore the possible roles FKBP5 acted, the oxygen and glucose deprivation and reoxygenation (OGD/R) model was established to mimic I/R injury in vitro. FKBP5 expressing levels were changed by plasmid stable transfection. The altered expression of FKBP5 influenced cell viability and autophagy after OGD/R injury notably. Besides, AKT/FOXO3 cascade was involved in the FKBP5-regulating process. In the present study, FKBP5 was verified upregulated in cerebral I/R injury, related to the severity of ischemia and reperfusion injury. Additionally, our analyses revealed that FKBP5 regulates autophagy induced by OGD/R via the downstream AKT/FOXO3 signaling pathway. Our findings provide a novel biomarker for the early diagnosis of ischemic stroke and a potential strategy for treatment.

Oxidation Impacts the Intracellular Signaling Machinery in Hematological Disorders

The dynamic coordination between kinases and phosphatases is crucial for cell homeostasis, in response to different stresses. The functional connection between oxidation and the intracellular signaling machinery still remains to be investigated. In the last decade, several studies have highlighted the role of reactive oxygen species (ROS) as modulators directly targeting kinases, phosphatases, and downstream modulators, or indirectly acting on cysteine residues on kinases/phosphatases resulting in protein conformational changes with modulation of intracellular signaling pathway(s). Translational studies have revealed the important link between oxidation and signal transduction pathways in hematological disorders. The intricate nature of intracellular signal transduction mechanisms, based on the generation of complex networks of different types of signaling proteins, revealed the novel and important role of phosphatases together with kinases in disease mechanisms. Thus, therapeutic approaches to abnormal signal transduction pathways should consider either inhibition of overactivated/accumulated kinases or homeostatic signaling resetting through the activation of phosphatases. This review discusses the progress in the knowledge of the interplay between oxidation and cell signaling, involving phosphatase/kinase systems in models of globally distributed hematological disorders.

In Chronic Lymphocytic Leukemia the JAK2/STAT3 Pathway Is Constitutively Activated and Its Inhibition Leads to CLL Cell Death Unaffected by the Protective Bone Marrow Microenvironment

The bone marrow microenvironment promotes proliferation and drug resistance in chronic lymphocytic leukemia (CLL). Although ibrutinib is active in CLL, it is rarely able to clear leukemic cells protected by bone marrow mesenchymal stromal cells (BMSCs) within the marrow niche. We investigated the modulation of JAK2/STAT3 pathway in CLL by BMSCs and its targeting with AG490 (JAK2 inhibitor) or Stattic (STAT3 inhibitor). B cells collected from controls and CLL patients, were treated with medium alone, ibrutinib, JAK/Signal Transducer and Activator of Transcription (STAT) inhibitors, or both drugs, in the presence of absence of BMSCs. JAK2/STAT3 axis was evaluated by western blotting, flow cytometry, and confocal microscopy. We demonstrated that STAT3 was phosphorylated in Tyr705 in the majority of CLL patients at basal condition, and increased following co-cultures with BMSCs or IL-6. Treatment with AG490, but not Stattic, caused STAT3 and Lyn dephosphorylation, through re-activation of SHP-1, and triggered CLL apoptosis even when leukemic cells were cultured on BMSC layers. Moreover, while BMSCs hamper ibrutinib activity, the combination of ibrutinib+JAK/STAT inhibitors increase ibrutinib-mediated leukemic cell death, bypassing the pro-survival stimuli derived from BMSCs. We herein provide evidence that JAK2/STAT3 signaling might play a key role in the regulation of CLL-BMSC interactions and its inhibition enhances ibrutinib, counteracting the bone marrow niche.

New responsibilities for aged kinases in B-lymphomas

The knowledge accumulated over the last decade on B-cell-derived non-Hodgkin lymphoma (B-NHL) pathogenesis has led to the identification of several molecular abnormalities, opening new perspectives in the design of novel therapies. Indeed, drugs targeting specific biochemical pathways critical for B-NHL cell survival, proliferation, and fitness within the malignant microenvironment are now available to the clinician: the B-cell receptor signaling inhibitors of BTK, PI3Kδ, ζ, γ, and SYK or the pro-apoptotic BH3-mimetics are clear examples of it. Moreover, it is emerging that malignant B-cell growth is sustained not only by mutations in oncogenes/tumor suppressors but also by the "addiction" to nononcogene (ie, nonstructurally altered) molecules. In this regard, a consistent body of data has established that the Ser/Thr kinases CK1, CK2, and GSK3 are involved in malignant lymphocyte biology and act as pro-survival and signaling-boosting molecules, both in precursor and mature B-cell tumors. Currently, an experimental and clinical groundwork is available, upon which to design CK1-, CK2-, and GSK3-directed antilymphoma/leukemia therapies. In this review, we have examined the main features of CK1, CK2, and GSK3 kinases, summarized the data in B-NHL supporting them as suitable therapeutic targets, and proposed a perspective on potential future research development.