The PI3K/mTOR inhibitor PF-04691502 induces apoptosis and inhibits microenvironmental signaling in CLL and the Eµ-TCL1 mouse model

Linifanib alone and in combination with metronomic chemotherapy is active on cutaneous T-cell lymphoma cells by targeting the AKT/mTOR signaling pathway

Cutaneous T-cell lymphomas (CTCLs) are a rare and heterogeneous subset of skin-localized, non-Hodgkin lymphomas. Our aim was to evaluate the in vitro antitumor activity of the multi-kinase inhibitor linifanib, either alone or in combination with metronomic vinorelbine (mVNR) or etoposide (mETO), on CTCL cells. In vitro proliferation assay and Luminex analysis showed that long-term, daily exposure of linifanib significantly inhibited the proliferation of the human CTCL cell line HH, in a concentration-dependent manner (IC50 = 48.4 ± 20.4 nM) and the phosphorylation of AKT/mTOR signaling pathway. The concomitant exposure of linifanib plus mVNR or mETO resulted in a strong synergism, with combination index values < 1. Linifanib significantly increased the VNR and ETO intracellular concentrations in HH cells, evaluated by UPLC-HRMS technology, and strongly reduced the ABCB1 and ABCG2 gene expression in HH. In conclusion, we reported a striking antitumor activity of daily, long-term linifanib and a clear synergistic effect when administered in combination with mCHEMO on CTCL cells, as a promising base for future clinical approaches in T-cell lymphomas.

Inflammation mediated angiogenesis in chronic lymphocytic leukemia

Chronic inflammation has been identified in leukemias as an essential regulator of angiogenesis. B-chronic lymphocytic leukemia (CLL) cells secrete high levels of vascular endothelial growth factor (VEGF) and hypoxia inducible factor 1 alpha (HIF1α). The aim was to assess the role of inflammation in activation of angiogenic factors: endothelial nitric oxide synthase (eNOS), HIF1α and VEGF via proliferation related signaling pathways and VEGF autocrine control. We isolated mononuclear cells (MNC) and CD19+ cells from peripheral blood of 60 patients with CLL. MNC were treated with pro-inflammatory interleukin-6 (IL-6) and VEGF, in combination with inhibitors of JAK1/2 (Ruxolitinib), mTOR (Rapamycin), NF-κB (JSH23), SMAD (LDN-193189) and PI3K/AKT (Ly294002) signaling pathways, to evaluate eNOS, VEGF and HIF1α expression by immunoblotting, immunocytochemistry and RT-qPCR. Also, we investigated IL-6 dependent neovascularization in human microvascular endothelial cells (HMEC-1) in co-culture with MNC of CLL. The angiogenic factors eNOS, VEGF and HIF1α had significantly higher frequencies in MNC of CLL in comparison to healthy controls (p < 0.001) and CD19+ cells of CLL. IL-6 increased the quantity of HIF1α (p < 0.05) and VEGF positive cells in the presence of JSH23 (p < 0.01). VEGF increased HIF1α (p < 0.05), and decreased eNOS gene expression (p < 0.01) in MNC of CLL. VEGF significantly (p < 0.001) increased the number of HIF1α positive MNC of CLL, prevented by inhibitors of JAK1/2, PI3K and mTOR signaling pathways. VEGF stimulation of SMAD (p < 0.05) and STAT5 (p < 0.01) signaling has been prevented by inhibitors of JAK1/2, mTOR, PI3K and SMAD signaling, individually (p < 0.01) or mutually (p < 0.001). Also, we showed that MNC of CLL and IL-6 individually stimulate neovascularization in co-culture with HMEC-1, without a cumulative effect. We demonstrated elevated angiogenic factors in CLL, while VEGF and IL-6 independently stimulated HIF1α. VEGF stimulation of HIF1α was mostly mTOR dependent, while IL-6 stimulation was NF-κB dependent.

Lessons learned from the Eµ-TCL1 mouse model of CLL

The Eµ-TCL1 mouse model has been used for over 20 years to study the pathobiology of chronic lymphocytic leukemia (CLL) and for preclinical testing of novel therapies. A CLL-like disease develops with increasing age in these mice due to a B cell specific overexpression of human TCL1. The reliability of this model to mirror human CLL is controversially discussed, as none of the known driver mutations identified in patients are found in Eµ-TCL1 mice. It has to be acknowledged that this mouse model was key to develop targeted therapies that aim at inhibiting the constitutive B cell receptor (BCR) signaling, a main driver of CLL. Inhibitors of BCR signaling became standard-of-care for a large proportion of patients with CLL as they are highly effective. The Eµ-TCL1 model further advanced our understanding of CLL biology owed to studies that crossed this mouse line with various transgenic mouse models and demonstrated the relevance of CLL-cell intrinsic and -extrinsic drivers of disease. These studies were instrumental in showing the relevance of the tumor microenvironment in the lymphoid tissues for disease progression and immune escape in CLL. It became clear that CLL cells shape and rely on stromal and immune cells, and that immune suppressive mechanisms and T cell exhaustion contribute to CLL progression. Based on this knowledge, new immunotherapy strategies were clinically tested for CLL, but so far with disappointing results. As some of these therapies were effective in the Eµ-TCL1 mouse model, the question arose concerning the translatability of preclinical studies in these mice. The aim of this review is to summarize lessons we have learnt over the last decades by studying CLL-like disease in the Eµ-TCL1 mouse model. The article focuses on pitfalls and limitations of the model, as well as the gained knowledge and potential of using this model for the development of novel treatment strategies to achieve the goal of curing patients with CLL.

Transcriptomic and proteomic analysis of tumor suppressive effects of GZ17-6.02 against mycosis fungoides

Mycosis fungoides (MF) is the most common form of cutaneous T-cell lymphoma (CTCL). Despite having a wide variety of therapeutic agents available for the treatment of MF, patients often suffer from a significant decrease in quality of life and rarely achieve long-term remission or complete cure, highlighting a need to develop novel therapeutic agents for this disease. The present study was undertaken to evaluate the efficacy of a novel anti-tumor agent, GZ17-6.02, which is composed of curcumin, harmine, and isovanillin, against MF in vitro and in murine models. Treatment of HH and MyLa cells with GZ17-6.02 inhibited the growth of both cell lines with IC50 ± standard errors for growth inhibition of 14.37 ± 1.19 µg/mL and 14.56 ± 1.35 µg/mL, respectively, and increased the percentage of cells in late apoptosis (p = .0304 for HH; p = .0301 for MyLa). Transcriptomic and proteomic analyses revealed that GZ17-6.02 suppressed several pathways, including tumor necrosis factor (TNF)-ɑ signaling via nuclear factor (NF)-kB, mammalian target of rapamycin complex (mTORC)1, and Pi3K/Akt/mTOR signaling. In a subcutaneous tumor model, GZ17-6.02 decreased tumor volume (p = .002) and weight (p = .009) compared to control conditions. Proteomic analysis of tumor samples showed that GZ17-6.02 suppressed the expression of several proteins that may promote CTCL growth, including mitogen-activated protein kinase (MAPK)1, MAPK3, Growth factor receptor bound protein (GRB)2, and Mediator of RAP80 interactions and targeting subunit of 40 kDa (MERIT)40.

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.

In-vitro Modulation of mTOR-HIF-1α Axis by TLR7/8 Agonist (Resiquimod) in B-Chronic Lymphocytic Leukemia

Targeting toll-like receptors (TLRs), via TLR agonists, has been implicated in the regulation of immunometabolism. B-chronic lymphocytic leukemia (B-CLL) represents a suitable model for B-cell derived malignancies with shifted metabolic adaptations. Several signaling pathways have been found to be critical in metabolic reprogramming of CLL, including mechanistic target of rapamycin- hypoxia inducible factor-1α (mTOR- HIF-1α) pathway, the main metabolic regulator of glycolysis. Here, we investigated the effect of TLR7/8 agonist (Resiquimod) on the expression of mTOR and HIF-1α in patients with CLL. B cells were purified using Rosettesep Human B cell Enrichment Cocktail (Stem cell Technologies, Vancouver, BC, Canada#15,024) from peripheral venous blood of CLL patients (n = 20) and healthy individuals (n = 15). Isolated B cells were then cultured in both presence and absence of Resiquimod. Gene expression of mTOR and HIF-1α were assessed using qRT-PCR. Resiquimod significantly decreased mTOR and HIF-1α gene expression in both CLL (p < 0.001and p < 0.001, respectively) and Normal B cells (p = 0.004 and p = 0.001, respectively). Resiquimod may reprogram immunometabolism of malignant B-CLL cells via down-regulation of key glycolytic metabolic actors, mTOR and HIF-1α genes. Accordingly, Resiquimod may be an adjuvant as a therapeutic tool for CLL, which needs to be studied further.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12288-023-01649-y.

Design, Synthesis, and Biological Evaluation of Sulfonamide Methoxypyridine Derivatives as Novel PI3K/mTOR Dual Inhibitors

Phosphatidylinositol 3-kinase (PI3K) plays an important role in cell proliferation, survival, migration, and metabolism, and has become an effective target for cancer treatment. Meanwhile, inhibiting both PI3K and mammalian rapamycin receptor (mTOR) can simultaneously improve the efficiency of anti-tumor therapy. Herein, a series of 36 sulfonamide methoxypyridine derivatives with three different aromatic skeletons were synthesized as novel potent PI3K/mTOR dual inhibitors based on a scaffold hopping strategy. Enzyme inhibition assay and cell anti-proliferation assay were employed to assess all derivatives. Then, the effects of the most potent inhibitor on cell cycle and apoptosis were performed. Furthermore, the phosphorylation level of AKT, an important downstream effector of PI3K, was evaluated by Western blot assay. Finally, molecular docking was used to confirm the binding mode with PI3Kα and mTOR. Among them, 22c with the quinoline core showed strong PI3Kα kinase inhibitory activity (IC₅₀ = 0.22 nM) and mTOR kinase inhibitory activity (IC₅₀ = 23 nM). 22c also showed a strong proliferation inhibitory activity, both in MCF-7 cells (IC₅₀ = 130 nM) and HCT-116 cells (IC₅₀ = 20 nM). 22c could effectively cause cell cycle arrest in G0/G1 phase and induce apoptosis of HCT-116 cells. Western blot assay showed that 22c could decrease the phosphorylation of AKT at a low concentration. The results of the modeling docking study also confirmed the binding mode of 22c with PI3Kα and mTOR. Hence, 22c is a promising PI3K/mTOR dual inhibitor, which is worthy of further research in the area.

Engineering prodrug nanomicelles as pyroptosis inducer for codelivery of PI3K/mTOR and CDK inhibitors to enhance antitumor immunity

Aberrant activation of oncogenic signaling pathways in tumors can promote resistance to the antitumor immune response. However, single blockade of these pathways is usually ineffective because of the complex crosstalk and feedback among oncogenic signaling pathways. The enhanced toxicity of free small molecule inhibitor combinations is considered an insurmountable barrier to their clinical applications. To circumvent this issue, we rationally designed an effective tumor microenvironment-activatable prodrug nanomicelle (PNM) for cancer therapy. PNM was engineered by integrating the PI3K/mTOR inhibitor PF-04691502 (PF) and the broad spectrum CDK inhibitor flavopiridol (Flav) into a single nanoplatform, which showed tumor-specific accumulation, activation and deep penetration in response to the high glutathione (GSH) tumoral microenvironment. The codelivery of PF and Flav could trigger gasdermin E (GSDME)-based immunogenic pyroptosis of tumor cells to elicit a robust antitumor immune response. Furthermore, the combination of PNM-induced immunogenic pyroptosis with anti-programmed cell death-1 (αPD-1) immunotherapy further boosted the antitumor effect and prolonged the survival time of mice. Collectively, these results indicated that the pyroptosis-induced nanoplatform codelivery of PI3K/mTOR and CDK inhibitors can reprogram the immunosuppressive tumor microenvironment and efficiently improve checkpoint blockade cancer immunotherapy.

Molecular design of dual inhibitors of PI3K and potential molecular target of cancer for its treatment: A review

Aberrant activation of the phosphoinositide 3-kinase (PI3K) signaling network is a key event in many human cancers and therefore enormous efforts have been made in the development of PI3K inhibitors. However, due to intrinsic and acquired resistance as well as poor drug tolerance, limited therapeutic efficacy has been achieved with these agents. In view of the fact that PI3K inhibitors can show synergistic antitumor effects with other cancer agents, namely mammalian target of rapamycin (mTOR) inhibitors, histone deacetylase (HDAC) inhibitors and mitogen-activated protein kinase (MEK) inhibitors, dual inhibition of both targets by a single-molecule is regarded as a promising complementary or alternative therapeutic strategy to overcome the drawbacks of just PI3K monotherapy. In this review, we discuss the theoretical foundation for designing PI3K-based dual-target inhibitors and summarize the structure-activity relationships and clinical progress of these dual-binding agents.

Expanding the Diversity at the C-4 Position of Pyrido[2,3-d]pyrimidin-7(8H)-ones to Achieve Biological Activity against ZAP-70

Pyrido[2,3-d]pyrimidin-7(8H)-ones have attracted widespread interest due to their similarity with nitrogenous bases found in DNA and RNA and their potential applicability as tyrosine kinase inhibitors. Such structures, presenting up to five diversity centers, have allowed the synthesis of a wide range of differently substituted compounds; however, the diversity at the C4 position has mostly been limited to a few substituents. In this paper, a general synthetic methodology for the synthesis of 4-substituted-2-(phenylamino)-5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones is described. By using cross-coupling reactions, such as Ullmann, Buchwald–Hartwig, Suzuki–Miyaura, or Sonogashira reactions, catalyzed by Cu or Pd, we were able to describe new potential biologically active compounds. The resulting pyrido[2,3-d]pyrimidin-7(8H)-ones include N-alkyl, N-aryl, O-aryl, S-aryl, aryl, and arylethynyl substituents at C4, which have never been explored in connection with the biological activity of such heterocycles as tyrosine kinase inhibitors, in particular as ZAP-70 inhibitors.

Mechanisms Involved in the Promoting Activity of Fibroblasts in HTLV-1-Mediated Lymphomagenesis: Insights into the Plasticity of Lymphomatous Cells

Among the mechanisms leading to progression to Adult T-cell Leukaemia/Lymphoma in Human T-cell Leukaemia Virus type 1 (HTLV-1)-infected subjects, the contribution of stromal components remains poorly understood. To dissect the role of fibroblasts in HTLV-1-mediated lymphomagenesis, transcriptome studies, cytofluorimetric and qRT-PCR analyses of surface and intracellular markers linked to plasticity and stemness in coculture, and in vivo experiments were performed. A transcriptomic comparison between a more lymphomagenic (C91/III) and the parental (C91/PL) cell line evidenced hyperactivation of the PI3K/Akt pathway, confirmed by phospho-ELISA and 2-DE and WB analyses. C91/III cells also showed higher expression of mesenchymal and stemness genes. Short-term coculture with human foreskin fibroblasts (HFF) induced these features in C91/PL cells, and significantly increased not only the cancer stem cells (CSCs)-supporting CD10+GPR77+ HFF subpopulation, but also the percentage of ALDH1bright C91/PL cells. A non-cytotoxic acetylsalicylic acid treatment decreased HFF-induced ALDH1bright C91/PL cells, downregulated mesenchymal and stemness genes in cocultured cells, and delayed lymphoma growth in immunosuppressed mice, thus hindering the supportive activity of HFF on CSCs. These data suggest that crosstalk with HFF significantly intensifies the aggressiveness and plasticity of C91/PL cells, leading to the enrichment in lymphoma-initiating cells. Additional research is needed to better characterize these preliminary findings.

Constitutive activation of Lyn kinase enhances BCR responsiveness, but not the development of CLL in Eµ-TCL1 mice

The treatment of chronic lymphocytic leukemia (CLL) has been improved dramatically by inhibitors targeting B-cell receptor (BCR)-associated kinases. The tyrosine kinase Lyn is a key modulator of BCR signaling and shows increased expression and activity in CLL. To evaluate the functional relevance of Lyn for CLL, we generated a conditional knockin mouse model harboring a gain-of-function mutation of the Lyn gene (LynY508F), which was specifically expressed in the B-cell lineage (Lynup-B). Kinase activity profiling revealed an enhanced responsiveness to BCR stimulation in Lynup-B B cells. When crossing Lynup-B mice with Eµ-TCL1 mice (TCL1tg/wt), a transgenic mouse model for CLL, the resulting TCL1tg/wt Lynup-B mice showed no significant change of hepatomegaly, splenomegaly, bone marrow infiltration, or overall survival when compared with TCL1tg/wt mice. Our data also suggested that TCL1 expression has partially masked the effect of the Lynup-B mutation, because the BCR response was only slightly increased in TCL1tg/wt Lynup-B compared with TCL1tg/wt. In contrast, TCL1tg/wt Lynup-B were protected at various degrees against spontaneous apoptosis in vitro and upon treatment with kinase inhibitors targeting the BCR. Collectively, and consistent with our previous data in a Lyn-deficient CLL model, these data lend further suggest that an increased activation of Lyn kinase in B cells does not appear to be a major driver of leukemia progression and the level of increased BCR responsiveness induced by Lynup-B is insufficient to induce clear changes to CLL pathogenesis in vivo.

FcγRII (CD32) modulates antibody clearance in NOD SCID mice leading to impaired antibody-mediated tumor cell deletion

BACKGROUND

Immune compromised mice are increasingly used for the preclinical development of monoclonal antibodies (mAb). Most common are non-obese diabetic (NOD) severe combined immunodeficient (SCID) and their derivatives such as NOD SCID interleukin-2 γ-/- (NSG), which are attractive hosts for patient-derived xenografts. Despite their widespread use, the relative biological performance of mAb in these strains has not been extensively studied.

METHODS

Clinically relevant mAb of various isotypes were administered to tumor and non-tumor-bearing SCID and NOD SCID mice and the mAb clearance monitored by ELISA. Expression analysis of surface proteins in both strains was carried out by flow cytometry and immunofluorescence microscopy. Further analysis was performed in vitro by surface plasmon resonance to assess mAb affinity for Fcγ receptors (FcγR) at pH 6 and pH 7.4. NOD SCID mice genetically deficient in different FcγR were used to delineate their involvement.

RESULTS

Here, we show that strains on the NOD SCID background have significantly faster antibody clearance than other strains leading to reduced antitumor efficacy of clinically relevant mAb. This rapid clearance is dependent on antibody isotype, the presence of Fc glycosylation (at N297) and expression of FcγRII. Comparable effects were not seen in the parental NOD or SCID strains, demonstrating the presence of a compound defect requiring both genotypes. The absence of endogenous IgG was the key parameter transferred from the SCID as reconstituting NOD SCID or NSG mice with exogenous IgG overcame the rapid clearance and recovered antitumor efficacy. In contrast, the NOD strain was associated with reduced expression of the neonatal Fc Receptor (FcRn). We propose a novel mechanism for the rapid clearance of certain mAb isotypes in NOD SCID mouse strains, based on their interaction with FcγRII in the context of reduced FcRn.

CONCLUSIONS

This study highlights the importance of understanding the limitation of the mouse strain being used for preclinical evaluation, and demonstrates that NOD SCID strains of mice should be reconstituted with IgG prior to studies of mAb efficacy.

Targeting autophagy-related protein kinases for potential therapeutic purpose

Autophagy, defined as a scavenging process of protein aggregates and damaged organelles mediated by lysosomes, plays a significant role in the quality control of macromolecules and organelles. Since protein kinases are integral to the autophagy process, it is critically important to understand the role of kinases in autophagic regulation. At present, intervention of autophagic processes by small-molecule modulators targeting specific kinases has becoming a reasonable and prevalent strategy for treating several varieties of human disease, especially cancer. In this review, we describe the role of some autophagy-related kinase targets and kinase-mediated phosphorylation mechanisms in autophagy regulation. We also summarize the small-molecule kinase inhibitors/activators of these targets, highlighting the opportunities of these new therapeutic agents.

AKT/mTORC2 Inhibition Activates FOXO1 Function in CLL Cells Reducing B-Cell Receptor-Mediated Survival

PURPOSE

To determine whether inhibition of mTOR kinase-mediated signaling represents a valid therapeutic approach for chronic lymphocytic leukemia (CLL).

EXPERIMENTAL DESIGN

Stratification of mTOR activity was carried out in patients with primary CLL samples and an aggressive CLL-like mouse model. The potency of dual mTOR inhibitor AZD8055 to induce apoptosis in primary CLL cells was assessed in the presence/absence of B-cell receptor (BCR) ligation. Furthermore, we addressed the molecular and functional impact of dual mTOR inhibition in combination with BTK inhibitor ibrutinib.

RESULTS

Differential regulation of basal mTORC1 activity was observed in poor prognostic CLL samples, with elevated p4EBP1T37/46 and decreased p70S6 kinase activity, suggesting that dual mTORC1/2 inhibitors may exhibit improved response in poor prognostic CLL compared with rapalogs. AZD8055 treatment of primary CLL cells significantly reduced CLL survival in vitro compared with rapamycin, preferentially targeting poor prognostic subsets and overcoming BCR-mediated survival advantages. Furthermore, AZD8055, and clinical analog AZD2014, significantly reduced CLL tumor load in mice. AKT substrate FOXO1, while overexpressed in CLL cells of poor prognostic patients in LN biopsies, peripheral CLL cells, and mouse-derived CLL-like cells, appeared to be inactive. AZD8055 treatment partially reversed FOXO1 inactivation downstream of BCR crosslinking, significantly inhibiting FOXO1T24 phosphorylation in an mTORC2-AKT-dependent manner, to promote FOXO1 nuclear localization, activity, and FOXO1-mediated gene regulation. FOXO1 activity was further significantly enhanced on combining AZD8055 with ibrutinib.

CONCLUSIONS

Our studies demonstrate that dual mTOR inhibitors show promise as future CLL therapies, particularly in combination with ibrutinib.

Blockage of autophagic flux is associated with lymphocytosis and higher percentage of tumoral cells in chronic lymphocytic leukemia of B cells

PURPOSE

Autophagy has lately emerged as an important biological process with implications in several hematological pathologies. Recently, a growing body of evidence supports a putative role of autophagy in chronic lymphocytic leukemia; however, no definitive clue has been established so far. To elucidate this issue, we have developed a pilot study to measure autophagic flux in peripheral blood mononuclear cells from chronic lymphocytic leukemia patients, and explored its correlation with classical clinical/analytical parameters.

METHODS/PATIENTS

Thirty-three chronic lymphocytic leukemia patients participated in the study. Autophagic flux in peripheral blood mononuclear cells was determined by western blot measuring the levels of the proteins p62 and lipidated LC3. Moreover, p62 mRNA levels were analyzed by RT-qPCR.

RESULTS

Lymphocytosis and the percentage of tumoral lymphocytes in chronic lymphocytic leukemia patients statistically correlate with a blocked autophagic flux.

CONCLUSION

Alterations in autophagic flux could play an important role in the physiopathology of chronic lymphocytic leukemia.

Molecular Interactions Between Innate and Adaptive Immune Cells in Chronic Lymphocytic Leukemia and Their Therapeutic Implications

Innate immunity constitutes the first line of host defense against various anomalies in humans, and it also guides the adaptive immune response. The function of innate immune components and adaptive immune components are interlinked in hematological malignancies including chronic lymphocytic leukemia (CLL), and molecular interactions between innate and adaptive immune components are crucial for the development, progression and the therapeutic outcome of CLL. In this leukemia, genetic mutations in B cells and B cell receptors (BCR) are key driving factors along with evasion of cytotoxic T lymphocytes and promotion of regulatory T cells. Similarly, the release of various cytokines from CLL cells triggers the protumor phenotype in macrophages that further edges the CLL cells. Moreover, under the influence of various cytokines, dendritic cells are unable to mature and trigger T cell mediated antitumor response. The phenotypes of these cells are ultimately controlled by respective signaling pathways, the most notables are BCR, Wnt, Notch, and NF-κB, and their activation affects the cytokine profile that controls the pathogenesis of CLL, and challenge its treatment. There are several novel substances for CLL under clinical development, including kinase inhibitors, antibodies, and immune-modulators that offer new hopes. DC-based vaccines and CAR T cell therapy are promising tools; however, further studies are required to precisely dissect the molecular interactions among various molecular entities. In this review, we systematically discuss the involvement, common targets and therapeutic interventions of various cells for the better understanding and therapy of CLL.

Cross Talk Networks of Mammalian Target of Rapamycin Signaling With the Ubiquitin Proteasome System and Their Clinical Implications in Multiple Myeloma

Multiple myeloma (MM) is the second most common hematological malignancy and results from the clonal amplification of plasma cells. Despite recent advances in treatment, MM remains incurable with a median survival time of only 5-6years, thus necessitating further insights into MM biology and exploitation of novel therapeutic approaches. Both the ubiquitin proteasome system (UPS) and the PI3K/Akt/mTOR signaling pathways have been implicated in the pathogenesis, and treatment of MM and different lines of evidence suggest a close cross talk between these central cell-regulatory signaling networks. In this review, we outline the interplay between the UPS and mTOR pathways and discuss their implications for the pathophysiology and therapy of MM.

The role of mTOR-mediated signaling in the regulation of cellular migration

Mechanistic target for rapamycin (mTOR) is a serine/threonine protein kinase that forms two distinct complexes mTORC1 and mTORC2, integrating mitogen and nutrient signals to regulate cell survival and proliferation; processes which are commonly deregulated in human cancers. mTORC1 and mTORC2 have divergent molecular associations and cellular functions: mTORC1 regulates in mRNA translation and protein synthesis, while mTORC2 is involved in the regulation of cellular survival and metabolism. Through AKT phosphorylation/activation, mTORC2 has also been reported to regulate cell migration. Recent attention has focused on the aberrant activation of the PI3K/mTOR pathway in B cell malignancies and there is growing evidence for its involvement in disease pathogenesis, due to its location downstream of other established novel drug targets that intercept B cell receptor (BCR) signals. Shared pharmacological features of BCR signal inhibitors include a striking "lymphocyte redistribution" effect whereby patients experience a sharp increase in lymphocyte count on initiation of therapy followed by a steady decline. Chronic lymphocytic leukemia (CLL) serves as a paradigm for migration studies as lymphocytes are among the most widely travelled cells in the body, a product of their role in immunological surveillance. The subversion of normal lymphocyte movement in CLL is being elucidated; this review aims to describe the migration impairment which occurs as part of the wider context of cancer cell migration defects, with a focus on the role of mTOR in mediating migration effects downstream of BCR ligation and other microenvironmental signals.

Casein kinase 1 is a therapeutic target in chronic lymphocytic leukemia

Casein kinase 1δ/ε (CK1δ/ε) is a key component of noncanonical Wnt signaling pathways, which were shown previously to drive pathogenesis of chronic lymphocytic leukemia (CLL). In this study, we investigated thoroughly the effects of CK1δ/ε inhibition on the primary CLL cells and analyzed the therapeutic potential in vivo using 2 murine model systems based on the Eµ-TCL1-induced leukemia (syngeneic adoptive transfer model and spontaneous disease development), which resembles closely human CLL. We can demonstrate that the CK1δ/ε inhibitor PF-670462 significantly blocks microenvironmental interactions (chemotaxis, invasion and communication with stromal cells) in primary CLL cells in all major subtypes of CLL. In the mouse models, CK1 inhibition slows down accumulation of leukemic cells in the peripheral blood and spleen and prevents onset of anemia. As a consequence, PF-670462 treatment results in a significantly longer overall survival. Importantly, CK1 inhibition has synergistic effects to the B-cell receptor (BCR) inhibitors such as ibrutinib in vitro and significantly improves ibrutinib effects in vivo. Mice treated with a combination of PF-670462 and ibrutinib show the slowest progression of disease and survive significantly longer compared with ibrutinib-only treatment when the therapy is discontinued. In summary, this preclinical testing of CK1δ/ε inhibitor PF-670462 demonstrates that CK1 may serve as a novel therapeutic target in CLL, acting in synergy with BCR inhibitors. Our work provides evidence that targeting CK1 can represent an alternative or addition to the therapeutic strategies based on BCR signaling and antiapoptotic signaling (BCL-2) inhibition.

The Dual Syk/JAK Inhibitor Cerdulatinib Antagonizes B-cell Receptor and Microenvironmental Signaling in Chronic Lymphocytic Leukemia

Purpose: B-cell receptor (BCR)-associated kinase inhibitors, such as ibrutinib, have revolutionized the treatment of chronic lymphocytic leukemia (CLL). However, these agents are not curative, and resistance is already emerging in a proportion of patients. IL4, expressed in CLL lymph nodes, can augment BCR signaling and reduce the effectiveness of BCR kinase inhibitors. Therefore, simultaneous targeting of the IL4- and BCR signaling pathways by cerdulatinib, a novel dual Syk/JAK inhibitor currently in clinical trials (NCT01994382), may improve treatment responses in patients.Experimental Design: PBMCs from patients with CLL were treated in vitro with cerdulatinib alone or in combination with venetoclax. Cell death, chemokine, and cell signaling assay were performed and analyzed by flow cytometry, immunoblotting, q-PCR, and ELISA as indicated.Results: At concentrations achievable in patients, cerdulatinib inhibited BCR- and IL4-induced downstream signaling in CLL cells using multiple readouts and prevented anti-IgM- and nurse-like cell (NLC)-mediated CCL3/CCL4 production. Cerdulatinib induced apoptosis of CLL cells, in a time- and concentration-dependent manner, and particularly in IGHV-unmutated samples with greater BCR signaling capacity and response to IL4, or samples expressing higher levels of sIgM, CD49d+, or ZAP70+ Cerdulatinib overcame anti-IgM, IL4/CD40L, or NLC-mediated protection by preventing upregulation of MCL-1 and BCL-XL; however, BCL-2 expression was unaffected. Furthermore, in samples treated with IL4/CD40L, cerdulatinib synergized with venetoclax in vitro to induce greater apoptosis than either drug alone.Conclusions: Cerdulatinib is a promising therapeutic for the treatment of CLL either alone or in combination with venetoclax, with the potential to target critical survival pathways in this currently incurable disease. Clin Cancer Res; 23(9); 2313-24. ©2016 AACR.

The duality of macrophage function in chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is the most common adult leukaemia and, in some patients, is accompanied by resistance to both chemotherapeutics and immunotherapeutics. In this review we will discuss the role of tumour associated macrophages (TAMs) in promoting CLL cell survival and resistance to immunotherapeutics. In addition, we will discuss mechanisms by which TAMs suppress T-cell mediated antitumour responses. Thus, targeting macrophages could be used to i) reduce the leukaemic burden via the induction of T-cell-mediated antitumour responses, ii) to reduce pro-survival signalling and enhance response to conventional chemotherapeutics or iii) enhance the response to therapeutic antibodies in current clinical use.

Impact on Autophagy and Ultraviolet B Induced Responses of Treatment with the MTOR Inhibitors Rapamycin, Everolimus, Torin 1, and pp242 in Human Keratinocytes

The mechanistic target of Rapamycin (MTOR) protein is a crucial signaling regulator in mammalian cells that is extensively involved in cellular biology. The function of MTOR signaling in keratinocytes remains unclear. In this study, we detected the MTOR signaling and autophagy response in the human keratinocyte cell line HaCaT and human epidermal keratinocytes treated with MTOR inhibitors. Moreover, we detected the impact of MTOR inhibitors on keratinocytes exposed to the common carcinogenic stressors ultraviolet B (UVB) and UVA radiation. As a result, keratinocytes were sensitive to the MTOR inhibitors Rapamycin, everolimus, Torin 1, and pp242, but the regulation of MTOR downstream signaling was distinct. Next, autophagy induction only was observed in HaCaT cells treated with Rapamycin. Furthermore, we found that MTOR signaling was insensitive to UVB but sensitive to UVA radiation. UVB treatment also had no impact on the inhibition of MTOR signaling by MTOR inhibitors. Finally, MTOR inhibition by Rapamycin, everolimus, or pp242 did not affect the series of biological events in keratinocytes exposed to UVB, including the downregulation of BiP and PERK, activation of Histone H2A and JNK, and cleavage of caspase-3 and PARP. Our study demonstrated that MTOR inhibition in keratinocytes cannot always induce autophagy, and the MTOR pathway does not play a central role in the UVB triggered cellular response.

Integrated Cellular and Plasma Proteomics of Contrasting B-cell Cancers Reveals Common, Unique and Systemic Signatures

Approximately 800,000 leukemia and lymphoma cases are diagnosed worldwide each year. Burkitt's lymphoma (BL) and chronic lymphocytic leukemia (CLL) are examples of contrasting B-cell cancers; BL is a highly aggressive lymphoid tumor, frequently affecting children, whereas CLL typically presents as an indolent, slow-progressing leukemia affecting the elderly. The B-cell-specific overexpression of the myc and TCL1 oncogenes in mice induce spontaneous malignancies modeling BL and CLL, respectively. Quantitative mass spectrometry proteomics and isobaric labeling were employed to examine the biology underpinning contrasting Eμ-myc and Eμ-TCL1 B-cell tumors. Additionally, the plasma proteome was evaluated using subproteome enrichment to interrogate biomarker emergence and the systemic effects of tumor burden. Over 10,000 proteins were identified (q<0.01) of which 8270 cellular and 2095 plasma proteins were quantitatively profiled. A common B-cell tumor signature of 695 overexpressed proteins highlighted ribosome biogenesis, cell-cycle promotion and chromosome segregation. Eμ-myc tumors overexpressed several methylating enzymes and underexpressed many cytoskeletal components. Eμ-TCL1 tumors specifically overexpressed ER stress response proteins and signaling components in addition to both subunits of the interleukin-5 (IL5) receptor. IL5 treatment promoted Eμ-TCL1 tumor proliferation, suggesting an amplification of IL5-induced AKT signaling by TCL1. Tumor plasma contained a substantial tumor lysis signature, most prominent in Eμ-myc plasma, whereas Eμ-TCL1 plasma contained signatures of immune-response, inflammation and microenvironment interactions, with putative biomarkers in early-stage cancer. These findings provide a detailed characterization of contrasting B-cell tumor models, identifying common and specific tumor mechanisms. Integrated plasma proteomics allowed the dissection of a systemic response and a tumor lysis signature present in early- and late-stage cancers, respectively. Overall, this study suggests common B-cell cancer signatures exist and illustrates the potential of the further evaluation of B-cell cancer subtypes by integrative proteomics.

PEITC-mediated inhibition of mRNA translation is associated with both inhibition of mTORC1 and increased eIF2α phosphorylation in established cell lines and primary human leukemia cells

Increased mRNA translation drives carcinogenesis and is an attractive target for the development of new anti-cancer drugs. In this work, we investigated effects of phenethylisothiocyanate (PEITC), a phytochemical with chemopreventive and anti-cancer activity, on mRNA translation. PEITC rapidly inhibited global mRNA translation in human breast cancer-derived MCF7 cells and mouse embryonic fibroblasts (MEFs). In addition to the known inhibitory effects of PEITC on mTORC1 activity, we demonstrate that PEITC increased eIF2α phosphorylation. PEITC also increased formation of stress granules which are typically associated with eIF2α phosphorylation and accumulation of translationally stalled mRNAs. Analysis of genetically modified MEFs demonstrated that optimal inhibition of global mRNA translation by PEITC was dependent on eIF2α phosphorylation, but not mTORC1 inhibition. We extended this study into primary leukemic B cells derived from patients with chronic lymphocytic leukaemia (CLL). CLL cells were stimulated in vitro with anti-IgM to mimic binding of antigen, a major driver of this leukemia. In CLL cells, PEITC increased eIF2α phosphorylation, inhibited anti-IgM-induced mTORC1 activation and decreased both basal and anti-IgM-induced global mRNA translation. PEITC also inhibited transcription and translation of MYC mRNA and accumulation of the MYC oncoprotein, in anti-IgM-stimulated cells. Moreover, treatment of CLL cells with PEITC and the BTK kinase inhibitor ibrutinib decreased anti-IgM-induced translation and induced cell death to a greater extent than either agent alone. Therefore, PEITC can inhibit both global and mRNA specific translation (including MYC) via effects on multiple regulatory pathways. Inhibition of mRNA translation may contribute to the chemopreventive and anti-cancer effects of PEITC.

Dual TORK/DNA-PK inhibition blocks critical signaling pathways in chronic lymphocytic leukemia

TORK/DNA-PK inhibition induces cytotoxicity and blocks signaling pathways important for CLL survival, proliferation, and drug resistance. Preliminary clinical effects of TORK/DNA-PK inhibition show 7 of 8 CLL patients with decreased lymphadenopathy.

Assessment of red blood cell distribution width as a prognostic marker in chronic lymphocytic leukemia

Red blood cell distribution width (RDW) is a quantitative measure of the variability in size of circulating erythrocytes. It was recently reported that RDW is a prognostic factor for infection diseases, cardiovascular and pulmonary diseases, as well as some neoplasms. Moreover, RDW is remarkably strong predictor of longevity, including all causes of death, for adults aged 45 years and older. To explain this occurrence it was proposed that persistent IGFs/mTOR signaling is one of the factors that play a role in affecting the RDW and mortality.The above observations induced us to analyze the prognostic role of RDW in chronic lymphocytic leukemia (CLL) being the most frequent type of adult leukemia in Western countries. The obtained results have shown that RDW may be considered as a potential CLL prognostic marker. Elevated RDW level at the moment of diagnosis was associated with advanced disease and presence of other poor prognostic factors. It is also connected with overall survival indicating shorter time in patients with elevated RDW. It is possible that the presently observed correlation between mortality and RDW of the CLL patients is affected by their metabolic (IGF-1/mTOR driven)- rather than chronological- aging. The patients with high level of RDW are expected to have an increased persistent level of IGF-1/mTOR signaling. Within the framework of personalized therapy, these CLL patients therefore would be expected to be more sensitive to the treatment with mTOR inhibitors.

Targeting the mTOR Pathway in Leukemia

Optimal function of multiple intracellular signaling pathways is essential for normal regulation of cellular transcription, translation, growth, proliferation, and survival. Dysregulation or aberrant activation of such cascades can lead to inappropriate cell survival and abnormal cell proliferation in leukemia. Successful treatment of chronic myeloid leukemia (CML) with tyrosine kinase inhibitors targeting the BCR-ABL fusion gene is a prime example of effectively inhibiting intracellular signaling cascades. However, even in these patients resistance can develop via emergence of mutations or feedback activation of other pathways that cause refractory disease. Constitutive activation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway has been observed in different types of leukemia, including CML, acute myeloid leukemia, and acute lymphoblastic leukemia. Abnormal mTOR activity may contribute to chemotherapy resistance, while it may also be effectively targeted via molecular means and/or development of specific pharmacological inhibitors. This review discusses the role of PI3K/Akt/mTOR dysre-gulation in leukemia and summarizes the emergence of preliminary data for the development of novel therapeutic approaches. J. Cell. Biochem. 117: 1745-1752, 2016. © 2016 Wiley Periodicals, Inc.

TCL1 transgenic mouse model as a tool for the study of therapeutic targets and microenvironment in human B-cell chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy with a mature phenotype. In spite of its relatively indolent nature, no radical cure is as yet available. CLL is not associated with either a unique cytogenetic or a molecular defect, which might have been a potential therapeutic target. Instead, several factors are involved in disease development, such as environmental signals which interact with genetic abnormalities to promote survival, proliferation and an immune surveillance escape. Among these, PI3-Kinase signal pathway alterations are nowadays considered to be clearly important. The TCL1 gene, an AKT co-activator, is the cause of a mature T-cell leukemia, as well as being highly expressed in all B-CLL. A TCL1 transgenic mouse which reproduces leukemia with a distinct immunophenotype and similar to the course of the human B-CLL was developed several years ago and is widely used by many groups. This is a review of the CLL biology arising from work of many independent investigators who have used TCL1 transgenic mouse model focusing on pathogenetic, microenviroment and therapeutic targets.

Pharmacological targeting of PI3K isoforms as a therapeutic strategy in chronic lymphocytic leukaemia

PI3Kδ inhibitors such as idelalisib are providing improved therapeutic options for the treatment of chronic lymphocytic leukaemia (CLL). However under certain conditions, inhibition of a single PI3K isoform can be compensated by the other PI3K isoforms, therefore PI3K inhibitors which target multiple PI3K isoforms may provide greater efficacy. The development of compounds targeting multiple PI3K isoforms (α, β, δ, and γ) in CLL cells, in vitro, resulted in sustained inhibition of BCR signalling but with enhanced cytotoxicity and the potential for improve clinical responses. This review summarises the progress of PI3K inhibitor development and describes the rationale and potential for targeting multiple PI3K isoforms.

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Inhibition of PI3K may still be effective in CLL patients resistant to ibrutinib.

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Functional redundancy between PI3K isoforms may be a mechanism of drug resistance.

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Targeting multiple PI3K isoforms can increase cytotoxicity against CLL cells.

The pan phosphoinositide 3-kinase/mammalian target of rapamycin inhibitor SAR245409 (voxtalisib/XL765) blocks survival, adhesion and proliferation of primary chronic lymphocytic leukemia cells

The phosphoinositide 3-kinases (PI3Ks) are critical components of the B-cell receptor (BCR) pathway and have an important role in the pathobiology of chronic lymphocytic leukemia (CLL). Inhibitors of PI3Kδ block BCR-mediated cross-talk between CLL cells and the lymph node microenvironment and provide significant clinical benefit to CLL patients. However, the PI3Kδ inhibitors applied thus far have limited direct impact on leukemia cell survival and thus are unlikely to eradicate the disease. The use of inhibitors of multiple isoforms of PI3K might lead to deeper remissions. Here we demonstrate that the pan-PI3K/mammalian target of rapamycin inhibitor SAR245409 (voxtalisib/XL765) was more pro-apoptotic to CLL cells--irrespective of their ATM/p53 status--than PI3Kα or PI3Kδ isoform selective inhibitors. Furthermore, SAR245409 blocked CLL survival, adhesion and proliferation. Moreover, SAR245409 was a more potent inhibitor of T-cell-mediated production of cytokines, which support CLL survival. Taken together, our in vitro data provide a rationale for the evaluation of a pan-PI3K inhibitor in CLL patients.