Targeted therapy in T-cell malignancies: dysregulation of the cellular signaling pathways

Iron-Imine Cocktail in Drug Development: A Contemporary Update

Organometallic drug development is still in its early stage, but recent studies show that organometallics having iron as the central atom have the possibility of becoming good drug candidates because iron is an important micro-nutrient, and it is compatible with many biological systems, including the human body. Being an eco-friendly Lewis acid, iron can accept the lone pair of electrons from imino(sp2)-nitrogen, and the resultant iron-imine complexes with iron as a central atom have the possibility of interacting with several proteins and enzymes in humans. Iron-imine complexes have demonstrated significant potential with anticancer, bactericidal, fungicidal, and other medicinal activities in recent years. This article systematically discusses major synthetic methods and pharmacological potentials of iron-imine complexes having in vitro activity to significant clinical performance from 2016 to date. In a nutshell, this manuscript offers a simplistic view of iron complexes in medicinal inorganic chemistry: for instance, iron is presented as an "eco-friendly non-toxic" metal (as opposed to platinum) that will lead to non-toxic pharmaceuticals. The abundant literature on iron chelators shows that many iron complexes, particularly if redox-active in cells, can be quite cytotoxic, which can be beneficial for future targeted therapies. While we made every effort to include all the related papers, any omission is purely unintentional.

An Anti-CD7 Antibody-Drug Conjugate Target Showing Potent Antitumor Activity for T-Lymphoblastic Leukemia (T-ALL)

Acute T-lymphoblastic leukemia (T-ALL) is a type of leukemia that can occur in both pediatric and adult populations. Compared to acute B-cell lymphoblastic leukemia (B-ALL), patients with T-cell T-ALL have a poorer therapeutic efficacy. In this study, a novel anti-CD7 antibody-drug conjugate (ADC, J87-Dxd) was successfully generated and used for T-ALL treatment. Firstly, to obtain anti-CD7 mAbs, we expressed and purified the CD7 protein extracellular domain. Utilizing hybridoma technology, we obtained three anti-CD7 mAbs (J87, G73 and A15) with a high affinity for CD7. Both the results of immunofluorescence and Biacore assay indicated that J87 (KD = 1.54 × 10-10 M) had the highest affinity among the three anti-CD7 mAbs. In addition, an internalization assay showed the internalization level of J87 to be higher than that of the other two mAbs. Next, we successfully generated the anti-CD7 ADC (J87-Dxd) by conjugating DXd to J87 via a cleavable maleimide-GGFG peptide linker. J87-Dxd also possessed the ability to recognize and bind CD7. Using J87-Dxd to treat T-ALL cells (Jurkat and CCRF-CEM), we observed that J87-Dxd bound to CD7 was internalized into T-ALL cells. Moreover, J87-Dxd treatment significantly induced the apoptosis of Jurkat and CCRF-CEM cells. The IC50 (half-maximal inhibitory concentration) value of J87-Dxd against CCRF-CEM obtained by CCK-8 assay was 6.3 nM. Finally, to assess the antitumor efficacy of a J87-Dxd in vivo, we established T-ALL mouse models and treated mice with J87-Dxd or J87. The results showed that on day 24 after tumor inoculation, all mice treated with J87 or PBS died, whereas the survival rate of mice treated with J87-Dxd was 80%. H&E staining showed no significant organic changes in the heart, liver, spleen, lungs and kidneys of all mice. In summary, we demonstrated that the novel anti-CD7 ADC (J87-Dxd) had a potent and selective effect against CD7-expressing T-All cells both in vitro and in vivo, and could thus be expected to be further developed as a new drug for the treatment of T-ALL or other CD7-expression tumors.

Integrating rapamycin with novel PI3K/Akt/mTOR inhibitor microRNAs on NOTCH1-driven T-cell acute lymphoblastic leukemia (T-ALL)

Introduction

The PI3K/AKT/mTOR signaling pathway plays a significant role in the development of T-cell acute lymphoblastic leukemia (T-ALL). Rapamycin is a potential therapeutic strategy for hematological malignancies due to its ability to suppress mTOR activity. Additionally, microRNAs (miRNAs) have emerged as key regulators in T-ALL pathophysiology and treatment. This study aimed to investigate the combined effects of rapamycin and miRNAs in inhibiting the PI3K/AKT/mTOR pathway in T-ALL cells.

Methods

Bioinformatic algorithms were used to find miRNAs that inhibit the PI3K/AKT/mTOR pathway. Twenty-five bone marrow samples were collected from T-ALL patients, alongside five control bone marrow samples from non-leukemia patients. The Jurkat cell line was chosen as a representative model for T-ALL. Gene and miRNA expression levels were assessed using quantitative real-time PCR (qRT-PCR). Two miRNAs exhibiting down-regulation in both clinical samples and Jurkat cells were transfected to the Jurkat cell line to investigate their impact on target gene expression. Furthermore, in order to evaluate the potential of combination therapy involving miRNAs and rapamycin, apoptosis and cell cycle assays were carried out.

Results

Six miRNAs (miR-3143, miR-3182, miR-99a/100, miR-155, miR-576-5p, and miR-501- 3p) were predicted as inhibitors of PI3K/AKT/mTOR pathway. The expression analysis of both clinical samples and the Jurkat cell line revealed a simultaneous downregulation of miR-3143 and miR-3182. Transfection investigation demonstrated that the exogenous overexpression of miR-3143 and miR-3182 can effectively inhibit PI3K/AKT/mTOR signaling in the Jurkat cell line. Moreover, when used as a dual inhibitor along with rapamycin, miR-3143 and miR-3182 significantly increased apoptosis and caused cell cycle arrest in the Jurkat cell line.

Conclusion

These preliminary results highlight the potential for improving T-ALL treatment through multi-targeted therapeutic strategies involving rapamycin and miR-3143/miR-3182.

Evaluation of the Anticancer and Biological Activities of Istaroxime via Ex Vivo Analyses, Molecular Docking and Conceptual Density Functional Theory Computations

Cancer is a disease that occurs as a result of abnormal or uncontrolled growth of cells due to DNA damage, among many other causes. Certain cancer treatments aim to increase the excess of DNA breaks to such an extent that they cannot escape from the general mechanism of cell checkpoints, leading to the apoptosis of mutant cells. In this study, one of the Sarco-endoplasmic reticulum Ca2+ATPase (SERCA2a) inhibitors, Istaroxime, was investigated. There has been very limited number of articles so far reporting Istaroxime's anticancer activity; thus, we aimed to evaluate the anticancer effects of Istaroxime by cell proliferation assay and revealed the cytotoxic activity of the compound. We further determined the interaction of Istaroxime with topoisomerase enzymes through enzyme activity tests and detailed molecular modeling analysis. Istaroxime exhibited an antiproliferative effect on A549, MCF7, and PC3 cell lines and inhibited Topoisomerase I, suggesting that Istaroxime can act as a Topoisomerase I inhibitor under in vitro conditions. Molecular docking analysis supported the experimental observations. A chemical reactivity analysis of the Istaroxime molecule was made in the light of Density Functional Theory computations. For this aim, important chemical reactivity descriptors such as hardness, electronegativity, and electrophilicity were computed and discussed as detailed.

CAR T-Cell Immunotherapy Treating T-ALL: Challenges and Opportunities

T-cell acute lymphoblastic leukemia (T-ALL), a form of T-cell malignancy, is a typically aggressive hematological malignancy with high rates of disease relapse and a poor prognosis. Current guidelines do not recommend any specific treatments for these patients, and only allogeneic stem cell transplant, which is associated with potential risks and toxicities, is a curative therapy. Recent clinical trials showed that immunotherapies, including monoclonal antibodies, checkpoint inhibitors, and CAR T therapies, are successful in treating hematologic malignancies. CAR T cells, which specifically target the B-cell surface antigen CD19, have demonstrated remarkable efficacy in the treatment of B-cell acute leukemia, and some progress has been made in the treatment of other hematologic malignancies. However, the development of CAR T-cell immunotherapy targeting T-cell malignancies appears more challenging due to the potential risks of fratricide, T-cell aplasia, immunosuppression, and product contamination. In this review, we discuss the current status of and challenges related to CAR T-cell immunotherapy for T-ALL and review potential strategies to overcome these limitations.

Molecular pathogenesis of Cutaneous T cell Lymphoma: Role of chemokines, cytokines, and dysregulated signaling pathways

Cutaneous T cell lymphomas (CTCLs) are a heterogeneous group of lymphoproliferative neoplasms that exhibit a wide spectrum of immune-phenotypical, clinical, and histopathological features. The biology of CTCL is complex and remains elusive. In recent years, the application of next-generation sequencing (NGS) has evolved our understanding of the pathogenetic mechanisms, including genetic aberrations and epigenetic abnormalities that shape the mutational landscape of CTCL and represent one of the important pro-tumorigenic principles in CTCL initiation and progression. Still, identification of the major pathophysiological pathways including genetic and epigenetic components that mediate malignant clonal T cell expansion has not been achieved. This is of prime importance given the role of malignant T cell clones in fostering T helper 2 (Th2)-bias tumor microenvironment and fueling progressive immune dysregulation and tumor cell growth in CTCL patients, manifested by the secretion of Th2-associated cytokines and chemokines. Alterations in malignant cytokine and chemokine expression patterns orchestrate the inflammatory milieu and influence the migration dynamics of malignant clonal T cells. Here, we highlight recent insights about the molecular mechanisms of CTCL pathogenesis, emphasizing the role of cytokines, chemokines, and associated downstream signaling networks in driving immune defects, malignant transformation, and disease progression. In-depth characterization of the CTCL immunophenotype and tumoral microenvironment offers a facile opportunity to expand the therapeutic armamentarium of CTCL, an intractable malignant skin disease with poor prognosis and in dire need of curative treatment approaches.

Phospho-Specific Flow Cytometry Reveals Signaling Heterogeneity in T-Cell Acute Lymphoblastic Leukemia Cell Lines

Several signaling pathways are aberrantly activated in T-ALL due to genetic alterations of their components and in response to external microenvironmental cues. To functionally characterize elements of the signaling network in T-ALL, here we analyzed ten signaling proteins that are frequently altered in T-ALL -namely Akt, Erk1/2, JNK, Lck, NF-κB p65, p38, STAT3, STAT5, ZAP70, Rb- in Jurkat, CEM and MOLT4 cell lines, using phospho-specific flow cytometry. Phosphorylation statuses of signaling proteins were measured in the basal condition or under modulation with H₂O₂, PMA, CXCL12 or IL7. Signaling profiles are characterized by a high variability across the analyzed T-ALL cell lines. Hierarchical clustering analysis documents that higher intrinsic phosphorylation of Erk1/2, Lck, ZAP70, and Akt, together with ZAP70 phosphorylation induced by H₂O₂, identifies Jurkat cells. In contrast, CEM are characterized by higher intrinsic phosphorylation of JNK and Rb and higher responsiveness of Akt to external stimuli. MOLT4 cells are characterized by higher basal STAT3 phosphorylation. These data document that phospho-specific flow cytometry reveals a high variability in intrinsic as well as modulated signaling networks across different T-ALL cell lines. Characterizing signaling network profiles across individual leukemia could provide the basis to identify molecular targets for personalized T-ALL therapy.

miR-1250-5p is a novel tumor suppressive intronic miRNA hypermethylated in non-Hodgkin's lymphoma: novel targets with impact on ERK signaling and cell migration

Background

miR-1250 is localised to the second intron of AATK at chromosome 17q25. As a CpG island is present at the putative promoter region of its host gene, AATK, we postulated that the intronic miR-1250-5p is a tumor suppressor miRNA co-regulated with its host gene, AATK, by promoter DNA methylation in non-Hodgkin’s lymphoma (NHL).

Methods

AATK/miR-1250 methylation was studied in healthy controls, including ten normal peripheral blood buffy coats and eleven normal tonsils, ten lymphoma cell lines, and 120 primary lymphoma samples by methylation-specific PCR (MSP). The expression of miR-1250-5p and AATK was investigated by quantitative real-time PCR. Tumor suppressor properties of miR-1250-5p were demonstrated by over-expression of precursor miR-1250-5p in lymphoma cells. The target of miR-1250-5p was verified by luciferase reporter assay.

Results

AATK/miR-1250 methylation was absent in healthy peripheral blood and tonsils, but detected in five (50%) NHL cell lines. AATK/miR-1250 methylation correlated with repression of miR-1250-5p and AATK in NHL cell lines. In completely methylated SU-DHL-6 and SUP-T1 cells, treatment with 5-AzadC led to promoter demethylation and re-expression of both miR-1250-5p and AATK. In primary lymphoma samples, AATK/miR-1250 was frequently methylated in B-cell lymphoma (n = 41, 44.09%) and T-cell lymphoma (n = 9, 33.33%) with a comparable frequency (P = 0.318). In SU-DHL-6 and SU-DHL-1 cells, restoration of miR-1250-5p resulted in decreased cellular proliferation by MTS assay, increased cell death by trypan blue staining and enhanced apoptosis by annexin V-PI assay. Moreover, MAPK1 and WDR1 were verified as direct targets of miR-1250-5p by luciferase assay. In 39 primary NHLs, miR-1250-5p expression was shown to be inversely correlated with each of MAPK1 (P = 0.05) and WDR1 (P = 0.031) by qRT-PCR. Finally, in SU-DHL-1 cells, overexpression of miR-1250-5p led to repression of MAPK1 and WDR1 at both transcript and protein levels, with downregulation of phospho-ERK2 by Western-blotting and inhibition of SDF-1-dependent cell migration by transwell assay.

Conclusions

miR-1250-5p is a novel tumor suppressive intronic miRNA co-regulated and silenced by promoter DNA methylation of its host gene AATK in NHL. MAPK1 and WDR1 are novel miR-1250-5p direct targets rendering inhibition of MAPK/ERK signaling and SDF-1-dependent cell migration, hence implicated in survival and dissemination of lymphoma.

Cell signaling in cutaneous T-cell lymphoma microenvironment: promising targets for molecular-specific treatment

Cutaneous T-cell lymphomas (CTCL) result from the infiltration and proliferation of a population of T cells in the skin, inducing changes in the activity of both T cells and surrounding skin cells. In the CTCL microenvironment, cell interactions mediated by cell signaling pathways are altered. Defining changes in cell signaling enables to understand T-cell deregulations in the CTCL microenvironment and thus the progression of the disease. Moreover, characterizing signaling networks activated in CTCL stages can lead to consider new molecular biomarkers and therapeutic targets. Focusing on mycosis fungoides (MF), the most frequent variant of CTCL, and Sézary syndrome (SS), its leukemic variant, this review highlights recent molecular and genetic findings revealing modifications of key signaling pathways involved in (1) cell proliferation, cell growth, and cell survival such as MAP kinases and PI3K/Akt; (2) immune responses derived from TCR, TLR, JAK/STAT, and NF-kB; and (3) changes in tissue conditions such as extracellular matrix remodeling, hypoxia, and angiogenesis. Alterations in these signaling networks promote malignant T-cell proliferation and survival, T-cell migration, inflammation, and suppression of immune regulation of malignant T cells, making a skin microenvironment that allows disease progression. Targeting key proteins of these signaling pathways, using molecules already available and used in research, in clinical trials, and with other disease indications, can open the way to different therapeutic options in CTCL treatment.

Overcoming Glucocorticoid Resistance in Acute Lymphoblastic Leukemia: Repurposed Drugs Can Improve the Protocol

Glucocorticoids (GCs) are a central component of multi-drug treatment protocols against T and B acute lymphoblastic leukemia (ALL), which are used intensively during the remission induction to rapidly eliminate the leukemic blasts. The primary response to GCs predicts the overall response to treatment and clinical outcome. In this review, we have critically analyzed the available data on the effects of GCs on sensitive and resistant leukemic cells, in order to reveal the mechanisms of GC resistance and how these mechanisms may determine a poor outcome in ALL. Apart of the GC resistance, associated with a decreased expression of receptors to GCs, there are several additional mechanisms, triggered by alterations of different signaling pathways, which cause the metabolic reprogramming, with an enhanced level of glycolysis and oxidative phosphorylation, apoptosis resistance, and multidrug resistance. Due to all this, the GC-resistant ALL show a poor sensitivity to conventional chemotherapeutic protocols. We propose pharmacological strategies that can trigger alternative intracellular pathways to revert or overcome GC resistance. Specifically, we focused our search on drugs, which are already approved for treatment of other diseases and demonstrated anti-ALL effects in experimental pre-clinical models. Among them are some “truly” re-purposed drugs, which have different targets in ALL as compared to other diseases: cannabidiol, which targets mitochondria and causes the mitochondrial permeability transition-driven necrosis, tamoxifen, which induces autophagy and cell death, and reverts GC resistance through the mechanisms independent of nuclear estrogen receptors (“off-target effects”), antibiotic tigecycline, which inhibits mitochondrial respiration, causing energy crisis and cell death, and some anthelmintic drugs. Additionally, we have listed compounds that show a classical mechanism of action in ALL but are not used still in treatment protocols: the BH3 mimetic venetoclax, which inhibits the anti-apoptotic protein Bcl-2, the hypomethylating agent 5-azacytidine, which restores the expression of the pro-apoptotic BIM, and compounds targeting the PI3K-Akt-mTOR axis. Accordingly, these drugs may be considered for the inclusion into chemotherapeutic protocols for GC-resistant ALL treatments.

BRAP2 inhibits the Ras/Raf/MEK and PI3K/Akt pathways in leukemia cells, thereby inducing apoptosis and inhibiting cell growth

Breast cancer susceptibility gene 1 (BRCA1)-associated protein 2 (BRAP2) is a novel protein that binds to BRCA1 and is located in the cytoplasm. BRAP2 has been demonstrated to bind to regulators of the Ras-Raf-MEK and PI3K/Akt pathways, both of which are involved in carcinogenesis. This suggests that BRAP2 may be capable of regulating both pathways. In the present study, the role of BRAP2 in both pathways was clarified during apoptosis and cell proliferation in a leukemia cell line. A BRAP2-deficient leukemia cell line was generated using CRISPR/Cas9, the BRAP2-deficient and parental cells were treated with a Ras, pan-Raf or PI3K inhibitor, and the changes in signal transduction, apoptosis and cell proliferation were evaluated. BRAP2 knockout attenuated the inhibition of signal transduction of the Ras-Raf-MEK and PI3K/Akt pathways by the Ras, pan-Raf or PI3K inhibitor. BRAP2 deletion also suppressed the cytotoxic and apoptotic effects of the Ras and pan-Raf inhibitors. However, the loss of BRAP2 did not suppress the cytotoxicity of the PI3K inhibitor but did suppress the PI3K inhibitor-induced inhibition of cell proliferation. The present results indicated that BRAP2 induces apoptosis and the inhibition of cell proliferation via regulating the Ras-Raf-MEK and PI3K/Akt pathways. In leukemia cells, because the Ras-Raf-MEK and PI3K/Akt pathways are activated aberrantly, the simultaneous inhibition of both pathways is desired. The current results indicated that enhancement of the function of BRAP2 may represent a new target in leukemia treatment.

New Drug Repositioning Candidates for T-ALL Identified Via Human/Murine Gene Signature Comparison

T-cell Acute Lymphoblastic Leukemia (T-ALL) is an aggressive subtype of leukemia for which important progress in treatment efficiency have been made in the past decades to reach a cure rate of 75%-80% nowadays. It is nevertheless mandatory to find new targets and active molecules for innovative therapeutic strategies as relapse is associated with a very dismal outcome. We designed an experimental workflow to highlight the conserved core pathways associated with leukemogenesis by confronting the gene expression profiles (GEPs) of human T-ALL cases to the GEP of a murine T-ALL representative model, generated by the conditional deletion of the PTEN tumor suppressor gene in T cell precursors (tPTEN-/-). We identified 844 differentially expressed genes, common GEPs (cGEP) that were conserved between human T-ALL and murine signatures, and also similarly differentially expressed, compared to normal T cells. Using bioinformatic tools we highlighted in cGEPan upregulation of E2F, MYC and mTORC1. Next, using Connectivity Map (CMAP) and CMAPViz a visualization procedure for CMAP data that we developed, we selected in silico three FDA-approved, bioactive molecule candidates: α-estradiol (α-E), nordihydroguaiaretic acid (NDGA) and prochlorperazine dimaleate (PCZ). At a biological level, we showed that the three drugs triggered an apoptotic cell death in a panel of T-ALL cell lines, activated a DNA damage response and interfered with constitutive mTORC1 activation and c-MYC expression. This analysis shows that the investigation of conserved leukemogenesis pathways could be a strategy to reveal new avenues for pharmacological intervention.

mPGES-1/PGE2 promotes the growth of T-ALL cells in vitro and in vivo by regulating the expression of MTDH via the EP3/cAMP/PKA/CREB pathway

T-cell acute lymphoblastic leukaemia (T-ALL) is an aggressive haematological malignancy that is characterized by a high frequency of induction failure and by early relapse. Many studies have revealed that metadherin (MTDH) is highly expressed in a variety of malignant solid tumours and plays an important role in the occurrence and development of tumours. However, the relationship between the expression of MTDH and T-ALL has not yet been reported, and the regulatory factors of MTDH are still unknown. Our previous studies found that mPGES-1/PGE2 was important for promoting the growth of leukaemia cells. In the present study, we found that MTDH was highly expressed in primary T-ALL cells and in the Jurkat cell line. Our results showed that mPGES-1/PGE2 regulates the expression of MTDH through the EP3/cAMP/PKA-CREB pathway in T-ALL cells. Downregulation of MTDH inhibits the growth of Jurkat cells in vitro and in vivo. Our results suggest that MTDH could be a potential target for the treatment of T-ALL.

Novel targeted therapeutic agents for the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma

Non-Hodgkin lymphomas (NHLs) are a heterogeneous group of malignancies. Most NHLs in children, adolescent and young adult patients are aggressive lymphomas that are generally treated with multi-agent chemotherapy or immunochemotherapy regimens. While overall survival is high, the treatment can lead to a high rate of acute and long-term toxicity. However, in the rarer instance of relapsed or refractory disease, outcomes are dismal. Novel therapeutic approaches to the treatment of both T-cell and B-cell NHLs are critical to improve outcomes while also minimising the associated toxicity of current treatment regimes. Potential therapeutic approaches in development include humoral and cellular immunotherapies, small molecule inhibitors of relevant signalling pathways and epigenetic modifying agents. In this review, we will highlight the current state of development of agents of interest with a focus on agents relevant to childhood, adolescent and young adult NHL.

MNK1 inhibitor CGP57380 overcomes mTOR inhibitor-induced activation of eIF4E: the mechanism of synergic killing of human T-ALL cells

Although the treatment of adult T-cell acute lymphoblastic leukemia (T-ALL) has been significantly improved, the heterogeneous genetic landscape of the disease often causes relapse. Aberrant activation of mammalian target of rapamycin (mTOR) pathway in T-ALL is responsible for treatment failure and relapse, suggesting that mTOR inhibition may represents a new therapeutic strategy. In this study, we investigated whether the mTOR complex 1 (mTORC1) inhibitor everolimus could be used as a therapeutic agent against human T-ALL. We showed that rapamycin and its analog RAD001 (everolimus) exerted only mild inhibition on the viability of Jurkat, CEM and Molt-4 cell lines (for everolimus the maximum inhibition was <40% at 100 nM), but greatly enhanced the phosphorylation of eIF4E, a downstream substrate of MAPK-interacting kinase (MNK) that was involved in promoting cell survival. Furthermore, we demonstrated in Jurkat cells that mTOR inhibitor-induced eIF4E phosphorylation was independent of insulin-like growth factor-1/insulin-like growth factor-1 receptor axis, but was secondary to mTOR inhibition. Then we examined the antileukemia effects of CGP57380, a MNK1 inhibitor, and we found that CGP57380 (4-16 μM) dose-dependently suppressed the expression of both phosphor-MNK1 and phosphor-eIF4E, thereby inhibiting downstream targets such as c-Myc and survivin in T-ALL cells. Importantly, CGP57380 produced a synergistic growth inhibitory effect with everolimus in T-ALL cells, and treatment with this targeted therapy overcame everolimus-induced eIF4E phosphorylation. In conclusion, our results suggest that dual-targeting of mTOR and MNK1/eIF4E signaling pathways may represent a novel therapeutic strategy for the treatment of human T-ALL.

Expression of the miR-150 tumor suppressor is restored by and synergizes with rapamycin in a human leukemia T-cell line

miR-150 functions as a tumor suppressor in malignancies of the lymphocyte lineage and its expression is significantly reduced in these cells. However, the mechanism of miR-150 repression is unknown and so are pharmacological interventions that can reverse it. Here, we report that reduced expression of miR-150 in human Jurkat T-cell acute lymphoblastic leukemia (T-ALL) cells is mediated by constitutive mTOR signaling, a common characteristic of T-ALL cell lines and clinical isolates. Activating mTOR signaling in non-malignant T cells also resulted in a significant miR-150 down-regulation. Conversely, treatment with a pharmacological mTOR inhibitor, rapamycin, increased miR-150 expression in a dose-dependent manner in Jurkat cells, as well as in other leukemia cells. Interestingly, ectopic over-expression of miR-150 acted in a feed-forward loop and further sensitized Jurkat cells to a rapamycin-induced cell cycle arrest by targeting a large network of cell cycle genes. These findings suggest that miR-150 is normally expressed in quiescent T lymphocytes to reinforce an anti-proliferative state, and that mTOR signaling promotes cell proliferation in part by inhibiting miR-150 expression. Restoration of the miR-150-dependent anti-proliferative loop constitutes a novel mechanism underlying the efficacy of rapamycin in a T-ALL cell line. Further investigation of this mechanism in clinical isolates of T-ALL and other hematopoietic malignancies could help better guide development of targeted therapies.

Regulation of mPGES-1 composition and cell growth via the MAPK signaling pathway in jurkat cells

Previous studies have suggested that microsomal prostaglandin E synthase-1 (mPGES-1) is highly expressed and closely associated with mitogen-activated protein kinase (MAPK) signaling pathways in various types of malignant cells. However, their expression patterns and function with respect to T-cell acute lymphoblastic leukemia (T-ALL) remain largely unknown. The present study investigated whether mPGES-1 served a crucial role in T-ALL and aimed to identify interactions between mPGES-1 and the MAPK signaling pathway in T-ALL. The results indicated that mPGES-1 overexpression in T-ALL jurkat cells was significantly decreased by RNA silencing. Decreasing mPGES-1 on a consistent basis may inhibit cell proliferation, induce apoptosis and arrest the cell cycle in T-ALL jurkat cells. Microarray and western blot analyses revealed that c-Jun N-terminal kinase served a role in the mPGES-1/prostaglandin E2/EP4/MAPK positive feedback loops. In addition, P38 and extracellular signal-regulated kinase 1/2 exhibited negative feedback effects on mPGES-1. In conclusion, the results suggested that cross-talk between mPGES-1 and the MAPK signaling pathway was very complex. Therefore, the combined regulation of mPGES-1 and the MAPK signaling pathway may be developed into a new candidate therapy for T-ALL in the future.

Healthy CD4+ T lymphocytes are not affected by targeted therapies against the PI3K/Akt/mTOR pathway in T-cell acute lymphoblastic leukemia

An attractive molecular target for novel anti-cancer therapies is the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway which is commonly deregulated in many types of cancer. Nevertheless, the effects of PI3K/Akt/mTOR inhibitors on T lymphocytes, a key component of immune responses, have been seldom explored. In this study we investigated the effects on human CD4+ T-cells of a panel of PI3K/Akt/mTOR inhibitors: BGT226, Torin-2, MK-2206, and ZSTK474. We also assessed their efficacy against two acute leukemia T cell lines. T lymphocytes were stimulated with phytohemagglutinin. Inhibitor effects on cell cycle and apoptosis were analyzed by flow cytometry, while cytotoxicity was assessed by MTT assays. In addition, the activation status of the pathway as well as induction of autophagy were analyzed by Western blotting. Quiescent healthy T lymphocytes were unaffected by the drugs whereas mitogen-stimulated lymphocytes as well as leukemic cell lines displayed a cell cycle block, caspase-dependent apoptosis, and dephosphorylation of key components of the signaling pathway. Autophagy was also induced in proliferating lymphocytes and in JURKAT and MOLT-4 cell lines. When autophagy was inhibited by 3-methyladenine or Bafilomycin A1, drug cytotoxicity was increased, indicating that autophagy is a protective mechanism. Therefore, our findings suggest that PI3K/Akt/mTOR inhibitors preserve lymphocyte viability. This is a valuable result to be taken into account when selecting drugs for targeted cancer therapy in order to minimize detrimental effects on immune function.

Calcineurin complex isolated from T-cell acute lymphoblastic leukemia (T-ALL) cells identifies new signaling pathways including mTOR/AKT/S6K whose inhibition synergize with calcineurin inhibition to promote T-ALL cell death

Calcineurin (Cn) is a calcium activated protein phosphatase involved in many aspects of normal T cell physiology, however the role of Cn and/or its downstream targets in leukemogenesis are still ill-defined. In order to identify putative downstream targets/effectors involved in the pro-oncogenic activity of Cn in T-cell acute lymphoblastic leukemia (T-ALL) we used tandem affinity chromatography, followed by mass spectrometry to purify novel Cn-interacting partners. We found the Cn-interacting proteins to be part of numerous cellular signaling pathways including eIF2 signaling and mTOR signaling. Coherently, modulation of Cn activity in T-ALL cells determined alterations in the phosphorylation status of key molecules implicated in protein translation such as eIF-2α and ribosomal protein S6. Joint targeting of PI3K-mTOR, eIF-2α and 14-3-3 signaling pathways with Cn unveiled novel synergistic pro-apoptotic drug combinations. Further analysis disclosed that the synergistic interaction between PI3K-mTOR and Cn inhibitors was prevalently due to AKT inhibition. Finally, we showed that the synergistic pro-apoptotic response determined by jointly targeting AKT and Cn pathways was linked to down-modulation of key anti-apoptotic proteins including Mcl-1, Claspin and XIAP. In conclusion, we identify AKT inhibition as a novel promising drug combination to potentiate the pro-apoptotic effects of Cn inhibitors.

Systems analysis of latent HIV reversal reveals altered stress kinase signaling and increased cell death in infected T cells

Viral latency remains the most significant obstacle to HIV eradication. Clinical strategies aim to purge the latent CD4+ T cell reservoir by activating viral expression to induce death, but are undercut by the inability to target latently infected cells. Here we explored the acute signaling response of latent HIV-infected CD4+ T cells to identify dynamic phosphorylation signatures that could be targeted for therapy. Stimulation with CD3/CD28, PMA/ionomycin, or latency reversing agents prostratin and SAHA, yielded increased phosphorylation of IκBα, ERK, p38, and JNK in HIV-infected cells across two in vitro latency models. Both latent infection and viral protein expression contributed to changes in perturbation-induced signaling. Data-driven statistical models calculated from the phosphorylation signatures successfully classified infected and uninfected cells and further identified signals that were functionally important for regulating cell death. Specifically, the stress kinase pathways p38 and JNK were modified in latently infected cells, and activation of p38 and JNK signaling by anisomycin resulted in increased cell death independent of HIV reactivation. Our findings suggest that altered phosphorylation signatures in infected T cells provide a novel strategy to more selectively target the latent reservoir to enhance eradication efforts.

JNK/AP-1 activation contributes to tetrandrine resistance in T-cell acute lymphoblastic leukaemia

T-cell acute lymphoblastic leukaemia (T-ALL) is a challenging malignancy with a high relapse rate attributed to drug resistance. Tetrandrine (TET), a bisbenzylisoquinoline alkaloid extracted from a Chinese herb, is a potential anti-cancer and anti-leukaemic drug. In this study we investigated the mechanisms of TET resistance in T-ALL cells in vitro. Among the four T-ALL cell lines tested, Jurkat and CEM cells exhibited the lowest and highest resistance to TET with IC₅₀ values at 24 h of 4.31±0.12 and 16.53±3.32 μmol/L, respectively. When treated with TET, the activity of transcription factor activator protein 1 (AP-1) was significantly decreased in Jurkat cells but nearly constant in CEM cells. To avoid cell-specific variation in drug resistance and transcription factor activities, we established a TET-R Jurkat subclone with the estimated IC₅₀ value of 10.90±.92 μmol/L by exposing the cells to increasing concentrations of TET. Interestingly, when treated with TET, TET-R Jurkat cells exhibited enhanced AP-1 and NF-κB activity, along with upregulation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) signaling pathways, whereas the expression of P-gp was not altered. Selective inhibition of JNK but not ERK suppressed AP-1 activity and TET resistance in TET-R Jurkat cells and in CEM cells. These results demonstrate that Jurkat cells acquire TET resistance through activation of the JNK/AP-1 pathway but not through P-gp expression. The JNK/AP-1 pathway may be a potential therapeutic target in relapsed T-ALL.

Acute lymphoblastic leukemia: a comprehensive review and 2017 update

Acute lymphoblastic leukemia (ALL) is the second most common acute leukemia in adults, with an incidence of over 6500 cases per year in the United States alone. The hallmark of ALL is chromosomal abnormalities and genetic alterations involved in differentiation and proliferation of lymphoid precursor cells. In adults, 75% of cases develop from precursors of the B-cell lineage, with the remainder of cases consisting of malignant T-cell precursors. Traditionally, risk stratification has been based on clinical factors such age, white blood cell count and response to chemotherapy; however, the identification of recurrent genetic alterations has helped refine individual prognosis and guide management. Despite advances in management, the backbone of therapy remains multi-agent chemotherapy with vincristine, corticosteroids and an anthracycline with allogeneic stem cell transplantation for eligible candidates. Elderly patients are often unable to tolerate such regimens and carry a particularly poor prognosis. Here, we review the major recent advances in the treatment of ALL.

Klotho suppresses tumor progression via inhibiting IGF-1R signaling in T‑cell lymphoma

Klotho is a transmembrane protein and acts as an upstream modulator of insulin-like growth factor-1 receptor (IGF-1R) signaling, which was indicated to be involved in the pathogenesis of solid cancer and hematological malignancies, including T‑cell lymphoma. Although Klotho was recently identified as a tumor suppressor in several types of human malignancies, the potential role of Klotho in T‑cell lymphoma has not been reported. In the present study, we investigated the expression level and the molecular events of Klotho in T‑cell lymphoma. Significantly lower expression of Klotho was observed in T‑cell lymphoma patient samples compared to normal lymph nodes. Functional analysis after Klotho overexpression revealed significantly inhibited tumor cell viability in T‑cell lymphoma. Moreover, apoptosis of T‑cell lymphoma cells were induced after transfected with Klotho-overexpressing vectors. Forced expression of Klotho resulted in decline of activation of IGF-1R signaling, accompanied by decreased phosphorylation of its downstream targets, including AKT and ERK1/2. These data indicated that Klotho acts as a tumor suppressor via inhibiting IGF-1R signaling, thus suppressing the viability and promoting apoptosis in T‑cell lymphoma. Taken together, Klotho may serve as a potential target for the therapeutic intervention of T‑cell lymphoma.

Regulation of PI3K signaling in T-cell acute lymphoblastic leukemia: a novel PTEN/Ikaros/miR-26b mechanism reveals a critical targetable role for PIK3CD

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy, and T-ALL patients are prone to early disease relapse and suffer from poor outcomes. The PTEN, PI3K/AKT, and Notch pathways are frequently altered in T-ALL. PTEN is a tumor suppressor that inactivates the PI3K pathway. We profiled miRNAs in Pten-deficient mouse T-ALL and identified miR-26b as a potentially dysregulated gene. We validated decreased expression levels of miR-26b in mouse and human T-ALL cells. In addition, expression of exogenous miR-26b reduced proliferation and promoted apoptosis of T-ALL cells in vitro, and hindered progression of T-ALL in vivo. Furthermore, miR-26b inhibited the PI3K/AKT pathway by directly targeting PIK3CD, the gene encoding PI3Kδ, in human T-ALL cell lines. ShRNA for PIK3CD and CAL-101, a PIK3CD inhibitor, reduced the growth and increased apoptosis of T-ALL cells. Finally, we showed that PTEN induced miR-26b expression by regulating the differential expression of Ikaros isoforms that are transcriptional regulators of miR-26b. These results suggest that miR-26b functions as a tumor suppressor in the development of T-ALL. Further characterization of targets and regulators of miR-26b may be promising for the development of novel therapies.

Biphasic Rapamycin Effects in Lymphoma and Carcinoma Treatment

mTOR drives tumor growth but also supports T-cell function, rendering the applications of mTOR inhibitors complex especially in T-cell malignancies. Here, we studied the effects of the mTOR inhibitor rapamycin in mouse EL4 T-cell lymphoma. Typical pharmacologic rapamycin (1-8 mg/kg) significantly reduced tumor burden via direct suppression of tumor cell proliferation and improved survival in EL4 challenge independent of antitumor immunity. Denileukin diftitox (DD)-mediated depletion of regulatory T cells significantly slowed EL4 growth in vivo in a T-cell-dependent fashion. However, typical rapamycin inhibited T-cell activation and tumor infiltration in vivo and failed to boost DD treatment effects. Low-dose (LD) rapamycin (75 μg/kg) increased potentially beneficial CD44hiCD62L⁺ CD8⁺ central memory T cells in EL4 challenge, but without clinical benefit. LD rapamycin significantly enhanced DD treatment efficacy, but DD plus LD rapamycin treatment effects were independent of antitumor immunity. Instead, rapamycin upregulated EL4 IL2 receptor in vitro and in vivo, facilitating direct DD tumor cell killing. LD rapamycin augmented DD efficacy against B16 melanoma and a human B-cell lymphoma, but not against human Jurkat T-cell lymphoma or ID8agg ovarian cancer cells. Treatment effects correlated with IL2R expression, but mechanisms in some tumors were not fully defined. Overall, our data define a distinct, biphasic mechanisms of action of mTOR inhibition at doses that are clinically exploitable, including in T-cell lymphomas. Cancer Res; 77(2); 520-31. ©2016 AACR.

Structure-function insights reveal the human ribosome as a cancer target for antibiotics

Many antibiotics in clinical use target the bacterial ribosome by interfering with the protein synthesis machinery. However, targeting the human ribosome in the case of protein synthesis deregulations such as in highly proliferating cancer cells has not been investigated at the molecular level up to now. Here we report the structure of the human 80S ribosome with a eukaryote-specific antibiotic and show its anti-proliferative effect on several cancer cell lines. The structure provides insights into the detailed interactions in a ligand-binding pocket of the human ribosome that are required for structure-assisted drug design. Furthermore, anti-proliferative dose response in leukaemic cells and interference with synthesis of c-myc and mcl-1 short-lived protein markers reveals specificity of a series of eukaryote-specific antibiotics towards cytosolic rather than mitochondrial ribosomes, uncovering the human ribosome as a promising cancer target.

The ribosome of bacteria and other unicellular pathogens is a common target for antibiotic drugs. Here the authors determine a structure of the human ribosome bound to the translation inhibitor cycloheximide, and provide evidence that targeting the ribosome is a promising avenue for cancer therapy.

Co-targeting of Bcl-2 and mTOR pathway triggers synergistic apoptosis in BH3 mimetics resistant acute lymphoblastic leukemia

Several chemo-resistance mechanisms including the Bcl-2 protein family overexpression and constitutive activation of the PI3K/Akt/mTOR signaling have been documented in acute lymphoblastic leukemia (ALL), encouraging targeted approaches to circumvent this clinical problem. Here we analyzed the activity of the BH3 mimetic ABT-737 in ALL, exploring the synergistic effects with the mTOR inhibitor CCI-779 on ABT-737 resistant cells. We showed that a low Mcl-1/Bcl-2 plus Bcl-xL protein ratio determined ABT-737 responsiveness. ABT-737 exposure further decreased Mcl-1, inducing apoptosis on sensitive models and primary samples, while not affecting resistant cells. Co-inhibition of Bcl-2 and the mTOR pathway resulted cytotoxic on ABT-737 resistant models, by downregulating mTORC1 activity and Mcl-1 in a proteasome-independent manner. Although Mcl-1 seemed to be critical, ectopic modulation did not correlate with apoptosis changes. Importantly, dual targeting proved effective on ABT-737 resistant samples, showing additive/synergistic effects. Together, our results show the efficacy of BH3 mimetics as single agent in the majority of the ALL samples and demonstrate that resistance to ABT-737 mostly correlated with Mcl-1 overexpression. Co-targeting of the Bcl-2 protein family and mTOR pathway enhanced drug-induced cytotoxicity by suppressing Mcl-1, providing a novel therapeutic approach to overcome BH3 mimetics resistance in ALL.

CDK6-mediated repression of CD25 is required for induction and maintenance of Notch1-induced T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is a high-risk subset of acute leukemia, characterized by frequent activation of Notch1 or AKT signaling, where new_therapeutic approaches are needed. We showed previously that Cyclin-dependent kinase 6 (CDK6) is required for thymic lymphoblastic lymphoma induced by activated AKT. Here, we show CDK6 is required for initiation and maintenance of Notch-induced T-ALL. In a mouse retroviral model, hematopoietic stem/progenitor cells lacking CDK6 protein or expressing kinase-inactive (K43M) CDK6 are resistant to induction of T-ALL by activated Notch, whereas those expressing INK4-insensitive (R31C) CDK6 are permissive. Pharmacologic inhibition of CDK6 kinase induces CD25 and RUNX1 expression, cell cycle arrest, and apoptosis in mouse and human T-ALL. Ablation of Cd25 in a K43M background restores Notch-induced T-leukemogenesis, with disease that is resistant to CDK6 inhibitors in vivo. These data support a model whereby CDK6-mediated suppression of CD25 is required for initiation of T-ALL by activated Notch1, and CD25 induction mediates the therapeutic response to CDK6 inhibition in established T-ALL. These results both validate CDK6 as a molecular target for therapy of this subset of T-ALL and suggest that CD25 expression could serve as a biomarker for responsiveness of T-ALL to CDK4/6 inhibitor therapy.

Clinicopathologic Effect of DNMT3A Mutation in Adult T-Cell Acute Lymphoblastic Leukemia

BACKGROUND

The present study aimed to determine the frequencies and clinicopathologic effect of a DNMT3A [DNA (cytosine-5)-methyltransferase 3A] mutation in patients with adult T-cell acute lymphoblastic leukemia (T-ALL).

PATIENTS AND METHODS

A total of 64 patients with T-ALL who had been admitted to Mansoura University Oncology Center were included in the present study. For all patients, DNA extraction and amplification with sequencing analysis using the 310 ABI genetic analyzer for detection of a mutation (R882H).

RESULTS

The DNMT3A mutation (R882H) was found in 12 of the 64 patients (18.8%). The DNMT3A mutation was frequently detected in the older age group and was associated with high leukocytic counts, a high bone marrow blast cell percentage, and the frequent presence of extramedullary disease. However, it was not associated with the hemoglobin level, red blood cell count, or platelet count. The patients with mutant T-ALL had a low tendency to achieve remission after induction. These patients had significantly shorter overall survival and shorter disease-free survival compared with those with wild-type T-ALL (P = .037 and P = .006, respectively).

CONCLUSION

DNMT3A is frequently mutated in T-ALL and is associated with distinct clinicopathologic entities and a poor prognosis. These findings could help in risk stratification and treatment decisions for patients with T-ALL.

MicroRNA181a Is Overexpressed in T-Cell Leukemia/Lymphoma and Related to Chemoresistance

MicroRNAs (miRs) play an important role in tumorogenesis and chemoresistance in lymphoid malignancies. Comparing with reactive hyperplasia, miR181a was overexpressed in 130 patients with T-cell leukemia/lymphoma, including acute T-cell lymphoblastic leukemia (n = 32), T-cell lymphoblastic lymphoma (n = 16), peripheral T-cell lymphoma, not otherwise specified (n = 45), anaplastic large cell lymphoma (n = 15), and angioimmunoblastic T-cell lymphoma (n = 22). Irrespective to histological subtypes, miR181a overexpression was associated with increased AKT phosphorylation. In vitro, ectopic expression of miR181a in HEK-293T cells significantly enhanced cell proliferation, activated AKT, and conferred cell resistance to doxorubicin. Meanwhile, miR181a expression was upregulated in Jurkat cells, along with AKT activation, during exposure to chemotherapeutic agents regularly applied to T-cell leukemia/lymphoma treatment, such as doxorubicin, cyclophosphamide, cytarabine, and cisplatin. Isogenic doxorubicin-resistant Jurkat and H9 cells were subsequently developed, which also presented with miR181a overexpression and cross-resistance to cyclophosphamide and cisplatin. Meanwhile, specific inhibition of miR181a enhanced Jurkat and H9 cell sensitivity to chemotherapeutic agents, further indicating that miR181a was involved in acquired chemoresistance. Collectively, miR181a functioned as a biomarker of T-cell leukemia/lymphoma through modulation of AKT pathway. Related to tumor cell chemoresistance, miR181a could be a potential therapeutic target in treating T-cell malignancies.

Targeting PI3K/AKT/mTOR network for treatment of leukemia

OBJECTIVE

Increased activity of PI3K/AKT/mTOR pathway has been observed in a huge number of malignancies. This pathway can function as a prosurvival factor in leukemia stem cells and early committed leukemic precursors and its inhibition is regarded as a therapeutic approach. Accordingly, the aim of this review is to evaluate the PI3K/Akt/mTOR inhibitors used in leukemia models.

DISCUSSION

Inhibition of the PI3K/AKT/mTOR pathway has been reported to have beneficial therapeutic effects in leukemias, both in vitro in leukemia cell lines and in vivo in animal models. Overall, the use of dual PI3K/mTOR inhibitor, dual Akt/RTK inhibitor, Akt inhibitor, selective inhibitor of PI3K, mTOR inhibitor and dual PI3K/PDK1 inhibitor in CML, AML, APL, CLL, B-ALL and T-ALL has a better therapeutic effect than conventional treatments.

CONCLUSIONS

Targeting the PI3K/Akt/mTOR pathway may have pro-apoptotic and antiproliferative effects on hematological malignancies. Furthermore, modulation of miRNA can be used as a novel therapeutic approach to regulate the PI3K/Akt/mTOR pathway. However, both aspects require further clinical studies.

Dysregulated choline metabolism in T-cell lymphoma: role of choline kinase-α and therapeutic targeting

Cancer cells have distinct metabolomic profile. Metabolic enzymes regulate key oncogenic signaling pathways and have an essential role on tumor progression. Here, serum metabolomic analysis was performed in 45 patients with T-cell lymphoma (TCL) and 50 healthy volunteers. The results showed that dysregulation of choline metabolism occurred in TCL and was related to tumor cell overexpression of choline kinase-α (Chokα). In T-lymphoma cells, pharmacological and molecular silencing of Chokα significantly decreased Ras-GTP activity, AKT and ERK phosphorylation and MYC oncoprotein expression, leading to restoration of choline metabolites and induction of tumor cell apoptosis/necropotosis. In a T-lymphoma xenograft murine model, Chokα inhibitor CK37 remarkably retarded tumor growth, suppressed Ras-AKT/ERK signaling, increased lysophosphatidylcholine levels and induced in situ cell apoptosis/necropotosis. Collectively, as a regulatory gene of aberrant choline metabolism, Chokα possessed oncogenic activity and could be a potential therapeutic target in TCL, as well as other hematological malignancies with interrupted Ras signaling pathways.

Targeting interleukin-2-inducible T-cell kinase (ITK) and resting lymphocyte kinase (RLK) using a novel covalent inhibitor PRN694

Interleukin-2-inducible T-cell kinase (ITK) and resting lymphocyte kinase (RLK or TXK) are essential mediators of intracellular signaling in both normal and neoplastic T-cells and natural killer (NK) cells. Thus, ITK and RLK inhibitors have therapeutic potential in a number of human autoimmune, inflammatory, and malignant diseases. Here we describe a novel ITK/RLK inhibitor, PRN694, which covalently binds to cysteine residues 442 of ITK and 350 of RLK and blocks kinase activity. Molecular modeling was utilized to design molecules that interact with cysteine while binding to the ATP binding site in the kinase domain. PRN694 exhibits extended target residence time on ITK and RLK and is highly selective for a subset of the TEC kinase family. In vitro cellular assays confirm that PRN694 prevents T-cell receptor- and Fc receptor-induced cellular and molecular activation, inhibits T-cell receptor-induced T-cell proliferation, and blocks proinflammatory cytokine release as well as activation of Th17 cells. Ex vivo assays demonstrate inhibitory activity against T-cell prolymphocytic leukemia cells, and in vivo assays demonstrate durable pharmacodynamic effects on ITK, which reduces an oxazolone-induced delayed type hypersensitivity reaction. These data indicate that PRN694 is a highly selective and potent covalent inhibitor of ITK and RLK, and its extended target residence time enables durable attenuation of effector cells in vitro and in vivo. The results from this study highlight potential applications of this dual inhibitor for the treatment of T-cell- or NK cell-mediated inflammatory, autoimmune, and malignant diseases.

L-type amino-acid transporter 1 (LAT1): a therapeutic target supporting growth and survival of T-cell lymphoblastic lymphoma/T-cell acute lymphoblastic leukemia

The altered metabolism of cancer cells is a treasure trove to discover new antitumoral strategies. The gene (SLC7A5) encoding system L amino-acid transporter 1 (LAT1) is overexpressed in murine lymphoma cells generated via T-cell deletion of the pten tumor suppressor, and also in human T-cell acute lymphoblastic leukemia (T-ALL)/lymphoma (T-LL) cells. We show here that a potent and LAT1 selective inhibitor (JPH203) decreased leukemic cell viability and proliferation, and induced transient autophagy followed by apoptosis. JPH203 could also alter the in vivo growth of luciferase-expressing-tPTEN-/- cells xenografted into nude mice. In contrast, JPH203 was nontoxic to normal murine thymocytes and human peripheral blood lymphocytes. JPH203 interfered with constitutive activation of mTORC1 and Akt, decreased expression of c-myc and triggered an unfolded protein response mediated by the C/EBP homologous protein (CHOP) transcription factor associated with cell death. A JPH203-resistant tPTEN-/-clone appeared CHOP induction deficient. We also demonstrate that targeting LAT1 may be an efficient broad spectrum adjuvant approach to treat deadly T-cell malignancies as the molecule synergized with rapamycin, dexamethasone, doxorubicin, velcade and l-asparaginase to alter leukemic cell viability.

Pathogenetic and diagnostic significance of microRNA deregulation in peripheral T-cell lymphoma not otherwise specified

Peripheral T-cell lymphomas not otherwise specified (PTCLs/NOS) are rare and aggressive tumours whose molecular pathogenesis and diagnosis are still challenging. The microRNA (miRNA) profile of 23 PTCLs/NOS was generated and compared with that of normal T-lymphocytes (CD4+, CD8+, naive, activated). The differentially expressed miRNA signature was compared with the gene expression profile (GEP) of the same neoplasms. The obtained gene patterns were tested in an independent cohort of PTCLs/NOS. The miRNA profile of PTCLs/NOS then was compared with that of 10 angioimmunoblastic T-cell lymphomas (AITLs), 6 anaplastic large-cell lymphomas (ALCLs)/ALK+ and 6 ALCLs/ALK−. Differentially expressed miRNAs were validated in an independent set of 20 PTCLs/NOS, 20 AITLs, 19 ALCLs/ALK− and 15 ALCLs/ALK+. Two hundred and thirty-six miRNAs were found to differentiate PTCLs/NOS from activated T-lymphocytes. To assess which miRNAs impacted on GEP, a multistep analysis was performed, which identified all miRNAs inversely correlated to different potential target genes. One of the most discriminant miRNAs was selected and its expression was found to affect the global GEP of the tumours. Moreover, two sets of miRNAs were identified distinguishing PTCL/NOS from AITL and ALCL/ALK−, respectively. The diagnostic accuracy of this tool was very high (83.54%) and its prognostic value validated.

Chemical metabolic inhibitors for the treatment of blood-borne cancers

Tumor cells, including leukemic cells, remodel their bioenergetic system in favor of aerobic glycolysis. This process is called "the Warburg effect" and offers an attractive pharmacological target to preferentially eliminate malignant cells. In addition, recent results show that metabolic changes can be linked to tumor immune evasion. Mouse models demonstrate the importance of this metabolic remodeling in leukemogenesis. Some leukemias, although treatable, remain incurable and resistance to chemotherapy produces an elevated percentage of relapse in most leukemia cases. Several groups have targeted the specific metabolism of leukemia cells in preclinical and clinical studies to improve the prognosis of these patients, i.e. using L-asparaginase to treat pediatric acute lymphocytic leukemia (ALL). Additional metabolic drugs that are currently being used to treat other diseases or tumors could also be exploited for leukemia, based on preclinical studies. Finally, we discuss the potential use of several metabolic drugs in combination therapies, including immunomodulatory drugs (IMiDs) or immune cell-based therapies, to increase their efficacy and reduce side effects in the treatment of hematological cancers.

Increased Expression of Phosphorylated FADD in Anaplastic Large Cell and Other T-Cell Lymphomas

FAS-associated protein with death domain (FADD) is a major adaptor protein involved in extrinsic apoptosis, embryogenesis, and lymphocyte homeostasis. Although abnormalities of the FADD/death receptor apoptotic pathways have been established in tumorigenesis, fewer studies have analyzed the expression and role of phosphorylated FADD (pFADD). Our identification of FADD as a lymphoma-associated autoantigen in T-cell lymphoma patients raises the possibility that pFADD, with its correlation with cell cycle, may possess role(s) in human T-cell lymphoma development. This immunohistochemical study investigated pFADD protein expression in a range of normal tissues and lymphomas, particularly T-cell lymphomas that require improved therapies. Whereas pFADD was expressed only in scattered normal T cells, it was detected at high levels in T-cell lymphomas (eg, 84% anaplastic large cell lymphoma and 65% peripheral T cell lymphomas, not otherwise specified). The increased expression of pFADD supports further study of its clinical relevance and role in lymphomagenesis, highlighting phosphorylation of FADD as a potential therapeutic target.

Therapeutic potential of targeting mTOR in T-cell acute lymphoblastic leukemia (review)

T-cell acute lymphoblastic leukemia (T-ALL) is a heterogeneous neoplastic disorder of immature hematopoietic precursors committed to the T-cell lineage. T-ALL comprises about 15% of pediatric and 25% of adult ALL cases. Even if the prognosis of T-ALL has improved especially in the childhood due to the use of new intensified treatment protocols, the outcome of relapsed patients who are resistant to conventional chemotherapeutic drugs or who relapse is still poor. For this reason, there is a need for novel and less toxic targeted therapies against signaling pathways aberrantly activated in T-ALL, such as the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR). Small molecules designed to target key components of this signaling axis have proven their efficacy both in vitro and in vivo in pre-clinical settings of T-ALL. In particular, different classes of mTOR inhibitors have been disclosed by pharmaceutical companies, and they are currently being tested in clinical trials for treating T-ALL patients. One of the most promising approaches for the treatment of T-ALL seems to be the combination of mTOR inhibitors with traditional chemotherapeutic agents. This could lead to a lower drug dosage that may circumvent the systemic side effects of chemotherapeutics. In this review, we focus on the different classes of mTOR inhibitors that will possibly have an impact on the therapeutic arsenal we have at our disposal against T-ALL.

Targeting Interleukin-2-Inducible T-cell Kinase (ITK) in T-Cell Related Diseases

IL2-inducible T-cell kinase (ITK), a member of the Tec family tyrosine kinases, is the predominant Tec kinase in T cells and natural killer (NK) cells mediating T cell receptor (TCR) and Fc receptor (Fc R) initiated signal transduction. ITK deficiency results in impaired T and NK cell functions, leading to various disorders including malignancies, inflammation, and autoimmune diseases. In this mini-review, the role of ITK in T cell signaling and the development of small molecule inhibitors of ITK for the treatment of T-cell related disorders is examined.

Therapy-resistant acute lymphoblastic leukemia (ALL) cells inactivate FOXO3 to escape apoptosis induction by TRAIL and Noxa

Forkhead transcription factors (FOXO) are downstream targets of the phosphoinositol-3-kinase (PI3K) protein kinase B (PKB) signaling cascade and play a pivotal role in cell differentiation, cell cycle and apoptosis. We found that cells from prednisone-resistant T-acute lymphoblastic leukemia (T-ALL) patients showed cytoplasmic localization of FOXO3 in comparison to prednisone-sensitive patients suggesting its inactivation. To determine the impact of FOXO3, T-ALL cells were infected with a 4OH-tamoxifen-regulated, phosphorylation-independent FOXO3(A3)ERtm allele. After FOXO3-activation these cells undergo caspase-dependent apoptosis. FOXO3 induces the death ligand TRAIL and the BH3-only protein Noxa implicating extrinsic as well as intrinsic death signaling. Whereas dnFADD partially inhibited cell death, CrmA and dnBID efficiently rescued ALL cells after FOXO3 activation, suggesting a caspase-8 amplifying feedback loop downstream of FADD. Knockdown of TRAIL and Noxa reduced FOXO3-induced apoptosis, implicating that mitochondrial destabilization amplifies TRAIL-signaling. The-reconstitution of the cell cycle inhibitor p16^INK4A, which sensitizes ALL cells to mitochondria-induced cell death, represses FOXO3 protein levels and reduces the dependency of these leukemia cells on PI3K-PKB signaling. This suggests that if p16^INK4A is deleted during leukemia development, FOXO3 levels elevate and FOXO3 has to be inactivated by deregulation of the PI3K-PKB pathway to prevent FOXO3-induced cell death.

Retama monosperma n-hexane extract induces cell cycle arrest and extrinsic pathway-dependent apoptosis in Jurkat cells

BACKGROUND

Retama monosperma L. (Boiss.) or Genista monosperma L. (Lam.), locally named as "R'tam", is an annual and spontaneous plant belonging to the Fabaceae family. In Morocco, Retama genus is located in desert regions and across the Middle Atlas and it has been widely used in traditional medicine in many countries. In this study, we show that Retama monosperma hexane extract presents significant anti-leukemic effects against human Jurkat cells.

METHODS

Human Jurkat cells, together with other cell lines were screened with different concentrations of Retama monosperma hexane extract at different time intervals. Growth inhibition was determined using luminescent-based viability assays. Cell cycle arrest and apoptosis were measured by flow cytometry analysis. Combined caspase 3 and 7 activities were measured using luminometric caspase assays and immunoblots were performed to analyze expression of relevant pro- and anti-apoptotic proteins. GC-MS were used to determine the chemical constituents of the active extract.

RESULTS

Retama monosperma hexane extract (Rm-HE) showed significant cytotoxicity against Jurkat cells, whereas it proved to be essentially ineffective against both normal mouse fibroblasts (NIH3T3) and normal lymphocytes (TK-6). Cytometric analysis indicated that Rm-HE promoted cell cycle arrest and apoptosis induction accompanied by DNA damage induction indicated by an increase in p-H2A.X levels. Rm-HE induced apoptosis was partially JNK-dependent and characterized by an increase in Fas-L levels together with activation of caspases 8, 3, 7 and 9, whereas neither the pro-apoptotic nor anti-apoptotic mitochondrial membrane proteins analyzed were significantly altered. Chemical identification analysis indicated that α-linolenic acid, campesterol, stigmasterol and sitosterol were the major bioactive components within the extract.

CONCLUSIONS

Our data suggest that bioactive compounds present in Rm-HE show significant anti leukemic activity inducing cell cycle arrest and cell death that operates, at least partially, through the extrinsic apoptosis pathway.

Inhibition of hedgehog signaling by GANT58 induces apoptosis and shows synergistic antitumor activity with AKT inhibitor in acute T cell leukemia cells

The hedgehog (Hh) signaling pathways have a crucial role in cell proliferation and survival, and the de-regulation of these pathways can lead to tumorigenesis. Here we investigated the expression and function of these pathways in acute T lymphocytic leukemia cells (T-ALL). Profiling of Hh pathway members revealed common expression of key Hh signaling effectors in all T-ALL cells. We found that T-ALL cells were insensitive to specific Smoothened (SMO) inhibition following the use of low concentrations of the SMO antagonist cyclopamine. In contrast, treatment with the novel GLI antagonist GANT58 reduced expression of the target gene Patched 1 as well as GLI family zinc finger 1 (GLI1) and preferentially decreased the viability of T-ALL cells. We also found perifosine, a novel AKT inhibitor, down-regulated GLI1 protein by dephosphorylation of AKT and GSK3β dose-dependently and that pre-treatment with PD98059, a MEK/ERK pathway inhibitor, enhanced this down-regulation by 20%-30%. Then we questioned whether use of both GANT58 and AKT inhibitor together could confer a synergistic effect to decrease T-ALL cell viability. By applying the Chou-Talalay method, low concentration of GANT58 induced T-ALL cell death in a synergism fashion with perifosine or GSK690693 when used simultaneously. These findings indicate that the combined use of GANT58 and AKT inhibitor could help treat a broad range of malignant tumors in conjunction with existing cancer treatments.

Autophagy as a pathogenic mechanism and drug target in lymphoproliferative disorders

Autophagy represents a key mechanism of cytoprotection that can be activated by a variety of extracellular and intracellular stresses and allows the cell to sequester cytoplasmic components and damaged organelles, delivering them to lysosomes for degradation and recycling. However, the autophagy process has also been associated with the death of the cell. It has been demonstrated to be constitutive in some instances and inducible in others, and the idea that it could represent a pathogenetic determinant as well as a possible prognostic tool and a therapeutic target in a plethora of human diseases has recently been considered. Among these, cancer represents a major one. In this review, we recapitulate the critical implications of autophagy in the pathogenesis, progression, and treatment of lymphoproliferative disorders. Leukemias and lymphomas, in fact, represent paradigmatic human diseases in which advances have recently been made in this respect.