CCR7 signalling as an essential regulator of CNS infiltration in T-cell leukaemia

Disrupting the leukemia niche in the central nervous system attenuates leukemia chemoresistance

Protection from acute lymphoblastic leukemia relapse in the central nervous system (CNS) is crucial to survival and quality of life for leukemia patients. Current CNS-directed therapies cause significant toxicities and are only partially effective. Moreover, the impact of the CNS microenvironment on leukemia biology is poorly understood. In this study we showed that leukemia cells associated with the meninges of xenotransplanted mice, or co-cultured with meningeal cells, exhibit enhanced chemoresistance due to effects on both apoptosis balance and quiescence. From a mechanistic standpoint, we found that leukemia chemoresistance is primarily mediated by direct leukemia-meningeal cell interactions and overcome by detaching the leukemia cells from the meninges. Next, we used a co-culture adhesion assay to identify drugs that disrupted leukemia-meningeal adhesion. In addition to identifying several drugs that inhibit canonical cell adhesion targets we found that Me6TREN (Tris[2-(dimethylamino)ethyl]amine), a novel hematopoietic stem cell-mobilizing compound, also disrupted leukemia-meningeal adhesion and enhanced the efficacy of cytarabine in treating CNS leukemia in xenotransplanted mice. This work demonstrates that the meninges exert a critical influence on leukemia chemoresistance, elucidates mechanisms of relapse beyond the well-described role of the blood-brain barrier, and identifies novel therapeutic approaches for overcoming chemoresistance.

New advances in targeting aberrant signaling pathways in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disorder characterized by malignant transformation of immature progenitors primed towards T-cell development. Over the past 15 years, advances in the molecular characterization of T-ALL have uncovered oncogenic key drivers and crucial signaling pathways of this disease, opening new chances for the development of novel therapeutic strategies. Currently, T-ALL patients are still treated with aggressive therapies, consisting of high dose multiagent chemotherapy. To minimize and overcome the unfavorable effects of these regimens, it is critical to identify innovative targets and test selective inhibitors of such targets. Major efforts are being made to develop small molecules against deregulated signaling pathways, which sustain T-ALL cell growth, survival, metabolism, and drug-resistance. This review will focus on recent improvements in the understanding of the signaling pathways involved in the pathogenesis of T-ALL and on the challenging opportunities for T-ALL targeted therapies.

Age-Related Gliosis Promotes Central Nervous System Lymphoma through CCL19-Mediated Tumor Cell Retention

How lymphoma cells (LCs) invade the brain during the development of central nervous system lymphoma (CNSL) is unclear. We found that NF-κB-induced gliosis promotes CNSL in immunocompetent mice. Gliosis elevated cell-adhesion molecules, which increased LCs in the brain but was insufficient to induce CNSL. Astrocyte-derived CCL19 was required for gliosis-induced CNSL. Deleting CCL19 in mice or CCR7 from LCs abrogated CNSL development. Two-photon microscopy revealed LCs transiently entering normal brain parenchyma. Astrocytic CCL19 enhanced parenchymal CNS retention of LCs, thereby promoting CNSL formation. Aged, gliotic wild-type mice were more susceptible to forming CNSL than young wild-type mice, and astrocytic CCL19 was observed in both human gliosis and CNSL. Therefore, CCL19-CCR7 interactions may underlie an increased age-related risk for CNSL.

Evaluation of multiplexed biomarkers in assessment of CSF infiltration in pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a very common pediatric malignancy with high survival rates. The course of treatment is modified according to the occurrence of central nervous system (CNS) disease. Aim: To relate serum and cerebrospinal fluid levels of five biomarkers (matrix metalloprotienase 9, CCL-2, sVCAM-1, IFN-γ and inducible protein 10) at diagnosis to the development of CNS infiltration. Methods: The present study was carried on 64 children with ALL and 20 controls. Multiplexed cytokines were measured by Luminex technology (Matrix metalloprotienase 9, CCL-2, sVCAM-1, IFN-γ and inducible protein 10). Results: Significantly higher sMMP-9 and lower sCCL2 were found in patients who developed CNS leukemia. Conclusion: Serum multiplexed parameters at diagnosis of childhood ALL may predict of development of CNS leukemia.

Desperately seeking a home marrow niche for T-cell acute lymphoblastic leukaemia

T-cell acute leukemia is a hematologic malignancy that results from the progressive acquisition of genomic abnormalities in T-cell progenitors/precursors. T-ALL is commonly thought to originate from the thymus albeit recent literature describes the possible acquisition of the first oncogenic hits in hematopoietic progenitor cells of the bone marrow (BM). The journey of T-ALL from its arising to full blown expansion meets different microenvironments, including the BM in which leukemic cells settle down early after the disease spreading. We take advantage of recent literature to give an overview of important cells and factors that participate in T-ALL, especially in the BM, arguing in favor of a home marrow niche for this rare leukemia.

Notch/CXCR4 Partnership in Acute Lymphoblastic Leukemia Progression

Acute lymphoblastic leukemia (ALL) is the most common cancer among children. Recent advances in chemotherapy have made ALL a curable hematological malignancy. In children, there is 25% chance of disease relapse, typically in the central nervous system. While in adults, there is a higher chance of relapse. ALL may affect B-cell or T-cell lineages. Different genetic alterations characterize the two ALL forms. Deregulated Notch, either Notch1 or Notch3, and CXCR4 receptor signaling are involved in ALL disease development and progression. By analyzing their relevant roles in the pathogenesis of the two ALL forms, new molecular mechanisms able to modulate cancer cell invasion may be visualized. Notably, the partnership between Notch and CXCR4 may have considerable implications in understanding the complexity of T- and B-ALL. These two receptor pathways intersect other critical signals in the proliferative, differentiation, and metabolic programs of lymphocyte transformation. Also, the identification of the crosstalks in leukemia-stroma interaction within the tumor microenvironment may unveil new targetable mechanisms in disease relapse. Further studies are required to identify new challenges and opportunities to develop more selective and safer therapeutic strategies in ALL progression, possibly contributing to improve conventional hematological cancer therapy.

Structural and functional consequences of the STAT5BN642H driver mutation

Hyper-activated STAT5B variants are high value oncology targets for pharmacologic intervention. STAT5BN642H, a frequently-occurring oncogenic driver mutation, promotes aggressive T-cell leukemia/lymphoma in patient carriers, although the molecular origins remain unclear. Herein, we emphasize the aggressive nature of STAT5BN642H in driving T-cell neoplasia upon hematopoietic expression in transgenic mice, revealing evidence of multiple T-cell subset organ infiltration. Notably, we demonstrate STAT5BN642H-driven transformation of γδ T-cells in in vivo syngeneic transplant models, comparable to STAT5BN642H patient γδ T-cell entities. Importantly, we present human STAT5B and STAT5BN642H crystal structures, which propose alternative mutation-mediated SH2 domain conformations. Our biophysical data suggests STAT5BN642H can adopt a hyper-activated and hyper-inactivated state with resistance to dephosphorylation. MD simulations support sustained interchain cross-domain interactions in STAT5BN642H, conferring kinetic stability to the mutant anti-parallel dimer. This study provides a molecular explanation for the STAT5BN642H activating potential, and insights into pre-clinical models for targeted intervention of hyper-activated STAT5B.

Powerful Anticolon Tumor Effect of Targeted Gene Immunotherapy Using Folate-Modified Nanoparticle Delivery of CCL19 To Activate the Immune System

Targeted gene delivery systems have recently shown potential clinical benefits in cancer treatment. Recently, the immunologic therapies application in cancer therapy also showed a continuously increase. CCL19 has shown its great potential as a candidate immunomodulator for colon cancer therapy by increasing the possibility of interaction among dendritic cells, T and B cells in secondary lymphatic tissue, thus regulating the primary (or secondary) adaptive immune responses. In this work, a folic acid modified targeted gene-delivery system consisting of DOTAP, MPEG-PLA, and Fa-PEG-PLA (F-DMA) was developed successfully through a self-assembly approach. We proved that CCL19 expression was much higher in cancer cells after transfection with F-DMA/CCL19 than after transfection with DMA/CCL19. The supernatant from cancer cells transfected with both F-DMA/CCL19 and DMA/CCL19 stimulated the activation and cytotoxicity of T lymphocytes, the maturation of DCs, and the polarization of macrophages in vitro. Moreover, the administration of F-DMA/CCL19 complex to treat tumor-bearing mice has shown significant cancer growth repression in both subcutaneous and peritoneal models. The underling antitumor mechanism is established through repressing neovascularization, promoting apoptosis, as well as reducing proliferation by activating the immune system. The CCL19 plasmid and F-DMA complex may be used as a novel method for colorectal cancer therapy in the clinic.

F-DMA carried the CCL19 gene into tumor cells expressing and secreting CCL19 protein factor, which induced activation of the immune system to kill cancer.

Molecular Players in Hematologic Tumor Cell Trafficking

The trafficking of neoplastic cells represents a key process that contributes to progression of hematologic malignancies. Diapedesis of neoplastic cells across endothelium and perivascular cells is facilitated by adhesion molecules and chemokines, which act in concert to tightly regulate directional motility. Intravital microscopy provides spatio-temporal views of neoplastic cell trafficking, and is crucial for testing and developing therapies against hematologic cancers. Multiple myeloma (MM), chronic lymphocytic leukemia (CLL), and acute lymphoblastic leukemia (ALL) are hematologic malignancies characterized by continuous neoplastic cell trafficking during disease progression. A common feature of these neoplasias is the homing and infiltration of blood cancer cells into the bone marrow (BM), which favors growth and survival of the malignant cells. MM cells traffic between different BM niches and egress from BM at late disease stages. Besides the BM, CLL cells commonly home to lymph nodes (LNs) and spleen. Likewise, ALL cells also infiltrate extramedullary organs, such as the central nervous system, spleen, liver, and testicles. The α4β1 integrin and the chemokine receptor CXCR4 are key molecules for MM, ALL, and CLL cell trafficking into and out of the BM. In addition, the chemokine receptor CCR7 controls CLL cell homing to LNs, and CXCR4, CCR7, and CXCR3 contribute to ALL cell migration across endothelia and the blood brain barrier. Some of these receptors are used as diagnostic markers for relapse and survival in ALL patients, and their level of expression allows clinicians to choose the appropriate treatments. In CLL, elevated α4β1 expression is an established adverse prognostic marker, reinforcing its role in the disease expansion. Combining current chemotherapies with inhibitors of malignant cell trafficking could represent a useful therapy against these neoplasias. Moreover, immunotherapy using humanized antibodies, CAR-T cells, or immune check-point inhibitors together with agents targeting the migration of tumor cells could also restrict their survival. In this review, we provide a view of the molecular players that regulate the trafficking of neoplastic cells during development and progression of MM, CLL, and ALL, together with current therapies that target the malignant cells.

Leukemia-derived exosomes and cytokines pave the way for entry into the brain

Infiltration of acute lymphoblastic leukemia (ALL) blasts into the CNS remains as a major clinical problem, with high risk for chemotherapy-resistant relapse and treatment-related morbidity. Despite the common inclusion of CNS prophylaxis treatments in therapy regimens, there are significant gaps in understanding the mechanisms that mediate leukemia cell entry into the CNS as well as roles for resident cells in the brain. In this study, we employ a xenograft model of human B cell precursor (BCP)-ALL in immunocompromised mice. This model system recapitulates key pathological characteristics of leptomeningeal involvement seen in patients and provides insights into rare cases that involve parenchymal invasion. We examine the infiltration of engrafted leukemia blasts into brains of recipient mice and provide evidence that the interaction between blasts and brain resident cells causes aberrant activation of host cells in the brain microenvironment. BCP-ALL blasts also release multiple cytokines and exosomes containing IL-15 that bind and are internalized by astrocytes and brain vessel endothelial cells. Leukemic invasion is linked to production of VEGF-AA by astrocytes and disruption of the blood-brain-barrier (BBB) integrity. Knockdown of either IL-15 or IL-15Rα in the NALM6 cell line decreases CNS infiltration in engrafted mice. These results provide important insights into the multiple mechanisms by which lymphoblasts modulate the brain microenvironment to breach the BBB for metastatic invasion.

USP7 Cooperates with NOTCH1 to Drive the Oncogenic Transcriptional Program in T-Cell Leukemia

PURPOSE

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disease, affecting children and adults. Chemotherapy treatments show high response rates but have debilitating effects and carry risk of relapse. Previous work implicated NOTCH1 and other oncogenes. However, direct inhibition of these pathways affects healthy tissues and cancer alike. Our goal in this work has been to identify enzymes active in T-ALL whose activity could be targeted for therapeutic purposes.

EXPERIMENTAL DESIGN

To identify and characterize new NOTCH1 druggable partners in T-ALL, we coupled studies of the NOTCH1 interactome to expression analysis and a series of functional analyses in cell lines, patient samples, and xenograft models.

RESULTS

We demonstrate that ubiquitin-specific protease 7 (USP7) interacts with NOTCH1 and controls leukemia growth by stabilizing the levels of NOTCH1 and JMJD3 histone demethylase. USP7 is highly expressed in T-ALL and is transcriptionally regulated by NOTCH1. In turn, USP7 controls NOTCH1 levels through deubiquitination. USP7 binds oncogenic targets and controls gene expression through stabilization of NOTCH1 and JMJD3 and ultimately H3K27me3 changes. We also show that USP7 and NOTCH1 bind T-ALL superenhancers, and inhibition of USP7 leads to a decrease of the transcriptional levels of NOTCH1 targets and significantly blocks T-ALL cell growth in vitro and in vivo.

CONCLUSIONS

These results provide a new model for USP7 deubiquitinase activity through recruitment to oncogenic chromatin loci and regulation of both oncogenic transcription factors and chromatin marks to promote leukemia. Our studies also show that targeting USP7 inhibition could be a therapeutic strategy in aggressive leukemia.

Eradication of Central Nervous System Leukemia of T-Cell Origin with a Brain-Permeable LSD1 Inhibitor

PURPOSE

Lysine-specific demethylase 1 (LSD1) regulates several biological processes via the bifunctional modulation of enhancer functions. Recently, we reported that LSD1 overexpression is a founder abnormality of T-cell leukemogenesis and is maintained in fully transformed T-cell acute lymphoblastic leukemia (T-ALL) cells. On the basis of this finding, we attempted to develop novel LSD1 inhibitors effective for T-ALL with central nervous system (CNS) involvement.

EXPERIMENTAL DESIGN

We chemically modified the prototype LSD inhibitor tranylcypromine (TCP) and screened for cytotoxicity against TCP-resistant T-ALL cell lines. In vivo efficacy of novel LSD1 inhibitors was examined in immunodeficient mice transplanted with luciferase-expressing T-ALL cell lines, which faithfully reproduce human T-ALL with CNS involvement.

RESULTS

We found robust cytotoxicity against T-ALL cells, but not normal bone marrow progenitors, for two N-alkylated TCP derivatives, S2116 and S2157. The two compounds induced apoptosis in TCP-resistant T-ALL cells in vitro and in vivo by repressing transcription of the NOTCH3 and TAL1 genes through increased H3K9 methylation and reciprocal H3K27 deacetylation at superenhancer regions. Both S2116 and S2157 significantly retarded the growth of T-ALL cells in xenotransplanted mice and prolonged the survival of recipients as monotherapy and in combination with dexamethasone. Notably, S2157 could almost completely eradicate CNS leukemia because of its ability to efficiently pass through the blood-brain barrier.

CONCLUSIONS

These findings provide a molecular basis and rationale for the inclusion of a brain-permeable LSD1 inhibitor, S2157, in treatment strategies for T-ALL with CNS involvement.

New Approaches to the Management of Adult Acute Lymphoblastic Leukemia

Traditional treatment regimens for adult acute lymphoblastic leukemia, including allogeneic hematopoietic cell transplantation, result in an overall survival of approximately 40%, a figure hardly comparable with the extraordinary 80% to 90% cure rate currently reported in children. When translated to the adult setting, modern pediatric-type regimens improve the survival to approximately 60% in young adults. The addition of tyrosine kinase inhibitors for patients with Philadelphia chromosome-positive disease and the measurement of minimal residual disease to guide risk stratification and postremission approaches has led to additional improvements in outcomes. Relapsed disease and treatment toxicity-sparing no patient but representing a major concern especially in the elderly-are the most critical current issues awaiting further therapeutic advancement. Recently, there has been considerable progress in understanding the disease biology, specifically the Philadelphia-like signature, as well as other high-risk subgroups. In addition, there are several new agents that will undoubtedly contribute to additional improvement in the current outcomes. The most promising agents are monoclonal antibodies, immunomodulators, and chimeric antigen receptor T cells, and, to a lesser extent, several new drugs targeting key molecular pathways involved in leukemic cell growth and proliferation. This review examines the evidence supporting the increasing role of the new therapeutic tools and treatment options in different disease subgroups, including frontline and relapsed or refractory disease. It is now possible to define the best individual approach on the basis of the emerging concepts of precision medicine.

Signaling-chemokine axis network in brain as a sanctuary site for metastasis

BACKGROUND

Brain metastasis remains a major cause of death in patients with solid cancers. The co-operation between several molecular factors such as chemokines, chemokine receptors, and signaling pathways is involved in the pathogenesis of brain metastasis mostly from solid tumors. In this review, we examine the possible role of chemokine/receptor axis, as well as signaling pathways as prognostic biomarkers in brain metastasis.

METHODS

Relevant English language literature were searched and retrieved from Google Scholar search engine (1993-2017). The following keywords were used: "chemokine," "signaling pathway," "brain," "metastasis," and "niche."

RESULTS

Increased expression of chemokines like CXCL12 and dysregulated signaling intermediates such as Notch in patients with solid tumors (e.g., breast cancer) is associated with brain metastasis.

CONCLUSIONS

As biomarkers for brain metastasis, chemokine, and signaling intermediates are potential prognostic factors in a number of solid tumor, including breast cancer, melanoma, and lung cancer.

Pediatric acute lymphoblastic leukemia-Conquering the CNS across the choroid plexus

Despite the high prevalence of central nervous system (CNS) involvement in relapsing pediatric acute lymphoblastic leukemia (ALL), our understanding of CNS invasion is still vague. As lymphoblasts have to overcome the physiological blood-CNS barriers to enter the CNS, we investigated the cellular interactions of lymphoblasts with the choroid plexus (CP) epithelium of the blood-cerebrospinal fluid barrier (BCSFB). Both a precurser B cell ALL (pB-ALL) cell line (SD-1) and a T cell ALL (T-ALL) cell line (P12-Ishikawa) were able to actively cross the CP epithelium in a human in vitro model. We could illustrate a transcellular and (supposedly) paracellular transmigration by 3-dimensional immunofluorescence microscopy as well as electron microscopy. Chemotactic stimulation with CXCL12 during this process led to a significantly increased transmigration and blocking CXCL12/CXCR4-signaling by the CXCR4-inhibitor AMD3100 inhibited this effect. However, CXCR4 expression in primary ALL samples did not correlate to CNS disease, indicating that CXCR4-driven CNS invasion across the BCSFB might be a general property of pediatric ALL. Notably, we present a unique in vitro BCSFB model suitable to study CNS invasion of lymphoblasts in a human setting, providing the opportunity to investigate experimental variables, which may determine CNS disease childhood ALL.

Therapeutic Targeting of mTOR in T-Cell Acute Lymphoblastic Leukemia: An Update

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive blood malignancy that arises from the clonal expansion of transformed T-cell precursors. Although T-ALL prognosis has significantly improved due to the development of intensive chemotherapeutic protocols, primary drug-resistant and relapsed patients still display a dismal outcome. In addition, lifelong irreversible late effects from conventional therapy are a growing problem for leukemia survivors. Therefore, novel targeted therapies are required to improve the prognosis of high-risk patients. The mechanistic target of rapamycin (mTOR) is the kinase subunit of two structurally and functionally distinct multiprotein complexes, which are referred to as mTOR complex 1 (mTORC1) and mTORC2. These two complexes regulate a variety of physiological cellular processes including protein, lipid, and nucleotide synthesis, as well as autophagy in response to external cues. However, mTOR activity is frequently deregulated in cancer, where it plays a key oncogenetic role driving tumor cell proliferation, survival, metabolic transformation, and metastatic potential. Promising preclinical studies using mTOR inhibitors have demonstrated efficacy in many human cancer types, including T-ALL. Here, we highlight our current knowledge of mTOR signaling and inhibitors in T-ALL, with an emphasis on emerging evidence of the superior efficacy of combinations consisting of mTOR inhibitors and either traditional or targeted therapeutics.

Wnt5a and CCL25 promote adult T-cell acute lymphoblastic leukemia cell migration, invasion and metastasis

Adult T-cell acute lymphoblastic leukemia (T-ALL) is a refractory leukemia. We previously showed that CCL25/CCR9 promotes T-ALL metastasis. In the present study, we assessed the effects of CCL25 on Wnt expression and the effects of Wnt5a and CCL25 on PI3K/Akt and RhoA activation. Transwell assays and mouse xenograft experiments were utilized to assess the effects of Wnt5a and CCL25 on MOLT4 cell invasion, migration and metastasis. The effects of Wnt5a on MOLT4 cell actin polarization and pseudopodium formation were examined using laser scanning confocal microscopy and scanning electron microscopy. CCL25 induced Wnt5a expression in MOLT4 cells by promoting protein kinase C (PKC) expression and activation. Wnt5a promoted MOLT4 cell migration, invasion, actin polarization, and lamellipodium and filopodia formation via PI3K/Akt-RhoA pathway activation. These effects were rescued by PI3K/Akt or RhoA knockdown or inhibition. Additionally, Wnt5a in cooperation with CCL25 promoted MOLT4 cell mouse liver metastasis and stimulated RhoA activation. These results show that CCL25/CCR9 upregulates Wnt5a by promoting PKC expression and activation in MOLT4 cells. This in turn promotes cell migration and invasion via PI3K/Akt-RhoA signaling, enhancing cell polarization and pseudopodium formation. These findings indicate that the PI3K/Akt-RhoA pathway is likely responsible for Wnt5a-induced adult T-ALL cell migration and invasion.

T-cell lymphomas associated gene expression signature: Bioinformatics analysis based on gene expression Omnibus

OBJECTIVES

Due to the low incidence and the heterogeneity of subtypes, the biological process of T-cell lymphomas is largely unknown. Although many genes have been detected in T-cell lymphomas, the role of these genes in biological process of T-cell lymphomas was not further analyzed.

METHODS

Two qualified datasets were downloaded from Gene Expression Omnibus database. The biological functions of differentially expressed genes were evaluated by gene ontology enrichment and KEGG pathway analysis. The network for intersection genes was constructed by the cytoscape v3.0 software. Kaplan-Meier survival curves and log-rank test were employed to assess the association between differentially expressed genes and clinical characters.

RESULTS

The intersection mRNAs were proved to be associated with fundamental processes of T-cell lymphoma cells. These intersection mRNAs were involved in the activation of some cancer-related pathways, including PI3K/AKT, Ras, JAK-STAT, and NF-kappa B signaling pathway. PDGFRA, CXCL12, and CCL19 were the most significant central genes in the signal-net analysis. The results of survival analysis are not entirely credible.

CONCLUSIONS

Our findings uncovered aberrantly expressed genes and a complex RNA signal network in T-cell lymphomas and indicated cancer-related pathways involved in disease initiation and progression, providing a new insight for biotargeted therapy in T-cell lymphomas.

Prostaglandin E2 Inhibits Prostate Cancer Progression by Countervailing Tumor Microenvironment-Induced Impairment of Dendritic Cell Migration through LXRα/CCR7 Pathway

Migration and homing of dendritic cells (DCs) to lymphoid organs are quite crucial for T cell-induced immune response against tumor. However, tumor microenvironment can make some tumor cells escape immune response by impairing DC migration. Prostaglandin E2 (PGE2) plays important roles in initiating and terminating inflammatory responses. In this study, we investigated whether PGE2 could inhibit murine prostate cancer progression by countervailing tumor microenvironment-induced impairment of dendritic cell migration. We found that murine prostate cancer cell line RM-1-conditioned medium impaired chemotactic movement of marrow-derived DCs and splenic cDCs toward CC chemokine receptor-7 (CCR7) ligand CCL19 in vitro and migration to draining lymph gland in vivo. Meanwhile, it also induced LXRα activation and CCR7 inhibition on maturing DCs. However, the treatment of PGE2 rescued this impairment of DC migration with upregulation of CCR7 and inhibition of LXRα. Further, it was observed that PGE2 also increased MMP9 expression and activated Notch1 signaling on DCs. In RM-1-bearing mouse model, PGE2 treatment was identified to inhibit tumor growth and induce more tumor-infiltrating T cells and CD11c dendritic cells in tumor sites. Therefore, our findings may demonstrate a new perspective for therapeutic interventions on prostate cancer immunoescape.

Chemotactic Cues for NOTCH1-Dependent Leukemia

The NOTCH signaling pathway is a conserved signaling cascade that regulates many aspects of development and homeostasis in multiple organ systems. Aberrant activity of this signaling pathway is linked to the initiation and progression of several hematological malignancies, exemplified by T-cell acute lymphoblastic leukemia (T-ALL). Interestingly, frequent non-mutational activation of NOTCH1 signaling has recently been demonstrated in B-cell chronic lymphocytic leukemia (B-CLL), significantly extending the pathogenic significance of this pathway in B-CLL. Leukemia patients often present with high-blood cell counts, diffuse disease with infiltration of the bone marrow, secondary lymphoid organs, and diffusion to the central nervous system (CNS). Chemokines are chemotactic cytokines that regulate migration of cells between tissues and the positioning and interactions of cells within tissue. Homeostatic chemokines and their receptors have been implicated in regulating organ-specific infiltration, but may also directly and indirectly modulate tumor growth. Recently, oncogenic NOTCH1 has been shown to regulate infiltration of leukemic cells into the CNS hijacking the CC-chemokine ligand 19/CC-chemokine receptor 7 chemokine axis. In addition, a crucial role for the homing receptor axis CXC-chemokine ligand 12/CXC-chemokine receptor 4 has been demonstrated in leukemia maintenance and progression. Moreover, the CCL25/CCR9 axis has been implicated in the homing of leukemic cells into the gut, particularly in the presence of phosphatase and tensin homolog tumor suppressor loss. In this review, we summarize the latest developments regarding the role of NOTCH signaling in regulating the chemotactic microenvironmental cues involved in the generation and progression of T-ALL and compare these findings to B-CLL.

Chemokines in homeostasis and diseases

For the past twenty years, chemokines have emerged as a family of critical mediators of cell migration during immune surveillance, development, inflammation and cancer progression. Chemokines bind to seven transmembrane G protein-coupled receptors (GPCRs) that are expressed by a wide variety of cell types and cause conformational changes in trimeric G proteins that trigger the intracellular signaling pathways necessary for cell movement and activation. Although chemokines have evolved to benefit the host, inappropriate regulation or utilization of these small proteins may contribute to or even cause diseases. Therefore, understanding the role of chemokines and their GPCRs in the complex physiological and diseased microenvironment is important for the identification of novel therapeutic targets. This review introduces the functional array and signals of multiple chemokine GPCRs in guiding leukocyte trafficking as well as their roles in homeostasis, inflammation, immune responses and cancer.

Loss of T-cell quiescence by targeting Slfn2 prevents the development and progression of T-ALL

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy of thymocytes. Despite significant improvement in the treatment of T-ALL, approximately 20% of children and most adults undergo relapse. Previous findings demonstrated that loss of T-cell quiescence due to a mutation in the Slfn2 gene (elektra) leads to acquisition of an aberrant developmental program by which T-cells lose their renewal capabilities and undergo apoptosis. Here we show that the elektra mutation in Slfn2 completely prevents a severe lymphoproliferative disease caused by overexpression of BCL2 in combination with Fas deficiency in mice. Moreover, Slfn2 impaired-function protects mice from experimental disease similar to human T-ALL by severely impairing the proliferation potential and survival of leukemic T-cells, partially by activation of the p53 tumor suppressor protein. Our study suggest that in certain malignancies, such as T-ALL, a novel therapeutic strategy may be applied by imposing aberrant development of leukemic cells. Furthermore, as the elektra mutation in Slfn2 seems to impair only T-cells and monocytes, targeting Slfn2 is expected to be harmless to other cell types, and thereby could be a promising target for treating malignancies. Together our results demonstrate the potential of targeting Slfn2 and its human paralog for T-ALL treatment.

Notch in Leukemia

Notch is commonly activated in lymphoid malignancies through ligand-independent and ligand-dependent mechanisms. In T-cell acute lymphoblastic leukemia/lymphoma (T-ALL), ligand-independent activation predominates. Negative Regulatory Region (NRR) mutations trigger supraphysiological Notch1 activation by exposing the S2 site to proteolytic cleavage in the absence of ligand. Subsequently, cleavage at the S3 site generates the activated form of Notch, intracellular Notch (ICN). In contrast to T-ALL, in mature lymphoid neoplasms such as chronic lymphocytic leukemia (CLL), the S2 cleavage site is exposed through ligand-receptor interactions. Thus, agents that disrupt ligand-receptor interactions might be useful for treating these malignancies. Notch activation can be enhanced by mutations that delete the C-terminal proline (P), glutamic acid (E), serine (S), and threonine (T) (PEST) domain. These mutations do not activate the Notch pathway per se, but rather impair degradation of ICN. In this chapter, we review the mechanisms of Notch activation and the importance of Notch for the genesis and maintenance of lymphoid malignancies. Unfortunately, targeting the Notch pathway with pan-Notch inhibitors in clinical trials has proven challenging. These clinical trials have encountered dose-limiting on-target toxicities and primary resistance. Strategies to overcome these challenges have emerged from the identification and improved understanding of direct oncogenic Notch target genes. Other strategies have arisen from new insights into the "nuclear context" that selectively directs Notch functions in lymphoid cancers. This nuclear context is created by factors that co-bind ICN at cell-type specific transcriptional regulatory elements. Disrupting the functions of these proteins or inhibiting downstream oncogenic pathways might combat cancer without the intolerable side effects of pan-Notch inhibition.

Characteristics and Therapeutic Targeting of Minimal Residual Disease in Childhood Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Early response to therapy, especially the measurement of minimal residual disease (MRD), remains the most reliable and strongest independent prognostic parameter. Intriguingly, little is known on the mechanisms sustaining MRD in that disease. Here, we summarize existing evidence on the influences of molecular genetics and clonal architecture of childhood ALL on disease persistence. Also, the impact of the leukemic niche on residual leukemia cells in the bone marrow and extramedullary compartments is reviewed. We further discuss existing in vivo models of minimal residual disease based on different cellular labelling strategies and engraftment of ALL cells in immunodeficient mouse strains. We finally draw some conclusions on potential strategies targeting residual ALL cells, with a focus on cellular and antibody-based immunotherapy.

Characterization of the Optical Properties of Turbid Media by Supervised Learning of Scattering Patterns

Fabricated tissue phantoms are instrumental in optical in-vitro investigations concerning cancer diagnosis, therapeutic applications, and drug efficacy tests. We present a simple non-invasive computational technique that, when coupled with experiments, has the potential for characterization of a wide range of biological tissues. The fundamental idea of our approach is to find a supervised learner that links the scattering pattern of a turbid sample to its thickness and scattering parameters. Once found, this supervised learner is employed in an inverse optimization problem for estimating the scattering parameters of a sample given its thickness and scattering pattern. Multi-response Gaussian processes are used for the supervised learning task and a simple setup is introduced to obtain the scattering pattern of a tissue sample. To increase the predictive power of the supervised learner, the scattering patterns are filtered, enriched by a regressor, and finally characterized with two parameters, namely, transmitted power and scaled Gaussian width. We computationally illustrate that our approach achieves errors of roughly 5% in predicting the scattering properties of many biological tissues. Our method has the potential to facilitate the characterization of tissues and fabrication of phantoms used for diagnostic and therapeutic purposes over a wide range of optical spectrum.

T cell acute lymphoblastic leukemia (T-ALL): New insights into the cellular origins and infiltration mechanisms common and unique among hematologic malignancies

T-cell acute lymphoblastic leukemia (T-ALL) accounts for 15% and 25% of total childhood and adult ALL cases, respectively. During T-ALL, patients are at risk of organ infiltration by leukemic T-cells. Infiltration is a major consequence of disease relapse and correlates with poor prognosis. Transendothelial migration of leukemic cells is required to exit the blood stream into target organs. While mechanisms of normal T-cell transmigration are well known, the mechanisms of leukemic T-cell extravasation remain elusive; but involvement of chemokines, integrins and Notch signaling play critical roles. Here, we summarize current knowledge about molecular mechanisms of leukemic T-cell infiltration with special emphasis on the newly identified subtype early T-cell-progenitor (ETP)-ALL. Furthermore, we compare the extravasation potential of T-ALL cells with that of other hematologic malignancies such as B-ALL and acute myeloid leukemia (AML).

From the outside, from within: Biological and therapeutic relevance of signal transduction in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological cancer that arises from clonal expansion of transformed T-cell precursors. In this review we summarize the current knowledge on the external stimuli and cell-intrinsic lesions that drive aberrant activation of pivotal, pro-tumoral intracellular signaling pathways in T-cell precursors, driving transformation, leukemia expansion, spread or resistance to therapy. In addition to their pathophysiological relevance, receptors and kinases involved in signal transduction are often attractive candidates for targeted drug development. As such, we discuss also the potential of T-ALL signaling players as targets for therapeutic intervention.

Central nervous system involvement in acute lymphoblastic leukemia is mediated by vascular endothelial growth factor

In acute lymphoblastic leukemia (ALL), central nervous system (CNS) involvement is a major clinical concern. Despite nondetectable CNS leukemia in many cases, prophylactic CNS-directed conventional intrathecal chemotherapy is required for relapse-free survival, indicating subclinical CNS manifestation in most patients. However, CNS-directed therapy is associated with long-term sequelae, including neurocognitive deficits and secondary neoplasms. Therefore, molecular mechanisms and pathways mediating leukemia-cell entry into the CNS need to be understood to identify targets for prophylactic and therapeutic interventions and develop alternative CNS-directed treatment strategies. In this study, we analyzed leukemia-cell entry into the CNS using a primograft ALL mouse model. We found that primary ALL cells transplanted onto nonobese diabetic/severe combined immunodeficiency mice faithfully recapitulated clinical and pathological features of meningeal infiltration seen in patients with ALL. ALL cells that had entered the CNS and were infiltrating the meninges were characterized by high expression of vascular endothelial growth factor A (VEGF). Although cellular viability, growth, proliferation, and survival of ALL cells were found to be independent of VEGF, transendothelial migration through CNS microvascular endothelial cells was regulated by VEGF. The importance of VEGF produced by ALL cells in mediating leukemia-cell entry into the CNS and leptomeningeal infiltration was further demonstrated by specific reduction of CNS leukemia on in vivo VEGF capture by the anti-VEGF antibody bevacizumab. Thus, we identified a mechanism of ALL-cell entry into the CNS, which by targeting VEGF signaling may serve as a novel strategy to control CNS leukemia in patients, replacing conventional CNS-toxic treatment.

Robust gene expression changes in the ganglia following subclinical reactivation in rhesus macaques infected with simian varicella virus

Varicella zoster virus (VZV) causes varicella during acute infection and establishes latency in the sensory ganglia. Reactivation of VZV results in herpes zoster, a debilitating and painful disease. It is believed that VZV reactivates due to a decline in cell-mediated immunity; however, the roles that CD4 versus CD8 T cells play in the prevention of herpes zoster remain poorly understood. To address this question, we used a well-characterized model of VZV infection where rhesus macaques are intrabronchially infected with the homologous simian varicella virus (SVV). Latently infected rhesus macaques were thymectomized and depleted of either CD4 or CD8 T cells to induce selective senescence of each T cell subset. After T cell depletion, the animals were transferred to a new housing room to induce stress. SVV reactivation (viremia in the absence of rash) was detected in three out of six CD8-depleted and two out of six CD4-depleted animals suggesting that both CD4 and CD8 T cells play a critical role in preventing SVV reactivation. Viral loads in multiple ganglia were higher in reactivated animals compared to non-reactivated animals. In addition, reactivation results in sustained transcriptional changes in the ganglia that enriched to gene ontology and diseases terms associated with neuronal function and inflammation indicative of potential damage as a result of viral reactivation. These studies support the critical role of cellular immunity in preventing varicella virus reactivation and indicate that reactivation results in long-lasting remodeling of the ganglia transcriptome.

Interplay between CCR7 and Notch1 axes promotes stemness in MMTV-PyMT mammary cancer cells

Background

Breast cancer is the major cause of cancer-related mortality in women. It is thought that quiescent stem-like cells within solid tumors are responsible for cancer maintenance, progression and eventual metastasis. We recently reported that the chemokine receptor CCR7, a multi-functional regulator of breast cancer, maintains the stem-like cell population.

Methods

This study used a combination of molecular and cellular assays on primary mammary tumor cells from the MMTV-PyMT transgenic mouse with or without CCR7 to examine the signaling crosstalk between CCR7 and Notch pathways.

Results

We show for the first time that CCR7 functionally intersects with the Notch signaling pathway to regulate mammary cancer stem-like cells. In this cell subpopulation, CCR7 stimulation activated the Notch signaling pathway, and deletion of CCR7 significantly reduced the levels of activated cleaved Notch1. Moreover, blocking Notch activity prevented specific ligand-induced signaling of CCR7 and augmentation of mammary cancer stem-like cell function.

Conclusion

Crosstalk between CCR7 and Notch1 promotes stemness in mammary cancer cells and may ultimately potentiate mammary tumor progression. Therefore, dual targeting of both the CCR7 receptor and Notch1 signaling axes may be a potential therapeutic avenue to specifically inhibit the functions of breast cancer stem cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0592-0) contains supplementary material, which is available to authorized users.

The Role of the Central Nervous System Microenvironment in Pediatric Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is the most common cancer in children. While survival rates for ALL have improved, central nervous system (CNS) relapse remains a significant cause of treatment failure and treatment-related morbidity. Accordingly, there is a need to identify more efficacious and less toxic CNS-directed leukemia therapies. Extensive research has demonstrated a critical role of the bone marrow (BM) microenvironment in leukemia development, maintenance, and chemoresistance. Moreover, therapies to disrupt mechanisms of BM microenvironment-mediated leukemia survival and chemoresistance represent new, promising approaches to cancer therapy. However, in direct contrast to the extensive knowledge of the BM microenvironment, the unique attributes of the CNS microenvironment that serve to make it a leukemia reservoir are not yet elucidated. Recent work has begun to define both the mechanisms by which leukemia cells migrate into the CNS and how components of the CNS influence leukemia biology to enhance survival, chemoresistance, and ultimately relapse. In addition to providing new insight into CNS relapse and leukemia biology, this area of investigation will potentially identify targetable mechanisms of leukemia chemoresistance and self-renewal unique to the CNS environment that will enhance both the durability and quality of the cure for ALL patients.

Risk stratification of adult T-cell leukemia/lymphoma using immunophenotyping

Adult T‐cell leukemia/lymphoma (ATL), a human T‐lymphotropic virus type 1 (HTLV‐1)‐associated disease, has a highly variable clinical course and four subtypes with therapeutic and prognostic implications. However, there are overlapping features between ATL subtypes and between ATL and nonmalignant (non‐ATL) HTLV‐1 infection complicating diagnosis and prognostication. To further refine the diagnosis and prognosis of ATL, we characterized the immunophenotype of HTLV‐1‐infected cells in ATL and non‐ATL. A retrospective study of peripheral blood samples from 10 HTLV‐1‐uninfected subjects (UI), 54 HTLV‐1‐infected patients with non‐ATL, and 22 with ATL was performed using flow cytometry. All patients with ATL had CD4⁺ CCR4⁺ CD26⁻ immunophenotype and the frequency of CD4⁺ CCR4⁺ CD26⁻ T cells correlated highly significantly with the proviral load in non‐ATL suggesting CD4⁺ CCR4⁺ CD26⁻ as a marker of HTLV‐1‐infected cells. Further immunophenotyping of CD4⁺ CCR4⁺  CD26⁻ cells revealed that 95% patients with ATL had a CD7⁻ (≤30% CD7⁺ cells), whereas 95% HTLV+ non‐ATL had CD7⁺ (>30% CD7⁺ cells) immunophenotype. All patients with aggressive ATL had a CCR7⁺ (≥30%), whereas 92% with indolent ATL and 100% non‐ATL had a CCR7⁻ (<30%) immunophenotype. Patients with nonprogressing indolent ATL were CD127⁺ but those with progressive lymphocytosis requiring systemic therapy had a CD127⁻ (≤30%) immunophenotype. In summary, HTLV‐1‐infected cells have a CD4⁺ CCR4⁺ CD26⁻ immunophenotype. Within this population, CD7⁻ phenotype suggests a diagnosis of ATL, CCR7⁺ phenotype identifies aggressive ATL, while CCR7⁻CD127⁻ phenotype identifies progressive indolent ATL.

Microenvironmental cues for T-cell acute lymphoblastic leukemia development

Intensive chemotherapy regimens have led to a substantial improvement in the cure rate of patients suffering from T-cell acute lymphoblastic leukemia (T-ALL). Despite this progress, about 15% and 50% of pediatric and adult cases, respectively, show resistance to treatment or relapse with dismal prognosis, calling for further therapeutic investigations. T-ALL is an heterogeneous disease, which presents intrinsic alterations leading to aberrant expression of transcription factors normally involved in hematopoietic stem/progenitor cell development and mutations in genes implicated in the regulation of cell cycle progression, apoptosis, and T-cell development. Gene expression profiling allowed the classification of T-ALL into defined molecular subgroups that mostly reflects the stage of their differentiation arrest. So far this knowledge has not translated into novel, targeted therapy. Recent evidence points to the importance of extrinsic signaling cues in controlling the ability of T-ALL to home, survive, and proliferate, thus offering the perspective of new therapeutic options. This review summarizes the present understanding of the interactions between hematopoietic cells and bone marrow/thymic niches during normal hematopoiesis, describes the main signaling pathways implicated in this dialog, and finally highlights how malignant T cells rely on specific niches to maintain their ability to sustain and propagate leukemia.

Leukemic blasts are present at low levels in spinal fluid in one-third of childhood acute lymphoblastic leukemia cases

BACKGROUND

Central nervous system (CNS) involvement is associated with relapse in childhood acute lymphoblastic leukemia (ALL) and is a diagnostic challenge.

PROCEDURE

In a Nordic/Baltic prospective study, we assessed centralized flow cytometry (FCM) of locally fixed cerebrospinal fluid (CSF) samples versus local conventional cytospin-based cytology (CC) for detecting leukemic cells and evaluating kinetics of elimination of leukemic cells in CSF.

RESULTS

Among 300 patients with newly diagnosed ALL, 87 (29%) had CSF involvement by FCM, while CC was positive in 30 (10%) of 299 patients with available CC data (P < 0.001). Patients with FCM+/CC+ had higher CSF leukemic blast counts compared to patients positive by FCM only (medians: 0.10 vs. 0.017 leukemic blasts/μl, P = 0.006). Patients positive by FCM had higher white blood cell counts in peripheral blood than patients negative by FCM (medians: 45 × 10(9) /l vs. 10 × 10(9) /l, P < 0.001), were younger (medians: 3 years vs. 4 years, P = 0.03), and more frequently had T-cell ALL (18/87 vs. 16/213, P = 0.001). At treatment day 15, five of 52 patients (10%) who had CSF positive by FCM at diagnosis remained so despite at least two doses of weekly intrathecal chemotherapy.

CONCLUSIONS

Longer follow-up is needed to clarify whether FCM positivity has prognostic significance and is an indicator for intensified CNS-directed therapy.

Serum stimulation of CCR7 chemotaxis due to coagulation factor XIIa-dependent production of high-molecular-weight kininogen domain 5

Chemokines and their receptors play a critical role in immune function by directing cell-specific movement. C-C chemokine receptor 7 (CCR7) facilitates entry of T cells into lymph nodes. CCR7-dependent chemotaxis requires either of the cognate ligands C-C chemokine ligand 19 (CCL19) or CCL21. Although CCR7-dependent chemotaxis can be augmented through receptor up-regulation or by increased chemokine concentrations, we found that chemotaxis is also markedly enhanced by serum in vitro. Upon purification, the serum cofactor activity was ascribed to domain 5 of high-molecular-weight kininogen. This peptide was necessary and sufficient for accelerated chemotaxis. The cofactor activity in serum was dependent on coagulation factor XIIa, a serine protease known to induce cleavage of high-molecular-weight kininogen (HK) at sites of inflammation. Within domain 5, we synthesized a 24-amino acid peptide that could recapitulate the activity of intact serum through a mechanism distinct from up-regulating CCR7 expression or promoting chemokine binding to CCR7. This peptide interacts with the extracellular matrix protein thrombospondin 4 (TSP4), and antibodies to TSP4 neutralize its activity. In vivo, an HK domain 5 peptide stimulated homing of both T and B cells to lymph nodes. A circulating cofactor that is activated at inflammatory foci to enhance lymphocyte chemotaxis represents a powerful mechanism coupling inflammation to adaptive immunity.

The role of ZAP70 kinase in acute lymphoblastic leukemia infiltration into the central nervous system

Central nervous system infiltration and relapse are poorly understood in childhood acute lymphoblastic leukemia. We examined the role of zeta-chain-associated protein kinase 70 in preclinical models of central nervous system leukemia and performed correlative studies in patients. Zeta-chain-associated protein kinase 70 expression in acute lymphoblastic leukemia cells was modulated using short hairpin ribonucleic acid-mediated knockdown or ectopic expression. We show that zeta-chain-associated protein kinase 70 regulates CCR7/CXCR4 via activation of extracellular signal-regulated kinases. High expression of zeta-chain-associated protein kinase 70 in acute lymphoblastic leukemia cells resulted in a higher proportion of central nervous system leukemia in xenografts as compared to zeta-chain-associated protein kinase 70 low expressing counterparts. High zeta-chain-associated protein kinase 70 also enhanced the migration potential towards CCL19/CXCL12 gradients in vitro CCR7 blockade almost abrogated homing of acute lymphoblastic leukemia cells to the central nervous system in xenografts. In 130 B-cell precursor acute lymphoblastic leukemia and 117 T-cell acute lymphoblastic leukemia patients, zeta-chain-associated protein kinase 70 and CCR7/CXCR4 expression levels were significantly correlated. Zeta-chain-associated protein kinase 70 expression correlated with central nervous system disease in B-cell precursor acute lymphoblastic leukemia, and CCR7/CXCR4 correlated with central nervous system involvement in T-cell acute lymphoblastic leukemia patients. In multivariate analysis, zeta-chain-associated protein kinase 70 expression levels in the upper third and fourth quartiles were associated with central nervous system involvement in B-cell precursor acute lymphoblastic leukemia (odds ratio=7.48, 95% confidence interval, 2.06-27.17; odds ratio=6.86, 95% confidence interval, 1.86-25.26, respectively). CCR7 expression in the upper fourth quartile correlated with central nervous system positivity in T-cell acute lymphoblastic leukemia (odds ratio=11.00, 95% confidence interval, 2.00-60.62). We propose zeta-chain-associated protein kinase 70, CCR7 and CXCR4 as markers of central nervous system infiltration in acute lymphoblastic leukemia warranting prospective investigation.

CXCR4 and CCR7: Two eligible targets in targeted cancer therapy

Cancer is one of the most common cause of death in the world with high negative emotional, economic, and social impacts. Conventional therapeutic methods, including chemotherapy and radiotherapy, have not proven satisfactory and relapse is common in most cases. Recent studies have focused on targeted therapy with more precise identification and targeted attacks to the cancer cells. For this purpose, chemokine receptors are proper targets and among them, CXCR4 and CCR7, with a crucial role in cancer metastasis, are being considered as desired candidates for investigation. In this review paper, the most important experimental results are highlighted on the potential targeted therapies based on CXCR4 and CCR7 chemokine receptors.

β-Catenin is required for T-cell leukemia initiation and MYC transcription downstream of Notch1

Notch activation is instrumental in the development of most T-cell acute lymphoblastic leukemia (T-ALL) cases, yet Notch mutations alone are not sufficient to recapitulate the full human disease in animal models. We here found that Notch1 activation at the fetal liver (FL) stage expanded the hematopoietic progenitor population and conferred it transplantable leukemic-initiating capacity. However, leukemogenesis and leukemic-initiating cell capacity induced by Notch1 was critically dependent on the levels of β-Catenin in both FL and adult bone marrow contexts. In addition, inhibition of β-Catenin compromised survival and proliferation of human T-ALL cell lines carrying activated Notch1. By transcriptome analyses, we identified the MYC pathway as a crucial element downstream of β-Catenin in these T-ALL cells and demonstrate that the MYC 3' enhancer required β-Catenin and Notch1 recruitment to induce transcription. Finally, PKF115-584 treatment prevented and partially reverted leukemogenesis induced by active Notch1.

Ribosomal Protein Rpl22 Controls the Dissemination of T-cell Lymphoma

Mutations in ribosomal proteins cause bone marrow failure syndromes associated with increased cancer risk, but the basis by which they do so remains unclear. We reported previously that the ribosomal protein Rpl22 is a tumor suppressor in T-cell acute lymphoblastic leukemia/lymphoma (T-ALL), and that loss of just one Rpl22 allele accelerates T-cell lymphomagenesis by activating NF-κB and inducing the stem cell factor Lin28B. Here, we show that, paradoxically, loss of both alleles of Rpl22 restricts lymphoma progression through a distinct effect on migration of malignant cells out of the thymus. Lymphoma-prone AKT2-transgenic or PTEN-deficient mice on an Rpl22(-/-) background developed significantly larger and markedly more vascularized thymic tumors than those observed in Rpl22(+/+) control mice. But, unlike Rpl22(+/+) or Rpl22(+/-) tumors, Rpl22(-/-) lymphomas did not disseminate to the periphery and were retained in the thymus. We traced the defect in the Rpl22(-/-) lymphoma migratory capacity to downregulation of the KLF2 transcription factor and its targets, including the key migratory factor sphingosine 1-phosphate receptor 1 (S1PR1). Indeed, reexpression of S1PR1 in Rpl22-deficient tumor cells restores their migratory capacity in vitro The regulation of KLF2 and S1PR1 by Rpl22 appears to be proximal as Rpl22 reexpression in Rpl22-deficient lymphoma cells restores expression of KLF2 and S1P1R, while Rpl22 knockdown in Rpl22-sufficient lymphomas attenuates their expression. Collectively, these data reveal that, while loss of one copy of Rpl22 promotes lymphomagenesis and disseminated disease, loss of both copies impairs responsiveness to migratory cues and restricts malignant cells to the thymus. Cancer Res; 76(11); 3387-96. ©2016 AACR.

Role of CXCR4-mediated bone marrow colonization in CNS infiltration by T cell acute lymphoblastic leukemia

Infiltration of the central nervous system is a severe trait of T cell acute lymphoblastic leukemia. Inhibition of CXC chemokine receptor 4 significantly ameliorates T cell acute lymphoblastic leukemia in murine models of the disease; however, signaling by CXC chemokine receptor 4 is important in limiting the divagation of peripheral blood mononuclear cells out of the perivascular space into the central nervous system parenchyma. Therefore, Inhibition of CXC chemokine receptor 4 potentially may untangle T cell acute lymphoblastic leukemia cells from retention outside the brain. Here, we show that leukemic lymphoblasts massively infiltrate cranial bone marrow, with diffusion to the meninges without invasion of the brain parenchyma, in mice that underwent xenotransplantation with human T cell acute lymphoblastic leukemia cells or that developed leukemia from transformed hematopoietic progenitors. We tested the hypothesis that T cell acute lymphoblastic leukemia neuropathology results from meningeal infiltration through CXC chemokine receptor 4-mediated bone marrow colonization. Inhibition of leukemia engraftment in the bone marrow by pharmacologic CXC chemokine receptor 4 antagonism significantly ameliorated neuropathologic aspects of the disease. Genetic deletion of CXCR4 in murine hematopoietic progenitors abrogated leukemogenesis induced by constitutively active Notch1, whereas lack of CCR6 and CCR7, which have been shown to be involved in T cell and leukemia extravasation into the central nervous system, respectively, did not influence T cell acute lymphoblastic leukemia development. We hypothesize that lymphoblastic meningeal infiltration as a result of bone marrow colonization is responsible for the degenerative alterations of the neuroparenchyma as well as the alteration of cerebrospinal fluid drainage in T cell acute lymphoblastic leukemia xenografts. Therefore, CXC chemokine receptor 4 may constitute a pharmacologic target for T cell acute lymphoblastic leukemia neuropathology.

Prolyl-isomerase Pin1 controls Notch3 protein expression and regulates T-ALL progression

Deregulated Notch signaling is associated with T-cell Acute Lymphoblastic Leukemia (T-ALL) development and progression. Increasing evidence reveals that Notch pathway has an important role in the invasion ability of tumor cells, including leukemia, although the underlying molecular mechanisms remain mostly unclear. Here, we show that Notch3 is a novel target protein of the prolyl-isomerase Pin1, which is able to regulate Notch3 protein processing and to stabilize the cleaved product, leading to the increased expression of the intracellular domain (N3_IC), finally enhancing Notch3-dependent invasiveness properties. We demonstrate that the combined inhibition of Notch3 and Pin1 in the Notch3-overexpressing human leukemic TALL-1 cells reduces their high invasive potential, by decreasing the expression of the matrix metalloprotease MMP9. Consistently, Pin1 depletion in a mouse model of Notch3-induced T-ALL, by reducing N3_IC expression and signaling, impairs the expansion/invasiveness of CD4⁺CD8⁺ DP cells in peripheral lymphoid and non-lymphoid organs. Notably, in in silico gene expression analysis of human T-ALL samples we observed a significant correlation between Pin1 and Notch3 expression levels, which may further suggest a key role of the newly identified Notch3-Pin1 axis in T-ALL aggressiveness and progression. Thus, combined suppression of Pin1 and Notch3 proteins may be exploited as an additional target therapy for T-ALL.

The ability to cross the blood-cerebrospinal fluid barrier is a generic property of acute lymphoblastic leukemia blasts

Prevention of central nervous system (CNS) relapse is critical for cure of childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Despite this, mechanisms of CNS infiltration are poorly understood, and the timing, frequency, and properties of BCP-ALL blasts entering the CNS compartment are unknown. We investigated the CNS-engrafting potential of BCP-ALL cells xenotransplanted into immunodeficient NOD.Cg- ITALIC! Prkdc (ITALIC! scid) ITALIC! Il2rg (ITALIC! tm1Wjl)/SzJ mice. CNS engraftment was seen in 23 of 29 diagnostic samples (79%): 2 of 2 from patients with overt CNS disease and 21 of 27 from patients thought to be CNS negative by diagnostic lumbar puncture. Histologic findings mimic human pathology and demonstrate that leukemic cells transit the blood-cerebrospinal fluid barrier situated close to the dural sinuses, the site of recently discovered CNS lymphatics. Retrieval of blasts from the CNS showed no evidence for chemokine receptor-mediated selective trafficking. The high frequency of infiltration and lack of selective trafficking led us to postulate that CNS tropism is a generic property of leukemic cells. To test this, we performed serial dilution experiments which showed CNS engraftment in 5 of 6 mice after transplant of as few as 10 leukemic cells. Clonal tracking techniques confirmed the polyclonal nature of CNS-infiltrating cells, with multiple clones engrafting in both the CNS and periphery. Overall, these findings suggest that subclinical seeding of the CNS is likely to be present in most BCP-ALL patients at original diagnosis, and efforts to prevent CNS relapse should concentrate on effective eradication of disease from this site rather than targeting entry mechanisms.