Notch protection against apoptosis in T-ALL cells mediated by GIMAP5

A novel iTreg-related signature for prognostic prediction in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is the most common subtype of lung cancer. Most patients are diagnosed at an advanced stage, therefore it is crucial to identify novel prognostic biomarkers for LUAD. As important regulatory cells, inducible regulatory T cells (iTregs) play a vital role in immune suppression and are important for the maintenance of immune homeostasis. This study explored the prognostic value and therapeutic effects of iTreg-related genes in LUAD. Data for LUAD patients, including immune infiltration data, RNA sequencing data, and clinical features, were acquired from The Cancer Genome Atlas, Gene Expression Omnibus, and Tumor Immune Single-cell Hub 2 databases. Immune-related subgroups with different infiltration patterns and iTreg-related genes were identified through univariate and multivariate Cox regression analyses and weighted correlation network analysis. Functional enrichment analyses were performed to explore the underlying mechanisms of iTreg-related genes. A prognostic risk signature was constructed using Cox regression analysis with the least absolute shrinkage and selection operator penalty. The ESTIMATE algorithm was applied to determine the immune status of LUAD patients. We applied the constructed signature to predict chemosensitivity and performed single-cell RNA sequencing analysis. The infiltration of iTregs was identified as an independent factor for predicting patient outcomes. We constructed a prognostic signature based on seven iTreg-related genes (GIMAP5, SLA, MS4A7, ZNF366, POU2AF1, MRPL12, and COL5A1), which was applied to subdivide patients into high- and low-risk subgroups. Our results revealed that patients in the iTreg-related low-risk subgroup had a better prognosis and possibly greater sensitivity to traditional chemotherapy. Our study provides a novel iTreg-related signature to elucidate the mechanisms underlying LUAD prognosis and promote individualized chemotherapy treatment.

Notch pathway is required for protection against heat stress in spermatogonial stem cells in medaka

Gamete production is a fundamental process for reproduction; however, exposure to stress, such as increased environmental temperature, can decrease or even interrupt this process, affecting fertility. Thus, the survival of spermatogonial stem cells (SSCs) is crucial for the recovery of spermatogenesis upon stressful situations. Here, we show that the Notch pathway is implicated in such survival, by protecting the SSCs against thermal stress. First, we corroborated the impairment of spermatogenesis under heat stress in medaka, observing an arrest in metaphase I at 10 days of heat treatment, an increase in the number of spermatocytes, and downregulation of ndrg1b and sycp3. In addition, at 30 days of treatment, an interruption of spermatogenesis was observed with a strong loss of spermatocytes and spermatids. Then, the exposure of adult males to thermal stress condition induced apoptosis mainly in spermatogenic and supporting somatic cells, with the exception of the germinal region, where SSCs are located. Concomitantly, the Notch pathway-related genes were upregulated, including the ligands (dll4, jag1-2) and receptors (notch1a-3). Moreover, during thermal stress presenilin enhancer-2 (pen-2), the catalytic subunit of γ-secretase complex of the Notch pathway was restricted to the germinal region of the medaka testis, observed in somatic cells surrounding type A spermatogonia (SGa). The importance of Notch pathway was further supported by an ex vivo approach, in which the inhibition of this pathway activity induced a loss of SSCs. Overall, this study supports the importance of Notch pathways for the protection of SSCs under chronic thermal stress.

IL-15 Prevents the Development of T-ALL from Aberrant Thymocytes with Impaired DNA Repair Functions and Increased NOTCH1 Activation

We previously reported that NOD.Scid mice lacking interleukin-15 (IL-15), or IL-15 receptor alpha-chain, develop T-acute lymphoblastic leukemia (T-ALL). To understand the mechanisms by which IL-15 signaling controls T-ALL development, we studied the thymocyte developmental events in IL-15-deficient Scid mice from NOD and C57BL/6 genetic backgrounds. Both kinds of mice develop T-ALL characterized by circulating TCR-negative cells expressing CD4, CD8 or both. Analyses of thymocytes in NOD.Scid.Il15^-/- mice prior to T-ALL development revealed discernible changes within the CD4^-CD8^- double-negative (DN) thymocyte developmental stages and increased frequencies of CD4⁺CD8⁺ double-positive cells with a high proportion of TCR-negative CD4⁺ and CD8⁺ cells. The DN cells also showed elevated expressions of CXCR4 and CD117, molecules implicated in the expansion of DN thymocytes. T-ALL cell lines and primary leukemic cells from IL-15-deficient NOD.Scid and C57BL/6.Scid mice displayed increased NOTCH1 activation that was inhibited by NOTCH1 inhibitors and blockers of the PI3K/AKT pathway. Primary leukemic cells from NOD.Scid.Il15^-/- mice survived and expanded when cultured with MS5 thymic stromal cells expressing Delta-like ligand 4 and supplemented with IL-7 and FLT3 ligand. These findings suggest that IL-15 signaling in the thymus controls T-ALL development from aberrant thymocytes with an impaired DNA repair capacity and increased NOTCH1 activation.

The GIMAP Family Proteins: An Incomplete Puzzle

Overview: Long-term survival of T lymphocytes in quiescent state is essential to maintain their cell numbers in secondary lymphoid organs and in peripheral circulation. In the BioBreeding diabetes-prone strain of rats (BB-DP), loss of functional GIMAP5 (GTPase of the immune associated nucleotide binding protein 5) results in profound peripheral T lymphopenia. This discovery heralded the identification of a new family of proteins initially called Immune-associated nucleotide binding protein (IAN) family. In this review we will use ‘GIMAP’ to refer to this family of proteins. Recent studies suggest that GIMAP proteins may interact with each other and also be involved in the movement of the cellular cargo along the cytoskeletal network. Here we will summarize the current knowledge on the characteristics and functions of GIMAP family of proteins.

Identification and validation of tumor microenvironment-related genes of prognostic value in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is a major subtype of non-small cell lung cancer. Despite significant progress in its diagnosis and treatment, the mortality and morbidity rate of LUAD remains high worldwide. The aim of the present study was to perform a systematic investigation of the tumor microenvironment (TME) and identify TME-related genes of prognostic value in patients with LUAD. Firstly, the immune scores and stromal scores of patients with LUAD from The Cancer Genome Atlas were calculated using the Estimation of STromal and Immune cells in MAlignant Tumors using Expression data algorithm, and a total of 281 prognostic TME-related genes were identified. Subsequently, functional analysis and protein-protein interaction network analysis revealed that these genes were mainly related to immune response, inflammatory response and chemotaxis. Finally, two independent LUAD cohorts from the Gene Expression Omnibus database were used to validate these genes, and 4 genes (GTPase IMAP family member 1, T-cell surface glycoprotein CD1b, integrin alpha-L and leukocyte surface antigen CD53) were identified, and downregulation of these genes was indicated to be associated with poor overall survival rate in patients with LUAD. In conclusion, a comprehensive analysis of TME was performed and 4 prognostic TME-related genes in patients with LUAD were identified.

Leukemia-Initiating Cells in T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is a hematological malignancy characterized by the clonal proliferation of immature T-cell precursors. T-ALL has many similar pathophysiological features to acute myeloid leukemia, which has been extensively studied in the establishment of the cancer stem cell (CSC) theory, but the CSC concept in T-ALL is still debatable. Although leukemia-initiating cells (LICs), which can generate leukemia in a xenograft setting, have been found in both human T-ALL patients and animal models, the nature and origin of LICs are largely unknown. In this review, we discuss recent studies on LICs in T-ALL and the potential mechanisms of LIC emergence in this disease. We focus on the oncogenic transcription factors TAL1, LMO2, and NOTCH1 and highlight the significance of the transcriptional regulatory programs in normal hematopoietic stem cells and T-ALL.

microRNA-99a Reduces Lipopolysaccharide-Induced Oxidative Injury by Activating Notch Pathway in H9c2 Cells

microRNA-99a (miR-99a) is recently recognized as a key regulator in various cancers and cardiovascular diseases. In the present study, we sought to investigate the effects of miR-99a in rat cardiomyocyte H9c2 cells against oxidative injury induced by lipopolysaccharide (LPS).MTT assay, reactive oxygen species (ROS) assay, flow cytometry and lactate dehydrogenase (LDH) assay were respectively used to explore viability, ROS levels, apoptosis, and cell death in H9c2 cells. Quantitative PCR (qRT-PCR) was performed to confirm the expression of miR-99a. Western blot was performed to determine the expression of Notch pathway factors.LPS could significantly suppress viability and increase cell death, apoptosis, and ROS level (P < 0.05). However, miR-99a could significantly increase the viability and decrease apoptosis and ROS level of H9c2 cells (P < 0.05). Overexpression of miR-99a could activate a Notch pathway and regulate the expression of B-cell CLL/lymphoma 2 (BCL2) and cleaved caspase 3.Our study found that overexpression of miR-99a could attenuate LPS-induced oxidative injury in H9c2 cells, possibly via a Notch pathway. These findings suggest that miR-99a may be a key factor in cardiomyocyte oxidative injury and could be a new therapeutic strategy for cardiovascular diseases.

Aberrant activation of the GIMAP enhancer by oncogenic transcription factors in T-cell acute lymphoblastic leukemia

The transcription factor TAL1/SCL is one of the most prevalent oncogenes in T-cell acute lymphoblastic leukemia (T-ALL), a malignant disorder resulting from leukemic transformation of thymus T-cell precursors. TAL1 is normally expressed in hematopoietic stem cells (HSCs) but is silenced in immature thymocytes. We hypothesize that TAL1 contributes to leukemogenesis by activating genes that are normally repressed in immature thymocytes. Herein, we identified a novel TAL1-regulated super-enhancer controlling the GIMAP locus, which resides within an insulated chromosomal locus in T-ALL cells. The GIMAP genes are expressed in HSCs and mature T-cells but are downregulated during the immature stage of thymocyte differentiation. The GIMAP enhancer is activated by TAL1, RUNX1 and GATA3 in human T-ALL cells but is repressed by E-proteins. Overexpression of human GIMAP genes in immature thymocytes alone does not induce tumorigenesis but accelerates leukemia development in zebrafish. Our results demonstrate that aberrant activation of the GIMAP enhancer contributes to T-cell leukemogenesis.

GIMAP1 Is Essential for the Survival of Naive and Activated B Cells In Vivo

An effective immune system depends upon regulation of lymphocyte function and homeostasis. In recent years, members of the GTPases of the immunity associated protein (GIMAP) family were proposed to regulate T cell homeostasis. In contrast, little is known about their function and mode of action in B cells. We used a combination of transgenic mice and in vivo and in vitro techniques to conditionally and electively ablate GIMAP1 in resting and activated peripheral B cells. Our data suggest that GIMAP1 is absolutely essential for the survival of peripheral B cells, irrespective of their activation state. Together with recent data showing increased expression of GIMAP1 in B cell lymphomas, our work points to the possible potential of GIMAP1 as a target for manipulation in a variety of B cell-mediated diseases.

Potential role of Notch signalling in CD34+ chronic myeloid leukaemia cells: cross-talk between Notch and BCR-ABL

Notch signalling is critical for haemopoietic stem cell (HSC) self-renewal and survival. The role of Notch signalling has been reported recently in chronic myeloid leukaemia (CML) – a stem cell disease characterized by BCR-ABL tyrosine kinase activation. Therefore, we studied the relationship between BCR-ABL and Notch signalling and assessed the expression patterns of Notch and its downstream target Hes1 in CD34⁺ stem and progenitor cells from chronic-phase CML patients and bone marrow (BM) from normal subjects (NBM). We found significant upregulation (p<0.05) of Notch1, Notch2 and Hes1 on the most primitive CD34⁺Thy⁺ subset of CML CD34⁺ cells suggesting that active Notch signalling in CML primitive progenitors. In addition, Notch1 was also expressed in distinct lymphoid and myeloid progenitors within the CD34⁺ population of primary CML cells. To further delineate the possible role and interactions of Notch with BCR-ABL in CD34⁺ primary cells from chronic-phase CML, we used P-crkl detection as a surrogate assay of BCR-ABL tyrosine kinase activity. Our data revealed that Imatinib (IM) induced BCR-ABL inhibition results in significant (p<0.05) upregulation of Notch activity, assessed by Hes1 expression. Similarly, inhibition of Notch leads to hyperactivation of BCR-ABL. This antagonistic relationship between Notch and BCR-ABL signalling was confirmed in K562 and ALL-SIL cell lines. In K562, we further validated this antagonistic relationship by inhibiting histone deacetylase (HDAC) - an effector pathway of Hes1, using valproic acid (VPA) - a HDAC inhibitor. Finally, we also confirmed the potential antagonism between Notch and BCR/ABL in In Vivo, using publically available GSE-database, by analysing gene expression profile of paired samples from chronic-phase CML patients pre- and post-Imatinib therapy. Thus, we have demonstrated an antagonistic relationship between Notch and BCR-ABL in CML. A combined inhibition of Notch and BCR-ABL may therefore provide superior clinical response over tyrosine-kinase inhibitor monotherapy by targeting both quiescent leukaemic stem cells and differentiated leukaemic cells and hence must be explored.

The immune system GTPase GIMAP6 interacts with the Atg8 homologue GABARAPL2 and is recruited to autophagosomes

The GIMAPs (GTPases of the immunity-associated proteins) are a family of small GTPases expressed prominently in the immune systems of mammals and other vertebrates. In mammals, studies of mutant or genetically-modified rodents have indicated important roles for the GIMAP GTPases in the development and survival of lymphocytes. No clear picture has yet emerged, however, of the molecular mechanisms by which they perform their function(s). Using biotin tag-affinity purification we identified a major, and highly specific, interaction between the human cytosolic family member GIMAP6 and GABARAPL2, one of the mammalian homologues of the yeast autophagy protein Atg8. Chemical cross-linking studies performed on Jurkat T cells, which express both GIMAP6 and GABARAPL2 endogenously, indicated that the two proteins in these cells readily associate with one another in the cytosol under normal conditions. The GIMAP6-GABARAPL2 interaction was disrupted by deletion of the last 10 amino acids of GIMAP6. The N-terminal region of GIMAP6, however, which includes a putative Atg8-family interacting motif, was not required. Over-expression of GIMAP6 resulted in increased levels of endogenous GABARAPL2 in cells. After culture of cells in starvation medium, GIMAP6 was found to localise in punctate structures with both GABARAPL2 and the autophagosomal marker MAP1LC3B, indicating that GIMAP6 re-locates to autophagosomes on starvation. Consistent with this finding, we have demonstrated that starvation of Jurkat T cells results in the degradation of GIMAP6. Whilst these findings raise the possibility that the GIMAPs play roles in the regulation of autophagy, we have been unable to demonstrate an effect of GIMAP6 over-expression on autophagic flux.

MicroRNAs and Glucocorticoid-Induced Apoptosis in Lymphoid Malignancies

The initial response of lymphoid malignancies to glucocorticoids (GCs) is a critical parameter predicting successful treatment. Although being known as a strong inducer of apoptosis in lymphoid cells for almost a century, the signaling pathways regulating the susceptibility of the cells to GCs are only partly revealed. There is still a need to develop clinical tests that can predict the outcome of GC therapy. In this paper, I discuss important parameters modulating the pro-apoptotic effects of GCs, with a specific emphasis on the microRNA world comprised of small players with big impacts. The journey through the multifaceted complexity of GC-induced apoptosis brings forth explanations for the differential treatment response and raises potential strategies for overcoming drug resistance.