RAG1 and RAG2 non-core regions are implicated in leukemogenesis and off-target V(D)J recombination in BCR-ABL1-driven B-cell lineage lymphoblastic leukemia.

The evolutionary conservation of non-core RAG regions suggests significant roles that might involve quantitative or qualitative alterations in RAG activity. Off-target V(D)J recombination contributes to lymphomagenesis and is exacerbated by RAG2' C-terminus absence in Tp53-/- mice thymic lymphomas. However, the genomic stability effects of non-core regions from both Rag1c/c and Rag2c/c in BCR-ABL1+ B-lymphoblastic leukemia (BCR-ABL1+ B-ALL), the characteristics, and mechanisms of non-core regions in suppressing off-target V(D)J recombination remain unclear. Here, we established three mouse models of BCR-ABL1+ B-ALL in mice expressing full-length RAG (Ragf/f), core RAG1 (Rag1c/c), and core RAG2 (Rag2c/c). The Ragc/c (Rag1c/c and Rag2c/c) leukemia cells exhibited greater malignant tumor characteristics compared to Ragf/f cells. Additionally, Ragc/c cells showed higher frequency of off-target V(D)J recombination and oncogenic mutations than Ragf/f. We also revealed decreased RAG cleavage accuracy in Ragc/c cells and a smaller recombinant size in Rag1c/c cells, which could potentially exacerbate off-target V(D)J recombination in Ragc/c cells. In conclusion, these findings indicate that the non-core RAG regions, particularly the non-core region of RAG1, play a significant role in preserving V(D)J recombination precision and genomic stability in BCR-ABL1+ B-ALL.

Peritoneal B1 and B2 cells respond differently to LPS and IL-21 stimulation.

Peritoneal B cells can be divided into B1 cells (CD11b+CD19+) and B2 cells (CD11b-CD19+) based on CD11b expression. B1 cells play a crucial role in the innate immune response by producing natural antibodies and cytokines. B2 cells share similar traits with B1 cells, influenced by the peritoneal environment. However, the response of both B1 and B2 cells to the same stimuli in the peritoneum remains uncertain. We isolated peritoneal B1 and B2 cells from mice and assessed differences in Interleukin-10(IL-10) secretion, apoptosis, and surface molecule expression following exposure to LPS and Interleukin-21(IL-21). Our findings indicate that B1 cells are potent IL-10 producers, possessing surface molecules with an IgMhiCD43+CD21low profile, and exhibit a propensity for apoptosis in vitro. Conversely, B2 cells exhibit lower IL-10 production and surface markers characterized as IgMlowCD43-CD21hi, indicative of some resistance to apoptosis. LPS stimulates MAPK phosphorylation in B1 and B2 cells, causing IL-10 production. Furthermore, LPS inhibits peritoneal B2 cell apoptosis by enhancing Bcl-xL expression. Conversely, IL-21 has no impact on IL-10 production in these cells. Nevertheless, impeding STAT3 phosphorylation permits IL-21 to increase IL-10 production in peritoneal B cells. Moreover, IL-21 significantly raises apoptosis levels in these cells, a process independent of STAT3 phosphorylation and possibly linked to reduced Bcl-xL expression. This study elucidates the distinct functional and response profiles of B1 and B2 cells in the peritoneum to stimuli like LPS and IL-21, highlighting their differential roles in immunological responses and B cell diversity.

Unlocking PD-1 antibody resistance: The MUC1 DNA vaccine augments CD8+ T cell infiltration and attenuates tumour suppression.

In light of increasing resistance to PD1 antibody therapy among certain patient populations, there is a critical need for in-depth research. Our study assesses the synergistic effects of a MUC1 DNA vaccine and PD1 antibody for surmounting PD1 resistance, employing a murine CT26/MUC1 colon carcinoma model for this purpose. When given as a standalone treatment, PD1 antibodies showed no impact on tumour growth. Additionally, there was no change observed in the intra-tumoural T-cell ratios or in the functionality of T-cells. In contrast, the sole administration of a MUC1 DNA vaccine markedly boosted the cytotoxicity of CD8+ T cells by elevating IFN-γ and granzyme B production. Our compelling evidence highlights that combination therapy more effectively inhibited tumour growth and prolonged survival compared to either monotherapy, thus mitigating the limitations intrinsic to single-agent therapies. This enhanced efficacy was driven by a significant alteration in the tumour microenvironment, skewing it towards pro-immunogenic conditions. This assertion is backed by a raised CD8+/CD4+ T-cell ratio and a decrease in immunosuppressive MDSC and Treg cell populations. On the mechanistic front, the synergistic therapy amplified expression levels of CXCL13 in tumours, subsequently facilitating T-cell ingress into the tumour setting. In summary, our findings advocate for integrated therapy as a potent mechanism for surmounting PD1 antibody resistance, capitalizing on improved T-cell functionality and infiltration. This investigation affords critical perspectives on enhancing anti-tumour immunity through the application of innovative therapeutic strategies.

Activation-induced cytidine deaminase displays an alternative co-factor for modulating PIM1 expression in diffuse large B cell lymphoma cell lines.

Diffuse large B cell lymphoma (DLBCL) is a B cell neoplasm characterized by high PIM1 expression, which is responsible for poor prognosis. Activation-induced cytidine deaminase (AID) is closely linked to PIM1 hypermutation in DLBCL. Here, we found that the DNA methyltransferase 1 (DNMT1) level decreased with AID depletion in the DLBCL cell line SU-DHL-4, and increased significantly when AID was highly expressed. The double ablation of AID and DNMT1 contributed to increased PIM1 expression, which initiated faster DLBCL cell proliferation, whereas ten-eleven translocation family member 2 (TET2) decreased with AID deficiency and increased with AID overexpression in DLBCL cell line OCI-LY7. The double depletion of AID and TET2 was associated with decreased PIM1 levels and showed slower cell division. We suggest an alternative role of AID as a co-factor of DNA methylation cooperated with DNMT1, or of DNA demethylation associated with TET2 in modulating PIM1 expression. Our findings demonstrate that AID interacts with either DNMT1 or TET2 to form a complex to bind with a PIM1 promoter and thus is responsible for the modulation of PIM1 expression. These results provide insights into an alternative role of AID to DLBCL-associated genes.

Inflammation accelerates BCR-ABL1+ B-ALL development through upregulation of AID.

Inflammation contributes to the initiation and disease progression of several lymphoid malignancies. BCR-ABL1-positive B-cell acute lymphoblastic leukemia (BCR-ABL1+ B-ALL) is triggered by the malignant cloning of immature B cells promoted by the BCR-ABL1 fusion gene. However, it is unclear whether the mechanism driving the disease progression of BCR-ABL1+ B-ALL involves inflammatory stimulation. Here, we evaluate BCR-ABL1+ B-ALL cells' response to inflammatory stimuli lipopolysaccharide (LPS) in vitro and in vivo. The results indicate that LPS promotes cell growth and genomic instability in cultured BCR-ABL1+ B-ALL cells and accelerates the BCR-ABL1+ B-ALL development in a mouse model. We show that the LPS-induced upregulation of activation-induced deaminase (AID) is required for the cell growth and disease progression of BCR-ABL1+ B-ALL. Moreover, AID modulates the expression of various genes that are dominated by suppressing apoptosis genes and upregulating DNA damage-repair genes. These genes lead to facilitation for BCR-ABL1+ B-ALL progression. The heat shock protein 90 (Hsp90) inhibitors significantly reduce AID protein level and delay the disease progression of BCR-ABL1+ B-ALL upon inflammatory stimulation. The present data demonstrate the causative role of AID in the development and progression of BCR-ABL1+ B-ALL during inflammation, thus highlighting potential therapeutic targets.

lncRNA GAS5, as a ceRNA, inhibits the proliferation of diffuse large B­cell lymphoma cells by regulating the miR­18a­5p/RUNX1 axis.

Diffuse large B­cell lymphoma (DLBCL) is a common and fatal malignant tumor caused by B­lymphocytes. Long non­coding RNA (lncRNA) GAS5 (growth arrest specific 5) has been reported to function as a tumor suppressor gene, and is differentially expressed in DLBCL. The present study aimed to explore the potential mechanisms of action of lncRNA GAS5 in the proliferation of DLBCL cells. The expression levels of GAS5, miR­18a­5p and Runt­related transcription factor 1 (RUNX1) in DLBCL cell lines were detected using reverse transcription­quantitative polymerase chain reaction, and their effects on cell proliferation, the cell cycle and apoptosis were determined using 5­ethynyl­2'­deoxyuridine assay and flow cytometry. Dual­luciferase reporter and RNA pull-down assays were used to evaluate the interaction between GAS5 and miR­18a­5p, or between miR­18a­5p and RUNX1. Chromatin immunoprecipitation assay was used to identify the interaction between RUNX1 and BAX. The expression levels of GAS5 and RUNX1 were downregulated; however, miR­18a­5p expression was upregulated in the DLBCL cell lines compared with the normal controls. GAS5 directly interacted with miR­18a­5p by acting as a competing endogenous RNA (ceRNA) and reversed the low expression of RUNX1 induced by miR­18a­5p. Additionally, the knockdown of RUNX1 reversed the inhibitory effects of GAS5 on the proliferation and cell cycle G1 arrest, and its promoting effects on the apoptosis of OCI­Ly3 and TMD8 cells. Moreover, RUNX1 enhanced BAX expression by directly binding to the BAX promoter. On the whole, the present study demonstrates that GAS5 functions as a ceRNA, inhibiting DLBCL cell proliferation by sponging miR­18a­5p to upregulate RUNX1 expression. These findings may provide a potential therapeutic strategy for DLBCL.

RAG enhances BCR-ABL1-positive leukemic cell growth through its endonuclease activity in vitro and in vivo.

BCR-ABL1 gene fusion associated with additional DNA lesions involves the pathogenesis of chronic myelogenous leukemia (CML) from a chronic phase (CP) to a blast crisis of B lymphoid (CML-LBC) lineage and BCR-ABL1+ acute lymphoblastic leukemia (BCR-ABL1+ ALL). The recombination-activating gene RAG1 and RAG2 (collectively, RAG) proteins that assemble a diverse set of antigen receptor genes during lymphocyte development are abnormally expressed in CML-LBC and BCR-ABL1+ ALL. However, the direct involvement of dysregulated RAG in disease progression remains unclear. Here, we generate human wild-type (WT) RAG and catalytically inactive RAG-expressing BCR-ABL1+ and BCR-ABL1- cell lines, respectively, and demonstrate that BCR-ABL1 specifically collaborates with RAG recombinase to promote cell survival in vitro and in xenograft mice models. WT RAG-expressing BCR-ABL1+ cell lines and primary CD34+ bone marrow cells from CML-LBC samples maintain more double-strand breaks (DSB) compared to catalytically inactive RAG-expressing BCR-ABL1+ cell lines and RAG-deficient CML-CP samples, which are measured by γ-H2AX. WT RAG-expressing BCR-ABL1+ cells are biased to repair RAG-mediated DSB by the alternative non-homologous end joining pathway (a-NHEJ), which could contribute genomic instability through increasing the expression of a-NHEJ-related MRE11 and RAD50 proteins. As a result, RAG-expressing BCR-ABL1+ cells decrease sensitivity to tyrosine kinase inhibitors (TKI) by activating BCR-ABL1 signaling but independent of the levels of BCR-ABL1 expression and mutations in the BCR-ABL1 tyrosine kinase domain. These findings identify a surprising and novel role of RAG in the functional specialization of disease progression in BCR-ABL1+ leukemia through its endonuclease activity.

Overexpression of miR-18a negatively regulates myocyte enhancer factor 2D to increase the permeability of the blood-tumor barrier via Krüppel-like factor 4-mediated downregulation of zonula occluden-1, claudin-5, and occludin.

miR-18a represses angiogenesis and tumor evasion by weakening vascular endothelial growth factor and transforming growth factor-ß signaling to prolong the survival of glioma patients, although it is thought to be an oncogene. This study investigates the potential effects of miR-18a on the permeability of the blood-tumor barrier (BTB) and its possible molecular mechanisms. An in vitro BTB model was successfully established. The endogenous expression of miR-18a in glioma vascular endothelial cells (GECs) was significantly lower than that in normal vascular ECs, and the overexpression of miR-18a significantly increased the permeability of the BTB as well as downregulating the mRNA and protein expressions of tight junction-related proteins zonula occluden-1 (ZO-1), claudin-5, and occludin in GECs. Dual luciferase reporter assays revealed that miR-18a bound to the 3'-untranslated region (3'UTR) of myocyte enhancer factor 2D (MEF2D). The overexpression of both miR-18a and MEF2D with the 3'UTR significantly weakened the effect caused by miR-18a of decreasing the mRNA and protein expressions of ZO-1, claudin-5 and occludin and of increasing the permeability of the BTB. Chromatin immunoprecipitation showed that MEF2D could directly bind to KLF4 promoter. This study shows that miR-18a targets and negatively regulates MEF2D, which further regulates tight junction-related proteins ZO-1, claudin-5, and occludin through transactivation of KLF4 and, finally, changes the permeability of the BTB. MiR-18a should garner growing attention because it might serve as a potential target in opening the BTB and providing a new strategy for the treatment of gliomas.

MiR-18a increased the permeability of BTB via RUNX1 mediated down-regulation of ZO-1, occludin and claudin-5.

The purposes of this study were to investigate the possible molecular mechanisms of miR-18a regulating the permeability of blood-tumor barrier (BTB) via down-regulated expression and distribution of runt-related transcription factor 1 (RUNX1). An in vitro BTB model was established with hCMEC/D3 cells and U87MG cells to obtain glioma vascular endothelial cells (GECs). The endogenous expressions of miR-18a and RUNX1 were converse in GECs. The overexpression of miR-18a significantly impaired the integrity and increased the permeability of BTB, which respectively were detected by TEER and HRP flux assays, accompanied by down-regulated mRNA and protein expressions and distributions of ZO-1, occludin and claudin-5 in GECs. Dual-luciferase reporter assay was carried out and revealed RUNX1 is a target gene of miR-18a. Meanwhile, mRNA and protein expressions and distribution of RUNX1 were downregulated by miR-18a. Most important, miR-18a and RUNX1 could reversely regulate the permeability of BTB as well as the expressions and distributions of ZO-1, occludin and claudin-5. Finally, chromatin immunoprecipitation verified that RUNX1 interacted with "TGGGGT" DNA sequence in promoter region of ZO-1, occludin and claudin-5 respectively. Taken together, our present study indicated that miR-18a increased the permeability of BTB via RUNX1 mediated down-regulation of tight junction related proteins ZO-1, occludin and claudin-5, which would attract more attention to miR-18a and RUNX1 as potential targets of drug delivery across BTB and provide novel strategies for glioma treatment.