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Activation and migration of donor T cells to the host target organs are critical mechanisms in the pathogenesis of graft-versus-host disease (GVHD). The role of monocyte chemoattractant protein-1 (MCP-1/CCL2) and its receptor CCR2 in the recruitment of T cells during immune or inflammatory response is also well known. For elucidation of the mechanism of the therapeutic effect of human bone marrow derived-mesenchymal stem cells (MSC) in GVHD, we studied the effect of these cells on migration of activated donor T cells through the CCL2-CCR2 axis in vitro. MSC were expanded from donors' bone marrow mononuclear cells. After co-culturing of IL-2-activated T cells with allogeneic MSC at different ratios, the levels of CCL2 in supernatants were measured by ELISA, and CCR2 expression in CD4+/CD8+ T cells subsets were detected by flow cytometry. The effect of MSC on the migration of activated T cells in the Transwell system was studied in the absence or presence of CCL2. Our results show that CCL2 levels in supernatants of co-cultures were significantly higher than in MSC monoculture and this increase depended on the number of MSC. MSC inhibited proliferation of T cells, but did not change the percentages of CD4+ and CD8+ T cells subsets. MSC can up-regulate the CCR2 expression in CD8+ subsets rather than in CD4+ subsets; MSC enhanced migration of IL-2-activated T cells to CCL2 by increasing the expression of CCR2. The data demonstrate that MSC can enhance chemotaxis of cytokine-activated T cells through the CCL2-CCR2 axis in vitro.

Background. It is well known that microRNAs (miRNAs) interfere with the progression of various human malignancies. This article is aimed at exploring the regulating role of miR-342-3p in acute myeloid leukemia (AML) and its mechanism. Methods. We used the Gene Expression Omnibus (GEO) database to determine miR-342-3p differential expression patterns in AML patients’ plasma and cells as well as healthy individuals’ plasma and T cells. Quantitative real-time PCR and Western blotting were performed for plasma and cell miR-342-3p and SRY-related high-mobility-group box (SOX12) expression quantification, and cell counting kit-8 assay and flow cytometry were used for the determination of AML cell growth, cycle, and apoptosis. A dual-luciferase reporter gene assay was further carried out to identify the targeted association between miR-342-3p and SOX12 mRNA 3 ′ UTR after prediction by a bioinformatics website. Pearson’s correlation analysis was performed to analyze the connection between miR-342-3p and SOX12 expressions. The LinkedOmics database was utilized to explore the downstream pathways in which SOX12 was enriched. Results. Evidently downregulated plasma miR-342-3p and markedly elevated SOX12 were observed in AML patients versus healthy individuals. miR-342-3p mimics suppressed AML cell growth, enhanced apoptosis, and induced G0/G1 phase arrest; conversely, enhanced capacity of AML cells to proliferate, suppressed apoptosis, and accelerated cell cycle were observed after treatment with miR-342-3p inhibitors. SOX12 was confirmed as miR-342-3p’s target gene. Overexpressing or knocking down SOX12 reversed miR-342-3p’s impacts on AML cell growth, apoptosis, and cycle. Upregulated SOX12 was positively related to DNA replication and RNA polymerase signaling pathways. Conclusion. miR-342-3p affects apoptosis of AML cells and their ability to proliferate via targeted regulation of SOX12.

Introduction: Chimeric antigen receptor (CAR) T cell therapy targeting CD19 has recently demonstrated high success but also shown limitations regarding their toxicity and development of CD19negative variants. Here we reported results from a phase I study designed to determine the safety of the CD19 CAR-T and CD22 CAR-T cocktail and the feasibility of making enough quantities to treat patients with CD19+CD22+ relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL). Patients and Methods: From July 2017 to July 2018, a total of 15 patients with CD19+CD22+ relapsed/refractory B-ALL were treated, including 5 children and 10 adults (Table 1). All patients received fludarabine 30mg/m2/d´3d and cyclophosphamide 250mg/m2/d´2d before infusion of CAR-T cells, followed by a cocktail CAR-T cell infusion with a median number of 2 (0.9-5)´105 CD19 CAR+ T cells/kg and a median number of 0.5 (0.4-12)´105 CD22 CAR+ T cells/kg. The lentiviral backbone containing constructs of CD19 CAR and CD22 CAR are shown in Figure 1. CD19 CAR includes a truncated EGFR sequence which can be used to identify and select CAR+ cells. CD22 CAR includes a single chain variable fragment (ScFv) sequence derived from a monoclonal antibody against human PD-L1 which attempts to reduce the exhaustion of CAR-T cells by blocking the PD-1/PD-L1. Real-time quantitative PCR using primers with specificity for the ScFv of CD19 CAR and ScFv of CD22 CAR can detect the in vivo CAR-T persistence for either CAR. Sequential transduction was performed 2 days after activation of sorted T cells stimulated with CD3 and CD28 antibodies. Percentages of CD19 CAR+ and CD22 CAR+ T cells were determined by flow cytometry through staining with an antibody against EGFR and a fusion protein of CD22-Fc, respectively, and expression of anti-PDL1 ScFv in CD22 CAR-T cells were demonstrated by flow cytometry through intracellular staining with a PD-L1-Fc fusion protein. The primary end points of this study were to evaluate feasibility and toxicity, and the secondary end points included disease response and persistent CAR-T engraftment of infused CAR-T cell. Results: The median observation period was 133 days (24-392 days). The median percentage of pre-treatment bone marrow CD19+CD22+ blasts was 21.5%(0.11-74.1%). On day 20-30 after CAR-T infusion, 15/15 (100%) cases achieved complete remission (CR) or incomplete CR(CRi), 14/15 (93.3%) cases had negative minimal residual disease (MRD). Patient P098 had residual (0.58%) CD19+CD22+ BM blasts at day 30 post-infusion and thereafter achieved negative MRD after re-infusion with CD19 CAR-T cells. 11/17 patients were bridged into allo-HSCT and have remained in remission state with a median follow up of 133 (97-214) days. 2/5 patients without bridging allo-HSCT relapsed on day 240 and day 105 post-infusion, respectively. Notably, both patients (100%) relapsed with CD19+CD22+ leukemia cells. Despite achievement of a very high CR rate, a very low treatment-related toxicity was observed in this trial. Only 1 patients experienced grade 3 cytokine release syndrome (CRS) and another patient (6.7%) developed grade 3 central nervous system (CNS) toxicity; all other patients were CRS grade Conclusion: This study demonstrates technical feasibility, high efficacy and low toxicities of CD19 and CD22 CAR-T cocktail in treating patients with CD19+CD22+ relapsed/refractory B-ALL. Both patients relapsed with CD19+ leukemia suggests this cocktail treatment may reduce the risk of CD19 negative relapse. Low toxicities may relate with small number of infused CAR-T, but involvement of anti-PDL1 ScFv which is co-expressed with CD22 CAR construct cannot be excluded. Therefore, related mechanisms are currently being investigated in the lab. Disclosures No relevant conflicts of interest to declare.