M2 macrophages drive leukemic transformation by imposing resistance to phagocytosis and improving mitochondrial metabolism.

It is increasingly becoming clear that cancers are a symbiosis of diverse cell types and tumor clones. Combined single-cell RNA sequencing, flow cytometry, and immunohistochemistry studies of the innate immune compartment in the bone marrow of patients with acute myeloid leukemia (AML) reveal a shift toward a tumor-supportive M2-polarized macrophage landscape with an altered transcriptional program, with enhanced fatty acid oxidation and NAD+ generation. Functionally, these AML-associated macrophages display decreased phagocytic activity and intra-bone marrow coinjection of M2 macrophages together with leukemic blasts strongly enhances in vivo transformation potential. A 2-day in vitro exposure to M2 macrophages results in the accumulation of CALRlow leukemic blast cells, which are now protected against phagocytosis. Moreover, M2-exposed "trained" leukemic blasts display increased mitochondrial metabolism, in part mediated via mitochondrial transfer. Our study provides insight into the mechanisms by which the immune landscape contributes to aggressive leukemia development and provides alternatives for targeting strategies aimed at the tumor microenvironment.

MLL5 improves ATRA driven differentiation and promotes xenotransplant engraftment in acute promyelocytic leukemia model.

Although the mixed lineage leukemia 5 (MLL5) gene has prognostic implications in acute promyelocyte leukemia (APL), the underlying mechanism remains to be elucidated. Here, we demonstrate the critical role exerted by MLL5 in APL regarding cell proliferation and resistance to drug-induced apoptosis, through mtROS regulation. Additionally, MLL5 overexpression increased the responsiveness of APL leukemic cells to all-trans retinoic acid (ATRA)-induced differentiation, via regulation of the epigenetic modifiers SETD7 and LSD1. In silico analysis indicated that APL blasts with MLL5high transcript levels were associated with retinoic acid binding and downstream signaling, while MLL5low blasts displayed decreased expression of epigenetic modifiers (such as KMT2C, PHF8 and ARID4A). Finally, APL xenograft transplants demonstrated improved engraftment of MLL5-expressing cells and increased myeloid differentiation over time. Concordantly, evaluation of engrafted blasts revealed increased responsiveness of MLL5-expressing cells to ATRA-induced granulocytic differentiation. Together, we describe the epigenetic changes triggered by the interaction of MLL5 and ATRA resulting in enhanced granulocytic differentiation.

Reduced SLIT2 is Associated with Increased Cell Proliferation and Arsenic Trioxide Resistance in Acute Promyelocytic Leukemia.

The SLIT-ROBO axis plays an important role in normal stem-cell biology, with possible repercussions on cancer stem cell emergence. Although the Promyelocytic Leukemia (PML) protein can regulate SLIT2 expression in the central nervous system, little is known about SLIT2 in acute promyelocytic leukemia. Hence, we aimed to investigate the levels of SLIT2 in acute promyelocytic leukemia (APL) and assess its biological activity in vitro and in vivo. Our analysis indicated that blasts with SLIT2high transcript levels were associated with cell cycle arrest, while SLIT2low APL blasts displayed a more stem-cell like phenotype. In a retrospective analysis using a cohort of patients treated with all-trans retinoic acid (ATRA) and anthracyclines, high SLIT2 expression was correlated with reduced leukocyte count (p = 0.024), and independently associated with improved overall survival (hazard ratio: 0.94; 95% confidence interval: 0.92-0.97; p < 0.001). Functionally, SLIT2-knockdown in primary APL blasts and cell lines led to increased cell proliferation and resistance to arsenic trioxide induced apoptosis. Finally, in vivo transplant of Slit2-silenced primary APL blasts promoted increased leukocyte count (p = 0.001) and decreased overall survival (p = 0.002) compared with the control. In summary, our data highlight the tumor suppressive function of SLIT2 in APL and its deteriorating effects on disease progression when downregulated.

The influence of physical activity in the anti-tumor immune response in experimental breast tumor.

This study aimed to investigate the influence of physical activity in innate immunity to conduce to an effective antitumoral immune response analyzing the phenotype and activation status of infiltrating cells. We analysed the intracellular cytokines and the transcription factors of tumor infiltrating lymphocytes (TILS) and spleen leukocytes. The Nos2 gene expression was evaluated in spleen cells and futhermore the ROS production was measured and spleen cells; another cell evaluated was dendritic cells (TIDCs), their cytokines expression and membrane molecules; finally to understood the results obtained, we analysed the dendritic cells obtained from bone marrow. Were used female Balb/c mice divided into 4 groups: two controls without tumor, sedentary (GI) and trained (GII) and two groups with tumor, sedentary (GIII) or trained (GIV). The physical activity (PA) was realized acoording swimming protocol. Tumor was induced by injection of 4T1 cells. All experiments were performed in biological triplicate. After the experimental period, the tumor was removed and the cells were identified by flow cytometry with labeling to CD4, CD8, CD11c, CD11b, CD80, CD86 and Ia, and intracelular staining IL-10, IL-12, TNF-α, IFN-γ, IL-17, Tbet, GATA3, RORγt and FoxP3. The bone marrow of the animals was obtained to analyse the derivated DCs by flow cytometry and culture cells to obtain the supernatant to measure the cytokines. Our results demonstrated that the PA inhibit the tumoral growth although not to change the number of TILS, but reduced expression of GATA-3, ROR-γT, related with poor prognosis, and TNF-α intracellular; however occur one significantly reduction in TIDCS, but these cells expressed more co-stimulatory and presentation molecules. Furthermore, we observed that the induced PA stimulated the gene expression of Tbet and the production of inflammatory cytokines suggesting an increase of Th1 systemic response. The results evaluating the systemic influence in DCs showed that the PA improve significantly the number of those cells in bone marrow as well the number of co-stimulatory molecules. Therefore, we could conclude that PA influence the innate immunity by interfering to promote in process of maturation of DCs both in tumor and systemically, that by its turn promote a modification in acquired immune cells, representing by T helper to induce an important alteration transcription factors that are responsible to maintain a suppressive microenviroment, and thereby, allowing the latter cells can thus activate antitumor immune response. The PA was able improve the Th1 systemic response by enhance to Tbet gene expression, promote a slightly increased of Th1-type cytokines and decrease Gata3 and Foxp3 gene expression in which can inhibit the Th1 immune response.