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Background Transition from intrauterine to extrauterine life is a critical phase during which several changes occur in cardiovascular system. In clinical practice, it is important to have a method that allows an easy, rapid and precise evaluation of hemodynamic status of a newborn for clinical management. We here propose a rapid, broadly applicable method to monitor cardiovascular function using ultrasonic cardiac output monitoring (USCOM). Methods We here present data obtained from a cohort of healthy term newborns (n = 43) born by programmed cesarean section at Fondazione MBBM, Ospedale San Gerardo. Measurements were performed during the first hour of life, then at 6 + 2, at 12–24, and 48 h of life. We performed a screening echocardiography to identify a patent duct at 24 h and, if patent, it was repeated at 48 h of life. Results We show that physiologically, during the first 48 h of life, blood pressure and systemic vascular resistance gradually increase, while there is a concomitant reduction in stroke volume, cardiac output, and cardiac index. The presence of patent ductus arteriosus significantly reduces cardiac output (p = 0.006) and stroke volume (p = 0.023). Furthermore, newborns born at 37 weeks of gestational age display significantly lower cardiac output (p p = 0.045) and stroke volume (p p = 0.0349), stroke volume (p p p = 0.0004). In particular, LGA infants display a transient increase in cardiac index, cardiac output and stroke volume up to 24 h of life; showing a different behavior from AGA and SGA infants. Conclusions Compared to previous studies, we expanded measurements to longer time-points and we analyzed the impact of commonly used clinical variables on hemodynamics during transition phase thus making our data clinically applicable in daily routine. We calculate reference values for each population, which can be of clinical relevance for quick bedside evaluation in neonatal intensive care unit.

MicroRNA (miRNA)-126 is a known regulator of hematopoietic stem cell quiescence. We engineered murine hematopoiesis to express miRNA-126 across all differentiation stages. Thirty percent of mice developed monoclonal B cell leukemia, which was prevented or regressed when a tetracycline-repressible miRNA-126 cassette was switched off. Regression was accompanied by upregulation of cell-cycle regulators and B cell differentiation genes, and downregulation of oncogenic signaling pathways. Expression of dominant-negative p53 delayed blast clearance upon miRNA-126 switch-off, highlighting the relevance of p53 inhibition in miRNA-126 addiction. Forced miRNA-126 expression in mouse and human progenitors reduced p53 transcriptional activity through regulation of multiple p53-related targets. miRNA-126 is highly expressed in a subset of human B-ALL, and antagonizing miRNA-126 in ALL xenograft models triggered apoptosis and reduced disease burden.

MicroRNAs are essential regulators of normal and malignant hematopoiesis. miRNAs are relevant for gene therapy, since they can be exploited to fine-tune the expression profile of vector constructs or to alter viral tropism (GentnerN Chiriaco et al, 2014; Escobar et al, 2014) and described the function of miR-126 in HSC where it regulates the balance between quiescence and self-renewal (Lechman et al, 2012). We here report a novel role for miR-126 in the induction and maintenance of high-grade B cell malignancies. By ectopically expressing miR-126 in transplanted BM cells, we observed that up to 60% of mice (n=71) developed B cell malignancies. LV insertion site (IS) analysis revealed that all tumors were monoclonal. We then tracked back leukemic clone to different hematopoietic lineages prospectively purified from the mice 2-6 months before disease onset. IS sharing between normal lineages and leukemic clone suggests stem or multipotent progenitor cell as origin for most tumors. Importantly, we show that miR-126 is the direct cause of genesis and maintenance of leukemia, since leukemogenesis is abolished when miRNA expression is inhibited by doxycycline (doxy) using a tetracycline-repressible miR-126 cassette, and established symptomatic leukemia completely regresses when miR-126 is switched off by doxy through induction of apoptosis. Transcriptional profiling indicated that miR-126 regulates multiple genes in p53 pathway both in murine blasts and in normal human CD34+ cells. Previous work suggested expression of miR-126 in acute lymphoblastic leukemia (ALL) and germinal center lymphoma. To further establish the relevance of miR-126 in human disease, we measured miR-126 expression in blasts from 16 adult patients with ALL. miR-126 was highly expressed in most studied ALL cases (Phil+: n=11, Phil-: n=5), at similar levels as CD34+ cells. We then down-regulated miR-126 in primary blasts from human B-ALL patients (n=5), and we observed increased apoptosis and impaired engraftment in xenograft models after primary and secondary transplantation (miR-126/KD: n=32 mice; Ctrl: n=37 mice), demonstrating the relevance of miR-126 in human B-ALL. In conclusion, we present a novel spontaneous mouse model for high grade B cell malignancies which are addicted to miR-126 expression, provide insight into the dynamic process of leukemogenesis by clonal IS tracking and unveil key tumor signaling pathways controlled by miR-126. Down-regulation of miR-126 could be exploited as therapeutic strategy in ALL, since it would deplete leukemic cells while expanding normal HSC, two ways to restore normal hematopoieis.

To investigate miRNA function in human acute myeloid leukemia (AML) stem cells (LSC), we generated a prognostic LSC-associated miRNA signature derived from functionally validated subpopulations of AML samples. For one signature miRNA, miR-126, high bioactivity aggregated all in vivo patient sample LSC activity into a single sorted population, tightly coupling miR-126 expression to LSC function. Through functional studies, miR-126 was found to restrain cell cycle progression, prevent differentiation, and increase self-renewal of primary LSC in vivo. Compared with prior results showing miR-126 regulation of normal hematopoietic stem cell (HSC) cycling, these functional stem effects are opposite between LSC and HSC. Combined transcriptome and proteome analysis demonstrates that miR-126 targets the PI3K/AKT/MTOR signaling pathway, preserving LSC quiescence and promoting chemotherapy resistance. Lechman et al. show that miR-126 targets the PI3K/AKT/MTOR signaling pathway to preserve quiescence, increase self-renewal, and promote chemotherapy resistance of acute myeloid leukemia stem cells (LSC). Reducing the miR-126 level impairs LSC maintenance in contrast to expanding normal hematopoietic stem cells.

A third of patients with critical limb ischemia (CLI) will eventually require limb amputation. Therapeutic neovascularization using unselected mononuclear cells to salvage ischemic limbs has produced modest results. The TIE2-expressing monocytes/macrophages (TEMs) are a myeloid cell subset known to be highly angiogenic in tumours. This study aimed to examine the kinetics of TEMs in patients with CLI and whether these cells promote neovascularization of the ischemic limb. Here we show that there are 10-fold more circulating TEMs in CLI patients, and removal of ischemia reduces their numbers to normal levels. TEM numbers in ischemic muscle are two-fold greater than normoxic muscle from the same patient. TEMs from patients with CLI display greater proangiogenic activity than TIE2-negative monocytes in vitro. Using a mouse model of hindlimb ischemia, lentiviral-based Tie2 knockdown in TEMs impaired recovery from ischemia, whereas delivery of mouse macrophages overexpressing TIE2, or human TEMs isolated from CLI patients, rescued limb ischemia. These data suggest that enhancing TEM recruitment to the ischemic muscle may have the potential to improve limb neovascularization in CLI patients.

MicroRNA-126 reinforces hematopoietic stem cell (HSC) quiescence by dampening PI3K-AKT signaling. We recently reported key functions of miR-126 in acute leukemia: in human AML, it was required to maintain leukemic stem cell (LSC) quiescence (Lechman et al, Cancer Cell 2016), while its ectopic expression in mouse HSC induced leukemia (75% B-ALL, 25% AML) that fully regressed when switching a tetracycline-repressible miR-126 cassette off (Nucera et al, Cancer Cell 2016). RNA sequencing showed that miR-126 targeted cell cycle, apoptosis and p53 response genes, prevented differentiation and sustained oncogenic/pro-survival pathways typically associated with stem and progenitor cells (Kit, Wnt, Thy1, Jak/Stat, Bcl2). We quantified miR-126 expression levels in a cohort of 45 newly diagnosed AML patients (n=38 de novo, of which 37% favorable, 34% int-1, 16% int-2, 13% adverse according to the ELN classification) presenting at the San Raffaele Hospital between 2010 and 2015 using a robust digital droplet PCR assay. In addition to core-binding factor (CBF) mutated AML, we found that the group of AML with chromosomal aneuploidy showed significantly elevated miR-126 levels, suggesting that this subgroup is characterized by high LSC frequencies and/or a specific need to suppress p53 responses, a hypothesis supported by the data obtained in our mouse model. To measure miR-126 at single cell resolution, we stably transduced primary AML blasts (n=5 diseases) with a lentiviral miR-126 reporter vector, xenotransplanted them into NSG mice and quantified miR-126 activity by FACS in the engrafted cells recovered from the mice's bone marrow. Across different genetic subgroups including CBF leukemia, cells with the highest miR-126 activity were enriched in the CD34+ or CD34+CD38- fractions, consistent with LSC. To facilitate prospective LSC isolation based on miRNA activity, we screened a series of combination miRNA reporters incorporating response elements for LSC-enriched and LSC-depleted miRNAs and have now identified an optimized construct that highlights easily sortable, distinct subpopulations that are currently undergoing functional validation. Applying this tool to AML with complex and monosomal karyotype, we are addressing whether high miR-126 expression refers to elevated LSC frequency or is a specific feature of this clinically relevant AML entity. We next applied the miR-126 reporter to n=15 primary, human B-ALL measuring miR-126 activity in the xenograft. Surprisingly, we identified well-separated blast subpopulations that differed in miR-126 activity within single diseases. Heterogeneity for miR-126 appeared to be a general feature of B-ALL as we detected 2-3 subpopulations in most of the diseases studied. We purified miR-126(high) and miR-126(low) B-ALL subpopulations from the primografts and verified up to 1log differences in miR-126 expression, while we detected equal levels of the BCR-ABL fusion transcript in all subpopulations from Philadelphia+ B-ALL confirming their neoplastic nature. When transplanting miR-126(high) and miR-126(low) subpopulations into secondary or tertiary recipients, post-sorting miR-126 levels were tightly maintained indicating that miR-126 levels were static rather than dynamically regulated in distinct B-ALL subpopulations, as expected from a subclonal architecture. RNAseq performed on miR-126(high) and miR-126(low) human B-ALL fractions evidenced a miR-126 signature reminiscent of the one obtained in the B-ALL mouse model and cord blood CD34+ cells, uncovering physiological miR-126 activity in human primary B-ALL. Taken together, these data support a broad, pathogenetically important role for miR-126 in human AML and B-ALL that goes beyond LSC and open up opportunities to better understand leukemia disease biology, dissect intratumoral heterogeneity and therapeutically target resistant and refractory disease, considering that miR-126 knockdown expands normal HSC while depleting the leukemia. Disclosures Ciceri: MolMed SpA: Consultancy.

We have recently shown that miR-126 expression faithfully identifies the engrafting fraction of bone marrow (BM) and cord blood (Gentner et al, Sci Transl Med 2010), in which it regulates hematopoietic stem cell (HSC) pool size by modulating cell cycle progression (Lechman et al., Cell Stem Cell 2012). Antagonizing miR-126 expands HSC by enhancing PI3K/AKT signaling, without causing their exhaustion or transformation. By reconstituting mice with lentivirally transduced BM cells ectopically expressing miR-126, we noted differential effects in HSC and progenitors: while miR-126 overexpressing (126OE) HSC were more quiescent and outcompeted by HSC with physiologic miR-126 expression, progenitor subsets were increased in number and proliferated more upon 126OE. In particular, B lymphopoiesis was enhanced, with the appearance of 126OE-vector marked, CD45(low)CD19+Ig(-) B cell progenitors in the peripheral blood. This abnormal population was transiently observed in all 126OE (n=45), but in none of the control mice (n=30), and BM B cell precursors and progenitors from 126OE mice showed significantly reduced levels of apoptosis, as well as a differentiation block at the immature B cell stage. At least part of this effect was due to interference of miR-126 with p53 activation. Consequentially, 20-30% of 126OE mice (as compared to 0% of control mice) followed over 1 year developed vector-marked, high-grade B-cell neoplasms which resembled diffuse large B-cell lymphoma, lymphoblastic lymphoma or acute lymphoblastic leukemia (ALL). Strikingly, by using a tetracycline-regulated, conditional miR-126OE vector, we observed full regression of the expanded abnormal B cell population after switching miR-126 expression off by doxycycline administration, demonstrating that miR-126 is an oncogenic driver in hematologic malignancies. To establish the relevance of miR-126 in human disease, we studied primary samples from patients with acute leukemia. We measured miR-126 expression in blasts from 12 adult patients with acute lymphoblastic leukemia (ALL). miR-126 was highly expressed in all studied cases of ALL (Phil+: n=7, Phil-: n=5), often surpassing the levels found in normal HSC. Unlike in HSC, miR-126 expression was independent from expression of its host gene EGFL7, suggesting an ALL-specific regulation of the miR-126 locus. By exploiting a lentiviral miR-126 reporter vector, we quantified miR-126 activity with single cell resolution after xenotransplantation of miR-126 reporter vector transduced ALL blasts into NSG mice. In 7 out of 12 ALL cases, we identified distinct subpopulations exhibiting different levels of miR-126 activity, and miR-126 (hi) ALL cells were more frequently contained in the CD34+ cell fraction. Moreover, high miR-126 expression correlated with faster and higher ALL engraftment in NSG mice. In acute myeloid leukemia (AML), miR-126 is significantly enriched in leukemic stem cells (LSC) where it governs quiescence and chemotherapy resistance (see abstract by Lechman et al), and analogous studies in ALL are ongoing. To further substantiate the role of miR-126 in AML, we studied miR-126 activity in 11 primary AML cases (4 AML with CBF, core binding factor, mutations; 7 AML with normal karyotype) using the reporter vector technology and the NSG xenotransplantation model. Globally, we found highest miR-126 activity in CBF-mutated AML. However, there was substantial heterogeneity in subpopulations of each single disease. Significantly higher miR-126 levels were found in CD34+, and particularly in CD34+CD38- AML cells, a fraction that is enriched for LSC. To see whether there is a correlation between miR-126 expression and disease progression, we measured miR-126 levels in sorted blasts from paired diagnosis/relapse (n=6) and diagnosis/chemotherapy-refractory (n=8) patient samples. Strikingly, we found a significant up-regulation of miR-126 in the disease progression sample, suggesting a mechanistic role for miR-126 in AML persistence after chemotherapy. In summary, these data support a clinically relevant role of miR-126 in the pathogenesis, treatment response and progession of acute leukemias. Authors AG and SN contributed equally, and LN and BG contributed equally. Disclosures: No relevant conflicts of interest to declare.

Rationale & Hypothesis: Combretastatin A-4-phosphate (CA-4-P), a tubulin-binding, vascular-disrupting agent (VDA), induces rapid and selective tumor vascular shutdown and secondary tumor cell death. However, acute revascularization contributes to treatment resistance. A group of myeloid cells in tumors, tumor associated macrophages (TAMs) are known to drive angiogenesis and tumor progression. A potently pro-angiogenic subpopulation of TAMs has also been identified – Tie2 expressing monocytes (TEMs). We hypothesize that TAMs and/or TEMs infiltrate CA-4-P-treated tumors and promote tumor recovery. Methodology, Results & Conclusions: Late-stage Polyoma Middle T (PyMT) spontaneous murine breast adenocarcinomas were excised from CA-4-P- and saline-treated mice. Significant tumor necrosis was evident 24h following a single injection of 50mg/kg CA-4-P (19.37 ± 4.60%) compared with saline controls (1.76 ± 0.34%). This was accompanied by tumor infiltration of F4/80+ TAMs (5.61 ± 0.46% of tumor volume w.r.t. 0.71± 0.08% in controls). Significant increases in the number of MMP-9 expressing macrophages, primarily TEMs, were evident following CA-4-P treatment (5.72 ± 0.34% compared with 2.66 ± 0.25% in controls). TEMs were constitutive expressers of hypoxia-regulated CXCR4, which interacts via CXCL12 as a monocyte/macrophage chemoattractant. AMD3100, a chemical antagonist of CXCR4, was employed in combination with CA-4-P to prevent TEM recruitment into drug-treated tumors. TEM numbers were significantly depleted, which corresponded to heightened vascular damage (27% tumor necrosis w.r.t. 8% in CA-4-P alone). These results were replicated in a subcutaneous N202 murine mammary carcinoma model following 3 daily doses of 50mg/kg CA-4-P. Tumor growth was also significantly reduced at 72h in the combined treatment group (mean tumor volume ∼200mm3 w.r.t. ∼300mm3 in CA-4-P alone). In addition, specific TEM depletion was achieved in the N202 carcinoma model via genetic manipulation and bone marrow transplantation. Tumor necrosis was increased significantly when CA-4-P was administered in combination with TEM depletion (22.45%), compared to saline controls (0.37%) and CA-4-P therapy alone (12.89%). This was attributed to a significant reduction in MMP-9 positive TEMs (0.08 ± 0.18% compared with 1.37 ± 0.21% in saline controls and 3.67± 0.11% in CA-4-P treated tumors). Collectively, these data suggest that TEMs protect against CA-4-P or promote recovery of tumors following CA-4-P treatment. Therefore, targeting TEMs, in combination with vascular-disrupting agents such as CA-4-P may provide a novel therapeutic strategy for solid tumors. A.F. Welford was funded by a Cancer Research UK PhD studentship. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2849. doi:10.1158/1538-7445.AM2011-2849