Asynchronous expression of myeloid antigens in leukemic cells in a PML/RARalpha transgenic mouse model

PML/RARa leukemia induced murine model for immunotherapy evaluation

Even though leukemia murine models are valuable tools for new drug therapy studies, most of these models consist of immunocompromised mice, which do not exhibit immune responses. In order to obtain an adequate leukemia model, we established an acute promyelocytic leukemia transplantation-based model (PML/RARa) in immunocompetent BALB/c mice, thus making it possible to study drug-induced cellular immune responses in leukemia. The development of PML/RARa leukemia was confirmed by leukocytosis (76.27 ± 21.8 vs. 3.40 ± 1.06; P < 0.0001), anemia (7.46 ± 1.86 vs. 15.10 ± 0.96; P < 0.0001), and thrombocytopenia (131.85 ± 39.32 vs. 839.50 ± 171.20; P < 0.0001), and the presence of blasts in the peripheral blood of mice (approximately 50% blasts; P < 0.0001), 15 days after the transplants. These findings were corroborated through differential counts, flow cytometry, and in vivo imaging, which indicated increased number of immature cells in the bone marrow (15.75 ± 3.30 vs 6.69 ± 0.55; P < 0.001), peripheral blood (7.88 ± 2.67 vs 1.22 ± 0.89; P < 0.001), and spleen (35.21 ± 4.12 vs 1.35 ± 0.86; P < 0.0001), as well as promyelocytes in the bone marrow (41.23 ± 4.80 vs 5.73 ± 1.50; P < 0.0001), peripheral blood (46.08 ± 7.52 vs 1.10 ± 0.59; P < 0.0001) and spleen (35.31 ± 8.26 vs 2.49 ± 0.29; P < 0.0001) of PML/RARa mice. Compared to basal conditions of untransplanted mice, the PML/RARa mice exhibited frequencies of T lymphocytes CD4 helper = 14.85 ± 2.91 vs 20.77 ± 2.9 in the peripheral blood (P < 0.05); 12.75 ± 1.33 vs 45.90 ± 2.02 in the spleen (P < 0.0001); CD8 cytotoxic = 11.27 ± 3.44 vs 11.05 ± 1.22 in the peripheral blood (P > 0.05); 10.48 ± 1.16 vs 30.02 ± 1.80 in the spleen (P < 0.0001); natural killer (NK) cells = 3.68 ± 1.35 vs 6.84 ± 0.52 in the peripheral blood (P < 0.001); 4.43 ± 0.57 vs 6.40 ± 1.14 in the spleen (P < 0.05); B cells 2.50 ± 0.60 vs 15.20 ± 5.34 in the peripheral blood (P < 0.001); 17.77 ± 4.39 vs 46.90 ± 5.92 in the spleen (P < 0.0001); neutrophils = 5.97% ± 1.88 vs 31.57 ± 9.14 (P < 0.0001); and monocytes = 6.45 ± 2.97 vs 15.85 ± 2.57 (P < 0.001), selected as classical (3.33 ± 3.40 vs 57.80 ± 16.51, P < 0.0001), intermediate (57.42 ± 10.61 vs 21.75 ± 5.90, P < 0.0001), and non-classical monocytes (37.51 ± 10.85 vs 18.08 ± 7.13, P < 0.05) in the peripheral blood; and as classically activated (M1) within in the bone marrow (3.70 ± 0.94 vs 1.88 ± 0.39, P < 0.05) and spleen 15.19 ± 3.32 vs 9.47 ± 1.61, P < 0.05), in addition to alternatively activated (M2) macrophages within the bone marrow (23.06 ± 5.25 vs 1.76 ± 0.74, P < 0.0001) and spleen (46.51 ± 11.18 vs 30.58 ± 2.64, P < 0.05) compartments. All-trans retinoic acid (ATRA) treatment of PML/RARa mice reduced blast (immature cells) in the bone marrow (8.62 ± 1.81 vs 15.76 ± 1.25; P < 0.05) and spleen (8.75 ± 1.31 vs 35.21 ± 1.55; P < 0.0001) with no changes in the peripheral blood (10.13 ± 3.33 vs 7.88 ± 1.01; P > 0.05), as well as reduced promyelocytes in the bone marrow (19.79 ± 4.84 vs 41.23 ± 1.81; P < 0.05), peripheral blood (31.65 ± 3.92 vs 46.09 ± 2.84; P < 0.05) and spleen (24.84 ± 2.03 vs 41.46 ± 2.39; P < 0.001), and increased neutrophils of the peripheral blood (35.48 ± 7.24 vs 7.83 ± 1.40; P < 0.05) which was corroborated by reducing of immature cells and increase of neutrophil in the stained smears from PML/RARa mice, thus confirming that this model can be used in drug development studies. Our results show the effective induction of PML/RARa leukemia in BALB/c mice, thus producing a low-priced and reliable tool for investigating cellular immune responses in leukemia.

(-)-Epigallocatechin-3-gallate induces apoptosis and differentiation in leukaemia by targeting reactive oxygen species and PIN1

(-)-Epigallocatechin-3-gallate (EGCG), the major active polyphenol extracted from green tea, has been shown to induce apoptosis and inhibit cell proliferation, cell invasion, angiogenesis and metastasis. Herein, we evaluated the in vivo effects of EGCG in acute myeloid leukaemia (AML) using an acute promyelocytic leukaemia (APL) experimental model (PML/RARα). Haematological analysis revealed that EGCG treatment reversed leucocytosis, anaemia and thrombocytopenia, and prolonged survival of PML/RARα mice. Notably, EGCG reduced leukaemia immature cells and promyelocytes in the bone marrow while increasing mature myeloid cells, possibly due to apoptosis increase and cell differentiation. The reduction of promyelocytes and neutrophils/monocytes increase detected in the peripheral blood, in addition to the increased percentage of bone marrow cells with aggregated promyelocytic leukaemia (PML) bodies staining and decreased expression of PML-RAR oncoprotein corroborates our results. In addition, EGCG increased expression of neutrophil differentiation markers such as CD11b, CD14, CD15 and CD66 in NB4 cells; and the combination of all-trans retinoic acid (ATRA) plus EGCG yield higher increase the expression of CD15 marker. These findings could be explained by a decrease of peptidyl-prolyl isomerase NIMA-interacting 1 (PIN1) expression and reactive oxygen species (ROS) increase. EGCG also decreased expression of substrate oncoproteins for PIN1 (including cyclin D1, NF-κB p65, c-MYC, and AKT) and 67 kDa laminin receptor (67LR) in the bone marrow cells. Moreover, EGCG showed inhibition of ROS production in NB4 cells in the presence of N-acetyl-L-cysteine (NAC), as well as a partial blockage of neutrophil differentiation and apoptosis, indicating that EGCG-activities involve/or are in response of oxidative stress. Furthermore, apoptosis of spleen cells was supported by increasing expression of BAD and BAX, parallel to BCL-2 and c-MYC decrease. The reduction of spleen weights of PML/RARα mice, as well as apoptosis induced by EGCG in NB4 cells in a dose-dependent manner confirms this assumption. Our results support further evaluation of EGCG in clinical trials for AML, since EGCG could represent a promising option for AML patient ineligible for current mainstay treatments.

Reactive oxygen species production triggers green tea-induced anti-leukaemic effects on acute promyelocytic leukaemia model

Green tea (GT) has been consumed as a beverage for thousands of years because of its therapeutic properties observed over time. Because there is no sufficient evidence supporting the protective role of tea intake during the development of acute myeloid leukaemia, we herein study GT extract effects on an acute promyelocytic leukaemia model. Our results demonstrated that GT reduces leucocytosis and immature cells (blasts) in peripheral blood, bone marrow (BM), and spleen of leukaemic mice, parallel with an increase of mature cells in the BM. In addition, GT induces apoptosis of cells in the BM and spleen, confirmed by activation of caspase-3, -8 and -9; GT reduces the malignant clones CD34⁺ and CD117+ in the BM and reduces CD117+ and Gr1+ immature myeloid cells in the spleen; GT increases intracellular reactive oxygen species (ROS) in the BM Gr1+ cells while reducing CD34⁺ and CD117+ cells; GT reduces CXCR4 expression on CD34⁺ and CD117+ cells, and reduces the nuclear translocation of HIF-1α. GT has anti-proliferative effects in leukaemia in vivo by inhibiting malignant clone expansion, probably by modulating the intracellular production of ROS.

Halofuginone inhibits phosphorylation of SMAD-2 reducing angiogenesis and leukemia burden in an acute promyelocytic leukemia mouse model

Background

Halofuginone (HF) is a low-molecular-weight alkaloid that has been demonstrated to interfere with Metalloproteinase-2 (MMP-2) and Tumor Growth Factor-β (TGF-β) function and, to present antiangiogenic, antiproliferative and proapoptotic properties in several solid tumor models. Based on the fact that high levels of Vascular Endothelial Growth Factor (VEGF) and increased angiogenesis have been described in acute myeloid leukemia and associated with disease progression, we studied the in vivo effects of HF using an Acute Promyelocytic Leukemia (APL) mouse model.

Methods

NOD/SCID mice were transplanted with leukemic cells from hCG-PML/RARA transgenic mice (TM) and treated with HF 150 μg/kg/day for 21 days. The leukemic infiltration and the percentage of VEGF+ cells were evaluated by morphology and flow cytometry. The effect of HF on the gene expression of several pro- and antiangiogenic factors, phosphorylation of SMAD2 and VEGF secretion was assessed in vitro using NB4 and HUVEC cells.

Results

HF treatment resulted in hematological remission with decreased accumulation of immature cell and lower amounts of VEGF in BM of leukemic mice. In vitro, HF modulated gene expression of several pro- and antiangiogenic factors, reduced VEGF secretion and phosphorylation of SMAD2, blocking TGF-β-signaling.

Conclusion

Taken together, our results demonstrate that HF inhibits SMAD2 signaling and reduces leukemia growth and angiogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0181-2) contains supplementary material, which is available to authorized users.

Synthetic phosphoethanolamine has in vitro and in vivo anti-leukemia effects

Background:

We recently showed that synthetic phosphoethanolamine reduces tumour growth and inhibits lung metastasis in vivo. Here, we investigated its anti-leukaemia effects using acute promyelocytic leukaemia (APL) as a model.

Methods:

Cytotoxic effects of Pho-s on leukaemia cells were evaluated by MTT assay. Leukaemic cells obtained from hCG-PML-RARa transgenic mice were transplanted to NOD/SCID mice. After the animals were diagnosed as leukaemic, treatment started with Pho-s using all-trans retinoid acid or daunorubicin as positive control or and saline control. Cell morphology and immunophenotyping were used to detect the undifferentiated blast cells in the spleen, liver and bone marrow. The induction of apoptosis in vitro and in malignant leukaemic clones was evaluated.

Results:

Synthetic phosphoethanolamine is cytotoxic and induces apoptosis through the mitochondrial pathway in vitro to leukaemia cell lines. In vivo Pho-s exhibits anti-proliferative effects in APL model reducing the number of CD117⁺ and Gr-1⁺ immature myeloid cells in the BM, spleen and liver. Synthetic phosphoethanolamine impairs the expansion of malignant clones CD34⁺/CD117⁺, CD34⁺ and Gr-1⁺ in the BM. In addition, Pho-s induces apoptosis of immature cells in the spleen and liver, a notable effect.

Conclusion:

Synthetic phosphoethanolamine has anti-leukaemic effects in an APL model by inhibiting malignant clone expansion, suggesting that it is an interesting compound for leukaemia treatment.

Methionine-induced hyperhomocysteinemia reverts fibrinolytic pathway activation in a murine model of acute promyelocytic leukemia

Increased fibrinolysis is an important component of acute promyelocytic leukemia (APL) bleeding diathesis. APL blasts overexpress annexin II (ANXII), a receptor for tissue plasminogen activator (tPA), and plasminogen, thereby increasing plasmin generation. Previous studies suggested that ANXII plays a pivotal role in APL coagulopathy. ANXII binding to tPA can be inhibited by homocysteine and hyperhomocysteinemia can be induced by L-methionine supplementation. In the present study, we used an APL mouse model to study ANXII function and the effects of hyperhomocysteinemia in vivo. Leukemic cells expressed higher ANXII and tPA plasma levels (11.95 ng/mL in leukemic vs 10.74 ng/mL in wild-type; P = .004). In leukemic mice, administration of L-methionine significantly increased homocysteine levels (49.0 μmol/mL and < 6.0 μmol/mL in the treated and nontreated groups, respectively) and reduced tPA levels to baseline concentrations. The latter were also decreased after infusion of the LCKLSL peptide, a competitor for the ANXII tPA–binding site (11.07 ng/mL; P = .001). We also expressed and purified the p36 component of ANXII in Pichia methanolica. The infusion of p36 in wild-type mice increased tPA and thrombin-antithrombin levels, and the latter was reversed by L-methionine administration. The results of the present study demonstrate the relevance of ANXII in vivo and suggest that methionine-induced hyperhomocysteinemia may reverse hyperfibrinolysis in APL.

(+)α-Tocopheryl succinate inhibits the mitochondrial respiratory chain complex I and is as effective as arsenic trioxide or ATRA against acute promyelocytic leukemia in vivo

The vitamin E derivative (+)α-tocopheryl succinate (α-TOS) exerts pro-apoptotic effects in a wide range of tumors and is well tolerated by normal tissues. Previous studies point to a mitochondrial involvement in the action mechanism; however, the early steps have not been fully elucidated. In a model of acute promyelocytic leukemia (APL) derived from hCG-PML-RARα transgenic mice, we demonstrated that α-TOS is as effective as arsenic trioxide or all-trans retinoic acid, the current gold standards of therapy. We also demonstrated that α-TOS induces an early dissipation of the mitochondrial membrane potential in APL cells and studies with isolated mitochondria revealed that this action may result from the inhibition of mitochondrial respiratory chain complex I. Moreover, α-TOS promoted accumulation of reactive oxygen species hours before mitochondrial cytochrome c release and caspases activation. Therefore, an in vivo antileukemic action and a novel mitochondrial target were revealed for α-TOS, as well as mitochondrial respiratory complex I was highlighted as potential target for anticancer therapy.