Transplantation of human acute myeloid leukemia (AML) cells in immunodeficient mice reveals altered cell surface phenotypes and expression of human endothelial markers

A robust and rapid xenograft model to assess efficacy of chemotherapeutic agents for human acute myeloid leukemia

Relevant preclinical mouse models are crucial to screen new therapeutic agents for acute myeloid leukemia (AML). Current in vivo models based on the use of patient samples are not easy to establish and manipulate in the laboratory. Our objective was to develop robust xenograft models of human AML using well-characterized cell lines as a more accessible and faster alternative to those incorporating the use of patient-derived AML cells. Five widely used AML cell lines representing various AML subtypes were transplanted and expanded into highly immunodeficient non-obese diabetic/LtSz-severe combined immunodeficiency IL2Rγ_c^null mice (for example, cell line-derived xenografts). We show here that bone marrow sublethal conditioning with busulfan or irradiation has equal efficiency for the xenotransplantation of AML cell lines. Although higher number of injected AML cells did not change tumor engraftment in bone marrow and spleen, it significantly reduced the overall survival in mice for all tested AML cell lines. On the basis of AML cell characteristics, these models also exhibited a broad range of overall mouse survival, engraftment, tissue infiltration and aggressiveness. Thus, we have established a robust, rapid and straightforward in vivo model based on engraftment behavior of AML cell lines, all vital prerequisites for testing new therapeutic agents in preclinical studies.

Nilotinib and imatinib are comparably effective in reducing growth of human eosinophil leukemia cells in a newly established xenograft model

We developed a xenograft model of human Chronic Eosinophilic Leukemia (CEL) to study disease progression and remission-induction under therapy with tyrosine kinase inhibitors using imatinib and nilotinib as examples. The FIP1L1/PDGFRA+ human CEL cell lineEOL-1 was injected intravenously into scid mice, and MR imaging and FACS analysis of mouse blood samples were performed to monitor disease development and the effects of imatinib and nilotinib. Organ infiltration was analyzed in detail by immunohistochemistry after sacrifice. All animals developed CEL and within one week of therapy, complete remissions were seen with both imatinib and nilotinib, resulting in reduced total tumor volumes by MR-imaging and almost complete disappearance of EOL-1 cells in the peripheral blood and in tissues. The new model system is feasible for the evaluation of new tyrosine kinase inhibitors and our data suggest that nilotinib may be a valuable additional targeted drug active in patients with FIP1L1/PDGFRA+ CEL.

The presence of JAK2V617F mutation in the liver endothelial cells of patients with Budd-Chiari syndrome

Patients with myeloproliferative disorders are at a high risk of developing thrombotic events. Several investigators have hypothesized that endothelial cell (EC) abnormalities might contribute to this prothrombotic state. Budd-Chiari syndrome (BCS) and portal vein thrombosis have been reported to be associated with JAK2V617F-positive hematopoiesis. We explored whether JAK2V617F was present in ECs in the vessels of polycythemia vera (PV) patients with BCS using laser capture microdissection followed by nested polymerase chain reaction or reverse-transcribed polymerase chain reaction. The ECs of the 2 BCS patients with PV were homozygous for the JAK2V617F and were shown to express transcripts characteristic of ECs but not hematopoietic cells. ECs of the other BCS patient with PV and 2 patients with hepatoportal sclerosis without PV contained exclusively wild-type JAK2. The presence of JAK2V617F in both ECs and hematopoietic cells belonging to BCS patients with PV indicate that ECs in PV are involved by the malignant process and that in a subpopulation of the patients the disease might originate from a common cell of origin for hematopoietic and ECs.

The aorta-gonad-mesonephros-derived stroma cell line DAS104-4 induces differentiation of leukemic cells

While critical steps in the regulation of leukemia cell development have been intensively studied in recent years, less is known about the interactions of leukemic cells with their stroma. Previously, we have shown that human acute myeloid leukemia (AML) cells differentiate upon injection into murine blastocysts. We here describe that human AML Kasumi-1 cells, cocultured with murine aorta-gonad-mesonephros (AGM) region-derived DAS104-4 stromal cells, decrease proliferation and colony formation efficiency; and up-regulate myelo-monocytic cell surface markers. Gene expression analysis showed decreased transcription of the AML1-ETO fusion gene and increased transcription of p16 (INK4A), p21 (WAF1) and C/EBPalpha genes. Coculture can induce myeloid differentiation also in patient-derived AML cells. Our findings strengthen the notion that the embryonic milieu can regulate the proliferation and differentiation of leukemic cells.

Xenograft models for the preclinical evaluation of new therapies in acute leukemia

Major advances in understanding the pathophysiology of acute leukemia have resulted in a dramatic increase in the availability of novel compounds for clinical trials. However, since the number of new drugs far exceeds the number of clinical trials that can be conducted because of the availability of eligible patients, there is an urgent need to utilize reliable preclinical models for the prioritization of the most promising potential therapies for those clinical trials. The most widely used preclinical models for the acute leukemias are human tumor xenografts established in immune-deficient mice, and genetically engineered mouse strains. This review summarizes the recent developments and considerations in the use of xenograft models of acute lymphoblastic leukemia, acute myeloid leukemia, and acute promyelocytic leukemia for the preclinical testing of new therapies.

Establishment of a novel childhood acute myeloid leukaemia cell line, KOPM-88, containing partial tandem duplication of the MLL gene and an in vivo model for childhood acute myeloid leukaemia using NOD/SCID mice

MLL gene rearrangement is common in both adult and childhood acute myeloid leukaemia (AML), and its role in oncogenesis has been investigated. While over 50 translocated-partner genes have been identified so far, few studies have detailed the molecular mechanism of partial tandem duplication (PTD) of the MLL gene. The prognostic impact and contribution to leukaemogenesis of MLL-PTD, especially in childhood cases, remain unknown. We have established a novel cell line containing MLL-PTD derived from an 11-year-old patient with AML and designated as KOPM-88. KOPM-88 cells exhibited certain characteristics associated with the myeloid lineage including abundant primary granules in the cytoplasm and the expression of myeloperoxidase. The cell growth of KOPM-88 was cytokine independent but was accelerated by granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor. MLL-PTD of exon 2 to exon 6 and exon 2 to exon 8 was revealed using Southern blotting, fluorescence in situ hybridisation, and reverse transcription polymerase chain reaction/DNA sequencing. Furthermore, non-obese diabetic/severe combined immunodeficient mice inoculated with KOPM-88 cells exhibited leukaemic infiltrations in the bone marrow and hemiparalysis because of compression myelopathy. This is the first report of an in vivo animal model exhibiting the systemic involvement of childhood AML containing MLL-PTD. KOPM-88 cells and our murine model may be useful for investigating the pathogenesis of childhood AML associated with MLL gene rearrangement.

Expression of Tie-2 and Other Receptors for Endothelial Growth Factors in Acute Myeloid Leukemias Is Associated with Monocytic Features of Leukemic Blasts

We investigated the expression of Tie-2 in primary blasts from 111 patients with acute myeloid leukemia (AML) to evaluate a possible linkage between the expression of this receptor and the immunophenotypic and biologic properties of leukemic blasts. Tie-2 was expressed at moderate and high levels in 39 and 23 of 111 AMLs, respectively. The analysis of the immunophenotype clearly showed that Tie-2 expression in AML was associated with monocytic features. Interestingly, Tie-2 expression on AML blasts was associated with concomitant expression of other receptors for endothelial growth factors, such as vascular endothelial growth factor receptor 1 (VEGF-R1), -R2, and -R3. Tie-2(+) AMLs were characterized by high blast cell counts at diagnosis, a high frequency of Flt3 mutations, and increased Flt3 expression. The survival of Tie-2(+) AMLs is sustained through an autocrine pattern involving Angiopoietin-1 and Tie-2, as suggested by experiments showing induction of apoptosis in Tie-2(+) AMLs by agents preventing the binding of angiopoietins to Tie-2. Finally, the in vitro growth of Tie-2(+) AMLs in endothelial culture medium supplemented with VEGF and angiopoietins resulted in their partial endothelial differentiation. These observations suggest that Tie-2(+) AMLs pertain to a mixed monocytic/endothelial lineage, derived from the malignant transformation of the normal counterpart represented by monocytic cells expressing endothelial markers. The autocrine angiopoietin/Tie-2 axis may represent a promising therapeutic target to improve the outcome of patients with monocytic AML. Disclosure of potential conflicts of interest is found at the end of this article.

Treatment of lycorine on SCID mice model with human APL cells

In our previous study, lycorine, a natural alkaloid extracted from Amaryllidaceae, exhibited anti-leukemia effects in vitro. To determine whether lycorine has an anti-tumor effect in vivo, a series of experiments were carried out in this study. HL-60 cells (5 × 10⁶) were inoculated i.v. into severe combined immuno-deficiency (SCID) mice after these mice had been irradiated (total body receiving 200 cGy χ irradiation). Treatment was given once a day from day 2 to 6, and from day 14 to 18. Lycorine (5 or 10 mg/kg/day i.p.) was found to decrease the percentages of immature granular leukocytes and of monocytes among the peripheral blood cells, and the mean survival time of both lycorine-treated groups was longer than that of the control group. Compared with the asynchronous and cytosine arabinoside- (Ara-C) treated (20 mg/kg/day i.p.) group, treatment with lycorine was more effective. Lycorine was also found to alleviate the infiltration of tumor cells into the liver, bone, and marrow. When SCID mice inoculated with HL-60 cells were then treated with lycorine, no severe adverse effects were observed. This study revealed that lycorine, when tested in the human leukemia xenograft models, appears to exhibit anti-tumor activity in vivo and is a useful therapy against acute promyelocytic leukemia.