Long non-coding RNA expression profile in cytogenetically normal acute myeloid leukemia identifies a distinct signature and a new biomarker in NPM1-mutated patients.

Long non-coding RNAs are defined as transcripts larger than 200 nucleotides but without protein-coding potential. There is growing evidence of the important role of long non-coding RNAs in cancer initiation, development and progression. In this study, we sought to evaluate the long non-coding RNA expression profile of patients with cytogenetically normal acute myeloid leukemia (AML). RNA-sequencing of 40 cytogenetically normal AML patients allowed us to quantify 11,036 long non-coding RNAs. Among these, more than 8000 were previously undescribed long non-coding RNAs. Using unsupervised analysis, we observed a specific long non-coding RNA expression profile dependent on the mutational status of the NPM1 gene. Statistical analysis allowed us to identify a minimal set of 12 long non-coding RNAs capable of discriminating NPM1-mutated from NPM1-wild-type patients. These results were validated by qRT-PCR on an independent cohort composed of 134 cytogenetically normal AML patients. Furthermore, we have identified one putative biomarker, the long non-coding RNA XLOC_109948 whose expression pattern predicts clinical outcome. Interestingly, low XLOC_109948 expression indicates a good prognosis especially for NPM1-mutated patients. Transient transfection of GapmeR against XLOC_109948 in NPM1-mutated OCI-AML3 cell line treated with Ara-C or ATRA enhances apoptosis suggesting XLOC_109948 plays a role in drug sensitivity. This study improves our knowledge of the long non-coding RNA transcriptome in cytogenetically normal AML patients. We observed a distinct long non-coding RNA expression profile in patients with the NPM1 mutation. The newly identified XLOC_109948 long non-coding RNA emerged as a strong prognostic factor able to better stratify NPM1-mutated patients.

Bendamustine for relapsed blastic plasmacytoid dendritic cell leukaemia.

Optimal treatment of blastic plasmacytoid dendritic cell neoplasm (BPDCN), a rare entity of dismal prognosis previously described as CD4+/CD56+ hematodermic malignancies, is not defined. We report five cases of relapsed BPDCN treated with bendamustine hydrochloride, a well-tolerated bifunctional drug acting as an alkylating and antimetabolite agent. All patients were above the age of 50 years and in advanced disease (early first relapse in two, subsequent relapse in three; multi-organ involvement in four; previous intensive chemotherapy in five; and stem cell transplantation in four). Four patients were evaluable for response. Two failed therapy, one died from tumor lysis syndrome after rapid blast clearance from blood, and one reached and maintained complete remission for 7 months. Bendamustine should be further evaluated in BPDCN. Copyright © 2015 John Wiley & Sons, Ltd.

Time from diagnosis to intensive chemotherapy initiation does not adversely impact the outcome of patients with acute myeloid leukemia.

In acute myeloid leukemia (AML), new strategies assess the potential benefit of genetically targeted therapy at diagnosis. This implies waiting for laboratory tests and therefore a delay in initiation of chemotherapy. We studied the impact of time from diagnosis to treatment (TDT) on overall survival, early death, and response rate in a retrospective series of 599 newly diagnosed AML patients treated by induction chemotherapy between 2000 and 2009. The effect of TDT was assessed using multivariate analysis. TDT was analyzed as a continuous variable using a specific polynomial function to model the shape and form of the relationship. The median TDT was 8 days (interquartile range, 4-16) and was significantly longer in patients with a white blood cell count (WBC) <50 Giga per liter (G/L) (P < .0001) and in older patients (P = .0004). In multivariate analysis, TDT had no impact on overall survival (P = .4095) compared with age >60 years, secondary AML, WBC >50 G/L, European LeukemiaNet risk groups, and Eastern Cooperative Oncology Group performance status. Furthermore, TDT was not associated with response rate and early death. Thus, waiting a short period of time for laboratory tests to characterize leukemias better and design adapted therapeutic strategies at diagnosis seems possible.

The cell cycle regulator CDC25A is a target for JAK2V617F oncogene.

The JAK2(V617F) mutation is present in the majority of patients with polycythemia vera and one-half of those with essential thrombocythemia and primary myelofibrosis. JAK2(V617F) is a gain-of-function mutation resulting in constitutive JAK2 signaling involved in the pathogenesis of these diseases. JAK2(V617F) has been shown to promote S-phase entry. Here, we demonstrate that the CDC25A phosphatase, a key regulator of the G1/S cell-cycle transition, is constitutively overexpressed in JAK2(V617F)-positive cell lines, JAK2-mutated patient CD36(+) progenitors, and in vitro-differentiated proerythroblasts. Accordingly, CDC25A is overexpressed in BM and spleen of Jak2(V617F) knock-in mice compared with wild-type littermates. By using murine FDC-P1-EPOR and human HEL and SET-2 cell lines, we found that JAK2(V617F)-induced CDC25A up-regulation was caused neither by increased CDC25A transcription or stability nor by the involvement of its upstream regulators Akt and MAPK. Instead, our results suggest that CDC25A is regulated at the translational level through STAT5 and the translational initiation factor eIF2α. CDC25A inhibition reduces the clonogenic and proliferative potential of JAK2(V617F)-expressing cell lines and erythroid progenitors while moderately affecting normal erythroid differentiation. These results suggest that CDC25A deregulation may be involved in hematopoietic cells expansion in JAK2(V617F) patients, making this protein an attracting potential therapeutic target.

Hemophagocytic syndrome in patients with acute myeloid leukemia undergoing intensive chemotherapy.

Hemophagocytic lymphohistiocytosis is a condition of immune dysregulation characterized by severe organ damage induced by a hyperinflammatory response and uncontrolled T-cell and macrophage activation. Secondary hemophagocytic lymphohistiocytosis typically occurs in association with severe infections or malignancies. Patients with acute myeloid leukemia may be prone to develop hemophagocytic lymphohistiocytosis because of an impaired immune response and a high susceptibility to severe infections. In a series of 343 patients treated by intensive chemotherapy over a 5-year period in our center, we identified 32 patients (9.3%) with fever, very high ferritin levels, and marrow hemophagocytosis (i.e. patients with hemophagocytic lymphohistiocytosis). Compared to patients without hemophagocytic lymphohistiocytosis, these 32 patients had hepatomegaly, pulmonary or neurological symptoms, liver abnormalities, lower platelet count and higher levels of C-reactive protein as well as prolonged pancytopenia. A microbial etiology for the hemophagocytosis was documented in 24 patients: 14 bacterial infections, 9 Herpesviridae infections and 11 fungal infections. The treatment of hemophagocytic lymphohistiocytosis consisted of corticosteroids and/or intravenous immunoglobulins along with adapted antimicrobial therapy. Patients with hemophagocytic lymphohistiocytosis had a median overall survival of 14.9 months, which was significantly shorter than that of patients without hemophagocytic lymphohistiocytosis (22.1 months) (P=0.0016). Hemophagocytic lymphohistiocytosis was significantly associated with a higher rate of induction failure, mainly due to deaths in aplasia. Hemophagocytic lymphohistiocytosis can be diagnosed in up to 10% of patients with acute myeloid leukemia undergoing intensive chemotherapy and is associated with early mortality. Fever, very high ferritin levels and marrow hemophagocytosis represent the cornerstone of the diagnosis. Further biological studies are needed to better characterize and recognize this syndrome in patients with acute myeloid leukemia.

Identification of a transforming MYB-GATA1 fusion gene in acute basophilic leukemia: a new entity in male infants.

Acute basophilic leukemia (ABL) is a rare subtype of acute leukemia with clinical features and symptoms related to hyperhistaminemia because of excessive growth of basophils. No known recurrent cytogenetic abnormality is associated with this leukemia. Rare cases of t(X;6)(p11;q23) translocation have been described but these were sporadic. We report here 4 cases of ABL with a t(X;6)(p11;q23) translocation occurring in male infants. Because of its location on chromosome 6q23, MYB was a good candidate gene. Our molecular investigations, based on fluorescence in situ hybridization and rapid amplification of cDNA ends, revealed that the translocation generated a MYB-GATA1 fusion gene. Expression of MYB-GATA1 in mouse lineage-negative cells committed them to the granulocyte lineage and blocked at an early stage of differentiation. Taken together, these results establish, for the first time, a link between a recurrent chromosomal translocation and the development of this particular subtype of infant leukemia.

Conditional TPM3-ALK and NPM-ALK transgenic mice develop reversible ALK-positive early B-cell lymphoma/leukemia.

NPM-ALK (nucleophosmin-anaplastic lymphoma kinase) and TPM3-ALK (nonmuscular tropomyosin 3-anaplastic lymphoma kinase) are oncogenic tyrosine kinases implicated in the pathogenesis of human ALK-positive lymphoma. We report here the development of novel conditional mouse models for ALK-induced lymphomagenesis, with the use of the tetracycline regulatory system under the control of the EmuSRalpha enhancer/promoter. The expression of either oncogene resulted in the arrest of the differentiation of early B cells and lymphomagenesis. We also observed the development of skin keratoacanthoma lesions, probably because of aberrant ALK expression in keratinocytes. The inactivation of the ALK oncogene on doxycycline treatment was sufficient to induce sustained regression of both hematopoietic tumors and skin disease. Importantly, treatment with the specific ALK inhibitor (PF-2341066) also reversed the pathologic states, showing the value of these mouse models for the validation of ALK tyrosine kinase inhibitors. Thus, our results show (1) that NPM-ALK and TPM3-ALK oncogenes are sufficient for lymphoma/leukemia development and required for tumor maintenance, hence validating ALK as potentially effective therapeutic target; and (2) for the first time, in vivo, the equal tumorigenic potential of the NPM-ALK and TPM3-ALK oncogenic tyrosine kinases. Our models offer a new tool to investigate in vivo the molecular mechanisms associated with ALK-induced lymphoproliferative disorders.

High levels of CD34+CD38low/-CD123+ blasts are predictive of an adverse outcome in acute myeloid leukemia: a Groupe Ouest-Est des Leucemies Aigues et Maladies du Sang (GOELAMS) study.

BACKGROUND: Acute myeloid leukemias arise from a rare population of leukemic cells, known as leukemic stem cells, which initiate the disease and contribute to frequent relapses. Although the phenotype of these cells remains unclear in most patients, these cells are enriched within the CD34(+)CD38(low/-) compartment expressing the interleukin-3 alpha chain receptor, CD123. The aim of this study was to determine the prognostic value of the percentage of blasts with the CD34(+)CD38(low/-)CD123(+) phenotype. DESIGN AND METHODS: The percentage of CD34(+)CD38(low/-)CD123(+) cells in the blast population was determined at diagnosis using flow cytometry. One hundred and eleven patients under 65 years of age with de novo acute myeloid leukemia and treated with intensive chemotherapy were retrospectively included in the study. Correlations with complete response, disease-free survival and overall survival were evaluated with univariate and multivariate analyses. RESULTS: A proportion of CD34(+)CD38(low/-)CD123(+) cells greater than 15% at diagnosis and an unfavorable karyotype were significantly correlated with a lack of complete response. By logistic regression analysis, a percentage of CD34(+)CD38(low/-)CD123(+) higher than 15% retained significance with an odds ratio of 0.33 (0.1-0.97; P=0.044). A greater than 1% population of CD34(+)CD38(low/-)CD123(+) cells negatively affected disease-free survival (0.9 versus 4.7 years; P<0.0001) and overall survival (1.25 years versus median not reached; P<0.0001). A greater than 1% population of CD34(+)CD38(low/-)CD123(+) cells retained prognostic significance for both parameters after multivariate analysis. CONCLUSIONS: The percentage of CD34(+)CD38(low/-)CD123(+) leukemic cells at diagnosis was significantly correlated with response to treatment and survival. This prognostic marker might be easily adopted in clinical practice to rapidly identify patients at risk of treatment failure.

Pre-eminence and persistence of immature natural killer cells in acute myeloid leukemia patients in first complete remission.

Despite substantial progress in the treatment of AML, a proportion of patients do not achieve first complete remission (1(st) CR) with the induction chemotherapy, and, among patients achieving it, a majority is expected to relapse within three years. As allogeneic hematopoietic stem cell transplantation has been established as the most effective form of antileukemic therapy in patients with AML in remission, many studies have focused on the reconstitution and the functionality of the innate immune system in this context, especially regarding cytotoxic effectors such as natural killer (NK) cells. On the contrary, very few data are available concerning the innate immune system of patients in 1st CR. Herein we investigated the phenotype of autologous NK cells of AML patients in 1st CR. We showed that immature NK cells were pre-eminent in the blood of these patients and that this immature phenotype was persistent during the first months after 1st CR.

VX-680, a potent and selective small-molecule inhibitor of the Aurora kinases, suppresses tumor growth in vivo.

The Aurora kinases are essential for the regulation of chromosome segregation and cytokinesis during mitosis. Aberrant expression and activity of these kinases occur in a wide range of human tumors, and lead to aneuploidy and tumorigenesis. Here we report the discovery of a highly potent and selective small-molecule inhibitor of Aurora kinases, VX-680, that blocks cell-cycle progression and induces apoptosis in a diverse range of human tumor types. This compound causes profound inhibition of tumor growth in a variety of in vivo xenograft models, leading to regression of leukemia, colon and pancreatic tumors at well-tolerated doses. Our data indicate that Aurora kinase inhibition provides a new approach for the treatment of multiple human malignancies.

Evaluation of Polo-like Kinase 1 inhibition on the G2/M checkpoint in Acute Myelocytic Leukaemia.

Polo-Kinase 1 (PLK1) is a key cell cycle regulator that is necessary for checkpoint recovery after DNA damage-induced G2 arrest. We have examined the effects of PLK inhibition in Acute Myelocytic Leukaemia (AML) cells, whose resistance to genotoxic agents is thought to be associated with checkpoint reinforcement. We report that in U937 AML cells, PLK1 participates in checkpoint recovery, and that inhibition of PLK by the GW843682X compound results in mitotic accumulation and apoptosis. We also found that when challenged with VP-16, inhibition of PLK1 prevented U937 cells from checkpoint exit. Finally, we found that treatment with GW843682X slightly reduced genotoxic-induced inhibition of colony formation efficiency of primary leukaemia cells (CFU-L) from AML patients.

Cell adhesion regulates CDC25A expression and proliferation in acute myeloid leukemia.

The effects of cell adhesion on leukemia cell proliferation remain poorly documented and somehow controversial. In this work, we investigated the effect of adhesion to fibronectin on the proliferation of acute myeloid leukemia (AML) cell lines (U937 and KG1a) and CD34+ normal or leukemic primary cells. We observed an increased rate of proliferation of AML cells when adhered to fibronectin, concomitant with accelerated S-phase entry and accumulation of CDC25A. Conversely, normal CD34+ cell proliferation was decreased by adhesion to fibronectin with a concomitant drop in CDC25A expression. Importantly, we showed that both small interfering RNA (siRNA)-mediated CDC25A down-regulation and a recently developed CDC25 pharmacologic inhibitor impaired this adhesion-dependent proliferation, establishing a functional link between CDC25A accumulation and adhesion-dependent proliferation in leukemic cells. CDC25A accumulation was found only slightly dependent on transcriptional regulation and essentially due to modifications of the proteasomal degradation of the protein as shown using proteasome inhibitors and reverse transcription-PCR. Interestingly, CDC25A regulation was Chk1 dependent in these cells as suggested by siRNA-mediated down-regulation of this protein. Finally, we identified activation of the phosphatidylinositol 3-kinase/Akt pathway as an adhesion-dependent regulation mechanism of CDC25A protein expression. Altogether, our data show that in leukemic cells adhesion to fibronectin increases CDC25A expression through proteasome- and Chk1-dependent mechanisms, resulting in enhanced proliferation. They also suggest that these adhesion-dependent proliferation properties of hematopoietic cells may be modified during leukemogenesis.

Dendrogenin A drives LXR to trigger lethal autophagy in cancers.

Dendrogenin A (DDA) is a newly discovered cholesterol metabolite with tumor suppressor properties. Here, we explored its efficacy and mechanism of cell death in melanoma and acute myeloid leukemia (AML). We found that DDA induced lethal autophagy in vitro and in vivo, including primary AML patient samples, independently of melanoma Braf status or AML molecular and cytogenetic classifications. DDA is a partial agonist on liver-X-receptor (LXR) increasing Nur77, Nor1, and LC3 expression leading to autolysosome formation. Moreover, DDA inhibited the cholesterol biosynthesizing enzyme 3ß-hydroxysterol-Δ8,7-isomerase (D8D7I) leading to sterol accumulation and cooperating in autophagy induction. This mechanism of death was not observed with other LXR ligands or D8D7I inhibitors establishing DDA selectivity. The potent anti-tumor activity of DDA, its original mechanism of action and its low toxicity support its clinical evaluation. More generally, this study reveals that DDA can direct control a nuclear receptor to trigger lethal autophagy in cancers.

Expression of focal adhesion kinase in acute myeloid leukemia is associated with enhanced blast migration, increased cellularity, and poor prognosis.

Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase playing an important role in cell motility and survival. However, very little is known about FAK in normal and leukemic myeloid cells. In this study, FAK protein expression and mRNA were detected in 25 of 60 cases (42%) of acute myeloid leukemia (AML). Whereas FAK was expressed in 46% of CD34+ AML cells, it was not detected in normal purified CD34+ cells. Conversely, the FAK homologue proline-rich tyrosine kinase 2 (PYK2) was found to be expressed both in normal and leukemic myeloid cells. When expressed, FAK displayed phosphorylation on Tyr-397, an important step for its activation. Moreover, FAK expression was correlated with the phosphorylation of PYK2 on Tyr-881, a critical site for the PYK2 function in cell migration. FAK+ AML cells displayed significantly higher migration capacities and resistance to daunorubicin, compared with FAK- cells. The implication of FAK in both cell motility and drug resistance was demonstrated by small interfering RNA experiments with the FAK-positive KG1 cell line. However, adhesion on fibronectin efficiently protected FAK- AML cells from daunorubicin-mediated killing, suggesting that cellular adhesion mediated-drug resistance is not mediated by FAK. Finally, in a retrospective cohort of 60 AML patients, FAK expression was significantly correlated with high blast cell count, early death, and shorter survival rate. Altogether, this study shows that FAK is aberrantly expressed and activated in about half of the cases of AML and suggests that FAK may contribute to the regulation of AML cell transit from the marrow to blood compartment and that it may influence clinical outcome.

Tumor necrosis factor alpha induces senescence and chromosomal instability in human leukemic cells.

Previous studies have documented that Tumor necrosis factor alpha (TNFalpha) is a potent negative regulator of normal hematopoiesis. However, the mechanism by which TNFalpha acts at the cellular level is not totally understood. Although apoptotic cell killing appears to be the most common cellular effect of TNFalpha, other studies suggest that this cytokine may elicit other cellular responses such as prolonged growth inhibition. In this context, we have investigated whether TNFalpha may induce senescence in hematopoietic cells, which display intrinsic defect in the apoptotic machinery. The present study described that, in the leukemic KG1 cells, TNFalpha induced no apoptosis but a senescence state characterized by prolonged growth arrest, increased beta-galactosidase activity, p21WAF-1 induction, decreased telomerase activity, telomeric disturbances (shortening, losses, fusions), and additional chromosomal aberrations. Telomerase inhibition correlated with reduced levels of hTERT transcripts. GM-CSF prevented TNFalpha effects and allowed leukemic cells to recover growth capacity. Finally, our study shows for the first time that, at least in some hematopoietic cells, TNFalpha may induce senescence with important functional consequences, including sustained growth inhibition and genetic instability, and that this cellular response is efficiently regulated by hematopoietic growth factors.

Role of ASXL1 and TP53 mutations in the molecular classification and prognosis of acute myeloid leukemias with myelodysplasia-related changes.

Acute myeloid leukemias (AML) with myelodysplasia-related changes (AML-MRC) are defined by the presence of multilineage dysplasia (MLD), and/or myelodysplastic syndrome (MDS)-related cytogenetics, and/or previous MDS. The goal of this study was to identify distinct biological and prognostic subgroups based on mutations of ASXL1, RUNX1, DNMT3A, NPM1, FLT3 and TP53 in 125 AML-MRC patients according to the presence of MLD, cytogenetics and outcome. ASXL1 mutations (n=26, 21%) were associated with a higher proportion of marrow dysgranulopoiesis (mutant vs. wild-type: 75% vs. 55%, p=0.030) and were mostly found in intermediate cytogenetic AML (23/26) in which they predicted inferior 2-year overall survival (OS, mutant vs. wild-type: 14% vs. 37%, p=0.030). TP53 mutations (n=28, 22%) were mostly found in complex karyotype AML (26/28) and predicted poor outcome within unfavorable cytogenetic risk AML (mutant vs. wild-type: 9% vs. 40%, p=0.040). In multivariate analysis, the presence of either ASXL1 or TP53 mutation was the only independent factor associated with shorter OS (HR, 95%CI: 2.53, 1.40-4.60, p=0.002) while MLD, MDS-related cytogenetics and previous MDS history did not influence OS. We conclude that ASXL1 and TP53 mutations identify two molecular subgroups among AML-MRCs, with specific poor prognosis. This could be useful for future diagnostic and prognostic classifications.

CDC25A governs proliferation and differentiation of FLT3-ITD acute myeloid leukemia.

We investigated cell cycle regulation in acute myeloid leukemia cells expressing the FLT3-ITD mutated tyrosine kinase receptor, an underexplored field in this disease. Upon FLT3 inhibition, CDC25A mRNA and protein were rapidly down-regulated, while levels of other cell cycle proteins remained unchanged. This regulation was dependent on STAT5, arguing for FLT3-ITD-dependent transcriptional regulation of CDC25A. CDC25 inhibitors triggered proliferation arrest and cell death of FLT3-ITD as well as FLT3-ITD/TKD AC-220 resistant cells, but not of FLT3-wt cells. Consistently, RNA interference-mediated knock-down of CDC25A reduced the proliferation of FLT3-ITD cell lines. Finally, the clonogenic capacity of primary FLT3-ITD AML cells was reduced by the CDC25 inhibitor IRC-083864, while FLT3-wt AML and normal CD34+ myeloid cells were unaffected. In good agreement, in a cohort of 100 samples from AML patients with intermediate-risk cytogenetics, high levels of CDC25A mRNA were predictive of higher clonogenic potential in FLT3-ITD+ samples, not in FLT3-wt ones.Importantly, pharmacological inhibition as well as RNA interference-mediated knock-down of CDC25A also induced monocytic differentiation of FLT3-ITD positive cells, as judged by cell surface markers expression, morphological modifications, and C/EBPα phosphorylation. CDC25 inhibition also re-induced monocytic differentiation in primary AML blasts carrying the FLT3-ITD mutation, but not in blasts expressing wild type FLT3. Altogether, these data identify CDC25A as an early cell cycle transducer of FLT3-ITD oncogenic signaling, and as a promising target to inhibit proliferation and re-induce differentiation of FLT3-ITD AML cells.

SAR103168: a tyrosine kinase inhibitor with therapeutic potential in myeloid leukemias.

SAR103168, a tyrosine kinase inhibitor of the pyrido [2,3-d] pyridimidine subclass, inhibited the kinase activities of the entire Src kinase family, Abl kinase, angiogenic receptor kinases (vascular endothelial growth factor receptor [VEGFR] 1 and 2), Tie2, platelet derived growth factor (PDGF), fibroblast growth factor receptor (FGFR) 1 and 3, and epidermal growth factor receptor (EGFR). SAR103168 was a potent Src inhibitor, with 50% inhibitory concentration (IC50) = 0.65 ± 0.02 nM (at 100 µM ATP), targeting the auto-phosphorylation of the kinase domain (Src(260-535)) and activity of the phosphorylated kinase. Phosphorylation of Src, Lyn and Src downstream signaling pathways (PYK2, P-130CAS, FAK, JNK and MAPK) were inhibited in a dose-dependent manner. SAR103168 inhibited the phosphorylation of STAT5 in KG1 cells and fresh cells from patients with acute myeloid leukemia (AML). SAR103168 inhibited proliferation and induced apoptosis in acute and chronic myeloid leukemic cells at nanomolar IC50. SAR103168 induced anti-proliferation of leukemic progenitors (CFU-L) from 29 patients with AML, and > 85% of AML patient samples were sensitive to SAR103168. These antagonist activities of SAR103168 were independent of FLT3 expression. SAR103168 treatment was effective in 50% of high-risk patient samples carrying chromosome 7 abnormalities or complex rearrangement. SAR103168 administration (intravenous or oral) impaired tumor growth and induced tumor regression in animals bearing human AML leukemic cells, correlating with potent inhibition of Src downstream signaling pathways in AML tumors. SAR103168 showed potent anti-tumor activity in SCID (severe combined immunodeficiency) mice bearing AML (KG1, EOL-1, Kasumi-1, CTV1) and chronic myeloid leukemia (CML) (K562) tumors. The combination of cytarabine and SAR103168 showed synergistic activity in AML and CML tumor models. These results highlight the therapeutic potential of SAR103168 in myeloid leukemias and support the rationale for clinical investigations.

Evaluation of checkpoint kinase targeting therapy in acute myeloid leukemia with complex karyotype.

There has been considerable interest in targeting cell cycle checkpoints particularly in emerging and alternative anticancer strategies. Here, we show that checkpoint abrogation by AZD7762, a potent and selective CHK1/2 kinase inhibitor enhances genotoxic treatment efficacy in immature KG1a leukemic cell line and in AML patient samples, particularly those with a complex karyotype, which display major genomic instability and chemoresistance. Furthermore, these data suggest that constitutive DNA-damage level might be useful markers to select AML patients susceptible to receive checkpoint inhibitor in combination with conventional chemotherapy. Moreover, this study demonstrates for the first time that AZD7762 inhibitor targets the CD34(+)CD38(-)CD123(+) primitive leukemic progenitors, which are responsible for the majority of AML patients relapse. Finally, CHK1 inhibition does not seem to affect clonogenic potential of normal hematopoietic progenitors.

Optical imaging of disseminated leukemia models in mice with near-infrared probe conjugated to a monoclonal antibody.

BACKGROUND: The assessment of anticancer agents to treat leukemia needs to have animal models closer to the human pathology such as implantation in immunodeficient mice of leukemic cells from patient samples. A sensitive and early detection of tumor cells in these orthotopic models is a prerequisite for monitoring engraftment of leukemic cells and their dissemination in mice. Therefore, we developed a fluorescent antibody based strategy to detect leukemic foci in mice bearing patient-derived leukemic cells using fluorescence reflectance imaging (FRI) to determine when to start treatments with novel antitumor agents. METHODS: Two mAbs against the CD44 human myeloid marker or the CD45 human leukocyte marker were labeled with Alexa Fluor 750 and administered to leukemia-bearing mice after having verified the immunoreactivity in vitro. Bioluminescent leukemic cells (HL60-Luc) were used to compare the colocalization of the fluorescent mAb with these cells. The impact of the labeled antibodies on disease progression was further determined. Finally, the fluorescent hCD45 mAb was tested in mice engrafted with human leukemic cells. RESULTS: The probe labeling did not modify the immunoreactivity of the mAbs. There was a satisfactory correlation between bioluminescence imaging (BLI) and FRI and low doses of mAb were sufficient to detect leukemic foci. However, anti-hCD44 mAb had a strong impact on the tumor proliferation contrary to anti-hCD45 mAb. The use of anti-hCD45 mAb allowed the detection of leukemic patient cells engrafted onto NOD/SCID mice. CONCLUSIONS: A mAb labeled with a near infrared fluorochrome is useful to detect leukemic foci in disseminated models provided that its potential impact on tumor proliferation has been thoroughly documented.