Chemotherapy-resistant human acute myeloid leukemia (AML) cells are thought to be enriched in quiescent immature leukemic stem cells (LSCs). To validate this hypothesis in vivo, we developed a clinically relevant chemotherapeutic approach treating patient-derived xenograft (PDX) with cytarabine. Cytarabine residual AML cells are enriched neither in immature, quiescent cells nor LSCs. Strikingly, cytarabine-resistant pre-existing and persisting cells displayed high levels of reactive oxygen species, showed increased mitochondrial mass, and retained active polarized mitochondria, consistent with a high oxidative phosphorylation (OXPHOS) status. Cytarabine residual cells exhibited increased fatty acid oxidation, upregulated CD36 expression and a HIGH OXPHOS gene signature predictive for treatment response in PDX and AML patients. HIGH OXPHOS but not LOW OXPHOS human AML cell lines were chemoresistant in vivo. Targeting mitochondrial protein synthesis, electron transfer, or fatty acid oxidation induced an energetic shift towards LOW OXPHOS and markedly enhanced anti-leukemic effects of cytarabine. Together, this study demonstrates that essential mitochondrial functions contribute to cytarabine resistance in AML and are a robust hallmark of cytarabine sensitivity and a promising therapeutic avenue to treat AML residual disease.
Key Points• Mutations of key transcription factor in myeloid malignancies.Congenital neutropenia is a group of genetic disorders that involve chronic neutropenia and susceptibility to infections. These neutropenias may be isolated or associated with immunologic defects or extra-hematopoietic manifestations. Complications may occur as infectious diseases, but also less frequently as myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). Recently, the transcription factor GATA2 has been identified as a new predisposing gene for familial AML/MDS. In the present study, we describe the initial identification by exome sequencing of a GATA2 R396Q mutation in a family with a history of chronic mild neutropenia evolving to AML and/or MDS. The subsequent analysis of the French Severe Chronic Neutropenia Registry allowed the identification of 6 additional pedigrees and 10 patients with 6 different and not previously reported GATA2 mutations (R204X, E224X, R330X, A372T, M388V, and a complete deletion of the GATA2 locus). The frequent evolution to MDS and AML in these patients reveals the importance of screening GATA2 in chronic neutropenia associated with monocytopenia because of the frequent hematopoietic transformation, variable clinical expression at onset, and the need for aggressive therapy in patients with poor clinical outcome. (Blood. 2013;121(5):822-829)
Key Points
The prognostic impact of time from diagnosis to treatment in AML is offset by other factors such as age, secondary AML, or genetic abnormalities. Waiting a short period of time to characterize leukemias better and design adapted treatments at diagnosis seems possible.
Background The aim of this cross-sectional study was to assess risk factors for bleeding in immune thrombocytopenia (ITP) adults, including the determination of platelet count thresholds. Methods We selected all newly diagnosed ITP adults included in the Cytopénies Auto-immunes Registre Midi-PyrénéEN (CARMEN) register and at the French referral center for autoimmune cytopenias. The frequencies of any bleeding, mucosal bleeding and severe bleeding (gastrointestinal, intracranial, or macroscopic hematuria) at ITP onset were assessed. Platelet count thresholds were assessed by the use of receiver operating characteristic curves. All potential risk factors were included in logistic regression models. Results Among the 302 patients, the frequencies of any, mucosal and severe bleeding were 57.9%, 30.1%, and 6.6%, respectively. The best discriminant threshold of platelet count for any bleeding was 20 × 10 L . In multivariate analysis, factors associated with any bleeding were platelet count (< 10 × 10 L versus ≥ 20 × 10 L , odds ratio [OR] 48.2, 95% confidence interval [CI] 20.0-116.3; between 10 × 10 L and 19 × 10 L versus ≥ 20 × 10 L , OR 5.2, 95% CI 2.3-11.6), female sex (OR 2.6, 95% CI 1.3-5.0), and exposure to non-steroidal anti-inflammatory drugs (NSAIDs) (OR 4.8, 95% CI 1.1-20.7). A low platelet count was also the main risk factor for mucosal bleeding. Exposure to anticoagulant drugs was associated with severe bleeding (OR 4.3, 95% CI 1.3-14.1). Conclusions Platelet counts of < 20 × 10 L and < 10 × 10 L were thresholds for major increased risks of any and mucosal bleeding. Platelet count, female sex and exposure to NSAIDs should be considered for assessment of the risk of any bleeding. Exposure to anticoagulant drugs was a major risk factor for severe bleeding.
Patients with acute myeloid leukemia and a high white blood cell count are at increased risk of early death and relapse. Because mediators of inflammation contribute to leukostasis and chemoresistance, dexamethasone added to chemotherapy could improve outcomes. This retrospective study evaluated the impact of adding or not adding dexamethasone to chemotherapy in a cohort of 160 patients with at least 50×109 white blood cells. In silico studies, primary samples, leukemic cell lines, and xenograft mouse models were used to explore the antileukemic activity of dexamethasone. There was no difference with respect to induction death rate, response, and infections between the 60 patients in the dexamethasone group and the 100 patients in the no dexamethasone group. Multivariate analysis showed that dexamethasone was significantly associated with improved relapse incidence (adjusted sub-HR: 0.30; 95% CI: 0.14–0.62; P=0.001), disease-free survival (adjusted HR: 0.50; 95% CI: 0.29–0.84; P=0.010), event-free survival (adjusted HR: 0.35; 95% CI: 0.21–0.58; P<0.001), and overall survival (adjusted HR: 0.41; 95% CI: 0.22–0.79; P=0.007). In a co-culture system, dexamethasone reduced the frequency of leukemic long-term culture initiating cells by 38% and enhanced the cytotoxicity of doxorubicin and cytarabine. In a patient-derived xenograft model treated with cytarabine, chemoresistant cells were enriched in genes of the inflammatory response modulated by dexamethasone. Dexamethasone also demonstrated antileukemic activity in NPM1-mutated samples. Dexamethasone may improve the outcome of acute myeloid leukemia patients receiving intensive chemotherapy. This effect could be due to the modulation of inflammatory chemoresistance pathways and to a specific activity in acute myeloid leukemia with NPM1 mutation.
Findings among a cohort of 26 patients who had hematologic malignancies and hepatitis E virus (HEV) infection support that HEV can induce chronic hepatitis. However, a 3-month course of ribavirin can induce a rapid viral clearance, reducing the risk for chronic hepatitis and enabling continuation of cytotoxic treatments for underlying malignancies.
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