Repositioning of bromocriptine for treatment of acute myeloid leukemia.

BACKGROUND: Treatment for acute myeloid leukemia (AML) has not significantly changed in the last decades and new therapeutic approaches are needed to achieve prolonged survival rates. Leukemia stem cells (LSC) are responsible for the initiation and maintenance of AML due to their stem-cell properties. Differentiation therapies aim to abrogate the self-renewal capacity and diminish blast lifespan. METHODS: An in silico screening was designed to search for FDA-approved small molecules that potentially induce differentiation of AML cells. Bromocriptine was identified and validated in an in vitro screening. Bromocriptine is an approved drug originally indicated for Parkinson's disease, acromegaly, hyperprolactinemia and galactorrhoea, and recently repositioned for diabetes mellitus. RESULTS: Treatment with bromocriptine reduced cell viability of AML cells by activation of the apoptosis program and induction of myeloid differentiation. Moreover, the LSC-enriched primitive AML cell fraction was more sensitive to the presence of bromocriptine. In fact, bromocriptine decreased the clonogenic capacity of AML cells. Interestingly, a negligible effect is observed in healthy blood cells and hematopoietic stem/progenitor cells. CONCLUSIONS: Our results support the use of bromocriptine as an anti-AML drug in a repositioning setting and the further clinical validation of this preclinical study.

Treatment with G-CSF reduces acute myeloid leukemia blast viability in the presence of bone marrow stroma.

BACKGROUND: The resulting clinical impact of the combined use of G-CSF with chemotherapy as a chemosensitizing strategy for treatment of acute myeloid leukemia (AML) patients is still controversial. In this study, the effect of ex vivo treatment with G-CSF on AML primary blasts was studied. METHODS: Peripheral blood mononuclear cells from AML patients were treated with G-CSF at increasing doses, alone or in co-culture with HS-5 stromal cells. Cell viability and surface phenotype was determined by flow cytometry 72 h after treatment. For clonogenicity assays, AML primary samples were treated for 18 h with G-CSF at increasing concentrations and cultured in methyl-cellulose for 14 days. Colonies were counted based on cellularity and morphology criteria. RESULTS: The presence of G-CSF reduced the overall viability of AML cells co-cultured with bone marrow stroma; whereas, in absence of stroma, a negligible effect was observed. Moreover, clonogenic capacity of AML cells was significantly reduced upon treatment with G-CSF. Interestingly, reduction in the AML clonogenic capacity correlated with the sensitivity to chemotherapy observed in vivo. CONCLUSIONS: These ex vivo results would provide a biological basis to data available from studies showing a clinical benefit with the use of G-CSF as a priming agent in patients with a chemosensitive AML and would support implementation of further studies exploring new strategies of chemotherapy priming in AML.

Germ line variants in patients with acute myeloid leukemia without a suspicion of hereditary hematologic malignancy syndrome.

Germ line predisposition in acute myeloid leukemia (AML) has gained attention in recent years because of a nonnegligible frequency and an impact on management of patients and their relatives. Risk alleles for AML development may be present in patients without a clinical suspicion of hereditary hematologic malignancy syndrome. In this study we investigated the presence of germ line variants (GVs) in 288 genes related to cancer predisposition in 47 patients with available paired, tumor-normal material, namely bone marrow stroma cells (n = 29), postremission bone marrow (n = 17), and saliva (n = 1). These patients correspond to 2 broad AML categories with heterogeneous genetic background (AML myelodysplasia related and AML defined by differentiation) and none of them had phenotypic abnormalities, previous history of cytopenia, or strong cancer aggregation. We found 11 pathogenic or likely pathogenic variants, 6 affecting genes related to autosomal dominant cancer predisposition syndromes (ATM, DDX41, and CHEK2) and 5 related to autosomal recessive bone marrow failure syndromes (FANCA, FANCM, SBDS, DNAJC21, and CSF3R). We did not find differences in clinical characteristics nor outcome between carriers of GVs vs noncarriers. Further studies in unselected AML cohorts are needed to determine GV incidence and penetrance and, in particular, to clarify the role of ATM nonsense mutations in AML predisposition.

Serotonin receptor type 1B constitutes a therapeutic target for MDS and CMML.

Myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML) are chronic myeloid clonal neoplasms. To date, the only potentially curative therapy for these disorders remains allogeneic hematopoietic progenitor cell transplantation (HCT), although patient eligibility is limited due to high morbimortality associated with this procedure coupled with advanced age of most patients. Dopamine receptors (DRs) and serotonin receptors type 1 (HTR1s) were identified as cancer stem cell therapeutic targets in acute myeloid leukemia. Given their close pathophysiologic relationship, expression of HTR1s and DRs was interrogated in MDS and CMML. Both receptors were differentially expressed in patient samples compared to healthy donors. Treatment with HTR1B antagonists reduced cell viability. HTR1 antagonists showed a synergistic cytotoxic effect with currently approved hypomethylating agents in AML cells. Our results suggest that HTR1B constitutes a novel therapeutic target for MDS and CMML. Due to its druggability, the clinical development of new regimens based on this target is promising.

Emetine induces chemosensitivity and reduces clonogenicity of acute myeloid leukemia cells.

Acute myeloid leukemia (AML) is an hematologic neoplasia characterized by the accumulation of transformed immature myeloid cells in bone marrow. Although the response rate to induction therapy is high, survival rate 5-year after diagnosis is still low, highlighting the necessity of new novel agents. To identify agents with the capability to abolish the self-renewal capacity of AML blasts, an in silico screening was performed to search for small molecules that induce terminal differentiation. Emetine, a hit compound, was validated for its anti-leukemic effect in vitro, ex vivo and in vivo. Emetine, a second-line anti-protozoa drug, differentially reduced cell viability and clonogenic capacity of AML primary patient samples, sparing healthy blood cells. Emetine treatment markedly reduced AML burden in bone marrow of xenotransplanted mice and decreased self-renewal capacity of the remaining engrafted AML cells. Emetine also synergized with commonly used chemotherapeutic agents such as ara-C. At a molecular level, emetine treatment was followed by a reduction in HIF-1α protein levels. This study validated the anti-leukemiceffect of emetine in AML cell lines, a group of diverse AML primary samples, and in a human AML-transplanted murine model, sparing healthy blood cells. The selective anti-leukemic effect of emetine together with the safety of the dose range required to exert this effect support the development of this agent in clinical practice.