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Modulators of epithelial to mesenchymal transition (EMT) have recently emerged as novel players in the field of leukemia biology. The mechanisms by which EMT modulators contribute to leukemia pathogenesis, however, remain to be elucidated. Here we show that overexpression of SNAI1, a key modulator of EMT, is a pathologically relevant event in human acute myeloid leukemia (AML) that contributes to impaired differentiation, enhanced self-renewal and proliferation of immature myeloid cells. We demonstrate that ectopic expression of Snai1 in hematopoietic cells predisposes mice to AML development. This effect is mediated by interaction with the histone demethylase KDM1A/LSD1. Our data shed new light on the role of SNAI1 in leukemia development and identify a novel mechanism of LSD1 corruption in cancer. This is particularly pertinent given the current interest surrounding the use of LSD1 inhibitors in the treatment of multiple different malignancies, including AML.

Inhibition of anti-apoptotic BCL-2 has recently emerged as a promising new therapeutic strategy for the treatment of a variety of human cancers, including leukemia. Here, we used T-cell acute lymphoblastic leukemia as a model system to identify novel synergistic drug combinations with the BH3 mimetic venetoclax . In vitro drug screening in primary leukemia specimens that were derived from patients with high risk of relapse or relapse and cell lines revealed synergistic activity between venetoclax and the BET bromodomain inhibitor JQ1. Notably, this drug synergism was confirmed in vivo using T-ALL cell line and patient-derived xenograft models. Moreover, the therapeutic benefit of this drug combination might, at least in part, be mediated by an acute induction of the pro-apoptotic factor BCL2L11 and concomitant loss of BCL-2 upon BET bromodomain inhibition, ultimately resulting in an enhanced binding of BIM (encoded by BCL2L11) to BCL-2. Altogether, our work provides a rationale to develop a new type of targeted combination therapy for selected subgroups of high-risk leukemia patients.Leukemia accepted article preview online, 11 January 2017. doi:10.1038/leu.2017.10. This is a PDF file of an unedited peer-reviewed manuscript that has been accepted for publication. NPG are providing this early version of the manuscript as a service to our customers. The manuscript will undergo copyediting, typesetting and a proof review before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers apply. Conflict of interestThe authors declare no conflict of interest.© 2017 Macmillan Publishers Limited. All rights reserved.3 AbstractInhibition of anti-apoptotic BCL-2 has recently emerged as a promising new therapeutic strategy for the treatment of a variety of human cancers, including leukemia. Here, we used T-cell acute lymphoblastic leukemia as a model system to identify novel synergistic drug combinations with the BH3 mimetic venetoclax . In vitro drug screening in primary leukemia specimens that were derived from patients with high risk of relapse or relapse and cell lines revealed synergistic activity between venetoclax and the BET bromodomain inhibitor JQ1. Notably, this drug synergism was confirmed in vivo using T-ALL cell line and patient-derived xenograft models. Moreover, the therapeutic benefit of this drug combination might, at least in part, be mediated by an acute induction of the pro-apoptotic factor BCL2L11 and concomitant loss of BCL-2 upon BET bromodomain inhibition, ultimately resulting in an enhanced binding of BIM (encoded by BCL2L11) to BCL-2.Altogether, our work provides a rationale to develop a new type of targeted combination therapy for selected subgroups of high-risk leukemia patients.

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T-cell acute lymphoblastic leukemia (T-ALL) and T-cell acute lymphoblastic lymphoma (T-LBL) are aggressive hematological malignancies that are currently treated with high-dose chemotherapy. Over the last several years, the search toward novel and less-toxic therapeutic strategies for T-ALL/T-LBL patients has largely focused on the identification of cell-intrinsic properties of the tumor cell. However, non–cell-autonomous activation of specific oncogenic pathways might also offer opportunities that could be exploited at the therapeutic level. In line with this, we here show that endogenous interleukin 7 (IL7) can increase the expression of the oncogenic kinase proviral integration site for Moloney-murine leukemia 1 (PIM1) in CD127+ T-ALL/T-LBL, thereby rendering these tumor cells sensitive to in vivo PIM inhibition. In addition, using different CD127+ T-ALL/T-LBL xenograft models, we also reveal that residual tumor cells, which remain present after short-term in vivo chemotherapy, display consistent upregulation of PIM1 as compared with bulk nontreated tumor cells. Notably, this effect was transient as increased PIM1 levels were not observed in reestablished disease after abrogation of the initial chemotherapy. Furthermore, we uncover that this phenomenon is, at least in part, mediated by the ability of glucocorticoids to cause transcriptional upregulation of IL7RA in T-ALL/T-LBL patient-derived xenograft (PDX) cells, ultimately resulting in non–cell-autonomous PIM1 upregulation by endogenous IL7. Finally, we confirm in vivo that chemotherapy in combination with a pan-PIM inhibitor can improve leukemia survival in a PDX model of CD127+ T-ALL. Altogether, our work reveals that IL7 and glucocorticoids coordinately drive aberrant activation of PIM1 and suggests that IL7-responsive CD127+ T-ALL and T-LBL patients could benefit from PIM inhibition during induction chemotherapy.

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Dopamine D 4 receptors (D 4 Rs) are G protein-coupled receptors that play a role in attention and cognition. In the present study, we investigated the dimerization properties of this receptor. Western blot analysis of the human D 4.2 R, D 4.4 R and D 4.7 R revealed the presence of higher molecular weight immunoreactive bands, which might indicate the formation of receptor dimers and multimers. Homo-and heterodimerization of the receptors was confirmed by co-immunoprecipitation and bioluminescence resonance energy transfer studies. Although dimerization of a large number of G protein-coupled receptors has been described, the functional importance often remains to be elucidated. Folding efficiency is rate-limiting for D 4 R biogenesis and quality control in the endoplasmic reticulum plays an important role for D 4 R maturation. Co-immunoprecipitation and immunofluorescence microscopy studies using wild-type and a nonfunctional D 4.4 R folding mutant show that oligomerization occurs in the endoplasmic reticulum and that this plays a role in the biogenesis and cell surface targeting of the D 4 R. The different polymorphic repeat variants of the D 4 R display differential sensitivity to the chaperone effect. In the present study, we show that this is also reflected by bioluminescence resonance energy transfer saturation assays, suggesting that the polymorphic repeat variants have different relative affinities to form homo-and heterodimers. In summary, we conclude that D 4 Rs form oligomers with different affinities and that dimerization plays a role in receptor biogenesis.Structured digital abstract l D4.4R physically interacts with D4.2R by anti tag coimmunoprecipitation (View interaction) l D4.xR physically interacts with D4.4R by anti tag coimmunoprecipitation (View interaction) l D4.xR and D4.xR physically interact by bioluminescence resonance energy transfer (View interaction)Abbreviations BRET, bioluminescence resonance energy transfer; CHO, Chinese hamster ovary; DAPI, 4¢,6-diamidino-2-phenylindole; D n R, dopamine D n receptor; ER, endoplasmic reticulum; GPCR, G protein-coupled receptor; HRP, horseradish peroxidase; MP, milk powder; YFP, yellow fluorescent protein.