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Targeting the first protein complex of the mitochondrial electron transport chain (MC1) in cancer has become an attractive therapeutic approach in the recent years, given the metabolic vulnerabilities of cancer cells. The anticancer effect exerted by the pleiotropic drug metformin and the associated reduction in hypoxia‐inducible factor 1α (HIF‐1α) levels putatively mediated by MC1 inhibition led to the development of HIF‐1α inhibitors, such as BAY87‐2243, with a more specific MC1 targeting. However, the development of BAY87‐2243 was stopped early in phase 1 due to dose‐independent emesis and thus there is still no clinical proof of concept for the approach. Given the importance of mitochondrial metabolism during cancer progression, there is still a strong therapeutic need to develop specific and safe MC1 inhibitors. We recently reported the synthesis of compounds with a novel chemotype and potent action on HIF‐1α degradation and MC1 inhibition. We describe here the selectivity, safety profile and anti‐cancer activity in solid tumors of lead compound EVT‐701. In addition, using murine models of lung cancer and of Non‐Hodgkin's B cell lymphoma we demonstrated that EVT‐701 reduced tumor growth and lymph node invasion when used as a single agent therapy. LKB1 deficiency in lung cancer was identified as a potential indicator of accrued sensitivity to EVT‐701, allowing stratification and selection of patients in clinical trials. Altogether these results support further evaluation of EVT‐701 alone or in combination in preclinical models and eventually in patients., The present study elucidates the mechanism of action and supports further preclinical and clinical investigation of EVT‐701, either as a single agent or in combination, for the treatment of solid tumors. LKB1 deficiency in lung cancer was identified as potential indicator of accrued sensitivity to EVT‐701, allowing stratification and selection of patients in clinical trials

Simple Summary Despite all of the advancements made in recent years in the treatment of acute myeloid leukemia (AML), long-term survival is achieved by only 30–40% of AML patients. Thus, new therapeutic strategies are strongly needed. This work confirms the increase in oxidative phosphorylation upon cytarabine resistance in AML murine cells, reinforcing the interest of targeting it. In addition, it identifies a new role of the first complex of the electron transport chain (ETCI) in the regulation of the immune checkpoints PD-L1 and CD39 in murine and human leukemic cells. Thus, this work opens the door to the evaluation of ETCI inhibitors in combination with immunotherapy. Abstract Oxidative metabolism is crucial for leukemic stem cell (LSC) function and drug resistance in acute myeloid leukemia (AML). Mitochondrial metabolism also affects the immune system and therefore the anti-tumor response. The modulation of oxidative phosphorylation (OxPHOS) has emerged as a promising approach to improve the therapy outcome for AML patients. However, the effect of mitochondrial inhibitors on the immune compartment in the context of AML is yet to be explored. Immune checkpoints such as ectonucleotidase CD39 and programmed dead ligand 1 (PD-L1) have been reported to be expressed in AML and linked to chemo-resistance and a poor prognosis. In the present study, we first demonstrated that a novel selective electron transfer chain complex (ETC) I inhibitor, EVT-701, decreased the OxPHOS metabolism of murine and human cytarabine (AraC)-resistant leukemic cell lines. Furthermore, we showed that while AraC induced an immune response regulation by increasing CD39 expression and by reinforcing the interferon-γ/PD-L1 axis, EVT-701 reduced CD39 and PD-L1 expression in vitro in a panel of both murine and human AML cell lines, especially upon AraC treatment. Altogether, this work uncovers a non-canonical function of ETCI in controlling CD39 and PD-L1 immune checkpoints, thereby improving the anti-tumor response in AML.

In breast cancer, a key feature of peritumoral adipocytes is their loss of lipid content observed both in vitro and in human tumors. The free fatty acids (FFAs), released by adipocytes after lipolysis induced by tumor secretions, are transferred and stored in tumor cells as triglycerides in lipid droplets. In tumor cell lines, we demonstrate that FFAs can be released over time from lipid droplets through an adipose triglyceride lipase–dependent (ATGL-dependent) lipolytic pathway. In vivo, ATGL is expressed in human tumors where its expression correlates with tumor aggressiveness and is upregulated by contact with adipocytes. The released FFAs are then used for fatty acid β-oxidation (FAO), an active process in cancer but not normal breast epithelial cells, and regulated by coculture with adipocytes. However, in cocultivated cells, FAO is uncoupled from ATP production, leading to AMPK/acetyl-CoA carboxylase activation, a circle that maintains this state of metabolic remodeling. The increased invasive capacities of tumor cells induced by coculture are completely abrogated by inhibition of the coupled ATGL-dependent lipolysis/FAO pathways. These results show a complex metabolic symbiosis between tumor-surrounding adipocytes and cancer cells that stimulate their invasiveness, highlighting ATGL as a potential therapeutic target to impede breast cancer progression.

International audience; Adipose tissue is an active endocrine organ that produces a variety of secretory factors involved in the initiation of angiogenic processes. The bioactive peptide apelin is the endogenous ligand of the G protein-coupled receptor, APJ. Here we investigated the potential role of apelin and its receptor, APJ, in the angiogenic responses of human endothelial cells and the development of a functional vascular network in a model of adipose tissue development in mice. Treatment of human umbilical vein endothelial cells with apelin dose-dependently increased angiogenic responses, including endothelial cell migration, proliferation, and Matrigel(R) capillary tubelike structure formation. These endothelial effects of apelin were due to activation of APJ, because siRNA directed against APJ, which led to long-lasting down-regulation of APJ mRNA, abolished cell migration induced by apelin in contrast to control nonsilencing siRNA. Hypoxia up-regulated the expression of apelin in 3T3F442A adipocytes, and we therefore determined whether apelin could play a role in adipose tissue angiogenesis in vivo. Epididymal white adipose tissue (EWAT) transplantation was performed as a model of adipose tissue angiogenesis. Transplantation led to increased apelin mRNA levels 2 and 5 days after transplantation associated with tissue hypoxia, as evidenced by hydroxyprobe staining on tissue sections. Graft revascularization evolved in parallel, as the first functional vessels in EWAT grafts were observed 2 days after transplantation and a strong angiogenic response was apparent on day 14. This was confirmed by determination of graft hemoglobin levels, which are indicative of functional vascularization and were strongly increased 5 and 14 days after transplantation. The role of apelin in the graft neovascularization was then assessed by local delivery of stable complex apelin-targeting siRNA leading to dramatically reduced apelin mRNA levels and vascularization (quantified by hemogloblin content) in grafted EWAT on day 5 when compared with control siRNA. Taken together, our data provide the first evidence that apelin/APJ signaling pathways play a critical role in the development of the functional vascular network in adipose tissue. In addition, we have shown that adipocyte-derived apelin can be up-regulated by hypoxia. These findings provide novel insights into the complex relationship between adipose tissue and endothelial vascular function and may lead to new therapeutic strategies to modulate angiogenesis.

Compound 15 (SAR107375), a novel potent dual thrombin and factor Xa inhibitor resulted from a rational optimization process. Starting from compound 14, with low factor Xa and modest anti-thrombin inhibitory activities (IC50's of 3.5 and 0.39 μM, respectively), both activities were considerably improved, notably through the incorporation of a neutral chlorothiophene P1 fragment and tuning of P2 and P3-P4 fragments. Final optimization of metabolic stability with microsomes led to the identification of 15, which displays strong activity in vitro vs factor Xa and thrombin (with Ki's of 1 and 8 nM, respectively). In addition 15 presents good selectivity versus related serine proteases (roughly 300-fold), including trypsin (1000-fold), and is very active (0.39 μM) in the thrombin generation time (TGT) coagulation assay in human platelet rich plasma (PRP). Potent in vivo activity in a rat model of venous thrombosis following iv and, more importantly, po administration was also observed (ED50 of 0.07 and 2.8 mg/kg, respectively). Bleeding liability was reduced in the rat wire coil model, more relevant to arterial thrombosis, with 15 (blood loss increase of 2-fold relative to the ED80 value) compared to rivaroxaban 2 and dabigatran etexilate 1a.