Fabienne De Toni

Adult Stromal Cells Derived from Human Adipose Tissue Provoke Pancreatic Cancer Cell Death both In Vitro and In Vivo

Background Normal tissue homeostasis is maintained by dynamic interactions between epithelial cells and their microenvironment. Disrupting this homeostasis can induce aberrant cell proliferation, adhesion, function and migration that might promote malignant behavior. Indeed, aberrant stromal-epithelial interactions contribute to pancreatic ductal adenocarcinoma (PDAC) spread and metastasis, and this raises the possibility that novel stroma-targeted therapies represent additional approaches for combating this malignant disease. The aim of the present study was to determine the effect of human stromal cells derived from adipose tissue (ADSC) on pancreatic tumor cell proliferation. Principal Findings Co-culturing pancreatic tumor cells with ADSC and ADSC-conditioned medium sampled from different donors inhibited cancer cell viability and proliferation. ADSC-mediated inhibitory effect was further extended to other epithelial cancer-derived cell lines (liver, colon, prostate). ADSC conditioned medium induced cancer cell necrosis following G1-phase arrest, without evidence of apoptosis. In vivo, a single intra-tumoral injection of ADSC in a model of pancreatic adenocarcinoma induced a strong and long-lasting inhibition of tumor growth. Conclusion These data indicate that ADSC strongly inhibit PDAC proliferation, both in vitro and in vivo and induce tumor cell death by altering cell cycle progression. Therefore, ADSC may constitute a potential cell-based therapeutic alternative for the treatment of PDAC for which no effective cure is available.

Human Adipose-Derived Stromal Cells Efficiently Support Hematopoiesis In Vitro and In Vivo: A Key Step for Therapeutic Studies

Adipose-derived stromal cells (ADSCs) are close relatives of bone marrow mesenchymal stromal cells (BM-MSCs). The ease of access to subcutaneous fat pad and the abundance of stromal precursors make fat tissue an attractive source of stromal cells for clinicians. However, their ability to support hematopoietic stem cells in vitro and in vivo has not been established definitively. Thus, their usefulness in supporting hematopoietic stem cell engraftment is not as clear as with BM-MSCs. In this article, we show that human ADSCs, cultured with a good manufacturing practice medium, maintain in vitro human early and committed hematopoietic progenitors and support their complete differentiation toward myeloid and lymphoid lineages. Compared with BM-MSCs, ADSCs elicit a more precocious early progenitor formation and faster proliferation and differentiation of hematopoietic progenitors. Further, in vivo, when co-injected in NOD.Cg-Prkdc(scid) Il2(rgtm1Wjl)/SzJ (NSG) mice with a low number of human CD34(+) cells, ADSCs enabled the higher production of immature human hematopoietic progenitors and CD45(+) cells when compared with BM-MSCs. As a whole, our results indicate that human ADSCs, isolated and expanded under clinical-grade conditions, support hematopoiesis in vitro and in vivo and thus provide the rationale for their use in supporting hematopoietic reconstitution in clinical settings.

Chemotherapy-Resistant Human Acute Myeloid Leukemia Cells Are Not Enriched for Leukemic Stem Cells but Require Oxidative Metabolism

Chemotherapy-resistant human acute myeloid leukemia (AML) cells are thought to be enriched in quiescent immature leukemic stem cells (LSC). To validate this hypothesis in vivo, we developed a clinically relevant chemotherapeutic approach treating patient-derived xenografts (PDX) with cytarabine (AraC). AraC residual AML cells are enriched in neither immature, quiescent cells nor LSCs. Strikingly, AraC-resistant preexisting 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. AraC residual cells exhibited increased fatty-acid oxidation, upregulated CD36 expression, and a high OXPHOS gene signature predictive for treatment response in PDX and patients with AML. 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 toward low OXPHOS and markedly enhanced antileukemic effects of AraC. Together, this study demonstrates that essential mitochondrial functions contribute to AraC resistance in AML and are a robust hallmark of AraC sensitivity and a promising therapeutic avenue to treat AML residual disease.Significance: AraC-resistant AML cells exhibit metabolic features and gene signatures consistent with a high OXPHOS status. In these cells, targeting mitochondrial metabolism through the CD36-FAO-OXPHOS axis induces an energetic shift toward low OXPHOS and strongly enhanced antileukemic effects of AraC, offering a promising avenue to design new therapeutic strategies and fight AraC resistance in AML. Cancer Discov; 7(7); 716-35. ©2017 AACR.See related commentary by Schimmer, p. 670This article is highlighted in the In This Issue feature, p. 653.

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.

Isocitrate dehydrogenase 1 mutations prime the all-trans retinoic acid myeloid differentiation pathway in acute myeloid leukemia

Boutzen et al. show that the IDH1 mutation and its oncometabolite, (R)-2-hydroxyglutarate, dysregulate downstream target pathways of myeloid-specific TFs, especially CEBPα, priming mutant IDH1-R132H AML blasts to the granulomonocytic lineage.

In situ production of innate immune cells in murine white adipose tissue

White adipose tissue (WAT) is the focus of new interest because of the presence of an abundant and complex immune cell population that is involved in key pathologies such as metabolic syndrome. Based on in vivo reconstitution assays, it is thought that these immune cells are derived from the bone marrow (BM). However, previous studies have shown that WAT exhibits specific hematopoietic activity exerted by an unknown subpopulation of cells. In the present study, we prospectively isolated a peculiar hematopoietic stem/progenitor cell population from murine WAT. The cells are phenotypically similar to BM hematopoietic stem cells and are able to differentiate into both myeloid and lymphoid lineages in vitro. In competitive repopulation assays in vivo, they reconstituted the innate immune compartment in WAT preferentially and more efficiently than BM cells, but did not reconstitute hematopoietic organs. They were also able to give rise to multilineage engraftment in both secondary recipients and in utero transplantation. Therefore, we propose that WAT hematopoietic cells constitute a population of immature cells that are able to renew innate immune cell populations. Considering the amount of WAT in adults, our results suggest that WAT hematopoietic activity controls WAT inflammatory processes and also supports innate immune responses in other organs.

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 3β-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.Dendrogenin A, cholesterol metabolite, has tumor suppressive properties but the mechanisms are unknown. Here the authors show that Dendrogenin A can induce autophagy-mediated cell death in both melanoma and acute myeloid leukaemia.

Lymphatic vasculature requires estrogen receptor alpha signaling to protect from lymphedema

Objective— Estrogens exert beneficial effect on the blood vascular system. However, their role on the lymphatic system has been poorly investigated. We studied the protective effect of the 17&bgr; estradiol—the most potent endogenous estrogen—in lymphedema—a lymphatic dysfunction, which results in a massive fluid and fat accumulation in the limb. Approach and Results— Screening of DNA motifs able to mobilize ERs (estrogen receptors) and quantitative real-time polymerase chain reaction analysis revealed that estradiol promotes transcriptional activation of lymphangiogenesis-related gene expression including VEGF (vascular endothelial growth factor)-D, VEGFR (VEGF receptor)-3, lyve-1, and HASs (hyaluronan synthases). Using an original model of secondary lymphedema, we observed a protective effect of estradiol on lymphedema by reducing dermal backflow—a representative feature of the pathology. Blocking ER&agr; by tamoxifen—the selective estrogen modulator—led to a remodeling of the lymphatic network associated with a strong lymphatic leakage. Moreover, the protection of lymphedema by estradiol treatment was abrogated by the endothelial deletion of the receptor ER&agr; in Tie2-Cre; ER&agr;lox/lox mice, which exhibit dilated lymphatic vessels. This remodeling correlated with a decrease in lymphangiogenic gene expression. In vitro, blocking ER&agr; by tamoxifen in lymphatic endothelial cells decreased cell–cell junctions, inhibited migration and sprouting, and resulted in an inhibition of Erk but not of Akt phosphorylation. Conclusions— Estradiol protection from developing lymphedema is mediated by an activation of its receptor ER&agr; and is antagonized by tamoxifen. These findings reveal a new facet of the estrogen influence in the management of the lymphatic system and provide more evidence that secondary lymphedema is worsened by hormone therapy.

Tissus adipeux, cellules hématopoïétiques et hématopoïèse

Le tissu adipeux blanc a fait l’objet de nombreuses etudes concernant son role metabolique et endocrine. Depuis quelques annees, l’identification dans ce tissu d’une population hematopoietique abondante et variee nous a amenes a faire un parallele avec le tissu adipeux medullaire. Situe au cœur des tissus hematopoietiques chez l’adulte, ce tissu pourrait jouer un role cle dans le controle de l’hematopoiese. Il existe en effet des relations etroites entre adipocytes medullaires et cellules hematopoietiques qui ont fait l’objet de nombreuses etudes, plutot anciennes. L’etude de l’hematopoiese dans le tissu adipeux extramedullaire est, en revanche, tres recente. Nous avons mis en evidence l’existence dans ce tissu d’une population de cellules souches hematopoietiques fonctionnelles, presentant cependant des proprietes particulieres vis-a-vis de leurs homologues medullaires. Comme dans la moelle osseuse, le micro-environnement compose de cellules stromales et d’adipocytes semble jouer un role sur les cellules hematopoietiques matures et immatures. Les donnees recentes suggerent donc que le tissu adipeux extramedullaire pourrait presenter une veritable fonction hematopoietique, dont l’importance physiologique reste a determiner. Il se degage de cette analyse que si l’hematopoiese medullaire est tres bien etudiee et decrite, les adipocytes medullaires et la moelle osseuse jaune sont encore peu connus. A l’inverse, alors que les tissus adipeux extramedullaires sont l’objet d’un grand nombre d’etudes dans une perspective metabolique, leurs liens et relations aux cellules hematopoietiques restent encore a preciser. Quoi qu’il en soit, cette capacite des tissus adipeux des mammiferes a assumer a la fois un role metabolique et controler une fonction immune via la production de cellules hematopoietiques pourrait provenir de l’evolution du corps gras, structure ancestrale presente chez les insectes et qui assume simultanement les deux fonctions.