Le trastuzumab est un anticorps monoclonal déjà utilisé dans le traitement du cancer du sein sur-exprimant la protéine HER2. Malgré son efficacité, la résistance est souvent apparue. Ici, nous avons étudié l'impact des cellules adipocytaires sur la cytotoxicité cellulaire dépendante de l'anticorps (ADCC), une des mécanismes d'action principaux du trastuzumab. Nous avons trouvé que les adipocytes, ainsi que les pré- adipocytes, inhibent l'ADCC médié par le trastuzumab. Nous avons montré que les factors dérivées d'adipocytes, comme des protéines ou des exosomes, causent l'inhibition d'ADCC. Aucune séquestration ou dégradation de l'anticorps a été observée. Des analyses phénotypiques n'ont pas révélé de modification des récepteurs des cellules NK, ni du niveau de HER2 sur les cellules cancéreuses en présence d'adipocytes. La pré-incubation des cellules cancéreuses avec le surnageant des adipocytes réduit la sensitivité tumorale à l'ADCC. Nous avons trouvé que le factor de croissance et de différenciation GDFI5 est rapidement induit dans les cellules cancéreuses exposées au surnageant d'adipocytes. Une diminution de l'expression de GDFI5 par les siRNA réverse l'inhibition d'ADCC induite par les adipocytes. En conclusion, nous avons démontré que les adipocytes jouent un rôle dans la résistance des cellules de cancer du sein à l'ADCC médié par le trastuzumab, et nous suggérons que cibler GDFI5 ou l'interaction entre les adipocytes et les cellules cancéreuses pourrait sensibiliser les cellules cancéreuses au traitement par l'anticorps monoclonal / Trastuzumab is a monoclonal antibody already approved in the treatment of HER2-expressing breast cancer. Despite its efficacy, resistance often occurs. Here, we investigated the impact of adipocytes on antibody dependent cellular cytotoxicity (ADCC), one of the main mechanisms of action of trastuzumab. We found that adipocytes, as well as preadipocytes, inhibited trastuzumab-mediated ADCC. We showed that adipocyte-derived factors, likely proteins or exosomes, mediated the inhibition of ADCC. No titration or degradation of the antibody was detected. Analysis of cell phenotype did not reveal any modification of NK cell receptors, nor of HER2 levels on cancer cells in the presence of adipocytes. Pre-incubation of cancer cells with adipocyte-conditioned medium reduced sensitivity of cancer cells to ADCC. We found that growth differentiation factor l5 (GDFl5) was rapidly induced in cancer cells exposed to adipocyte-conditioned medium. Down-regulation of GDFl5 by siRNA reversed the adipocyte-induced inhibition of ADCC. In conclusion, we demonstrated that adipocytes play a role in the resistance of breast cancer to trastuzumab-mediated ADCC, and suggested that targeting GDFl5 or the crosstalk between adipocytes and cancer cells may sensitize cancer cells to monoclonal antibody treatment

Objective. Similar to obesity, lipodystrophy (LD) causes adipose tissue dysfunction and severe metabolic complications. Growth differentiation factor 15 (GDF15) belongs to the transforming growth factor β superfamily and is dysregulated in metabolic disease including obesity and diabetes mellitus. Circulating levels in LD and the impact of leptin treatment have not been investigated so far. Material and Methods. GDF15 serum levels were quantified in 60 LD patients without human immunodeficiency virus infection and 60 controls matched for age, gender, and body mass index. The impact of metreleptin treatment on circulating GDF15 was assessed in a subgroup of patients. GDF15 mRNA expression was determined in metabolic tissues of leptin-deficient lipodystrophic aP2-nSREBP1c-Tg mice, obese ob/ob mice, and control C57Bl6 mice. Results. Median GDF15 serum concentrations were significantly higher in LD patients (819 ng/L) as compared to the control group (415 ng/L) (p < 0.001). In multiple linear regression analysis, an independent and positive association remained between GDF15 on one hand and age, patient group, hemoglobin A1c, triglycerides, and C-reactive protein on the other hand. Moreover, there was an independent negative association between GFD15 and estimated glomerular filtration rate. Circulating GDF15 was not significantly affected by metreleptin treatment in LD patients. Gdf15 was upregulated in leptin-deficient lipodystrophic mice as compared to controls. Moreover, Gdf15 mRNA expression was downregulated by leptin treatment in lipodystrophic and obese animals. Conclusions. Serum concentrations of GDF15 are elevated in LD patients and independently associated with markers of metabolic dysfunction. Gdf15 expression is higher in lipodystrophic mice and downregulated by leptin treatment.

Objective. Similar to obesity, lipodystrophy (LD) causes adipose tissue dysfunction and severe metabolic complications. Growth differentiation factor 15 (GDF15) belongs to the transforming growth factor superfamily and is dysregulated in metabolic disease including obesity and diabetes mellitus. Circulating levels in LDand the impact of leptin treatment have not been investigated so far.Material and Methods. GDF15 serum levels were quantified in 60 LD patients without human immunodeficiency virus infection and 60 controlsmatched for age, gender, and bodymass index. The impact ofmetreleptin treatment on circulating GDF15 was assessed in a subgroup of patients. GDF15 mRNA expression was determined in metabolic tissues of leptin-deficient lipodystrophic aP2-nSREBP1c-Tg mice, obese ob/ob mice, and control C57Bl6 mice. Results. Median GDF15 serum concentrations were significantly higher in LD patients (819 ng/L) as compared to the control group (415 ng/L) (p < 0.001). In multiple linear regression analysis, an independent and positive association remained between GDF15 on one hand and age, patient group, hemoglobin A1c, triglycerides, and C-reactive protein on the other hand. Moreover, there was an independent negative association between GFD15 and estimated glomerular filtration rate. Circulating GDF15 was not significantly affected by metreleptin treatment in LD patients. Gdf15 was upregulated in leptin-deficient lipodystrophic mice as compared to controls. Moreover, Gdf15 mRNA expression was downregulated by leptin treatment in lipodystrophic and obese animals. Conclusions. Serum concentrations of GDF15 are elevated in LD patients and independently associated withmarkers of metabolic dysfunction. Gdf15 expression is higher in lipodystrophic mice and downregulated by leptin treatment.

L’érythropoïèse est le processus de différentiation d’un progéniteur érythroïde multipotent en globules rouges. La différentiation érythroïde est essentiellement contrôlée par le récepteur à l’érythropoïétine (EPOR). Nous avons montré que le récepteur à la transferrine de type 2 (TFR2) est un membre important du complexe formé par l’EPOR. Le TFR2 présente, comme l’EPOR une expression restreinte qui dépend du type cellulaire. Ainsi son expression n’a pu être détectée que dans le foie, l’érythron et l’intestin grêle. Le rôle du TFR2 a été exploré dans les hépatocytes et il a été montré qu’il joue le rôle d’un senseur de fer dans cette lignée et de ce fait contribue à l’homéostasie du fer. Nous avons déterminé le rôle du TFR2 dans les érythroblastes et montré que TFR2 est une protéine escorte de l’EPOR qui contribue à l’érythropoïèse in vitro et in vivo. De plus, nos travaux montrent que le TFR2 est requis pour la production de GDF15 (Growth Differentiation Factor 15) dans les érythroblastes. D’autre part nous avons démontré que la production de GDF15 est augmentée par l’EPO, la déplétion intracellulaire en fer et l’activité transactivatrice de P53. L’inhibition de l’expression de P53, réalisée au cours de l’étude de son rôle dans la production de GDF15, a révélé son implication dans l’érythropoïèse normale. Nous avons mis en évidence l’existence de plusieurs formes du TFR2. Deux d’entre elles résultent de l’utilisation de sites distincts d’initiation de la traduction. Ces deux isoformes sont régulée différemment au cours de la maturation des érythroblastes. La troisième isoforme, appelée TFR2 soluble (sTFR2), est relargée dans le plasma suite au clivage du TFR2. Nous avons montré que la production du sTFR2 est inhibée en présence du ligand de TFR2, la transferrine saturée en fer (holoTF) alors que le TFR2 est stabilisé dans ces mêmes conditions. Les rôles spécifiques des trois formes du TFR2 doivent encore être élucidés. / Erythropoiesis is the differentiation process of a multipotent erythroid progenitor into red blood cells. Erythroid differentiation is primarily controlled by the erythropoietin receptor (EPOR). We showed that the Transferrin receptor 2 (TFR2) is an important member of the EPOR complex. TFR2 has like EPOR a lineage-restricted expression and can solely be detected in the liver, erythron and small intestine. TFR2 function has been explored in hepatocytes where it plays the role of an iron sensor and contributes to iron homeostasis. We determined the role of TFR2 in erythroblasts and showed that TFR2 is an escort protein for EPOR that contributes to optimal erythropoiesis in vitro and in vivo. Moreover we evidenced that TFR2 is absolutely required for the production of Growth differentiation factor 15 (GDF15) in erythroblasts. We further demonstrated that GDF15 production is increased by EPO levels, by intracellular iron depletion as well as by P53 trans-activation activity. The inhibition of P53 expression, realized for the study of its role in GDF15 production, revealed its implication in normal erythropoiesis. We evidenced that TFR2 is expressed under several forms, two of which result from the utilization of distinct translational initiation sites. These two isoforms are differently regulated during erythroid maturation. The third form called soluble TFR2 (sTFR2) is released in the plasma after TFR2 cleavage. We showed that sTFR2 production is inhibited in the presence of TFR2 ligand, iron loaded transferrin (holoTF) whereas cell surface TFR2 expression is stabilized by holoTF. The specific roles of the three forms of TFR2 expressed by erythroblasts remain to be elucidated.