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Supplementary Figure S1. Coculture with preadipocytes has no effect on cancer cell invasion and coculture with mature adipocytes has no effect on prostate cancer cell number. Supplementary Figure S2. Adrenergic receptors do not control adipocyte lipolysis in response to tumor cell secretions. Supplementary Figure S3. The metabolic remodeling towards uncoupled FAO observed in cocultivated cells is not involved in the increase in prostate cancer invasion induced by adipocytes. Supplementary Figure S4. ROS positively regulate prostate cancer cells invasion. Supplementary Figure S5. 10mM NAC and 10μM DPI do not affect PC3 viability. Supplementary Figure S6. Coculture and palmitate stimulate tumor invasion through NOX in Du-145 cells. Supplementary Figure S7. NOX5 invalidation leads to a strong decrease in cell survival.

Prostate gland is surrounded by periprostatic adipose tissue (PPAT), which is increasingly believed to play a paracrine role in prostate cancer progression. Our previous work demonstrates that adipocytes promote homing of prostate cancer cells to PPAT and that this effect is upregulated by obesity. Here, we show that once tumor cells have invaded PPAT (mimicked by an in vitro model of coculture), they establish a bidirectional crosstalk with adipocytes, which promotes tumor cell invasion. Indeed, tumor cells induce adipocyte lipolysis and the free fatty acids (FFA) released are taken up and stored by tumor cells. Incubation with exogenous lipids also stimulates tumor cell invasion, underlining the importance of lipid transfer in prostate cancer aggressiveness. Transferred FFAs (after coculture or exogenous lipid treatment) stimulate the expression of one isoform of the pro-oxidant enzyme NADPH oxidase, NOX5. NOX5 increases intracellular reactive oxygen species (ROS) that, in turn, activate a HIF1/MMP14 pathway, which is responsible for the increased tumor cell invasion. In obesity, tumor-surrounding adipocytes are more prone to activate the depicted signaling pathway and to induce tumor invasion. Finally, the expression of NOX5 and MMP14 is upregulated at the invasive front of human tumors where cancer cells are in close proximity to adipocytes and this process is amplified in obese patients, underlining the clinical relevance of our results.Implications:Our work emphasizes the key role of adjacent PPAT in prostate cancer dissemination and proposes new molecular targets for the treatment of obese patients exhibiting aggressive diseases.

Proteins identified by mass-spectrometry in adipocyte exosomes

Malignant progression results from a dynamic cross-talk between stromal and cancer cells. Recent evidence suggests that this cross-talk is mediated to a significant extent by exosomes, nanovesicles secreted by most cell types and which allow the transfer of proteins, lipids, and nucleic acids between cells. Adipocytes are a major component of several tumor microenvironments, including that of invasive melanoma, where cells have migrated to the adipocyte-rich hypodermic layer of the skin. We show that adipocytes secrete exosomes in abundance, which are then taken up by tumor cells, leading to increased migration and invasion. Using mass spectrometry, we analyzed the proteome of adipocyte exosomes. Interestingly, these vesicles carry proteins implicated in fatty acid oxidation (FAO), a feature highly specific to adipocyte exosomes. We further show that, in the presence of adipocyte exosomes, FAO is increased in melanoma cells. Inhibition of this metabolic pathway completely abrogates the exosome-mediated increase in migration. Moreover, in obese mice and humans, both the number of exosomes secreted by adipocytes as well as their effect on FAO-dependent cell migration are amplified. These observations might in part explain why obese melanoma patients have a poorer prognosis than their nonobese counterparts. Cancer Res; 76(14); 4051–7. ©2016 AACR.

1) Adipocyte exosomes promote melanoma migration but have no effect on melanoma proliferation; 2) Preadipocytes secrete less exosomes than adipocytes, and these exosomes have no effect on melanoma behavior; 3) Adipocyte exosomes promote prostate tumor cell migration but have no effect on their proliferation; 4) All common exosomal markers are present in the adipocyte exoproteome; 5) Adipocyte exosomes increase FAO enzymes in SKMEL28 cells; 6) Adipocyte exosomes have no effect on SKMEL28 lactate production; 7) Adipocyte exosomes promote prostate tumor cell migration dependent on FAO 8) Primary adipocytes secrete exosomes in lean and obese conditions which promote prostate cancer cell migration

Periprostatic adipose tissue (PPAT) abundance correlates with prostate cancer progression, but the mechanism remains unexplained. Here, we used a statistical approach to define abundant PPAT by normalizing PPAT volume to prostate volume in a cohort of 351 patients with a linear regression model. Applying this definition, we find tumors specifically from patients with abundant PPAT exhibit several hallmarks of aggressiveness, suggesting that PPAT abundance might be used to improve risk stratification. We show that abundant PPAT expands by adipocyte hypertrophy but this does not result in inflammation. Extensive extracellular matrix remodeling, notably of the collagen network, and decreased expression of mechano-sensing proteins in adipocytes explains this inflammation-free expansion by decreasing the mechanical constraints on the adipocytes. Moreover, collagen VI degradation in abundant PPAT is associated with production of endotrophin, a matrikine that promotes cancer progression. We find high levels of endotrophin specifically in the urine of patients with abundant PPAT, indicating the clinical relevance of our findings.SummaryThe abundance of periprostatic adipose tissue favors prostate cancer aggressiveness. The increase in extracellular matrix remodeling that occurs in expanded periprostatic fat allows adipocyte hypertrophy without tissue inflammation and generates a matrikine, endotrophin, which favors tumor progression.

Prostate is surrounded by a specific fat depot called periprostatic adipose tissue (PPAT) that contributes through paracrine mechanisms to prostate cancer (PCa) progression. Like other white adipose tissues, PPAT stores lipids and is an endocrine organ. However, PPAT is still poorly characterized. Nevertheless, current evidence highlights that soluble factors secreted from PPAT might promote PCa aggressiveness and local dissemination. In addition, the ability of adipocytes to provide lipids to tumor cells participates in tumor aggressiveness. The secretory and metabolic profile of PPAT is modified by obesity, a state associated with greater occurrences of aggressive diseases. Beyond obesity, the excessive accumulation of PPAT, independently of the ponderal status of the patients, is an emerging risk factor in aggressive diseases. Characterization of the role of human PPAT on PCa progression will undoubtedly provide, in the near future, new therapeutic strategies and new risk stratification factors in PCa.

International audience; White adipose tissue accumulates at various sites throughout the body and some adipose tissue depots exist in close proximity to organs, whose function they could influence in a paracrine manner. Prostate gland is surrounded by a poorly characterized adipose depot called periprostatic adipose tissue (PPAT) playing emerging roles in prostate-related disorders. Unlike all other adipose depots, PPAT secretes pro-inflammatory cytokines even in lean individuals and does not increase in volume during obesity. These unique features remain unexplained due to the poor structural and functional characterization of this tissue. We characterized the structural organization of PPAT in patients in comparison to abdominopelvic adipose tissue (APAT), an extraperitoneal adipose depot whose accumulation is correlated to BMI. Confocal microscopy followed by 3D reconstructions showed a sparse vascular network in PPAT when compared with that in APAT, suggesting that this tissue is hypoxic. Unbiased comparisons of PPAT and APAT transcriptomes found that most differentially expressed genes were related to the hypoxia response. High levels of the hypoxia-inducible factor HIF-2α confirmed the presence of an adaptive response to hypoxia in PPAT. This chronic hypoxic state was associated with inflammation and fibrosis, which were not further upregulated by obesity. This fibrosis and inflammation explain the failure of PPAT to expand in obesity and open new mechanistic avenues to explain its role in prostate-related disorders including cancer

Prostate gland is surrounded by periprostatic adipose tissue (PPAT), which is increasingly believed to play a paracrine role in prostate cancer progression. Our previous work demonstrates that adipocytes promote homing of prostate cancer cells to PPAT and that this effect is upregulated by obesity. Here, we show that once tumor cells have invaded PPAT (mimicked by an in vitro model of coculture), they establish a bidirectional crosstalk with adipocytes, which promotes tumor cell invasion. Indeed, tumor cells induce adipocyte lipolysis and the free fatty acids (FFA) released are taken up and stored by tumor cells. Incubation with exogenous lipids also stimulates tumor cell invasion, underlining the importance of lipid transfer in prostate cancer aggressiveness. Transferred FFAs (after coculture or exogenous lipid treatment) stimulate the expression of one isoform of the pro-oxidant enzyme NADPH oxidase, NOX5. NOX5 increases intracellular reactive oxygen species (ROS) that, in turn, activate a HIF1/MMP14 pathway, which is responsible for the increased tumor cell invasion. In obesity, tumor-surrounding adipocytes are more prone to activate the depicted signaling pathway and to induce tumor invasion. Finally, the expression of NOX5 and MMP14 is upregulated at the invasive front of human tumors where cancer cells are in close proximity to adipocytes and this process is amplified in obese patients, underlining the clinical relevance of our results. Implications: Our work emphasizes the key role of adjacent PPAT in prostate cancer dissemination and proposes new molecular targets for the treatment of obese patients exhibiting aggressive diseases.

Malignant progression results from a dynamic cross-talk between stromal and cancer cells. Recent evidence suggests that this cross-talk is mediated to a significant extent by exosomes, nanovesicles secreted by most cell types and which allow the transfer of proteins, lipids, and nucleic acids between cells. Adipocytes are a major component of several tumor microenvironments, including that of invasive melanoma, where cells have migrated to the adipocyte-rich hypodermic layer of the skin. We show that adipocytes secrete exosomes in abundance, which are then taken up by tumor cells, leading to increased migration and invasion. Using mass spectrometry, we analyzed the proteome of adipocyte exosomes. Interestingly, these vesicles carry proteins implicated in fatty acid oxidation (FAO), a feature highly specific to adipocyte exosomes. We further show that, in the presence of adipocyte exosomes, FAO is increased in melanoma cells. Inhibition of this metabolic pathway completely abrogates the exosome-mediated increase in migration. Moreover, in obese mice and humans, both the number of exosomes secreted by adipocytes as well as their effect on FAO-dependent cell migration are amplified. These observations might in part explain why obese melanoma patients have a poorer prognosis than their nonobese counterparts. Cancer Res; 76(14); 4051–7. ©2016 AACR.

Metabolic reprogramming represents an important hallmark of cancer cells. Besides de novo fatty acid synthesis, it is now clear that cancer cells can acquire Fatty Acids (FA) from tumor-surrounding adipocytes to increase their invasive capacities. Indeed, adipocytes release FA in response to tumor secreted factors that are transferred to tumor cells to be either stored as triglycerides and other complex lipids or oxidized in mitochondria. Like all cells, FA can be released over time from triglyceride stores through lipolysis and then oxidized in mitochondria in cancer cells. This metabolic interaction results in specific metabolic remodeling in cancer cells, and underpins adipocyte stimulated tumor progression. Lipolysis and fatty acid oxidation therefore represent novel targets of interest in the treatment of cancer. In this review, we summarize the recent advances in our understanding of the metabolic reprogramming induced by adipocytes, with a focus on breast cancer. Then, we recapitulate recent reports studying the effect of lipolysis and fatty acid oxidation inhibitors on tumor cells and discuss the interest to target these metabolic pathways as new therapeutic approaches for cancer.

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.

D609 is known to modulate death receptor-induced ceramide generation and cell death. We show that in Jurkat cells, non-toxic D609 concentrations inhibit sphingomyelin synthase and, to a lesser extent, glucosylceramide synthase, and transiently increase the intracellular ceramide level. D609 significantly enhanced FasL-induced caspase activation and apoptosis. D609 stimulated FasL-induced cell death in caspase-8-deficient Jurkat cells, indicating that D609 acts downstream of caspase-8. At high FasL concentration (500 ng/mL), cell death was significantly, but not completely, inhibited by zVAD-fmk, a broad-spectrum caspase inhibitor, indicating that FasL can activate both caspase-dependent and -independent cell death signaling pathways. FasL-induced caspase activation was abolished by zVAD-fmk, whereas ceramide production was only partially impaired. D609 enhanced caspase-independent ceramide increase and cell death in response to FasL. Also, D609 overcame zVAD-fmk-conferred resistance to a FasL concentration as low as 50 ng/mL and bypassed RIP deficiency. It is likely that mitochondrial events were involved, since Bcl-xL over-expression impaired D609 effects. In PHA-activated human T lymphocytes, D609 enhanced FasL-induced cell death in the presence or absence of zVAD-fmk. Altogether, our data strongly indicate that the inhibition of ceramide conversion to complex sphingolipids by D609 is accompanied by an enhancement of FasL-induced caspase-dependent and -independent cell death in T lymphocytes.

In contrast to caspase-8, controversy exists as to the ability of caspase-10 to mediate apoptosis in response to FasL. Herein, we have shown activation of caspase-10, -3, and -7 as well as B cell lymphoma-2-interacting domain (Bid) cleavage and cytochrome c release in caspase-8-deficient Jurkat (I9-2) cells treated with FasL. Apoptosis was clearly induced as illustrated by nuclear and DNA fragmentation. These events were inhibited by benzyloxycarbonyl-VAD-fluoromethyl ketone, a broad spectrum caspase inhibitor, indicating that caspases were functionally and actively involved. Benzyloxycarbonyl-AEVD-fluoromethyl ketone, a caspase-10 inhibitor, had a comparable effect. FasL-induced cell death was not completely abolished by caspase inhibitors in agreement with the existence of a cytotoxic caspase-independent pathway. In subpopulations of I9-2 cells displaying distinct caspase-10 expression levels, cell sensitivity to FasL correlated with caspase-10 expression. A robust caspase activation, Bid cleavage, and DNA fragmentation were observed in cells with high caspase-10 levels but not in those with low levels. In vitro, caspase-10, as well as caspase-8, could cleave Bid to generate active truncated Bid (p15). Altogether, our data strongly suggest that caspase-10 can serve as an initiator caspase in Fas signaling leading to Bid processing, caspase cascade activation, and apoptosis.

BACKGROUND: Upon CD95/Fas ligation, the initiator caspase-8 is known to activate effector caspases leading to apoptosis. In the presence of zVAD-fmk, a broad-spectrum caspase inhibitor, Fas engagement can also trigger an alternative, non-apoptotic caspase-independent form of cell death, which is initiated by RIP1. Controversy exists as to the ability of caspase-10 to mediate cell death in response to FasL (CD95L or CD178). Herein, the role of caspase-10 in FasL-induced cell death has been re-evaluated. METHODOLOGY AND PRINCIPAL FINDINGS: The present study shows that FasL-induced cell death was completely impaired in caspase-8- and caspase-10-doubly deficient (I9-2e) Jurkat leukaemia T-cell lines. Over-expressing of either caspase-8 or caspase-10 in I9-2e cells triggered cell death and restored sensitivity to FasL, further arguing for a role of both initiator caspases in Fas apoptotic signalling. In the presence of zVAD-fmk, FasL triggered an alternative form of cell death similarly in wild-type (A3) and in caspase-8-deficient Jurkat cells expressing endogenous caspase-10 (clone I9-2d). Cell death initiated by Fas stimulation in the presence of zVAD-fmk was abrogated in I9-2e cells as well as in HeLa cells, which did not express endogenous caspase-10, indicating that caspase-10 somewhat participates in this alternative form of cell death. Noteworthy, ectopic expression of caspase-10 in I9-2e and HeLa cells restored the ability of FasL to trigger cell death in the presence of zVAD-fmk. As a matter of fact, FasL-triggered caspase-10 processing still occurred in the presence of zVAD-fmk. CONCLUSIONS AND SIGNIFICANCE: Altogether, these data provide genetic evidence for the involvement of initiator caspase-10 in FasL-induced cell death and indicate that zVAD-fmk does not abrogate caspase-10 processing and cytotoxicity in Fas signalling. Our study also questions the existence of an alternative caspase-independent cell death pathway in Fas signalling.

International audience; Ceramide can be converted into sphingomyelin by sphingomyelin synthases (SMS) 1 and 2. In this study, we show that in human leukemia Jurkat cells, which express mainly SMS1, Fas ligand (FasL) treatment inhibited SMS activity in a dose- and time-dependent manner before nuclear fragmentation. The SMS inhibition elicited by FasL (1) was abrogated by benzyloxycarbonyl valyl-alanyl-aspartyl-(O-methyl)-fluoromethylketone (zVAD-fmk), a broad-spectrum caspase inhibitor; (2) did not occur in caspase-8-deficient cells and (3) was not affected in caspase-9-deficient cells. Western blot experiments showed SMS1 cleavage in a caspase-dependent manner upon FasL treatment. In a cell-free system, caspase-2, -7, -8 and -9, but not caspase-3 and -10, cleaved SMS1. In HeLa cells, SMS1 was Golgi localized and relocated throughout the cytoplasm in cells exhibiting an early apoptotic phenotype on FasL treatment. zVAD-fmk prevented FasL-induced SMS1 relocation. Thus, FasL-mediated SMS1 inhibition and relocation depend on caspase activation and likely represent proximal events in Fas signaling. FasL-induced ceramide production and cell death were enhanced in cells stably expressing an siRNA against SMS1. Conversely, in cells stably overexpressing SMS1, FasL neither increased ceramide generation nor efficiently induced cell death. Altogether, our data show that SMS1 is a novel caspase target that is functionally involved in the regulation of FasL-induced apoptosis.

International audience; Much is known about the pathways that control the biosynthesis, transport and degradation of sphingolipids. During the last two decades, considerable progress has been made regarding the roles this complex group of lipids play in maintaining membrane integrity and modulating responses to numerous signals. Further novel insights have been provided by the analysis of newly discovered genetic diseases in humans as well as in animal models harboring mutations in the genes whose products control sphingolipid metabolism and action. Through the description of the phenotypic consequences of genetic defects resulting in the loss of activity of the many proteins that synthesize, transport, bind, or degrade sphingolipids, this review summarizes the (patho)physiological functions of these lipids.

Ceramide metabolism has emerged as a potential target for anticancer therapy. Here, the potential usefulness of two novel synthetic ceramide analogs as anti-leukemic drugs was investigated. Compounds AD2646 and AD2687 were able to dose-and time-dependently decrease the viability of Jurkat leukemic cells. This was accompanied by an accumulation of endogenous ceramide owing to perturbed ceramide metabolism. Cytotoxicity involved caspase activation but also necrotic-like features, as evidenced by phosphatidylserine externalization, membrane permeability, hypodiploidy, caspase processing and only partial protection from cell death by a pan-caspase inhibitor. Ceramide analogs also induced cell death in Jurkat mutants that are deficient in cell death signaling proteins, including FADD, caspase-8 and 10, and RIP. While overexpression of Bcl-xL did not suppress ceramide accumulation, it conferred robust protection from caspase activation and cell death. Altogether, these novel ceramide analogs are able to kill leukemic cells through distinct pathways implicating caspase activation and mitochondrial events, and represent a new group of bioactive molecules with potential applications in anticancer therapy.

The plasma membrane is a major resource for production of bioactive lipids and contains a large proportion of the cellular sphingomyelin (SM) content. Consequently, the regulation of SM levels at the plasma membrane by enzymes such as sphingomyelinase (SMase) and SM synthase 2 (SMS2) can have profound effects – both on biophysical properties of the membrane, but also on cellular signaling. Over the past twenty years, there has been considerable research into the physiological and cellular functions associated with regulation of SM levels, notably with regards to the production of ceramide. In this review, we will summarize this research with particular focus on the SMases and SMS2. We will outline what biological functions are associated with SM metabolism/production at the PM, and discuss what we believe are major challenges that need to be addressed in future studies.

Prostate cancer (PCa) is the most common cancer in men in Western countries. It is a heterogeneous disease ranging from indolent to very aggressive, life-threatening forms. The molecular mechanisms implicated in tumor progression have not been clearly identified yet. The aim of my thesis was to characterize the role of one of the main components of prostate cancer microenvironment, the periprostatic adipose tissue (PPAT), an adipose depot surrounding the prostate. Indeed, PPAT invasion by tumor cells is recognized as a poor prognosis factor in PCa, suggesting that PPAT (and more specifically their main cellular component, adipocytes) could be a key player in tumor progression. First, we focused on the paracrine role of this PPAT in the context of obesity, which is known as a poor prognosis factor for PCa. We have shown that a chemokine secreted by adipocytes (CCL7), by binding to its receptor CCR3 on the surface of tumor cells, is able to chemoattract these cells outside of the prostate gland, thus favoring the local dissemination of PCa, this phenomenon being amplified in the context of obesity. Once tumor cells have crossed the prostatic capsule, they come into direct contact with PPAT adipocytes and a bidirectional crosstalk between the two cell types is established. Our results show that this crosstalk begins with an increased lipolysis in adipocytes, that release free fatty acids (FFA) then taken up by tumor cells. Those FFA activate a signaling cascade in tumor cells, by stimulating the expression of pro-oxidant enzymes, especially NOX5 (NADPH-oxidase 5), that leads to an increase in intracellular ROS (Reactive Oxygen Species). This accumulation of ROS leads to an increase in the expression of some MMP (Matrix Metalloproteinases) participating in tumor invasion. We have also shown that all this signaling pathways is upregulated in a context of obesity. Aside from obesity, recent studies suggest that some patients could present an unusual accumulation of PPAT, independently from BMI (Body Mass Index), those abundant PPAT being correlated with more aggressive prostate cancers. We have shown, by measuring PPAT volume on the MRI of 147 patients with prostate cancer, that PPAT abundance is dissociated from BMI and the accumulation of other adipose depots. [...]; Le cancer de la prostate (CaP) est la première cause de cancer chez l'homme dans les pays industrialisés. Il s'agit d'une maladie hétérogène pouvant être indolente ou très agressive et mettant alors en jeu le pronostic des patients. Les mécanismes moléculaires impliqués dans cette progression tumorale sont mal connus. L'objectif de ma thèse était de caractériser le rôle d'un des composants majeurs du microenvironnement de ces tumeurs, le tissu adipeux périprostatique (TAPP), dépôt adipocytaire entourant la glande prostatique. En effet, l'invasion de ce TAPP par les cellules tumorales est reconnue comme un facteur de mauvais pronostic, suggérant que ce TAPP (en particulier les adipocytes) pourrait être un acteur clé de la progression tumorale. Dans un premier temps nous nous sommes intéressés au rôle paracrine de ce TAPP en condition d'obésité, qui est un facteur pronostique négatif dans le cancer de la prostate. Nous avons montré qu'une chimiokine adipocytaire (CCL7), en se liant à son récepteur CCR3 présent à la surface des cellules tumorales, attire ces dernières, favorisant ainsi la dissémination locale du cancer de la prostate, ce phénomène étant amplifié en conditions d'obésité. Une fois que les cellules tumorales ont franchi la capsule prostatique, elles entrent en contact direct avec les adipocytes du TAPP et un dialogue s'établit entre les deux types cellulaires. Nos résultats montrent que ce dialogue se manifeste par une lipolyse accrue dans les adipocytes qui relarguent des acides gras libres (AGL) qui sont ensuite captés par les cellules tumorales. Ces AGL activent une cascade de signalisation dans les cellules tumorales, en stimulant l'expression d'enzymes pro-oxydantes, et en particulier la NOX5 (NADPH-oxydase 5), qui va entraîner une augmentation des ROS (espèces réactives de l'oxygène) intracellulaires. Cette augmentation des ROS va entraîner une augmentation de certaines MMP (Matrix Metalloproteinases) impliquées dans l'invasion tumorale. Cette voie de signalisation est également amplifiée dans un contexte d'obésité. En dehors de l'obésité, des études récentes montrent que certains patients pourraient présenter une accumulation anormale de ce TAPP indépendamment de l'indice de masse corporelle (IMC), ces TAPP abondants étant associés à des cancers agressifs. Nous avons montré, en mesurant le volume de TAPP sur les IRM de 147 patients atteints de CaP, que l'abondance du TAPP est dissociée de l'IMC et des autres dépôts adipeux. [...]

Prostate cancer (PCa) is the most common cancer in men in Western countries. It is a heterogeneous disease ranging from indolent to very aggressive, life-threatening forms. The molecular mechanisms implicated in tumor progression have not been clearly identified yet. The aim of my thesis was to characterize the role of one of the main components of prostate cancer microenvironment, the periprostatic adipose tissue (PPAT), an adipose depot surrounding the prostate. Indeed, PPAT invasion by tumor cells is recognized as a poor prognosis factor in PCa, suggesting that PPAT (and more specifically their main cellular component, adipocytes) could be a key player in tumor progression. First, we focused on the paracrine role of this PPAT in the context of obesity, which is known as a poor prognosis factor for PCa. We have shown that a chemokine secreted by adipocytes (CCL7), by binding to its receptor CCR3 on the surface of tumor cells, is able to chemoattract these cells outside of the prostate gland, thus favoring the local dissemination of PCa, this phenomenon being amplified in the context of obesity. Once tumor cells have crossed the prostatic capsule, they come into direct contact with PPAT adipocytes and a bidirectional crosstalk between the two cell types is established. Our results show that this crosstalk begins with an increased lipolysis in adipocytes, that release free fatty acids (FFA) then taken up by tumor cells. Those FFA activate a signaling cascade in tumor cells, by stimulating the expression of pro-oxidant enzymes, especially NOX5 (NADPH-oxidase 5), that leads to an increase in intracellular ROS (Reactive Oxygen Species). This accumulation of ROS leads to an increase in the expression of some MMP (Matrix Metalloproteinases) participating in tumor invasion. We have also shown that all this signaling pathways is upregulated in a context of obesity. Aside from obesity, recent studies suggest that some patients could present an unusual accumulation of PPAT, independently from BMI (Body Mass Index), those abundant PPAT being correlated with more aggressive prostate cancers. We have shown, by measuring PPAT volume on the MRI of 147 patients with prostate cancer, that PPAT abundance is dissociated from BMI and the accumulation of other adipose depots. [...]; Le cancer de la prostate (CaP) est la première cause de cancer chez l'homme dans les pays industrialisés. Il s'agit d'une maladie hétérogène pouvant être indolente ou très agressive et mettant alors en jeu le pronostic des patients. Les mécanismes moléculaires impliqués dans cette progression tumorale sont mal connus. L'objectif de ma thèse était de caractériser le rôle d'un des composants majeurs du microenvironnement de ces tumeurs, le tissu adipeux périprostatique (TAPP), dépôt adipocytaire entourant la glande prostatique. En effet, l'invasion de ce TAPP par les cellules tumorales est reconnue comme un facteur de mauvais pronostic, suggérant que ce TAPP (en particulier les adipocytes) pourrait être un acteur clé de la progression tumorale. Dans un premier temps nous nous sommes intéressés au rôle paracrine de ce TAPP en condition d'obésité, qui est un facteur pronostique négatif dans le cancer de la prostate. Nous avons montré qu'une chimiokine adipocytaire (CCL7), en se liant à son récepteur CCR3 présent à la surface des cellules tumorales, attire ces dernières, favorisant ainsi la dissémination locale du cancer de la prostate, ce phénomène étant amplifié en conditions d'obésité. Une fois que les cellules tumorales ont franchi la capsule prostatique, elles entrent en contact direct avec les adipocytes du TAPP et un dialogue s'établit entre les deux types cellulaires. Nos résultats montrent que ce dialogue se manifeste par une lipolyse accrue dans les adipocytes qui relarguent des acides gras libres (AGL) qui sont ensuite captés par les cellules tumorales. Ces AGL activent une cascade de signalisation dans les cellules tumorales, en stimulant l'expression d'enzymes pro-oxydantes, et en particulier la NOX5 (NADPH-oxydase 5), qui va entraîner une augmentation des ROS (espèces réactives de l'oxygène) intracellulaires. Cette augmentation des ROS va entraîner une augmentation de certaines MMP (Matrix Metalloproteinases) impliquées dans l'invasion tumorale. Cette voie de signalisation est également amplifiée dans un contexte d'obésité. En dehors de l'obésité, des études récentes montrent que certains patients pourraient présenter une accumulation anormale de ce TAPP indépendamment de l'indice de masse corporelle (IMC), ces TAPP abondants étant associés à des cancers agressifs. Nous avons montré, en mesurant le volume de TAPP sur les IRM de 147 patients atteints de CaP, que l'abondance du TAPP est dissociée de l'IMC et des autres dépôts adipeux. [...]