Study of the mechanism of action of an onco-metabolite involved in proliferation of triple-negative breast cancers

Le cancer du sein est la 1ère cause de décès par cancer chez la femme. Il existe trois sous-types de cancers du sein : ceux qui expriment les récepteurs hormonaux des œstrogènes (REα+), ceux qui amplifient le récepteur 2 du facteur de croissance épidermique humain (HER2) et ceux qui n’expriment aucun de ces récepteurs, dits cancers triple négatifs (TN). Pour ce dernier sous-type, il n'existe aucune thérapie ciblée. Le métabolisme du cholestérol est dérégulé dans le cancer du sein comparé au tissu normal. En effet, dans les tissus mammaires normaux, les 5,6-époxydes de cholestérol (ECs) sont transformés par la cholestérol époxyde hydrolase (ChEH) en cholestane-triol (CT). Dans le tissu tumoral mammaire, le CT est transformé en un onco-métabolite, le 6-oxo-cholestan-3β, 5α-diol (OCDO), par l'enzyme 11β-hydroxystéroïde déshydrogénase de type 2 (11βHSD2). La 11βHSD2, est connue pour réguler le métabolisme des glucocorticoïdes en convertissant le cortisol, un agoniste actif des récepteurs aux glucocorticoïdes (GR), en cortisone inactif. De plus, l’OCDO stimule la prolifération de différents modèles de cancer du sein TN via le GR. Les données de la littérature indiquent que la surexpression du GR est corrélée à une faible survie sans progression et sans survie globale chez les patientes atteintes d'un cancer du sein TN. L’objet de ma thèse fut consacré à la caractérisation des mécanismes impliqués dans la prolifération tumorale induite par l’OCDO via le GR. J’ai ainsi pu montré que la voie mitogène AP-1 est activée par l’OCDO via le GR et qu’elle a un rôle majeur dans la progression tumorale de ces modèles cellulaires in vitro et in vivo. Ainsi, le ciblage du GR et de la voie AP-1 pourrait représenter de nouvelles stratégies thérapeutiques pour les cancers du sein TN.Breast cancer is the leading cause of cancer death in women. There are three subtypes of breast cancer: those that express estrogen hormone receptors (REα +), those that amplify the human epidermal growth factor receptor 2 (HER2) and those that don’t express any of these receptors, triple negative cancers (TN). For the last subtype, there is no targeted therapy. Cholesterol metabolism is deregulated in breast cancer compared to normal tissue. Indeed, in normal mammary tissues, cholesterol-5,6-epoxides (ECs) are transformed by cholesterol epoxide hydrolase (ChEH) into cholestan-triol (CT). In mammary tumor tissue, CT is converted into an onco-metabolite, 6-oxo-cholestan-3β, 5α-diol (OCDO), by the enzyme 11β-hydroxystéroïde déshydrogénase type 2 (11βHSD2). 11βHSD2 is known to regulate glucocorticoid metabolism by converting cortisol, an active glucocorticoid receptor (GR) agonist, to inactive cortisone. In addition, the OCDO stimulates the proliferation of different models of breast cancer TN by the GR. Data from the literature indicate that overexpression of GR correlates with poor progression-free survival and overall survival in patients with TN breast cancer. The purpose of my thesis was to characterize the mechanisms involved in OCDO-mediated tumor proliferation by the GR. I then showed that the AP-1 mitogenic pathway is activated by OCDO by the GR and has a major role in the tumor progression of these cell models in vitro and in vivo. Thus, targeting GR and the AP-1 pathway may represent new therapeutic strategies for TN breast cancers

Chemistry, biochemistry, metabolic fate and mechanism of action of 6-oxo-cholestan-3β,5α-diol (OCDO), a tumor promoter and cholesterol metabolite

International audienceOxygenation products of cholesterol, named oxysterols, were suspected since the 20th century to be involved in carcinogenesis. Among the family of oxysterol molecules, cholesterol-5,6-epoxides (5,6-EC) retained the attention of scientists because they contain a putative alkylating epoxide group. However, studies failed into demonstrating that 5,6-EC were direct carcinogens and revealed a surprising chemical stability and unreactivity towards nucleophiles in standard conditions. Analyses of 5,6-EC metabolism in normal cells showed that they were extensively transformed into cholestane-3β,5α,6β-triol (CT) by the cholesterol-5,6-epoxide hydrolase (ChEH). Studies performed in cancer cells showed that CT was additionally metabolized into an oxysterol identified as the 6-oxo-cholestan-3β,5α-diol (OCDO), by the 11β-hydroxysteroid dehydrogenase of type 2 (HSD2), the enzyme which inactivates cortisol into cortisone. Importantly, OCDO was shown to display tumor promoter properties in breast cancers, by binding to the glucocorticoid receptor, and independently of their estrogen receptor status, revealing the existence of a new tumorigenic pathway centered on 5,6-EC. In breast tumors from patients, OCDO production as well as the expression of the enzymes involved in the pathway producing OCDO, namely ChEH subunits and HSD2, were higher compared to normal tissues, and overexpression of these enzymes correlate with a higher risk of patient death, indicating that this onco-metabolism is of major importance to breast cancer pathology. Herein, we will review the actual knowledge and the future trends in OCDO chemistry, biochemistry, metabolism and mechanism of action and will discuss the impact of OCDO discovery on new anticancer therapeutic strategies

The cholesterol-derived metabolite dendrogenin A functionally reprograms breast adenocarcinoma and undifferentiated thyroid cancer cells

International audienceDendrogenin A (DDA) is a tumor suppressor mammalian cholesterol-derived metabolite and a new class of ligand of the Liver X receptor (LXR), which displays tumor cell differentiation. In human MCF7 breast adenocarcinoma cells, DDA-induced cell differentiation was associated with an increased accumulation of neutral lipids and proteins found in milk indicating that DDA re-activates some functions of lactating cells. Active iodide transport occurs in the normal lactating mammary cells through the sodium/iodide symporter (NIS) and iodide (I) is secreted into milk to be used by the nursing newborn for thyroid hormones biosynthesis. In the present study, we assessed whether DDA may induce other characteristic of lactating cells such as NIS expression and iodine uptake in MCF7 breast cancer cells and extended this study to the papillary B-CPAP and undifferentiated anaplastic 8505c thyroid cancer cells. Moreover, we evaluated DDA impact on the expression of thyroid specific proteins involved in thyroid hormone biogenesis. We report here that DDA induces NIS expression in MCF7 cells and significantly increases the uptake of 131-I by acting through the LXR. In addition, DDA induces phenotypic, molecular and functional characteristics of redifferentiation in the two human thyroid carcinoma cell lines and the uptake of 131-I in the undifferentiated 8505c cells was associated with a strong expression of all the specific proteins involved in thyroid hormone biosynthesis, TSH receptor, thyroperoxidase and thyroglobulin. 131-I incorporation in the 8505c cells was stimulated by DDA as well as by the synthetic LXR ligand, GW3965. Together these data show that the re-differentiation of breast and thyroid cancer cells by DDA, is associated with the recovery of functional NIS expression and involves an LXR-dependent mechanism. These results open new avenues of research for the diagnosis of thyroid cancers as well as the development of new therapeutic approaches for radioiodine refractory thyroid cancers

Identification of a tumor-promoter cholesterol metabolite in human breast cancers acting through the glucocorticoid receptor

International audienceBreast cancer (BC) remains the primary cause of death from cancer among women worldwide. Cholesterol-5,6-epoxide (5,6-EC) metabolism is deregulated in BC but the molecular origin of this is unknown. Here, we have identified an oncometabolism downstream of 5,6-EC that promotes BC progression independently of estrogen receptor α expression. We show that cholesterol epoxide hydrolase (ChEH) metabolizes 5,6-EC into cholestane-3β,5α,6β-triol, which is transformed into the oncometabolite 6-oxo-cholestan-3β,5α-diol (OCDO) by 11β-hydroxysteroid-dehydrogenase-type-2 (11βHSD2). 11βHSD2 is known to regulate glucocorticoid metabolism by converting active cortisol into inactive cortisone. ChEH inhibition and 11βHSD2 silencing inhibited OCDO production and tumor growth. Patient BC samples showed significant increased OCDO levels and greater ChEH and 11βHSD2 protein expression compared with normal tissues. The analysis of several human BC mRNA databases indicated that 11βHSD2 and ChEH overexpression correlated with a higher risk of patient death, highlighting that the biosynthetic pathway producing OCDO is of major importance to BC pathology. OCDO stimulates BC cell growth by binding to the glucocorticoid receptor (GR), the nuclear receptor of endogenous cortisol. Interestingly, high GR expression or activation correlates with poor therapeutic response or prognosis in many solid tumors, including BC. Targeting the enzymes involved in cholesterol epoxide and glucocorticoid metabolism or GR may be novel strategies to prevent and treat BC