Les Spreading Initiations Centers et la traduction locale régulent l'adhésion et l'étalement des cellules mésenchymateuses

Au Canada, il est estimé qu’une personne sur deux sera diagnostiqué pour un cancer et qu’une personne sur quatre en décédera, faisant du cancer la première cause de mortalité (Statistiques canadiennes sur le cancer 2017. Toronto, ON: Société canadienne du cancer, 2017). La formation de métastases est la principale cause des décès puisqu’elle y est associée à 90%. Lors de ce processus, les cellules épithéliales cancéreuses quittent la tumeur primaire et envahissent les tissus distants après avoir subi la transition épithéliale mésenchymateuse (EMT), ce qui leur permet d’accroître leur capacité migratoire. Plusieurs travaux ont montré un lien de causalité entre les protéines liant l’ARN et la progression tumorale. C’est le cas de l’étude qui a identifié les SICs (Spreading Initiation Centers), une structure transitoire présente lors de l’initiation de l’adhésion et défini comme présente uniquement dans les cellules mésenchymateuses. Nous proposons que les SICs contrôlent l’adhésion et la transition vers l’étalement cellulaire. Ainsi, nous avons cherché à caractériser cette structure et sa fonction. Nos données indiquent que la formation des SICs est contrôlée par l’activation de la voie RhoA et que son inhibition affecte leur formation et la consolidation de l’adhésion des cellules mésenchymateuses. Cette consolidation est liée au recrutement et à l’enrichissement spécifique de certaines protéines liant l’ARN, d’ARNm et d’un fort taux de traduction locale au niveau des SICs. De plus, nous montrons que lors de l’adhésion, une reprogrammation traductionnelle s’effectue afin de traduire des ARNm impliqués dans l’adhésion cellulaire. À l’aide d’une nouvelle méthode basée sur la puromycine, nous avons été capable d’identifier les protéines synthétisées lors de ce processus et avons montré que l’enrichissement de leur ARNm au niveau des SICs est dépendant de leur région 3’UTR. Enfin, l'inhibition de la traduction lors de l’adhésion diminue uniquement la capacité d’adhésion des lignées cellulaires mésenchymateuses et des cellules cancéreuses hautement métastatiques qui ont subi l’EMT. En conclusion, nous montrons que le métabolisme des SICs est régulé par leur capacité à traduire des ARNm spécifiques. Nous proposons que les SICs agissent comme un point de contrôle d’adhérence dans les cellules métastatiques leur permettant ainsi de moduler leur dissémination.In Canada, one person out of two will be diagnosed with cancer and one out of four will die of it, making cancer the leading cause of death (Statistiques canadiennes sur le cancer 2017. Toronto, ON: Société canadienne du cancer, 2017). This is mainly caused by metastasis formation, which is associated to more than 90% of the death related to cancer. While majority of cancers mostly originates from epithelial tissues, pre-metastatic cancerous cells can only leave the primary tumor after undergoing the epithelial mesenchymal transition (EMT). This transition allows cancerous cell lines to increase their ability to migrate through the highly structured stroma, invade the blood stream in order to disseminate in distant tissues. Increasing studies have shown causality in between RNA binding protein (RBP) and tumor progression. Our discoveries strengthen this hypothesis, as our work on Spreading initiation center (SIC), a transient structure during early adhesion, showed that RBPs regulation translation regulates these structure during mesenchymal cells adhesion and spreading. We found that SICs formation is controlled by RhoA activation and its inhibition will affect their formation and adhesion consolidation of mesenchymal cells. This consolidation is done with recruitment and enrichment of specific RBPs, mRNA and a high level of local translation in SICs. We also showed translational reprograming events during early adhesion, allowing us to find adhesion-regulated translation of specific mRNAs known to be implicated in cellular adhesion. Using our specifically engineered methods based on puromycin incorporation capacities, we identified neosynthesized proteins during early adhesion, showing a distinct translational activity. This also led us to show a specific enrichment of the mRNA coding for the newly synthetized proteins, through 3’UTR, within SICs. Finally, we showed that translation inhibition decreased the adhesion ability of mesenchymal cells and highly metastatic cancerous cells that undergo EMT, while not affecting epithelial cells or non-metastatic ones. Taken together, we conclude that SIC-regulated mechanism regulate mesenchymal cell adhesion through their ability to translate specific RNA, and that SICs can act as an adhesion checkpoint for metastatic cells, thus modulating their ability to disseminate and form metastases

The oncometabolite 2-hydroxyglutarate activates the mTOR signalling pathway

The identification of cancer-associated mutations in the tricarboxylic acid (TCA) cycle enzymes isocitrate dehydrogenases 1 and 2 (IDH1/2) highlights the prevailing notion that aberrant metabolic function can contribute to carcinogenesis. IDH1/2 normally catalyse the oxidative decarboxylation of isocitrate into α-ketoglutarate (αKG). In gliomas and acute myeloid leukaemias, IDH1/2 mutations confer gain-of-function leading to production of the oncometabolite R-2-hydroxyglutarate (2HG) from αKG. Here we show that generation of 2HG by mutated IDH1/2 leads to the activation of mTOR by inhibiting KDM4A, an αKG-dependent enzyme of the Jumonji family of lysine demethylases. Furthermore, KDM4A associates with the DEP domain-containing mTOR-interacting protein (DEPTOR), a negative regulator of mTORC1/2. Depletion of KDM4A decreases DEPTOR protein stability. Our results provide an additional molecular mechanism for the oncogenic activity of mutant IDH1/2 by revealing an unprecedented link between TCA cycle defects and positive modulation of mTOR function downstream of the canonical PI3K/AKT/TSC1-2 pathway

Flecainide Is Associated With a Lower Incidence of Arrhythmic Events in a Large Cohort of Patients With Catecholaminergic Polymorphic Ventricular Tachycardia

BACKGROUND: In severely affected patients with catecholaminergic polymorphic ventricular tachycardia, beta-blockers are often insufficiently protective. The purpose of this study was to evaluate whether flecainide is associated with a lower incidence of arrhythmic events (AEs) when added to beta-blockers in a large cohort of patients with catecholaminergic polymorphic ventricular tachycardia. METHODS: From 2 international registries, this multicenter case cross-over study included patients with a clinical or genetic diagnosis of catecholaminergic polymorphic ventricular tachycardia in whom flecainide was added to beta-blocker therapy. The study period was defined as the period in which background therapy (ie, beta-blocker type [beta1-selective or nonselective]), left cardiac sympathetic denervation, and implantable cardioverter defibrillator treatment status, remained unchanged within individual patients and was divided into pre-flecainide and on-flecainide periods. The primary end point was AEs, defined as sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter defibrillator shock, and arrhythmic syncope. The association of flecainide with AE rates was assessed using a generalized linear mixed model assuming negative binomial distribution and random effects for patients. RESULTS: A total of 247 patients (123 [50%] females; median age at start of flecainide, 18 years [interquartile range, 14-29]; median flecainide dose, 2.2 mg/kg per day [interquartile range, 1.7-3.1]) were included. At baseline, all patients used a beta-blocker, 70 (28%) had an implantable cardioverter defibrillator, and 21 (9%) had a left cardiac sympathetic denervation. During a median pre-flecainide follow-up of 2.1 years (interquartile range, 0.4-7.2), 41 patients (17%) experienced 58 AEs (annual event rate, 5.6%). During a median on-flecainide follow-up of 2.9 years (interquartile range, 1.0-6.0), 23 patients (9%) experienced 38 AEs (annual event rate, 4.0%). There were significantly fewer AEs after initiation of flecainide (incidence rate ratio, 0.55 [95% CI, 0.38-0.83]; P=0.007). Among patients who were symptomatic before diagnosis or during the pre-flecainide period (n=167), flecainide was associated with significantly fewer AEs (incidence rate ratio, 0.49 [95% CI, 0.31-0.77]; P=0.002). Among patients with ≥1 AE on beta-blocker therapy (n=41), adding flecainide was also associated with significantly fewer AEs (incidence rate ratio, 0.25 [95% CI, 0.14-0.45]; P&lt;0.001). CONCLUSIONS: For patients with catecholaminergic polymorphic ventricular tachycardia, adding flecainide to beta-blocker therapy was associated with a lower incidence of AEs in the overall cohort, in symptomatic patients, and particularly in patients with breakthrough AEs while on beta-blocker therapy.</p

Flecainide Is Associated With a Lower Incidence of Arrhythmic Events in a Large Cohort of Patients With Catecholaminergic Polymorphic Ventricular Tachycardia.

BACKGROUND: In severely affected patients with catecholaminergic polymorphic ventricular tachycardia, beta-blockers are often insufficiently protective. The purpose of this study was to evaluate whether flecainide is associated with a lower incidence of arrhythmic events (AEs) when added to beta-blockers in a large cohort of patients with catecholaminergic polymorphic ventricular tachycardia. METHODS: From 2 international registries, this multicenter case cross-over study included patients with a clinical or genetic diagnosis of catecholaminergic polymorphic ventricular tachycardia in whom flecainide was added to beta-blocker therapy. The study period was defined as the period in which background therapy (ie, beta-blocker type [beta1-selective or nonselective]), left cardiac sympathetic denervation, and implantable cardioverter defibrillator treatment status, remained unchanged within individual patients and was divided into pre-flecainide and on-flecainide periods. The primary end point was AEs, defined as sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter defibrillator shock, and arrhythmic syncope. The association of flecainide with AE rates was assessed using a generalized linear mixed model assuming negative binomial distribution and random effects for patients. RESULTS: A total of 247 patients (123 [50%] females; median age at start of flecainide, 18 years [interquartile range, 14-29]; median flecainide dose, 2.2 mg/kg per day [interquartile range, 1.7-3.1]) were included. At baseline, all patients used a beta-blocker, 70 (28%) had an implantable cardioverter defibrillator, and 21 (9%) had a left cardiac sympathetic denervation. During a median pre-flecainide follow-up of 2.1 years (interquartile range, 0.4-7.2), 41 patients (17%) experienced 58 AEs (annual event rate, 5.6%). During a median on-flecainide follow-up of 2.9 years (interquartile range, 1.0-6.0), 23 patients (9%) experienced 38 AEs (annual event rate, 4.0%). There were significantly fewer AEs after initiation of flecainide (incidence rate ratio, 0.55 [95% CI, 0.38-0.83]; P=0.007). Among patients who were symptomatic before diagnosis or during the pre-flecainide period (n=167), flecainide was associated with significantly fewer AEs (incidence rate ratio, 0.49 [95% CI, 0.31-0.77]; P=0.002). Among patients with ≥1 AE on beta-blocker therapy (n=41), adding flecainide was also associated with significantly fewer AEs (incidence rate ratio, 0.25 [95% CI, 0.14-0.45]; P&lt;0.001). CONCLUSIONS: For patients with catecholaminergic polymorphic ventricular tachycardia, adding flecainide to beta-blocker therapy was associated with a lower incidence of AEs in the overall cohort, in symptomatic patients, and particularly in patients with breakthrough AEs while on beta-blocker therapy