Anna Sanchez

Le cancer de la prostate est le deuxième cancer le plus fréquent chez l’homme dans le monde. Les changements épigénétiques en réponse à des événements externes (alimentation, activités sportives, etc.) et internes sont de plus en plus impliqués dans l'initiation et la progression des tumeurs. La dérégulation des mécanismes épigénétiques conduit à une modification de la compaction de la chromatine et par conséquent, de l’expression de gènes ayant potentiellement un pouvoir oncogène ou suppresseur de tumeur. Cette thèse s’intéresse aux modifications post-traductionnelles des histones et, plus particulièrement, à la tri méthylation de la lysine 27 de l'histone 3 (H3K27me3) dans le cancer de la prostate. H3K27me3 est une marque épigénétique répressive souvent sous- ou surexprimée dans un large éventail de cancers. Trois acteurs régulent la méthylation de H3K27: La méthyltransférase EZH2 et les déméthylases JMJD3 et UTX. Premièrement, grâce à l’utilisation d’épidrogues et de siARNs dirigés spécifiquement contre ces trois acteurs, nous avons montré in vitro qu’EZH2, JMJD3 et UTX étaient impliquées dans la régulation des gènes MGMT, TRA2A, U2AF1 et RPS6KA2, précédemment établis comme étant une signature génique du cancer de la prostate. Cette étude in vitro a également permis de mettre en évidence un possible lien entre EZH2, JMJD3 et le récepteur aux androgènes. Ensuite, H3K27me3 et EZH2 étant largement étudiées, notre étude s’est focalisée sur JMJD3. Après inhibition de JMJD3 in vivo par son inhibiteur chimique, GSK-J4, nous avons obtenu une augmentation de la croissance tumorale dans les xénogreffes RA- et à une diminution dans les xénogreffes RA+, ajoutant une preuve d’un possible lien entre le récepteur aux androgènes et JMJD3. La caractérisation des altérations épigénétiques comme l’expression aberrante de H3K27me3 dans le cancer de la prostate est indispensable pour identifier de nouveaux marqueurs de diagnostic. La compréhension du rôle de H3K27me3, EZH2, JMJD3 et UTX dans la progression tumorale prostatique reste importante en vue de l’utilisation d’épidrogues qui pourrait prochainement devenir une nouvelle stratégie thérapeutique.

Background/Aim: Histone methylation status is required to control gene expression. H3K27me3 is an epigenetic tri-methylation modification to histone H3 controlled by the demethylase JMJD3. JMJD3 is dysregulated in a wide range of cancers and has been shown to control the expression of a specific growth-modulatory gene signature, making it an interesting candidate to better understand prostate tumor progression in vivo. This study aimed to identify the impact of JMJD3 inhibition by its inhibitor, GSK4, on prostate tumor growth in vivo. Materials and Methods: Prostate cancer cell lines were implanted into Balb/c nude male mice. The effects of the selective JMJD3 inhibitor GSK-J4 on tumor growth were analyzed by bioluminescence assays and H3K27me3-regulated changes in gene expression were analyzed by ChIP-qPCR and RT-qPCR. Results: JMJD3 inhibition contributed to an increase in tumor growth in androgen-independent (AR-) xenografts and a decrease in androgen-dependent (AR+). GSK-J4 treatment modulated H3K27me3 enrichment on the gene panel in DU-145-luc xenografts while it had little effect on PC3-luc and no effect on LNCaP-luc. Effects of JMJD3 inhibition affected the panel gene expression. Conclusion: JMJD3 has a differential effect in prostate tumor progression according to AR status. Our results suggest that JMJD3 is able to play a role independently of its demethylase function in androgen-independent prostate cancer. The effects of GSK-J4 on AR+ prostate xenografts led to a decrease in tumor growth.

OMICS: A Journal of Integrative Biology

OMICS: A Journal of Integrative Biology

Cancer is a major cause of death worldwide. Epigenetic changes in response to external (diet, sports activities, etc.) and internal events are increasingly implicated in tumor initiation and progression. In this review, we focused on post-translational changes in histones and, more particularly, the tri methylation of lysine from histone 3 (H3K27me3) mark, a repressive epigenetic mark often under- or overexpressed in a wide range of cancers. Two actors regulate H3K27 methylation: Jumonji Domain-Containing Protein 3 demethylase (JMJD3) and Enhancer of zeste homolog 2 (EZH2) methyltransferase. A number of studies have highlighted the deregulation of these actors, which is why this scientific review will focus on the role of JMJD3 and, consequently, H3K27me3 in cancer development. Data on JMJD3’s involvement in cancer are classified by cancer type: nervous system, prostate, blood, colorectal, breast, lung, liver, ovarian, and gastric cancers.

Background/Aim: In breast cancer, initiation of carcinogenesis leads to epigenetic dysregulation, which can lead for example to the loss of the heterochromatin skeleton SUV39H1/H3K9me3/HP1 or the supposed secondary skeleton TIP60/P400/H4K12ac/BRD (2/4), which allows the maintenance of chromatin integrity and plasticity. This study investigated the relationship between TIP60, P400 and H4K12ac and their implications in breast tumors. Materials and Methods: Seventy-seven patients diagnosed with breast cancer were included in this study. Chromatin immunoprecipitation (ChIP) assay was used to identify chromatin modifications. Western blot and reverse transcription and quantitative real-time PCR were used to determine protein and gene expression, respectively. Results: We verified the variation in H4K12ac enrichment and the co-localization of H4K12ac and TIP60 on the euchromatin and heterochromatin genes, respectively, by ChIP-qPCR and ChIP-reChIP, which showed an enrichment of H4K12ac on specific genes in tumors compared to the adjacent healthy tissue and a co-localization of H4K12ac with TIP60 in different breast tumor types. Furthermore, RNA and protein expression of TIP60 and P400 was investigated and overexpression of TIP60 and P400 mRNA was associated with tumor aggressiveness. Conclusion: There is a potential interaction between H4K12ac and TIP60 in heterochromatin or euchromatin in breast tumors.

Breast cancer is often sporadic due to several factors. Among them, the deregulation of epigenetic proteins may be involved. TIP60 or KAT5 is an acetyltransferase that regulates gene transcription through the chromatin structure. This pleiotropic protein acts in several cellular pathways by acetylating proteins. RNA and protein expressions of TIP60 were shown to decrease in some breast cancer subtypes, particularly in triple-negative breast cancer (TNBC), where a low expression of TIP60 was exhibited compared with luminal subtypes. In this study, the inhibition of the residual activity of TIP60 in breast cancer cell lines was investigated by using two chemical inhibitors, TH1834 and NU9056, first on the acetylation of the specific target, lysine 4 of histone 3 (H3K4) by immunoblotting, and second, by chromatin immunoprecipitation (ChIP)-qPCR (-quantitative Polymerase Chain Reaction). Subsequently, significant decreases or a trend toward decrease of H3K4ac in the different chromatin compartments were observed. In addition, the expression of 48 human nuclear receptors was studied with TaqMan Low-Density Array in these breast cancer cell lines treated with TIP60 inhibitors. The statistical analysis allowed us to comprehensively characterize the androgen receptor and NR3C2 receptors in TNBC cell lines after TH1834 or NU9056 treatment. The understanding of the residual activity of TIP60 in the evolution of breast cancer might be a major asset in the fight against this disease, and could allow TIP60 to be used as a biomarker or therapeutic target for breast cancer progression in the future.

Triple-negative breast cancer (TNBC) types with poor prognosis are due to the absence of estrogen receptors, progesterone receptors and HEGFR-2. The lack of suitable therapy for TNBC has led the re...