Since the discovery of DNA packaging into chromatin, and McClintock's (1951) work on position-effect variegation providing evidence of non-mendelian inheritance, the principal of a genome maintaining 'on' and 'off' states has been widely adopted. However, the underlying mechanisms that regulate these dynamic chromatin states and their effect on disease are still poorly understood. DNA methylation and histone trimethylation at H3K9 and H4K20 are the core hallmarks of the heterochromatic constitutively 'off' state. Constitutive heterochromatin is predominantly comprised of repetitive satellite containing pericentromeric regions and telomeres and in mouse heterochromatin clusters into large chromocenters. These regions are cytologically more compact and generally transcriptionally silent across embryonic and differentiated mouse cell types. However, in addition to increased genomic instability, mouse tumour cells sustain increased satellite expression suggesting constitutive heterochromatin is disrupted. Therefore how constitutive heterochromatin is maintained has important implications for genome regulation and disease, and remains poorly understood. While satellite DNA sequences are not evolutionarily conserved, pericentromeric and telomeric heterochromatin occurs across species. Heterochromatin formation is therefore independent of the underlying DNA sequence, supporting the hypothesis that epigenetic components can regulate chromatin structure. DNA methylation is generally thought to be associated with transcriptional silencing and chromatin compaction. However, Gilbert et al (2007) showed that the complete loss of DNA methylation did not affect the compaction at heterochromatin or global genome compaction. The role of H3K9me3 in regulating heterochromatin has also been an area of keen interest. H3K9me3 patterns are established by suppressor of variegation 3-9 homologues and provide the binding site for heterochromatic protein 1 [HP1] which can in turn recruit Suv39h1. This Suv3-9h-HP1-H3K9 axis enables its propagation throughout heterochromatin. Peters et al (2001) demonstrated that in mice loss of suv39 homologues 1 and 2 caused a loss of H3K9me3 at constitutive heterochromatic domains. These Suv39h null mice demonstrated decreased genome stability, and an increased prevalence of oncogenesis. However cytological chromocenters are still present in the absence of H3K9me3. Therefore the function of H3K9me3 as a causative agent in heterochromatin formation is still debated. Broadly the aim was to investigate the phenotypic role of heterochromatic epigenetic components in cancer progression, and address whether H3K9me3 effects large scale chromatin structure. To identify heterochromatic gene silencing components, an inhibitor screen was performed in an artificial silenced reporter system. The reporter fluorophore was silenced by the presence of centromeric arrays from yeast/bacterial artificial chromosomes and human alpha satellite repeats enriched for H3K9me3. To address the function of the de-silencing components identified in cancer, the fitness of colon cancer cells [HCT116] was investigated before and after the development of resistance to the MEK inhibitor trametinib. The most intriguing result was that BET protein inhibition resulted in derepression of the reporter construct and trametinib resistant HCT116 cells were more sensitive to BET inhibitors, while subsequent investigation showed HP1 protein levels were altered. Analysis of publically available datasets of tumour drug resistance, showed elevated BET protein binding at HP1 promoters in resistant cell lines suggesting an indirect role in gene silencing. To investigate the consequence of H3K9me3 loss on chromatin structure, mouse embryonic stem cells that lacked both Suv39 homologues were used. Microccocal nuclease digestion and sucrose sedimentation demonstrated a global decompaction of large-scale chromatin fibres whilst re-expression of suv39h1 rescued H3K9me3 at chromocenters and global chromatin decompaction. Loss of Suv39h also increased chromatin associated RNA levels that were also rescued by Suv39h1 re-expression. This suggests that H3K9me3 has a role chromatin fibre compaction globally as well as at constitutive heterochromatin, potentially mediated by chromatin associated RNA. To conclude, multiple components were identified that are involved in transcriptional silencing. Evaluating their function in tumour progression demonstrated a possible role of BET proteins in the development of MEKi resistance that may be mediated through HP1 proteins. H3K9me3 and its binding partner HP1 affect global chromatin compaction. The global decompaction after Suv39h loss correlates with an increase in chromatin associated RNA, suggesting a possible mechanism for changes in chromatin compaction beyond H3K9me3.

acase@tulane.edu / Triple-negative breast cancer (TNBC) presents a clinical challenge due to the aggressive nature of the disease and a lack of targeted therapies. Constitutive activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway has been linked to chemoresistance and metastatic progression through distinct mechanisms, including activation of epithelial-to-mesenchymal transition (EMT) whereby cells adopt a motile and invasive phenotype through loss of epithelial markers, namely Cadherin 1/E-Cadherin (CDH1), and acquisition of mesenchymal markers, such as vimentin (VIM) and Cadherin 2/N-Cadherin (CDH2). While MAPK/ERK1/2 kinase inhibitors (MEKi) have shown promise as antitumor agents in the preclinical setting, application has had limited success clinically. Activation of compensatory signaling, potentially contributing to the emergence of drug resistance, has shifted the therapeutic strategy to combine MEK1/2 inhibitors with agents targeting oncoproteins (RAF) or parallel growth pathways (PI3K). Conventional MAPK family members have been well-characterized in modulation of cellular processes involved in tumor initiation and progression, yet the role of MEK5-ERK5 in cancer biology is not completely understood. Recent studies have highlighted the importance of the MEK5 pathway in metastatic progression of various cancer types, including those of the prostate, colon, bone and breast. Furthermore, elevated levels of ERK5 expression and activity observed in breast carcinomas are linked to worse prognosis in TNBC patients. The purpose of this work is to explore MEK5 regulation of the EMT axis and to evaluate a novel pan-MEK inhibitor on clinically aggressive TNBC cells. Our results show a distinction between the MEK1/2 and MEK5 cascades in maintenance of the mesenchymal phenotype, suggesting that the MEK5 pathway may be necessary and sufficient in EMT regulation while MEK1/2 signaling further sustains the mesenchymal state of TNBC cells. Furthermore, additive effects on MET induction are evident through the inhibition of both MEK1/2 and MEK5. Taken together, these data demonstrate the need for a better understanding of the individual roles of MEK1/2 and MEK5 signaling in breast cancer and provide rationale for combined targeting of these pathways to circumvent compensatory signaling and subsequent therapeutic resistance. / 1 / Van Hoang

Epithelial to mesenchymal transition (EMT) is an important process in embryonic development, tissue repair, inflammation, and cancer. During EMT, epithelial cells disassemble cell-cell adhesions, lose apicobasal polarity, and initiate migratory and invasive processes that allow individual cells to colonize distant sites. It is the means by which non-invasive tumors progress into malignant, metastatic carcinomas. In vitro, EMT occurs in two steps. First, cells spread out, increasing in surface area and pushing the colony borders out. Then cells contract, pulling away from neighboring cells and rupturing cell-cell junctions, resulting in individual highly migratory cells. Recent discoveries indicate that calcium signaling is central in EMT. Both previous data with patch clamping and new calcium imaging data show a series of calcium influxes in cells induced to undergo EMT with hepatocyte growth factor (HGF). It has also been shown that blocking calcium signaling prevents EMT from progressing normally. However, it is not known if calcium alone is sufficient to drive EMT behaviors. By experimentally triggering calcium influxes with an optigenetic cation channel, the behaviors that calcium influxes induce can be determined noninvasively, without use of drugs that may have secondary effects. The results of using the optigenetic set up along with live cell imaging are that cells become more motile and disrupt normal epithelial cell-cell adhesions. This behavior is believed to be due to increased cell contractility downstream of calcium signaling, and is dependent on Ca2+/calmodulin-dependent protein kinase II (CaMKII). When cells are pre-treated with CaMKII inhibitor before HGF addition, they undergo the spreading step of EMT without subsequent cellular contraction and rupture of cell-cell junctions. CaMKII is a protein kinase that is activated by binding Ca2+/calmodulin, and is a known downstream component of calcium signaling. CaMKII is known to affect the actin cytoskeleton by both physically bundling actin filaments to increase their rigidity, and through signaling by activation of myosin light chain kinase (MLCK), which has a role in stress fiber formation. Immunofluorescence did not show colocalization of CaMKII with actin, ruling out regulation through actin bundling. However, CaMKII does appear to have a role in stress fiber formation. EMT induced with HGF treatment results in increased numbers of stress fibers as well as trans-cellular actin network formation, both actin structures decorated with non-muscle myosin II (NMII). CaMKII inhibition not only blocks these actin formations, but it also decreases stress fiber levels below basal unstimulated levels in cells that have not been treated with HGF. This suggests that CaMKII has a role in regulating contractility through cellular actin networks, indicating a mechanism for calcium's role in cellular contractility in EMT.

Pulmonary fibrosis is a potentially deadly pathology characterized by excessive deposition of extracellular matrix (ECM), increased tissue stiffness, and loss of tissue structure and function. Recent evidence has suggested epithelial to mesenchymal transition (EMT), the transdifferentiation of an epithelial cell into a mesenchymal fibroblast, is one mechanism that results in the accumulation of myofibroblasts and excessive deposition of ECM. EMT is a highly orchestrated process involving the integration of biochemical signals from specific integrin mediated interactions with ECM proteins and soluble growth factors including TGFβ. TGFβ, a potent inducer of EMT, can be activated by cell contraction mediated mechanical release of the growth factor from a macromolecular latent complex. Therefore, TGFβ activity and subsequent EMT may be influenced by both the biochemical composition and biophysical state of the surrounding ECM. Based on these knowns it was first investigated how changes in the biochemical composition of the matrix and changes in tissue rigidity together modulate EMT due to changes in epithelial cell contraction and TGFβ activation. Here we show that integrin specific interactions with fibronectin (Fn) variants displaying both the RGD and PHSRN binding sites facilitate cell binding through α3β1 and α5β1 integrins, and that these interactions maintain an epithelial phenotype despite engagement of increased tissue rigidities. Conversely, Fn fragments that facilitate cell binding through αv integrins drive TGFβ activation and subsequent EMT even while engaging soft underlying substrates. Adding to the complexity of studying mechanisms that contribute to pulmonary fibrosis, is exposure of the lung to injuries from environmental particulates. Therefore, we investigated how EMT is altered in response to particulate matter (PM). Here we show that PM exposure further drives TGFβ activation, EMT, and increases intracellular levels of reactive oxygen species (ROS). Additionally, cells binding the ECM through α5β1 and α3β1 integrins only partially recover an epithelial phenotype, suggesting ROS may be a secondary driver of TGFβ and EMT. Taken together these results suggest dynamic changes to the ECM microenvironment are major contributors to the control of EMT responses and provide insights into the design of biomaterial-based microenvironments for control of epithelial cell phenotype.

No description available.

It is a well established phenomenon that the epithelial lining of the urinary bladder (urothelium) when implanted into skeletal muscle induces ectopic ossification. However, despite numerous observations, this reaction is poorly understood. This research further studied this reaction by - (a) demonstrating the reaction in a suitable small animal model; (b) attempting to induce the reaction by implanting urothelial cells purified by cell culture techniques; and (c) comparing the bone forming reaction induced by implanted urothelium to the reaction induced by implanting Bone Marrow Stem Cells (BMSC's) and Osteophyte Stem Cells (OSC's). By demonstrating newly formed bone after the implantation of guinea pig urothelium into the skeletal muscle of a Severe Combined Immuno-Deficient Mouse (SCID-Mouse) this research demonstrated that a suitable small animal model had been established. This is despite inherent difficulties (particularly bacterial contamination) associated with establishing a primary cell culture of guinea pig urothelial cells. Additionally, the intramuscular ectopic osteoinductive potential of human BMSC's (hBMSC's) in the SCID-mouse has also been demonstrated. Confirming that the injection of cultured cells in suspension is an adequate intramuscular delivery technique, this research demonstrates that hBMSC's induce ectopic ossification by non-immunological means. This research has demonstrated a number of differences between urothelium induced ectopic ossification and ectopic ossification induced by BMSC's, suggesting they are two separate processes. This is important because the chemotaxis and subsequent osteogenic differentiation of BMSC's has previously been one of the more popular postulated mechanisms of urothelium induced ectopic ossification. Finally, this research has demonstrated the ectopic osteoinductive potential of stem cells isolated from the marrow of human osteophytes (human Osteophyte Stem Cells, hOSC's). This observation has not been previously reported, and will hopefully provide a valuable contribution to a body of knowledge that has important ramifications in both the treatment of osteoarthritis, and the use of BMSC's in tissue engineering.

The ovarian surface epithelium (OSE) is a monolayer of cells surrounding the ovary that is ruptured during ovulation. After ovulation the wound is repaired, however this process, and the mechanisms to maintain OSE homeostasis after the wound is repaired are poorly understood. We have shown the mouse OSE (mOSE) contains a stem cell population that is expanded by Transforming Growth Factor Beta 1 (TGFB1), a factor present in follicular fluid. These data suggest that components in the follicular fluid such as TGFB1 may promote wound repair and OSE homeostasis through maintenance of the OSE stem cell population. Additionally, TGFB1 may promote wound repair through induction of an epithelial-to-mesenchymal transition (EMT) and activation of pro-survival pathways, as seen in other tissues. To elucidate the mechanism for TGFB1-mediated ovulatory wound repair, mOSE cells were treated with TGFB1, which induced an EMT seen with increased Snai1 expression and cell migration. Snai1 overexpression also increased cell migration and sphere formation (a stem cell characteristic). RNA sequencing results suggest this is at least in part through elevated collagen deposition in SNAI1 overexpressing cells. A TGFB signalling targets array identified Cox2 induction following TGFB1 treatment. Constitutive Cox2 expression did not promote an EMT, but enhanced sphere formation and cell survival. Finally, TGFB1 treatment decreased Brca1 expression, which when deleted from mOSE cells also increased sphere formation. RNA sequencing results suggest that Brca1 deletion promotes stemness through activation of the stem cell genes Ly6a and Lgr5. RNA sequencing was also used to compare mOSE cells cultured as monolayers and as spheroids, with and without TGFB1. These results validate our findings that TGFB1 promotes an EMT partially through Snail induction and the upregulation of Cox2. mOSE cells cultured as spheroids acquire a mesenchymal transcriptional profile that is further enhanced with TGFB1 treatment. These data suggest that TGFB1 may promote ovulatory wound repair and maintain OSE homeostasis through the induction of an EMT, maintenance of the stem cell population and activation of a pro-survival pathway. Interestingly, mOSE spheroids also decrease Brca1 expression and upregulate cancer associated genes such as Pax8 and Greb1. The induction of survival pathways, while simultaneously increasing stemness and repressing Brca1 could render cells more susceptible to transformation. This work provides novel insights as to why ovulation is the primary non-hereditary risk factor for ovarian cancer.

Le cancer gastrique (CG) est une maladie multifactorielle, fréquemment associée à l’infection chronique par des souches CagA+ d’Helicobacter pylori. La transition épithélio-mésenchymateuse (EMT) est un processus réversible dans lequel une cellule épithéliale polarisée acquiert un phénotype mésenchymateux. L’EMT est à l’émergence de cellules souches cancéreuses (CSC) qui expriment CD44 et présentent une activité ALDH élevée. L’infection des cellules épithéliales gastriques humaines (CEGs) par CagA+ H. pylori induit des cellules CD44+ avec des propriétés des CSCs via une EMT. La voie Hippo est composée par les kinases MST et LATS, et leurs cibles, les YAP1 et TAZ. Suite à la phosphorylation, YAP1 et TAZ sont inhibés. YAP1 et TAZ activés lient les facteurs TEAD pour promouvoir la croissance cellulaire et l’inhibition de l’apoptose.Notre premier objectif était de rechercher si H. pylori change l’état d’activation de la voie Hippo et l'effet sur l’EMT et les CSC in vitro et in vivo. Le deuxième but est la caractérisation du rôle de YAP1/TEAD dans les propriétés de CSCs gastriques in vitro et les conséquences de son inhibition dans la croissance tumorale in vivo.Pour étudier la régulation de la voie Hippo pendant l’infection par H. pylori, LATS2, YAP1 et CD44 ont été évalués dans la muqueuse gastrique de sujets non-infectés et infectés par H. pylori, qui ont été augmentés avec l’infection et leur surexpression a été associée avec la gastrite et la métaplasie intestinale. Dans les CEGs l’expression de gènes de la voie Hippo a été altérée par l’infection. La régulation de la voie Hippo par H. pylori a une cinétique diphasique et dépendante de CagA. Dans l’infection précoce, H. pylori déclenche l’activité transcriptionelle de YAP1. Cette période d’inactivité de la voie Hippo est suivi de son activation progressive, soutenue par l’accumulation de LATS2 et la phosphorylation inhibitrice de YAP1. La répression de LATS2 avec siRNAs a accéléré l’acquisition du phénotype mésenchymateux après l’infection, l’augmentation de marqueurs de l’EMT (Zeb1 et Snail1), et la diminution des miR-200 épithéliaux. Les CSC induites par H. pylori ont été potentialisées par l’inhibition de LATS2, ce qui suggère que LATS2 limite l’EMT et le phénotype de CSC acquis pendant l’infection. L’inhibition de LATS2 ou YAP1 diminue l’expression de ces deux protéines, révélant ainsi une boucle de régulation positive. Dans des coupes de tissu de CG, l’expression de LATS2 et YAP1 est hétérogène et positivement corrélée, fait qui a été confirmé dans 38 CEGs de la CCLE. L’expression LATS2 est fortement corrélée à celle de CTGF et CYR61, ce qui suggère que LATS2 peut aussi être un gène cible de YAP1/TEAD.La verteporfine (VP) est capable d’interrompre l’interaction YAP1/TEAD, et donc d’inhiber son activité transcriptionelle. In vitro, utilisant CEGs et des cellules de tumeurs de patients amplifiées chez la souris (patient-derived xenograft PDX), le traitement à la VP a diminué la croissance cellulaire, l’expression de gènes cible de YAP1/TAZ/TEAD, l’activité du rapporteur TEAD-luciférase et la capacité de formation de sphères. L’activité de la VP a été testée in vivo par injection péri-tumorale dans un modèle de greffe sous-cutanés des CEGs MKN45 et MKN74 et le PDX GC10 chez la souris NSG. La croissance tumorale a été diminuée. Le poids des tumeurs, l’analyse par IHC (CD44, ALDH, Ki67) et la capacité de formation de sphères des CSCs résiduelles ont été diminuées. Ces résultats montrent une activité inhibitrice de la VP sur les CSCs gastriques in vitro et in vivo.Ce travail montre pour la première fois que l’axe LATS2/YAP1/TEAD est précocement activé pendant l’infection chronique avec H. pylori et que celui-ci contrôle l’EMT et les propriétés de CSC. Le ciblage de la voie Hippo a été montré comme étant efficace dans la prévention de la croissance tumorale, mettant en évidence le potentiel de son inhibition dans le traitement du cancer gastrique. / Gastric cancer (GC) is a multifactorial disease, most frequently associated to chronic infection with CagA-positive Helicobacter pylori strains. Epithelial-to-mesenchymal transition (EMT) is reversible process in which polarized epithelial cells acquire a mesenchymal phenotype. EMT is at the origin of cancer stem cells (CSC). In GC, CSCs express CD44 and high aldehyde-dehydrogenase (ALDH) activity. Infection with H. pylori of human gastric cancer cell lines (hGECs) in vitro induces the emergence of a population of CD44+ cells with CSC-properties through an EMT process in a CagA-dependent manner. The Hippo pathway is composed by the kinases MST and LATS, and their phosphorylation targets,YAP1 and TAZ. Upon phosphorylation by LATS, YAP1 and TAZ are inhibited. Active YAP1 and TAZ bind to TEAD transcription factors to promote the expression of genes that regulate cell growth and apoptosis.The first aim of this work was to investigate whether H. pylori affects the activation state of the Hippo pathway, and its effect on the EMT process and the CSCs. Second, we intended to characterize the role of YAP1/TEAD in gastric CSC properties in vitro and the consequences of its pharmacological inhibition on tumor growth in vivo.To study the Hippo pathway regulation during infection, LATS2, YAP1 and CD44 were evaluated in gastric mucosae of non-infected or H. pylori-infected patients. They were upregulated in infected mucosae and were associated to pathology. Hippo pathway regulation by H. pylori infection has biphasic kinetics and is CagA-dependent. Early in infection, H. pylori transiently triggered YAP1 expression and co-transcriptional activity, along with LATS2. This period of Hippo pathway inactivity is followed by a progressive activation, sustained by LATS2 accumulation and inhibitory YAP1Ser127-phosphorylation. LATS2 siRNA-mediated repression accelerated the acquisition of the EMT-phenotype upon infection, the up-regulation of EMT-markers ZEB1 and Snail1, and the decrease of the epithelial miR-200. H. pylori-induced CD44 upregulation, invasion and sphere-forming capacity were further enhanced upon LATS2 knockdown, suggesting that LATS2 restricts the EMT and CSC-like phenotype in hGECs upon H. pylori infection. Inhibition of either LATS2 or YAP1 reduced the expression of both proteins, revealing a positive feedback loop. In tissue sections of GC, LATS2 and YAP1 were heterogeneous and co-expressed. The positive correlation between LATS2 and YAP1 was confirmed in the 38 hGECs of the CCLE. The expression of CTGF and CYR61 was also strongly correlated to LATS2, suggesting that LATS2 could also be a YAP1/TEAD target gene.hGECs of the CCLE. The expression of CTGF and CYR61 was also strongly correlated to LATS2, suggesting that LATS2 could also be a YAP1/TEAD target gene.Verteporfin (VP) disrupts the YAP1/TEAD interaction inhibiting its transcriptional activity. In vitro, using hGECs and cells from patient derived primary tumor xenogratfs (PDXs), we showed that treatment with VP decreased cell growth, expression of YAP1/TAZ/TEAD target genes, TEAD-luciferase reporter activity and sphere-forming capacity. The activity of VP was tested in vivo, by peritumoral injection in a model of subcutaneous graft of hGECs (MKN45 and MKN74) and PDX (GC10) in NGS mice. Tumor growth was followed and a decrease was observed. Tumor weight measurement, IHC analysis (CD44, ALDH and Ki67), and CSCs were decreased in treated tumors. These results show the CSC-inhibitory activity of VP both in vitro and in vivo.We showed for the first time that the LATS2/YAP1/TEAD axis is early activated during the carcinogenesis process induced by chronic H. pylori infection and controls the subsequent EMT and CSC-like features. Targeting the Hippo pathway efficiently prevented tumor growth in a PDX model, highlighting the potential of its inhibition to be implemented in gastric cancer therapy.

Colorectal cancer (CRC) is the fourth most common cause of cancer related deaths in the UK with the prognosis dependent on the degree of tumour invasion and presence of metastasis at diagnosis. An important step in the invasion and metastasis of solid tumours is the loss of cell-cell junctions and the acquirement of a more motile mesenchymal phenotype which is facilitated by the epithelial-mesenchymal transition (EMT). The presence of EMT is linked with a more aggressive, invasive tumour and subsequent poor prognosis. In addition to roles in motility and invasion, EMT can induce a cancer stem cell phenotype in a subset of tumour cells. Cancer stem cells (CSCs) are a subpopulation of cells capable of self-renewal and maintaining a cellular population whilst displaying increased therapeutic resistance. Induction of EMT and CSCs can be regulated by common signalling pathways with expression of EMT transcription factors inducing CSCs expression. Understanding the signalling pathways regulating EMT and CSC formation in cancer is important for preventing of metastasis and combating therapeutic resistance. Aspirin’s role in cancer prevention has been established for a number of years with aspirin treatment reducing the incidence of CRC. Recently, evidence has emerged suggesting aspirin treatment may have post-diagnosis benefits and increase survival rates of CRC patients. A potential mechanism for the post-diagnosis benefit of aspirin is the inhibition of EMT and CSC formation which both facilitate tumour progression and metastasis. Aspirin has been demonstrated to suppress the migratory and invasive capacity of lung cancer cell lines by inhibiting EMT. Whilst aspirin has been shown to inhibit platelet-induced EMT in CRC, the direct effects of aspirin on EMT in CRC cell lines has not been established. I hypothesis that aspirin inhibits cell migration, invasion and EMT in CRC which results in a reduction in the CSC population and contributes to the clinical benefit of post-diagnosis aspirin. Using CRC cell lines, I have demonstrated that aspirin treatment inhibits cell migration, invasion, motility and promotes an epithelial phenotype. These results have been confirmed in human organoids and mouse intestinal adenoma in vivo models. Aspirin also promotes a budding phenotype in Apc deficient organoids and reduces expression of stem cell markers in both mouse and human tissue. Aspirin inhibits the mTOR and Wnt signalling pathways in vivo which have the ability to regulate EMT and CSCs although signalling dependency has not been determined. Regardless, aspirin is decreasing the cancer stem cell population and promoting a non-invasive epithelial phenotype which may explain some of the previously described post-diagnosis benefits.

O desenvolvimento e a progressão do câncer bucal envolvem processos complexos de múltiplas etapas levando a modificações fenotípicas nas células epiteliais, aumento da proliferação e invasão dos tecidos subjacentes. Diversos fatores vem sendo associados à carcinogênese, dentre eles os mecanismos epigenéticos como a acetilação de histonas, que promovem mudanças na expressão de genes independente de mutações. O objetivo do presente estudo observacional transversal foi analisar a relação entre acetilação da histona 3 (acetil Histona H3) com proliferação celular e transição epitélio-mesênquima na mucosa bucal normal (MBN), leucoplasias bucais (LB) e carcinomas espinocelulares (CEC) de boca, bem como correlacioná-los com dados clínico-demográficos, graduação histopatológica e o comportamento das lesões. Foram analisados 10 casos de mucosa bucal normal (MBN), 20 casos de LB e 75 casos de CEC de boca. Todos os casos foram submetidas a análise imunoistoquímica utilizando anticorpos anti-acetil Histona H3, Ki67, vimentina e TGF-β1. A imunomarcação da acetil histona H3 foi significativamente menor nos casos de CEC quando comparados a LB (p=0.03). Não foi encontrado diferença entre os casos de MBN e LB. Paralelamente, foi observado um aumento estatisticamente significativo na proliferação durante o processo de carcinogênese (p<0.00) e o mesmo foi observado quando avaliados os marcadores da transição epitélio-mesênquima, vimentina (p=0.03) e TGF-β1 (p<0.00). A análise da associação dos marcadores com fatores clínicos-demográficos não mostrou diferença significativa. Entretanto, maior média de acetil histona H3 foi associada ao bom prognóstico (p=0.01) e também, foi observado uma tendência de uma melhor taxa de sobrevida (p=0.06). Conclui-se que os CEC de boca são hipoacetilados, exibem maior perfil proliferativo e de transição epitélio-mesênquima. Além disso, a acetil histona H3 pode ser considerada um marcador prognostico nestas lesões. / The development and progression of oral cancer involve multi-step processes leading phenotypic changes in epithelial cells, proliferation increase and invasion of adjacent tissue. Several factors have been associated with carcinogenesis, including epigenetic mechanisms such as histone acetylation, which promote changes in the expression independent of gene mutations. The aim of the present study was to analyze the association of acetylation of histone 3 (acetyl-histone H3) with cell proliferation and epithelial-mesenchymal transition in oral leukoplakia (OL) and oral squamous cell carcinoma (OSCC) and correlate them with data clinic-demographic, histopathological grading and the behavior of these lesions. We analyzed 10 cases of normal oral mucosa (NOM), 20 cases of OL and 75 cases of OSCC. All samples were submitted to immunohistochemical analysis using anti-acetyl histone H3, Ki67, vimentin and TGF-β1. Acetyl-histone H3 labeling was significantly lower in cases of OSCC compared to LB (p=0.03). It was not found difference between NOM and OL. In parallel, the proliferation analysis revealed a gradual increase on Ki67 labeling (p<0.00) during oral carcinogenesis with highest value detected in OSCC Also, an increase on EMT markers, vimentin (p=0.03) and TGF-β1 (p<0.00) were noted. A higher mean acetyl-histone H3 was associated with good prognosis (p= 0.01) and similarly a tendency to improved survival rate was observed (p=0.06). As conclusion, OSCC are hypoacetylated, exhibit higher proliferative profile and epithelial-mesenchymal transition characteristics. Furthermore, acetyl histone H3 can be considered a prognostic marker in OSCC.