Mouse embryonic stem cells (mESCs) are pluripotent cells capable of differentiating into all three germ layers present in the adult mouse. In this thesis, I have investigated the transcriptional changes that mESCs undergo as they are induced to differentiate towards the mesoderm lineage by 2i/LIF withdrawal and dimethyl sulfoxide (DMSO) treatment. 5 days of differentiation causes significant drops in expression of Sox2 and Oct4 primary transcript, while expression of Nanog and Kit significantly drops after only 1 day. It was determined that DMSO has no effect on the short-term changes in Nanog and Kit expression induced by 2i/LIF withdrawal. An expanded look at pluripotency-associated genes shows significant up-regulation of Oct4 and down-regulation of Klf4 and Stat3 following only 6 hours of 2i/LIF withdrawal. This data indicates that while some aspects of the transcriptional networks underlying pluripotency respond quickly to mesodermal differentiation cues, others remain unchanged for up to 5 days.

Mouse embryonic stem cells (mESCs) are pluripotent cells capable of differentiating into all three germ layers present in the adult mouse. In this thesis, I have investigated the transcriptional changes that mESCs undergo as they are induced to differentiate towards the mesoderm lineage by 2i/LIF withdrawal and dimethyl sulfoxide (DMSO) treatment. 5 days of differentiation causes significant drops in expression of Sox2 and Oct4 primary transcript, while expression of Nanog and Kit significantly drops after only 1 day. It was determined that DMSO has no effect on the short-term changes in Nanog and Kit expression induced by 2i/LIF withdrawal. An expanded look at pluripotency-associated genes shows significant up-regulation of Oct4 and down-regulation of Klf4 and Stat3 following only 6 hours of 2i/LIF withdrawal. This data indicates that while some aspects of the transcriptional networks underlying pluripotency respond quickly to mesodermal differentiation cues, others remain unchanged for up to 5 days.

ESC/iPSC-derive somatic cells may be ideal for treating disorders caused by cellular deficiency or dysfunction. To form a lineage-specific cell population, ESCs/iPSCs undergo a multi-step process that recapitulates embryonic development. ESC/iPSC differentiation protocols are hampered by the limitation of our understanding in development. Zebrafish embryos are fertilized and developed externally, a feature facilitates the observation and manipulation of embryonic development. To explore the zebrafish as a system to study cell lineage determination, in this thesis, I 1) identified an ortholog of the key pluripotency regulator Nanog in zebrafish and examined its role in early cell fate determination; 2) developed a high-throughput image-based chemical screening system in zebrafish blastomere cell culture that is very similar to, but much faster than, ESC/iPSC differentiation screens. Specifically, in an effort to examine the role of Nanog in vivo, I identified a zebrafish Nanog ortholog, and found that its knockdown impaired endoderm formation. Genome-wide transcription analysis revealed that nanog-like morphants fail to develop the extra-embryonic yolk syncytial layer (YSL), which produces Nodal required for endoderm induction. I examined the genes that were regulated by Nanog-like, and identified the homeobox gene mxtx2, which is both necessary and sufficient for YSL induction. Chromatin immunoprecipitation assays and genetic studies indicated that Nanog-like directly activates mxtx2, which in turn specifies the YSL lineage by directly activating YSL genes. The study identifies a Nanog-like-Mxtx2-Nodal pathway and establishes a role for Nanog-like in regulating the formation of the extra-embryonic tissue required for endoderm induction. In the second part of the thesis, I developed a system that allows high-throughput image-based chemical screening using cultured zebrafish blastomere cells. To demonstrate its potential, this system is utilized to study skeletal muscle development. I screened 2,400 chemicals, finding 11 chemicals that block mature muscle cell differentiation and 17 chemicals that block skeletal muscle progenitor formation. The subsequent studies of these hits illustrate an RTK-PI3K-mTOR- GSK3 signaling cascade that is critical for skeletal muscle development. Preliminary data in mouse Skeletal Muscle Precursors (SMPs) suggest the pathway is conserved in murine adult muscle stem cells. This system, which can be modified for any cell lineage, promises to enhance our understanding of fundamental biology and to identify chemicals for cell-based therapies for many diseases.

Mouse embryonic stem cells (ESCs) are known to possess an “open” global chromatin architecture characterized by dispersed chromatin fibres throughout the nucleus. This is in contrast to differentiated cell types, where chromatin generally congregates into numerous compact domains. Core transcription factors in ESCs regulate many genes involved in maintaining pluripotency and previous research has hinted a connection between these factors and chromatin organization. My hypothesis is that Nanog, one of the core transcription factors, functions in maintaining an “open” chromatin organization in mouse ESCs. In this study, the chromatin organization in ESCs expressing varying levels of Nanog was examined at the sub-micron level through electron spectroscopic imaging. An inverse correlation was identified between Nanog expression level and the chromatin fibre density in constitutive heterochromatic regions. Furthermore, global chromatin in the more differentiated epiblast stem cells became less compact upon Nanog overexpression. Altogether, these findings support the idea that Nanog plays a role in maintaining dispersed chromatin in mouse ESCs.

Mouse embryonic stem cells (ESCs) are known to possess an “open” global chromatin architecture characterized by dispersed chromatin fibres throughout the nucleus. This is in contrast to differentiated cell types, where chromatin generally congregates into numerous compact domains. Core transcription factors in ESCs regulate many genes involved in maintaining pluripotency and previous research has hinted a connection between these factors and chromatin organization. My hypothesis is that Nanog, one of the core transcription factors, functions in maintaining an “open” chromatin organization in mouse ESCs. In this study, the chromatin organization in ESCs expressing varying levels of Nanog was examined at the sub-micron level through electron spectroscopic imaging. An inverse correlation was identified between Nanog expression level and the chromatin fibre density in constitutive heterochromatic regions. Furthermore, global chromatin in the more differentiated epiblast stem cells became less compact upon Nanog overexpression. Altogether, these findings support the idea that Nanog plays a role in maintaining dispersed chromatin in mouse ESCs.

Doctor of Philosophy / Department of Animal Sciences and Industry / David M. Grieger / Early in embryonic development a series of events occur whereby pluripotent cells undergo differentiation to give rise to the three germ layers and extraembryonic tissues of the developing conceptus. Nanog, Sox-2, and Oct-4 genes have been identified as having key roles in maintaining pluripotency in undifferentiated human and mouse cells but recent evidence suggests they may have different roles in farm animals. We cloned the coding sequence for porcine Nanog including 452 base pairs of the Nanog promoter, and partial coding sequences of Oct-4 and Sox-2. Embryos were flushed from sows 10, 12, 15, and 17 days post insemination. RNA was isolated from whole d-10 and -12 conceptuses, d-15 embryonic disk, distal and proximal extraembryonic tissue, and d-17 embryonic disk, distal and proximal extraembryonic tissue, and allantois for real-time PCR. RNA from d-40 maternal myometrium and endometrium, fetal placenta, and liver were also used in real-time PCR. The homeodomain and c-terminal tryptophan repeats are highly conserved in porcine Nanog compared to the mouse, human and bovine. In the promoter, the highly conserved Octamer and Sox binding sequences are also present. The Nanog expression pattern was different when compared to Oct-4 and Sox-2. Day-40 tissues demonstrated the highest expression including endometrium (7 fold) fetal liver (27 fold), placenta (40 fold) and myometrium (72 fold) when compared to day 15 distal extraembryonic tissue. Oct-4 and Sox-2 expression was lowest in d-40 tissues except for fetal liver which was 20 and 71 fold, respectively, higher than endometrium. Oct-4 levels were consistent in d-10, -12, and -15 conceptuses and disk but dropped 3 fold in d-17 disk. On the other hand, Sox-2 was upregulated a 1000 fold in the d-15 disk and 2000 fold in the d-17 disk when compared to the d-12 conceptus. Nanog may have other roles in than maintenance of pluripotency including a possible role in multipotent or progenitor stem cells. Expression of all 3 markers in fetal liver suggests a more primitive cell type is present such as hematopoietic stem cells.

Lors de la fécondation, le sperme et l'ovule s'unissent pour former un zygote totipotent. Initialement, le zygote est transcriptionnellement inactif. Au cours des premiers clivages a lieu la mise en route du génome embryonnaire (EGA) et le développement passe alors sous le contrôle de l’information embryonnaire (au stade 8-16-cellules chez le bovin). Cette transition d’un contrôle maternel à un contrôle embryonnaire est appelée « maternal to embryonic transition (MET) ». De la même façon, lors du transfert nucléaire (clonage), un noyau de cellule somatique placé dans un ovocyte énucléé devient totipotent. Ce processus est appelé «reprogrammation nucléaire somatique?». En fait, la reprogrammation nucléaire lors du clonage est équivalente à la MET, toutefois, le clonage est très peu efficace. Les objectifs de cette étude chez les bovins sont a) d'explorer le processus de reprogrammation lors de la MET dans des embryons fécondés in vitro (FIV) et b) d’estimer l'efficacité de la reprogrammation génique après le transfert nucléaire lors du clonage. Nous émettons l'hypothèse que l'acquisition d'un profil d'expression génique correct pourrait être prédictif d’un potentiel de développement à terme de l'embryon, et pourrait être évalué dès juste après l'activation du génome embryonnaire (EGA) chez les bovins. Nous avons développé notre travail selon deux axes a) des analyses globales d'expression génique utilisant une puce dédiée à l’EGA et b) l’analyse du profil d'expression de gènes candidats par qRT-PCR dans les embryons fécondés et clonés. Dans un premier temps nous avons optimisé le protocole d'amplification d'ARNm pour l'analyse du transcriptome de matériels rares. Puis nous avons fait l'analyse du transcriptome avant et après EGA d’embryons issus d’ovocytes prélevés sur des vaches phénotypées comme « bonnes » ou « mauvaises » donneuses d’embryons. En outre, ces ovocytes ont été maturés soit in vivo soit in vitro. Nos analyses montrent que l'effet individuel est plus important que l'effet « bonne ou mauvaise donneuse » ou même que l’effet « conditions de maturation ». Nous avons ensuite analysé les expressions géniques de 5 types d'embryons clonés ayant différents potentiels de développement à terme en fonction de la lignée cellulaire utilisée comme source de cellules donneuses. Globalement, leur expression génique est proche de celle de morulae FIV, mais quelques gènes présentent une expression différente. Ces gènes varient avec la lignée de cellules donneuses et leur nombre n’est pas lié à l’aptitude au développement à terme. L’analyse d’un lien éventuel entre leur nature et cette aptitude devra être poursuivie. Dans un deuxième temps, nous avons analysé les profils d'expression spatio-temporelle des transcrits et des protéines des gènes de pluripotence (OCT4, SOX2 et NANOG) et les niveaux d'ARNm de certains de leurs cibles dans les ovocytes et les embryons précoces chez le bovin. Les profils d'expression de ces gènes ont aussi été analysés dans des embryons clonés présentant différents potentiels de développement à terme. Nos résultats montrent que (1) la triade de gènes de pluripotence n'est probablement pas impliquée dans l’EGA bovine. (2) les transcrits et protéines de SOX2 et de NANOG sont restreints au lignage pluripotent plus tôt que ceux de OCT4, (3) les embryons à faible taux de développement à terme ont un taux de transcription plus élevé, néanmoins, l’équilibre précaire entre les gènes de pluripotence est maintenue. Cet équilibre pourrait permettre un développement normal in vitro, mais le taux de transcription plus élevé pourrait avoir des conséquences délétères sur le développement ultérieur. / In natural fertilization, sperm and ovum unite to form a totipotent zygote. Initially, the zygote is transcriptionally inactive and after few cleavages (8-16-cell stage in bovine) embryonic genome activation (EGA) takes place and embryo shifts from maternal to embryonic control, the process called maternal to embryonic transition (MET). Likewise, in nuclear transplantation (cloning) a somatic cell nucleus achieves totipotency when placed in an enucleated oocyte, the process called “nuclear reprogramming”. In fact, nuclear reprogramming in cloning experiments is equivalent to MET; however, this process is afflicted with low efficiency. The objectives of this study in bovine were a) to explore the process of MET reprogramming of in vitro fertilized (IVF) embryos and b) to estimate the efficiency of gene reprogramming after nuclear transfer in animal cloning. We hypothesized that the acquisition of a proper gene expression pattern could herald development potential of the embryos, which could be assessed as early as morula stage or after embryonic genome activation (EGA) in bovine. Here, we opted for a study plan consisting of two axes a) global gene expression analysis using an EGA-dedicated microarray and b) candidate gene expression profiling through qRT-PCR in the fertilized and cloned bovine embryos. Firstly, we optimized the protocol of mRNA amplification for transcriptome analysis which generates antisens-RNA (aRNA). Then we did transcriptomic analysis of the 4-cell and morulae derived from two genotypes having better and two genotypes having poorer in vitro embryonic development potentials. In addition, these oocytes were either matured in vivo or in vitro. We observed that the effect of individual genotype was more important than the effect of the phenotypic category (poorer or better) or conditions of oocyte maturation. Furthermore, we explored the expression patterns of 5 types of cloned embryos having different full term developmental potentials depending upon the donor cell line used. Their genes expression patterns closely resembled to the IVF morulae, except for few genes which present differences. These genes vary with the cell line used as somatic cell donor for SCNT and the number of these deregulated genes did not increase with the poorer developmental potential of the cloned embryos. The analysis of an eventual correlation between the potential for embryonic development to term and nature of the deregulated genes should be addressed. Secondly, we charted quantitative and/or qualitative spatio-temporal expression patterns of transcripts and proteins of pluripotency genes (OCT4, SOX2 and NANOG) and mRNA levels of some of their downstream targets in bovine oocytes and early embryos. Furthermore, to correlate expression patterns of these genes with term developmental potential, we used cloned embryos, instead of gene ablation, having similar in vitro but different full term development rates. We chose these genes to be analysed since pluripotency genes are implicated in mouse embryonic genome activation (EGA) and pluripotent lineage specification. Moreover, their expression levels have been correlated with embryonic term development. Our findings affirm: first, the core triad of pluripotency genes probably is not implicated in bovine EGA since their proteins were not detected during pre-EGA phase, despite the transcripts for OCT4 and SOX2 were present. Second, an earlier ICM specification of SOX2 and NANOG makes them better candidates of bovine pluripotent lineage specification than OCT4. Third, embryos with low term development potential have higher transcription rates; nevertheless, precarious balance between pluripotency genes is maintained. This balance presages normal in vitro development but, probably higher transcription rate disturbs it at later stage that abrogates term development.

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2016-12-16T18:14:58Z No. of bitstreams: 2 Tese - Constanza Thaise Xavier Silva - 2016.pdf: 3305701 bytes, checksum: 6bb860eedef867f3085559fcca9d7190 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-12-26T12:28:18Z (GMT) No. of bitstreams: 2 Tese - Constanza Thaise Xavier Silva - 2016.pdf: 3305701 bytes, checksum: 6bb860eedef867f3085559fcca9d7190 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-12-26T12:28:18Z (GMT). No. of bitstreams: 2 Tese - Constanza Thaise Xavier Silva - 2016.pdf: 3305701 bytes, checksum: 6bb860eedef867f3085559fcca9d7190 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-12-13 / Cutaneous melanoma is a type of skin cancer that originates in melanocytes, predominantly affecting young and middle-aged adults. Several evidence suggests that cancer stem cells exist for melanoma. The POU5F1 / OCT4, NANOG genes have been studied as cancer stem markers. OCT4 and NANOG are involved in the maintenance of pluripotency and self-renewal of undifferentiated embryonic stem cells. This study aims to evaluate the epidemiological, clinical-pathological and expression of the OCT4 and NANOG proteins in cutaneous melanoma samples. We selected 102 cases for the epidemiological, clinical and pathological study, diagnosed between the years 2004 to 2008. For survival study, patients with a followup of up to 60 months were selected, with a recorded death. Of the 102 cases evaluated, 62.7% were female and 37.3% male; With mean age of 57.2 years and 63.1 years respectively (p= 0.0026). The most prevalent age at diagnosis of melanoma was between 51 and 70 years (44.1% p= 0.023). In this study, there was a predominance of lesions located in the trunk (32.3%). Histopathological examination of the type of tumor growth showed a predominance of the superficial extensive type in 52.9% of the cases. According to the Breslow index, lesions with ≤1.0 mm predominated in 39.2% of the individuals, followed by lesions> 4.0 mm in 23.5% of the cases. According to the Clark level 29.4% of the cases were classified in level IV; Followed by 25.5% cases with level V; Clark II in 23.5%; Clark III in 20.6%; And Clark I in only 1 case (1.0%). There were metastases in 47% of the cases and the main localization sites were: lymph nodes, brain, skin and lung. Regarding the clinical evolution of the patients, there were 26 cases of deaths due to melanoma (25.5%). The survival curve calculated at the 60-month follow-up was 73.0%. Univariate analysis revealed significant associations between nuclear overexpression of OCT4 and the following variables: Breslow index with thickness > 2.1 mm (p = 0.021, OR: 2.64, 95% CI: 1.15-6.05 ); Levels of Clark, IV and V (p = 0.001, OR: 4.11, 95% CI: 1.79-9.46); ulceration present (p≤0.0001; OR: 459.0; 95% CI: 51.67-4077.27); Presence of metastases (p <0.0001, OR: 40.25, 95% CI: 12.90- 125.62), and death from cutaneous melanoma (p <0.0001). The significant associations between cytoplasmic hyperexpression of OCT4 and the following variables were: present ulceration (p = 0.015, OR: 2.73, 95% CI: 1.21-6.16); Presence of metastases (p = 0.004, OR: 3.34, 95% CI: 1.47 - 7.62) and death from cutaneous melanoma (p = 0.039, OR 2.67, 95% CI 1.05 - 6,77). And the significant associations between the cytoplasmic hyperexpression of NANOG and the following variables were: present ulceration (p≤ 0.0001); Presence of metastases (p ≤ 0.0001) and death due to cutaneous melanoma (p = 0.030). Our study demonstrated a strong association of the OCT4 / O melanoma cutâneo é um tipo de câncer de pele que tem origem nos melanócitos, afetando predominantemente adultos jovens e de meia-idade. Diversas evidências sugerem a existência células-tronco tumorais para o melanoma. Os genes POU5F1/OCT4, NANOG vem sendo estudados como marcadores células-tronco tumorais. O OCT4 e o NANOG estão envolvidos na manutenção da pluripotência e autorrenovação das células-tronco embrionárias indiferenciadas. Este estudo tem por objetivo avaliar os fatores epidemiológicos, clínico-patológicos e expressão da proteína OCT4 e NANOG em amostras de melanoma cutâneo. Foram selecionados 102 casos para o estudo epidemiológico, clínico e patológico, diagnosticados entre os anos de 2004 a 2008. Para estudo de sobrevida foram selecionadas pacientes com seguimento de até 60 meses, com óbito registrado. Dos 102 casos avaliados foram observados 62,7% do gênero feminino e 37,3% masculino; com média de idade de 57,2 anos e 63,1 respectivamente (p= 0,0026). A idade de maior prevalência ao diagnóstico do melanoma foi entre 51 a 70 anos (44,1% p= 0,023). Nesse estudo, houve predomínio das lesões localizadas no tronco (32,3%). Ao exame histopatológico quanto ao tipo de crescimento do tumor, houve predomínio do tipo extensivo superficial em 52,9% dos casos. Segundo o índice de Breslow predominaram as lesões com ≤1,0mm em 39,2% dos indivíduos, seguidas pelas lesões >4,0mm em 23,5% dos casos. De acordo com o nível de Clark 29,4% dos casos foram classificados no nível IV; seguidas por 25,5% casos com nível V; Clark II em 23,5%; Clark III em 20,6%; e Clark I em apenas 1 caso (1,0%). Houve metástases em 47% dos casos e os principais sítios de localização foram: linfonodos, cérebro, pele e pulmão. Em relação à evolução clínica dos pacientes ocorreram 26 casos de óbitos por melanoma (25,5%). A curva de sobrevida calculada no seguimento de 60 meses foi de 73,0%. A análise univariada revelou associações significativas entre a hiperexpressão nuclear de OCT4 e as seguintes variáveis: índice de Breslow com espessura de > 2,1 mm (p= 0,021; OR: 2,64; IC 95%: 1,15 - 6,05); níveis de Clark, IV e V (p= 0,001; OR: 4,11; IC 95%: 1,79 - 9,46); ulceração presente (p≤ 0,0001; OR: 459,0; IC 95%: 51,67 - 4077,27); presença de metástases (p≤ 0,0001; OR: 40,25; IC 95%: 12,90 - 125,62) e óbito por melanoma cutâneo (p≤ 0,0001). As associações significativas entre a hiperexpressão citoplasmática de OCT4 e as seguintes variáveis foram: ulceração presente (p= 0,015; OR: 2,73; IC 95%: 1,21 - 6,16); presença de metástases (p= 0,004; OR: 3,34; IC 95%: 1,47 - 7,62) e óbito por melanoma cutâneo (p= 0,039; OR: 2,67; IC 95%: 1,05 - 6,77). E as associações significativas entre a hiperexpressão citoplasmática de NANOG e as seguintes variáveis foram: ulceração presente (p≤ 0,0001); presença de metástases (p≤ 0,0001) e óbito por melanoma cutâneo (p= 0,030). Nosso estudo demostraram uma forte associação dos genes OCT4 e NANOG como os piores fatores prognósticos do melanoma cutâneo.

O adenoma pleomórfico (AP) é a neoplasia mais frequente das glândulas salivares e a sua transformação maligna em um carcinoma ex-adenoma pleomórfico (CXAP) é um evento incomum que ocorre em menos de 10% dos casos. O CXAP é tipicamente uma neoplasia infiltrativa, de alto grau e associada com metástase linfonodal no momento do diagnóstico. Acredita-se que a patogênese do CXAP tenha como base o acúmulo de alterações genéticas em APs de longa duração. Evidências recentes têm demonstrado que neoplasias podem conter subpopulações de células raras, com capacidade de auto-renovação e potencial proliferativo indefinido, as chamadas células-tronco neoplásicas (CTN). As CTN parecem estar envolvidas nos processos de iniciação e progressão neoplásicas, assim como metástases e resistência terapêutica. O objetivo deste trabalho foi avaliar a expressão imuno-histoquímica, tanto nas áreas benignas quanto nas malignas, dos fatores de transcrição relacionados à pluripotência de células-tronco Bmi-1, SOX2 e Nanog em CXAPs em fases precoces (7 intracapsulares e 3 minimamente invasivos) e avançada (14 francamente invasivos) de progressão histológica. A análise dos resultados de imuno-histoquímica foi realizada de maneira semi-quantitativa de acordo com o escore 0 (ausência de células positivas), 1 (<30% de células positivas), 2 (30-60% de células positivas e 3 (>60% de células positivas). Correlacionou-se, ainda, esses resultados com parâmetros anatomopatológicos de agressividade neoplásica através do teste Exato de Fisher. A parótida foi a glândula mais acometida em ambos os grupos (62,5%), e homens e mulheres foram igualmente acometidos. A média de idade foi 61,1 anos. No grupo de CXAPs precoces, Bmi-1 foi expresso no componente carcinomatoso de todos os casos e em escassas células das áreas benignas de 1 caso. O fator SOX2 foi expresso pelas células carcinomatosas em 90% desses casos e em escassas células do AP residual de 1 caso. Já Nanog foi expresso apenas no componente maligno de 60% dos casos. Por outro lado, Bmi-1 foi expresso nas áreas malignas de 71,4% dos CXAPs avançados e em ocasionais células da área benigna de 1 caso. O AP residual de nenhum caso desse grupo foi positivo para SOX2 e Nanog, que foram expressos pelas áreas malignas em 92,8% e 35,7% dos casos, respectivamente. Assim, notou-se queda na expressão de Bmi-1 e Nanog na progressão do CXAP. Ainda, a expressão de SOX2 parece correlacionar-se com necrose neoplásica (p=0,06) e metástase linfonodal ao diagnóstico (p=0,08), entretanto a amostra estudada parece pequena para evidenciar esse dado estatístico. Concluiu-se que Bmi-1, SOX2 e Nanog são superexpressos na transformação maligna do AP. Entretanto, Bmi-1 e Nanog aparentemente não exercem função determinante no processo de progressão neoplásica, ao passo que SOX2 parece contribuir com o processo de metástase em CXAP. / Pleomorphic adenoma (PA) is the most common salivary gland tumor and its malignant transformation into a carcinoma ex pleomorphic adenoma (CXPA) is an unusual event occuring in less than 10% of the cases. The CXPA is typically an infiltrative and high-grade neoplasm at diagnosis associated with lymph node metastases. It is believed that the pathogenesis of CXPA is based on the accumulation of genetic changes in long-standing PAs. Recent evidences have shown that tumors may contain subpopulations of rare cells, capable of self-renewal, and with indefinite proliferative potential, the so-called neoplastic stem cells (NSC). The NSC appears to be involved in neoplastic initiation and progression, as well as metastasis and treatment resistance. The objective of this study was to evaluate the immunohistochemical expression of stem cell-related pluripotency transcription factors Bmi-1, SOX2, and Nanog in benign and malignant areas of CXPA at early (7 intracapsular and 3 minimally invasive) and advanced (14 frankly invasive) stages of histological progression. Immunohistochemical analysis was performed semiquantitatively according to the scores 0 (no positive cell), 1 (<30% positive cells), 2 (30-60% of cells positive, and 3 (>60% positive cells). These results were also correlated with pathological parameters of neoplastic aggressiveness using the Fisher\'s Exact test. The parotid gland was the most affected site in both groups (62.5%), and men and women were equally affected. The mean age was 61.1 years. In the early CXPA group, Bmi-1 was expressed in carcinomatous component of all cases and in occasional cells of benign areas of 1 case. The SOX2 factor was expressed by the carcinomatous cells in 90% of cases and scant cells in residual PA of 1 case. Nanog was expressed in 60% of cases, only in the malignant component. On the other hand, Bmi-1 was expressed in malignant areas of 71.4% of advanced CXPAs and in occasional cells of benign area of 1 case. The residual PA of none of the cases in this group was positive to SOX2 and Nanog, which were expressed by carcinomatous areas in 92.8% and 35.7% of cases, respectively. Thus, it was noted that Bmi-1 and Nanog expression decreases in CXPA progression. Yet, SOX2 expression seems to be correlated with neoplastic necrosis (p= 0.06) and lymph node metastasis at diagnosis (p=0.08), but the current sample seems to be small to evidence this statistic data. It was concluded that Bmi-1, Nanog, and SOX2 are overexpressed in malignant transformation of PA. However, Bmi-1 and Nanog apparently do not exert a decisive role in the process of neoplastic progression, while SOX2 seems to contribute to the process of metastasis in CXPA.

O adenoma pleomórfico (AP) é a neoplasia mais frequente das glândulas salivares e a sua transformação maligna em um carcinoma ex-adenoma pleomórfico (CXAP) é um evento incomum que ocorre em menos de 10% dos casos. O CXAP é tipicamente uma neoplasia infiltrativa, de alto grau e associada com metástase linfonodal no momento do diagnóstico. Acredita-se que a patogênese do CXAP tenha como base o acúmulo de alterações genéticas em APs de longa duração. Evidências recentes têm demonstrado que neoplasias podem conter subpopulações de células raras, com capacidade de auto-renovação e potencial proliferativo indefinido, as chamadas células-tronco neoplásicas (CTN). As CTN parecem estar envolvidas nos processos de iniciação e progressão neoplásicas, assim como metástases e resistência terapêutica. O objetivo deste trabalho foi avaliar a expressão imuno-histoquímica, tanto nas áreas benignas quanto nas malignas, dos fatores de transcrição relacionados à pluripotência de células-tronco Bmi-1, SOX2 e Nanog em CXAPs em fases precoces (7 intracapsulares e 3 minimamente invasivos) e avançada (14 francamente invasivos) de progressão histológica. A análise dos resultados de imuno-histoquímica foi realizada de maneira semi-quantitativa de acordo com o escore 0 (ausência de células positivas), 1 (<30% de células positivas), 2 (30-60% de células positivas e 3 (>60% de células positivas). Correlacionou-se, ainda, esses resultados com parâmetros anatomopatológicos de agressividade neoplásica através do teste Exato de Fisher. A parótida foi a glândula mais acometida em ambos os grupos (62,5%), e homens e mulheres foram igualmente acometidos. A média de idade foi 61,1 anos. No grupo de CXAPs precoces, Bmi-1 foi expresso no componente carcinomatoso de todos os casos e em escassas células das áreas benignas de 1 caso. O fator SOX2 foi expresso pelas células carcinomatosas em 90% desses casos e em escassas células do AP residual de 1 caso. Já Nanog foi expresso apenas no componente maligno de 60% dos casos. Por outro lado, Bmi-1 foi expresso nas áreas malignas de 71,4% dos CXAPs avançados e em ocasionais células da área benigna de 1 caso. O AP residual de nenhum caso desse grupo foi positivo para SOX2 e Nanog, que foram expressos pelas áreas malignas em 92,8% e 35,7% dos casos, respectivamente. Assim, notou-se queda na expressão de Bmi-1 e Nanog na progressão do CXAP. Ainda, a expressão de SOX2 parece correlacionar-se com necrose neoplásica (p=0,06) e metástase linfonodal ao diagnóstico (p=0,08), entretanto a amostra estudada parece pequena para evidenciar esse dado estatístico. Concluiu-se que Bmi-1, SOX2 e Nanog são superexpressos na transformação maligna do AP. Entretanto, Bmi-1 e Nanog aparentemente não exercem função determinante no processo de progressão neoplásica, ao passo que SOX2 parece contribuir com o processo de metástase em CXAP. / Pleomorphic adenoma (PA) is the most common salivary gland tumor and its malignant transformation into a carcinoma ex pleomorphic adenoma (CXPA) is an unusual event occuring in less than 10% of the cases. The CXPA is typically an infiltrative and high-grade neoplasm at diagnosis associated with lymph node metastases. It is believed that the pathogenesis of CXPA is based on the accumulation of genetic changes in long-standing PAs. Recent evidences have shown that tumors may contain subpopulations of rare cells, capable of self-renewal, and with indefinite proliferative potential, the so-called neoplastic stem cells (NSC). The NSC appears to be involved in neoplastic initiation and progression, as well as metastasis and treatment resistance. The objective of this study was to evaluate the immunohistochemical expression of stem cell-related pluripotency transcription factors Bmi-1, SOX2, and Nanog in benign and malignant areas of CXPA at early (7 intracapsular and 3 minimally invasive) and advanced (14 frankly invasive) stages of histological progression. Immunohistochemical analysis was performed semiquantitatively according to the scores 0 (no positive cell), 1 (<30% positive cells), 2 (30-60% of cells positive, and 3 (>60% positive cells). These results were also correlated with pathological parameters of neoplastic aggressiveness using the Fisher\'s Exact test. The parotid gland was the most affected site in both groups (62.5%), and men and women were equally affected. The mean age was 61.1 years. In the early CXPA group, Bmi-1 was expressed in carcinomatous component of all cases and in occasional cells of benign areas of 1 case. The SOX2 factor was expressed by the carcinomatous cells in 90% of cases and scant cells in residual PA of 1 case. Nanog was expressed in 60% of cases, only in the malignant component. On the other hand, Bmi-1 was expressed in malignant areas of 71.4% of advanced CXPAs and in occasional cells of benign area of 1 case. The residual PA of none of the cases in this group was positive to SOX2 and Nanog, which were expressed by carcinomatous areas in 92.8% and 35.7% of cases, respectively. Thus, it was noted that Bmi-1 and Nanog expression decreases in CXPA progression. Yet, SOX2 expression seems to be correlated with neoplastic necrosis (p= 0.06) and lymph node metastasis at diagnosis (p=0.08), but the current sample seems to be small to evidence this statistic data. It was concluded that Bmi-1, Nanog, and SOX2 are overexpressed in malignant transformation of PA. However, Bmi-1 and Nanog apparently do not exert a decisive role in the process of neoplastic progression, while SOX2 seems to contribute to the process of metastasis in CXPA.