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No description available.

Existeixen moltes evidències que indiquen que les diferents funcions descrites de p21(Cip1) es deuen, en certa part, a la seva localització intracel·lular. Mentre que la p21(Cip1) nuclear inhibeix la proliferació cel·lular, la p21(Cip1) citoplasmàtica és capaç de regular la supervivència i la mobilitat cel·lular. El fet que les funcions de p21(Cip1) en cada un dels compartiments cel·lulars tinguin papers oposats fa que sigui d'un gran interès l'estudi dels canvis de localització de p21(Cip1) i els mecanismes que regulen aquesta translocació, així com les possibles vies que p21(Cip1) pugui fer servir per a localitzar-se en els diferents compartiments cel·lulars.En aquesta tesi s'han realitzat dos estudis diferenciats, però amb un objectiu comú ja que tots dos es centren en l'anàlisi dels mecanismes reguladors de la localització cel·lular de p21(Cip1). En la primera part d'aquesta tesi, observem la importància de la fosforilació de p21(Cip1) per part de la proteïna cinasa C (PKC). Aquesta fosforilació té lloc en el residu Ser153, molt proper a la senyal de localització nuclear (NLS) de la p21(Cip1) i es capaç de regular la localització cel·lular de p21(Cip1). Aquests resultats, juntament amb altres treballs, demostren que la fosforilació de p21(Cip1) afavoreix la seva localització en el citoplasma. Diferents aproximacions experimentals ens van permetre observar com aquesta fosforilació inhibeix la unió entre p21(Cip1) i CaM. D'aquest primer treball se'n deriva un model de regulació de la localització cel·lular de p21(Cip1) en el qual la unió a CaM i la fosforilació per PKC tenen papers oposats. D'una banda, la unió de p21(Cip1) a CaM inhibeix la seva fosforilació per part de PKC i afavoreix la localització de p21(Cip1) en el nucli. D'altra banda, la fosforilació de p21(Cip1) en el residu Ser153 indueix una localització citoplasmàtica de p21(Cip1). Treballs posteriors ens van permetre observar com la sortida de p21(Cip1) del nucli cap al citoplasma també està regulada. Després del dany al DNA, els nivells cel·lulars de p21(Cip1) incrementen, especialment en el nucli, per tal d'assegurar una aturada del cicle cel·lular. Observem com en resposta al dany al DNA, p21(Cip1) s'acumula no només en el nucleoplasma de les cèl·lules sinó que també s'acumula en el nuclèol. En les cèl·lules danyades els components nucleolars es troben desorganitzats i el nuclèol perd els contactes amb l'embolcall nuclear i presenta unes estructures esfèriques en el seu interior. La p21(Cip1) present en les estructures esfèriques del nuclèol està en un equilibri dinàmic amb la p21(Cip1) del nucleoplasma i la presència de p21(Cip1) en aquestes estructures correlaciona amb una inhibició de l'export p21(Cip1) cap al citoplasma. Aquests resultats donen suport a l'existència d'una via d'export de proteïnes nuclears a través del nuclèol, semblant a la que intervé en l'export de ribosomes, la qual es veuria afectada amb la desestructuració dels nuclèols en resposta al dany cel·lular. A més, amb els resultats obtinguts no descartem la possibilitat que p21(Cip1) pugui ser modificada en el nuclèol ja que en resposta al dany al DNA també s'hi localitzen altres proteïnes implicades en diferents vies de modificació post-traduccional. Així doncs, l'acumulació nuclear de p21(Cip1) en resposta al dany al DNA no es deu únicament a un increment de la seva transcripció sinó que aquesta acumulació també es deguda a la inhibició de la sortida de p21(Cip1) cap al citoplasma a través del nuclèol.En conclusió, tant l'entrada com la sortida de la p21(Cip1) del nucli és un mecanisme altament regulat que farà que la localització de p21(Cip1) pugui variar en diferents situacions fisiològiques de la cèl·lula. Aquest fet és de gran importància per al correcte funcionament cel·lular ja que com hem descrit anteriorment, p21(Cip1) és una proteïna amb funcions oposades depenent de la seva localització intracel·lular: oncogènica al citoplasma i supressora de tumors al nucli. / It is well known that p21(Cip1) is a protein with a dual function in oncogenesis depending mainly on its intracellular localization: tumor suppressor in the nucleus and oncogenic in the cytoplasm. The importance of p21(Cip1) cellular localization indicates that it has to be precisely regulated.On one side we observed the importance of p21(Cip1) phosphorylation by PKC inducing its cytoplasmic localization. PKC phosphorylates p21(Cip1) at Ser 153 and when phosphorylated, p21(Cip1) can not bind to CaM. From this study we conclude that CaM and PKC have an opposite role in the regulation of p21(Cip1) localization: CaM binding to p21(Cip1) prevents its phosphorylation by PKC at Ser153 and consequently allows its nuclear localization; while when phosphorylated at Ser153, p21(Cip1) is located at the cytoplasm.On the other side the export of p21(Cip1) from the nucleus to the cytoplasm is also regulated. After DNA damage, p21(Cip1) increases and accumulates in the nucleus to ensure cell cycle arrest. We observed that after DNA damage p21(Cip1) accumulates not only in the nucleoplasm but also in the disrupted nucleoli. In damaged cells the nucleolar components are disorganized and nucleoli have lost their contacts with the nuclear envelope and appear with spherical structures inside. The nucleolar p21(Cip1) forms a dynamic equilibrium between the nucleolus and the nucleoplasm and correlates with the inhibition of p21(Cip1) nuclear export. This result proves the existence of a nucleolar export route to the cytoplasm for p21(Cip1) similar to the one described for the ribosome export. Moreover, the results obtained suggested that p21(Cip1) could be modified in the nucleolus in response to DNA damage as different proteins involved in post-translation modifications also localize in the nucleoli after the damage. Thus, after DNA damage, p21(Cip1) accumulates in the nucleus due to an increase in its transcription and due to an inhibition of its export to the cytoplasm.All this results together indicate the importance of p21(Cip1) localization depending on the cellular context and that its localization is precisely regulated by different pathways.

IKAROS est un facteur de transcription majeur dans l’hématopoïèse qui agit en recrutant à la chromatine de nombreux partenaires décisifs dans le renouvellement cellulaire et l’engagement vers des lignages spécifiques. Il est notamment requis dans les cellules lymphoïdes pour réprimer les gènes cibles de la voie de signalisation NOTCH. IKAROS est aussi important dans le développement des cellules érythroïdes dans lesquelles il facilite le passage d’une globine fœtale à adulte chez l’embryon grâce au recrutement des complexes remodeleurs de la chromatine NuRD et BAF. En condition normale, la voie de signalisation NOTCH réprime la différenciation en cellules érythroïdes. Il est donc important que les gènes cibles de la voie NOTCH soient finement régulés afin d’amener une cellule progénitrice à se différencier en érythrocyte énucléé. Dans les cellules hématopoïétiques, incluant les cellules érythroïdes, IKAROS est un régulateur important du gène Hes1, cible effectrice majeure de la voie NOTCH. En effet, IKAROS participe activement à la répression du gène Hes1, permettant le développement des cellules érythroïdes. Nous avons donc émis l’hypothèse que dans ces cellules, IKAROS pourrait avoir une action plus généralisée sur le contrôle des gènes ciblés par NOTCH, comme observé dans les cellules lymphoïdes. Il pourrait ainsi agir en recrutant les complexes enzymatiques nécessaires à la régulation de ces gènes comme NuRD et BAF afin d’assurer le développement des cellules érythroïdes. Étant donné que la régulation des gènes est aussi dépendante du motif de méthylation de l’ADN, nous avons étendu notre questionnement à cet autre aspect de la régulation qu’IKAROS pourrait utiliser pour contrôler les gènes de la voie NOTCH. Pour ce faire, nous avons procédé à l’analyse bio-informatique d’un séquençage d’ARN de cellules érythroïdes murines préalablement réalisé au laboratoire afin d’en extraire les gènes régulés par IKAROS, mais aussi par NOTCH. L’analyse nous a permis d’extraire deux motifs d’expression intéressants observés dans les cellules érythroïdes pour lesquels IKAROS réprime ou active des gènes qui sont normalement réceptifs à l’activation de la voie NOTCH. Parmi les gènes réprimés par IKAROS en sont ressortis les gènes cibles de NOTCH Cdkn1a (P21WAF1/CIP1) et Trp53 (TP53), dont l’expression augmente fortement quand IKAROS est muté et que NOTCH est actif. Parmi les gènes activés par IKAROS en sont ressortis les gènes cibles de NOTCH Prdm16 et Nrarp, dont l’expression diminue fortement quand IKAROS est muté et que NOTCH est actif. IKAROS est donc un régulateur pouvant être répresseur, mais aussi activateur d’une multitude de gènes ciblés par NOTCH dans les cellules érythroïdes. Par des expériences d’immunoprécipitation de la chromatine, nous avons pu observer qu’IKAROS semblait toujours agir en partenariat avec le complexe NuRD et que la présence du complexe BAF était plutôt dépendante de la voie NOTCH. L’association IKAROS-NuRD semble servir de plateforme pour imposer un état de chromatine bivalente (avec co-présence de H3K4me3 et de H3K27me3) associée à une pause transcriptionnelle. Dans ce contexte, les éléments nécessaires à l’initiation de la transcription (présence de la marque H3K4me3) des gènes ciblés par NOTCH sont recrutés mais, l’élongation transcriptionnelle est affectée. L’état de chromatine bivalente peut être associé à l’activité des déméthylases de l’ADN Ten-Eleven-Translocation (TET) qui empêchent alors l’hyperméthylation de ces régions. Nos résultats démontrent qu’IKAROS peut utiliser la protéine TET1 pour réguler des gènes cibles de la voie NOTCH, en y formant l’hydroxyméthylcytosine (5-hmC). Celle-ci peut aussi marquer les régions de régulation génique caractérisées par une chromatine bivalente et une pause transcriptionnelle. Ces travaux décrivent IKAROS comme un facteur agissant de façons multiples dans la régulation des gènes cibles de NOTCH dans les cellules érythroïdes. Nous proposons qu’IKAROS et son partenaire NuRD soient requis pour mettre en place un état de chromatine bivalente et de pause transcriptionnelle pour faciliter l’activation physiologique des gènes cibles de NOTCH lors de la signalisation. IKAROS peut ainsi prendre part à l’activation ou la répression de gènes cibles de NOTCH, tout en facilitant la déméthylation de l’ADN ainsi que le recrutement d’éléments transcriptionnels qui favorisent un état de pause transcriptionnelle. NOTCH ainsi que d’autres éléments de régulation sont alors requis pour induire l’activation ou la répression des gènes cibles. / IKAROS is a critical transcription factor in hematopoiesis. It facilitates the chromatin binding of many important co-factors required for chromatin organization during cell renewal and lineage commitment. IKAROS is particularly important in lymphoid cells whereby it is involved in the repression of target genes of the NOTCH signaling pathway. IKAROS is also important in the development of other hematopoietic lineages, including the erythroid cells, in which it facilitates the passage of a fetal to adult globin in the embryo through the recruitment of the chromatin remodeling complexes NuRD and BAF. Under normal conditions, the NOTCH signaling pathway represses development of erythroid cells. It is therefore important to precisely understand how the NOTCH target genes are regulated during passage from hematopoietic progenitor to the enucleated circulating erythrocyte. IKAROS has been demonstrated to be an important regulator of Hes1 gene expression in hematopoietic cells of different lineages. Hes1 is the major effector target of the NOTCH pathway and IKAROS actively participates in its repression. In erythroid cells, the regulation of Hes1 imposed by IKAROS is required for terminal differentiation. We therefore investigated the importance of IKAROS in the regulation of NOTCH-targeted genes in erythroid cells. The combined effect of the mutation of IKAROS with NOTCH signaling was particularly investigated in these cells. To define how IKAROS influences the regulation of NOTCH target genes, we performed the bioinformatics analysis of a RNA-sequencing performed in murine erythroid cells activated or not for NOTCH signaling and whereby IKAROS is absent. We identified genes influenced by IKAROS expression and by NOTCH, and defined the effect of the combination of the absence of IKAROS expression and NOTCH pathway activation. Two particular expression patterns were identified and characterized the combined effect of the absence of IKAROS and NOTCH pathway activation in erythroid cells. Indeed, the absence of IKAROS either favors the overexpression of NOTCH target genes or prevents their response to NOTCH pathway activation. To understand how IKAROS could have an opposite effect on different NOTCH target genes we analysed the effect of IKAROS on their regulation. Among the genes repressed by IKAROS are the target genes of NOTCH Cdkn1a (encoding the P21WAF1/CIP1 protein) and Trp53 (encoding the TP53 protein), whose expression increases strongly when IKAROS is mutated and the NOTCH pathway is activated. Prdm16 and Nrarp are, instead, requiring IKAROS expression for their activation by NOTCH. The characterization of these NOTCH target genes suggests that IKAROS can work in partnership with the NuRD complex to influence the expression. The chromatin characterization of these genes led us to posit that the IKAROS-NuRD could act as a ‘platform’ to impose a bivalent chromatin organization associated with poised transcription. Then, the regulation imposed by IKAROS-NuRD would be required for the physiological activation of NOTCH targets upon external signaling. Finally, since in embryonic stem cells the Ten-Eleven Translocation (TET) enzymes are reported to be frequently associated to bivalent chromatin in order to prevent DNA hypermethylation, we assessed whether IKAROS could interact and ‘use’ TET enzymes to regulate NOTCH target genes. We determined that IKAROS can co-immunoprecipitate with the TET1 enzymes. We show that IKAROS influences both recruitment and activity of TET1 to different NOTCH target genes and favors the accumulation of hydroxymethylcytosine (5-hmC) to these genes. 5-hmC can be considered as a mark of transcriptional pausing/bivalence. Thus, these studies bring new information on the mechanism used by IKAROS to influence gene regulation in hematopoietic cells. Our results suggest that IKAROS primary function is to organize a bivalent chromatin and to promote transcriptional pausing to multiple NOTCH target genes. IKAROS is required to set the epigenetic and promoter organization for rapid activation upon NOTCH signaling.

4 Abstract Senescence is a specific cell state distinquished by cessation of cell division and proliferation and changes in gene expression. Normal cells enter senescence after distinct number of cell divisions or in case of an unrepairable damage. Senescence in cancer cells can be induced by subliminal stress as sublethal treatment with certain drugs. Senescent cancer cells persist in the tissue and may secrete a number of factors and nutrients affecting surrounding cells. Senescence can thus change the response of cancer cells to various apoptogens during cancer therapy. In this study, we focused on the elucidation of presumed differences between normal proliferating and senescent cancer cells in their response to selected apoptogens. Implementing bromodeoxyuridine (BrdU)-mediated replication stress in cancer cells derived from pancreatic (PANC-1) or mesothelioma (H28) tumors, we efficiently forced these cells to acquire senescent phenotype. We document that these senescent cells gain higher resistance to combined TRAIL and homoharringtonine (HHT) treatment and enhance sensitivity to other apoptogens such as FasL, camptothecin and mVES. These cells also showed increased expression of anti-apoptotic protein c-FLIP in senescent cells and changes in the expression of some Bcl-2 family proteins....

INTRODUÇÃO: No mundo ocidental, a prevalência de adenocarcinoma da junção esofagogástrica vem crescendo nas últimas décadas. Atualmente, é aceito que o adenocarcinoma do esôfago se desenvolve de uma lesão pré-maligna: esôfago de Barrett. Este carcinoma é de difícil diagnóstico nos seus estágios iniciais, o que resulta em uma mortalidade significativa. O estudo da biologia molecular tem demonstrado que grande parte dos tumores malignos tem origem na interação entre o componente hereditário e influências externas, que em indivíduos predispostos podem ocasionar alterações genéticas que influenciem o controle da diferenciação e crescimento celular. O p21 (WAF1/CIP1) tem um papel fundamental na regulação do ciclo celular, e sua expressão imunoistoquímica tem sido estudada em diversos tumores, mostrando influência no prognóstico de várias neoplasias. OBJETIVO: Verificar a prevalência da expressão da proteína p21 em pacientes com adenocarcinoma de esôfago diagnosticados nos últimos cinco anos no Grupo de Cirurgia de Esôfago e Estômago do Hospital de Clínicas de Porto Alegre (GCEE/HCPA). METODOLOGIA: A população em estudo foi constituída de 42 pacientes com adenocarcinoma de esôfago diagnosticados no GCEE/HCPA entre janeiro de 1998 e dezembro de 2002. A expressão da proteína p21 foi realizada por meio de imunoistoquímica, com anticorpo primário, p21, clone SX118, código M7202 da DAKO, e avaliada de acordo com o Sistema de Escore de Imunorreatividade (Immunoreactive scoring system – IRS). RESULTADOS: Foram estudados 42 pacientes. 83,3% eram do sexo masculino, com idade superior a 40 anos. Destes, 56,2% foram submetidos a procedimentos cirúrgicos com intenção curativa: Gastrectomia total e Esofagogastrectomia transiatal. Os demais foram submetidos à cirurgia paliativa ou não sofreram tratamento cirúrgico. Apenas cinco pacientes receberam tratamento adjuvante com quimioterapia e radioterapia, isoladas ou combinadas. Quanto ao estadiamento, 78,6% dos pacientes apresentavam doença avançada, estádios III e IV. Apenas 9 apresentaram positividade para o p21, quando considerado o Sistema de Escore de Imunorreatividade (em que p21+ é ³ 3). CONCLUSÃO: A proteína p21 esteve expressa em 9 dos 42 pacientes (21,4%) com adenocarcinoma de esôfago diagnosticados nos últimos cinco anos no Grupo de Cirurgia de Esôfago e Estômago do Hospital de Clínicas de Porto Alegre. Nessa casuística, o acúmulo de p21 não se mostrou essencial no processo de carcinogênese do adenocarcinoma esofágico. / INTRODUCTION: In western societies, the prevalence of adenocarcinoma of the gastroesophageal junction has increased in recent years. It is commonly accepted today that esophageal adenocarcinoma develops from a premalignant lesion: Barrett’s esophagus. This type of carcinoma is hardly diagnosed at early stages, which results in significant mortality. Molecular biology studies have shown that most malignant tumors originate from the interaction between inherited characteristics and external factors, which may cause genetic changes that interfere with the control over the differentiation and growth of cells in susceptible individuals. p21 (WAF1/CIP1) has a key role in the regulation of the cell cycle, and its immunohistochemical expression has been investigated in several tumors, showing that it influences the prognosis of various neoplasms. OBJECTIVE: To check the prevalence of p21 protein expression in patients with esophageal adenocarcinoma diagnosed in the last five years by the Group for Surgeries of the Esophagus and Stomach of Hospital de Clínicas de Porto Alegre (GCEE/HCPA). METHODS: The study population consisted of 42 patients with esophageal adenocarcinoma diagnosed by the GCEE/HCPA between January 1998 and December 2002. The expression of p21 protein was determined by immunohistochemistry using primary antibody, p21, clone SX118, code M7202 (Dako), and assessed according to the Immunoreactive scoring system (IRS). RESULTS: Of 42 analyzed patients, 83.3% were male and older than 40 years. Among these, 56.2% were submitted to curative resection: total gastrectomy and transhiatal esophagogastrectomy. The remaining patients were submitted to palliative surgery or did not undergo any surgical treatment. Only five patients received adjuvant chemotherapy and radiation therapy, either alone or combined. Advanced disease (stages III and IV) was detected in 78.6% of the patients. Only nine patients were positive for p21, according to the immunoreactive scoring system (p21+ ³ 3). CONCLUSION: p21 was expressed in 9 of 42 patients (21.4%) with esophageal adenocarcinoma diagnosed in the last five years by the Group for Surgeries of the Esophagus and Stomach of Hospital de Clínicas de Porto Alegre. In our patient population, the accumulation of p21 did not play a key role in the carcinogenesis of esophageal adenocarcinoma.

INTRODUÇÃO: No mundo ocidental, a prevalência de adenocarcinoma da junção esofagogástrica vem crescendo nas últimas décadas. Atualmente, é aceito que o adenocarcinoma do esôfago se desenvolve de uma lesão pré-maligna: esôfago de Barrett. Este carcinoma é de difícil diagnóstico nos seus estágios iniciais, o que resulta em uma mortalidade significativa. O estudo da biologia molecular tem demonstrado que grande parte dos tumores malignos tem origem na interação entre o componente hereditário e influências externas, que em indivíduos predispostos podem ocasionar alterações genéticas que influenciem o controle da diferenciação e crescimento celular. O p21 (WAF1/CIP1) tem um papel fundamental na regulação do ciclo celular, e sua expressão imunoistoquímica tem sido estudada em diversos tumores, mostrando influência no prognóstico de várias neoplasias. OBJETIVO: Verificar a prevalência da expressão da proteína p21 em pacientes com adenocarcinoma de esôfago diagnosticados nos últimos cinco anos no Grupo de Cirurgia de Esôfago e Estômago do Hospital de Clínicas de Porto Alegre (GCEE/HCPA). METODOLOGIA: A população em estudo foi constituída de 42 pacientes com adenocarcinoma de esôfago diagnosticados no GCEE/HCPA entre janeiro de 1998 e dezembro de 2002. A expressão da proteína p21 foi realizada por meio de imunoistoquímica, com anticorpo primário, p21, clone SX118, código M7202 da DAKO, e avaliada de acordo com o Sistema de Escore de Imunorreatividade (Immunoreactive scoring system – IRS). RESULTADOS: Foram estudados 42 pacientes. 83,3% eram do sexo masculino, com idade superior a 40 anos. Destes, 56,2% foram submetidos a procedimentos cirúrgicos com intenção curativa: Gastrectomia total e Esofagogastrectomia transiatal. Os demais foram submetidos à cirurgia paliativa ou não sofreram tratamento cirúrgico. Apenas cinco pacientes receberam tratamento adjuvante com quimioterapia e radioterapia, isoladas ou combinadas. Quanto ao estadiamento, 78,6% dos pacientes apresentavam doença avançada, estádios III e IV. Apenas 9 apresentaram positividade para o p21, quando considerado o Sistema de Escore de Imunorreatividade (em que p21+ é ³ 3). CONCLUSÃO: A proteína p21 esteve expressa em 9 dos 42 pacientes (21,4%) com adenocarcinoma de esôfago diagnosticados nos últimos cinco anos no Grupo de Cirurgia de Esôfago e Estômago do Hospital de Clínicas de Porto Alegre. Nessa casuística, o acúmulo de p21 não se mostrou essencial no processo de carcinogênese do adenocarcinoma esofágico. / INTRODUCTION: In western societies, the prevalence of adenocarcinoma of the gastroesophageal junction has increased in recent years. It is commonly accepted today that esophageal adenocarcinoma develops from a premalignant lesion: Barrett’s esophagus. This type of carcinoma is hardly diagnosed at early stages, which results in significant mortality. Molecular biology studies have shown that most malignant tumors originate from the interaction between inherited characteristics and external factors, which may cause genetic changes that interfere with the control over the differentiation and growth of cells in susceptible individuals. p21 (WAF1/CIP1) has a key role in the regulation of the cell cycle, and its immunohistochemical expression has been investigated in several tumors, showing that it influences the prognosis of various neoplasms. OBJECTIVE: To check the prevalence of p21 protein expression in patients with esophageal adenocarcinoma diagnosed in the last five years by the Group for Surgeries of the Esophagus and Stomach of Hospital de Clínicas de Porto Alegre (GCEE/HCPA). METHODS: The study population consisted of 42 patients with esophageal adenocarcinoma diagnosed by the GCEE/HCPA between January 1998 and December 2002. The expression of p21 protein was determined by immunohistochemistry using primary antibody, p21, clone SX118, code M7202 (Dako), and assessed according to the Immunoreactive scoring system (IRS). RESULTS: Of 42 analyzed patients, 83.3% were male and older than 40 years. Among these, 56.2% were submitted to curative resection: total gastrectomy and transhiatal esophagogastrectomy. The remaining patients were submitted to palliative surgery or did not undergo any surgical treatment. Only five patients received adjuvant chemotherapy and radiation therapy, either alone or combined. Advanced disease (stages III and IV) was detected in 78.6% of the patients. Only nine patients were positive for p21, according to the immunoreactive scoring system (p21+ ³ 3). CONCLUSION: p21 was expressed in 9 of 42 patients (21.4%) with esophageal adenocarcinoma diagnosed in the last five years by the Group for Surgeries of the Esophagus and Stomach of Hospital de Clínicas de Porto Alegre. In our patient population, the accumulation of p21 did not play a key role in the carcinogenesis of esophageal adenocarcinoma.

INTRODUÇÃO: No mundo ocidental, a prevalência de adenocarcinoma da junção esofagogástrica vem crescendo nas últimas décadas. Atualmente, é aceito que o adenocarcinoma do esôfago se desenvolve de uma lesão pré-maligna: esôfago de Barrett. Este carcinoma é de difícil diagnóstico nos seus estágios iniciais, o que resulta em uma mortalidade significativa. O estudo da biologia molecular tem demonstrado que grande parte dos tumores malignos tem origem na interação entre o componente hereditário e influências externas, que em indivíduos predispostos podem ocasionar alterações genéticas que influenciem o controle da diferenciação e crescimento celular. O p21 (WAF1/CIP1) tem um papel fundamental na regulação do ciclo celular, e sua expressão imunoistoquímica tem sido estudada em diversos tumores, mostrando influência no prognóstico de várias neoplasias. OBJETIVO: Verificar a prevalência da expressão da proteína p21 em pacientes com adenocarcinoma de esôfago diagnosticados nos últimos cinco anos no Grupo de Cirurgia de Esôfago e Estômago do Hospital de Clínicas de Porto Alegre (GCEE/HCPA). METODOLOGIA: A população em estudo foi constituída de 42 pacientes com adenocarcinoma de esôfago diagnosticados no GCEE/HCPA entre janeiro de 1998 e dezembro de 2002. A expressão da proteína p21 foi realizada por meio de imunoistoquímica, com anticorpo primário, p21, clone SX118, código M7202 da DAKO, e avaliada de acordo com o Sistema de Escore de Imunorreatividade (Immunoreactive scoring system – IRS). RESULTADOS: Foram estudados 42 pacientes. 83,3% eram do sexo masculino, com idade superior a 40 anos. Destes, 56,2% foram submetidos a procedimentos cirúrgicos com intenção curativa: Gastrectomia total e Esofagogastrectomia transiatal. Os demais foram submetidos à cirurgia paliativa ou não sofreram tratamento cirúrgico. Apenas cinco pacientes receberam tratamento adjuvante com quimioterapia e radioterapia, isoladas ou combinadas. Quanto ao estadiamento, 78,6% dos pacientes apresentavam doença avançada, estádios III e IV. Apenas 9 apresentaram positividade para o p21, quando considerado o Sistema de Escore de Imunorreatividade (em que p21+ é ³ 3). CONCLUSÃO: A proteína p21 esteve expressa em 9 dos 42 pacientes (21,4%) com adenocarcinoma de esôfago diagnosticados nos últimos cinco anos no Grupo de Cirurgia de Esôfago e Estômago do Hospital de Clínicas de Porto Alegre. Nessa casuística, o acúmulo de p21 não se mostrou essencial no processo de carcinogênese do adenocarcinoma esofágico. / INTRODUCTION: In western societies, the prevalence of adenocarcinoma of the gastroesophageal junction has increased in recent years. It is commonly accepted today that esophageal adenocarcinoma develops from a premalignant lesion: Barrett’s esophagus. This type of carcinoma is hardly diagnosed at early stages, which results in significant mortality. Molecular biology studies have shown that most malignant tumors originate from the interaction between inherited characteristics and external factors, which may cause genetic changes that interfere with the control over the differentiation and growth of cells in susceptible individuals. p21 (WAF1/CIP1) has a key role in the regulation of the cell cycle, and its immunohistochemical expression has been investigated in several tumors, showing that it influences the prognosis of various neoplasms. OBJECTIVE: To check the prevalence of p21 protein expression in patients with esophageal adenocarcinoma diagnosed in the last five years by the Group for Surgeries of the Esophagus and Stomach of Hospital de Clínicas de Porto Alegre (GCEE/HCPA). METHODS: The study population consisted of 42 patients with esophageal adenocarcinoma diagnosed by the GCEE/HCPA between January 1998 and December 2002. The expression of p21 protein was determined by immunohistochemistry using primary antibody, p21, clone SX118, code M7202 (Dako), and assessed according to the Immunoreactive scoring system (IRS). RESULTS: Of 42 analyzed patients, 83.3% were male and older than 40 years. Among these, 56.2% were submitted to curative resection: total gastrectomy and transhiatal esophagogastrectomy. The remaining patients were submitted to palliative surgery or did not undergo any surgical treatment. Only five patients received adjuvant chemotherapy and radiation therapy, either alone or combined. Advanced disease (stages III and IV) was detected in 78.6% of the patients. Only nine patients were positive for p21, according to the immunoreactive scoring system (p21+ ³ 3). CONCLUSION: p21 was expressed in 9 of 42 patients (21.4%) with esophageal adenocarcinoma diagnosed in the last five years by the Group for Surgeries of the Esophagus and Stomach of Hospital de Clínicas de Porto Alegre. In our patient population, the accumulation of p21 did not play a key role in the carcinogenesis of esophageal adenocarcinoma.