Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2002. / Härtill 5 uppsatser.

Dissertation (Ph.D.)--University of South Florida, 2007. / Title from PDF of title page. Document formatted into pages; contains 131 pages. Includes vita. Includes bibliographical references.

Dissertation (Ph.D.)--University of South Florida, 2007. / Includes vita. Includes bibliographical references. Also available online.

Dissertation (Ph.D.)--University of South Florida, 2005. / Includes vita. Includes bibliographical references. Also available online in PDF format.

Dissertation (Ph.D.)--University of South Florida, 2007. / Title from PDF of title page. Document formatted into pages; contains 128 pages. Includes vita. Includes bibliographical references.

Orientador: José Andrés Yunes / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-20T16:36:11Z (GMT). No. of bitstreams: 1 Conte_AnaLuizaOngaroSeidinger_D.pdf: 7461860 bytes, checksum: a44751dc1556a30853dcde70f024aed9 (MD5) Previous issue date: 2012 / Resumo: O gene supressor de tumor TP53 é um dos mais bem caracterizados genes cujo papel na etiologia é conhecido tanto em tumores hereditários como esporádicos. Mutações germinativas neste gene normalmente estão associadas à Síndrome de Li-Fraumeni, uma síndrome de predisposição ao câncer cujos portadores apresentam alto risco de desenvolvimento de uma variedade de tumores ao longo da vida. Uma mutação específica deste gene é altamente prevalente na população brasileira, chegando a estar presente em 0.3% da população saudável. Esta mutação, a R337H, não foi descrita como uma mutação associada a um amplo espectro tumoral e, sim, como uma mutação tecido-específica associada somente ao desenvolvimento do tumor do córtex da adrenal (TCA). Entretanto, algumas evidências indicavam que ela poderia contribuir para a etiologia de outros tumores, além do TCA. A R337H foi encontrada em 06 famílias com Síndrome de Li- Fraumeni like e em 2.4% de pacientes diagnosticadas com câncer de mama. Com o objetivo de obter maiores evidências sobre a contribuição da R337H na etiologia de outros tumores além do TCA, investigamos a prevalência desta mutação em 493 pacientes diagnosticados com diferentes tumores pediátricos. Além disto, buscamos investigar alterações cromossômicas que poderiam estar associadas ao processo de tumorigênese em portadores desta mutação. Os resultados mostraram que além do TCA e câncer de mama, a R337H está fortemente associada ao carcinoma de plexo coroide (69%) e ao osteossarcoma (7%) na faixa etária pediátrica. Em nossa instituição, foi observado um aumento da incidência relativa do carcinoma de plexo coroide em relação ao papiloma de plexo coroide. Uma deleção do gene TP53 em células do sangue periférico sob a forma de um mosaico foi identificada nos pacientes portadores da R337H que desenvolveram o TCA. Os dados mostraram que se trata de uma deleção intersticial do cromossomo 17, a qual especula-se ter ocorrido durante o período embrionário. Os resultados sobre a prevalência desta mutação em diferentes tumores pediátricos poderão contribuir para um adequado aconselhamento genético das famílias em que a R337H está presente. Adicionalmente, o mosaicismo encontrado nos portadores da R337H que desenvolveram o TCA nos permitiu formular uma hipótese sobre a tumorigênese adrenocortical associada à R337H e talvez possa também contribuir para a futura compreensão do comportamento oncogênico desta mutação / Abstract: The tumor suppressor gene TP53 is a well characterized gene whose role in the etiology of hereditary and sporadic cancer is well established. Germline mutations in this gene are usually associated with the Li-Fraumeni Syndrome (LFS), a cancer predisposition syndrome in which individuals are at a high risk to develop a wide spectrum of tumors during their lives. A specific mutation of TP53 gene is highly prevalent among the Brazilian population, reaching 0.3% of healthy individuals. This mutation, R337H, was not described as a mutation associated to a wide spectrum of tumors but as a tissue-specific mutation, predisposing individuals only to adrenocortical tumors (ACT). However, some evidences have indicated that it could contribute to the etiology of other tumors besides ACT. The R337H was found in six families diagnosed with LFS-like and also in 2.4% of patients diagnosed with breast cancer. In order to obtain more evidence regarding the role of R337H in the etiology of tumors besides ACT, we have investigated the prevalence of this mutation among 493 pediatric patients diagnosed with cancer. Moreover, we have looked for chromosomal changes potentially involved in tumorigenic process among R337H carriers. Our results demonstrated that, besides ACT and breast cancer, the R337H mutation is strongly associated to choroid plexus carcinoma (69%) and osteosarcoma (7%) in the pediatric age. At our institution it was observed a raise in the relative incidence of choroid plexus carcinoma to choroid plexus papilloma. It was identified a mosaic of cells presenting TP53 deletion in peripheral blood of R337H carriers who developed ACT. Our data showed that is an interstitial deletion affecting the short arm of chromosome 17 that may have occurred during the embryonic life. The results regarding the R337H prevalence among different pediatric tumors may potentially contribute to a more accurate genetic counseling of families bearing this mutation. Additionally, the TP53 deletion found in R337H carriers who developed ACT prompted us to formulate a hypothesis on the adrenocortical tumorigenesis associated to this mutation. Finally, our findings may be useful to better understand the oncogenic behavior of this mutation / Doutorado / Genetica Animal e Evolução / Doutor em Genetica e Biologia Molecular

Hepatocellular carcinoma (HCC) is a common malignancy of the liver that is one of the most frequent causes of cancer-related death in the world. Surgical resection and liver transplantation are the only curative options for HCC, and tumor invasion and metastasis render many patients ineligible for these treatments. Identification of the mechanisms that contribute to invasive and metastatic disease may enlighten therapeutic strategies for those not eligible for surgical treatments. In this dissertation, I describe two sets of experiments to elucidate mechanisms underlying HCC dissemination, involving the activities of Krüppel-like factor 6 and a particular p53 point mutation, R172H. Gene expression profiling of migratory HCC subpopulations demonstrated reduced expression of Krüppel-like factor 6 (KLF6) in invasive HCC cells. Knockdown of KLF6 in HCC cells increased cell transformation and migration. Single-copy deletion of Klf6 in a HCC mouse model results in increased tumor formation, increased metastasis to the lungs, and decreased survival, indicating that KLF6 suppresses both tumor formation and metastasis in HCC. To elucidate the mechanism of KLF6-mediated tumor and metastasis suppression, we performed gene expression profiling and ChIP-sequencing to identify direct transcriptional targets of KLF6 in HCC cells. This analysis revealed novel transcriptional targets of KLF6 in HCC including CDC42EP3 and VAV3, both of which are positive regulators of Rho family GTPases. Concordantly, KLF6 knockdown cells demonstrate increased activity of the Rho family GTPases RAC1 and CDC42, and RAC1 is required for migration induced following KLF6 knockdown. Moreover, VAV3 and CDC42EP3 are also required for enhanced cell migration in HCC cells with KLF6 knockdown. Together, this work describes a novel signaling axis through which KLF6-mediated repression of VAV3 and CDC42EP3 inhibits RAC1Gmediated HCC cell migration in culture, and potentially HCC metastasis in vivo. TP53 gene mutations are commonly found in HCC and are associated with poor prognosis. Prior studies have suggested that p53 mutants can display gain-of- function properties in other tumor types. Therefore, I sought to determine if a particular hotspot p53 mutation, p53R172H, provided enhanced, gain-of-function properties compared to p53 loss in HCC. In vitro, soft agar colony formation and cell migration is reduced upon knockdown of p53R172H, indicating that this mutation is required for transformation-associated phenotypes in these cells. However, p53R172H-expressing mice did not have enhanced tumor formation or metastasis compared to p53-null mice. These data suggest that p53R172H and p53 deletion are functionally equivalent in vivo, and that p53R172H is not a gain-of-function mutant in HCC. Inhibition of the related transcription factors p63 and p73 has been suggested as a potential mechanism by which mutant p53 exerts its gain-of-function effects. Analysis of p63 and p73 target genes demonstrated that they are similarly suppressed in p53-null and p53R172H-expressing HCC cell lines, suggesting a potential explanation for the phenotypes I observed in vivo and in vitro. Together, the studies described in this dissertation increase our understanding of the mechanisms underlying HCC progression and metastasis. Specifically, we find and characterize KLF6 as a novel suppressor of HCC metastasis, and determine the contribution of a common p53 point mutation in HCC. This work contributes to ongoing efforts to improve treatment options for HCC patients.