A presença de metástase em linfonodos cervicais é o fator prognóstico mais importante para o carcinoma epidermóide de boca (CEB), uma das neoplasias malignas mais comuns da região de cabeça e pescoço. Estudos têm associado os mecanismos de progressão tumoral, recorrência e metástase com a presença e manutenção de células-tronco de câncer (CSC, do inglês cancer stem cells), que correspondem à subpopulação celular mais migratória e altamente metastática quando comparada com outras subpopulações presentes no tumor. Ainda, evidências recentes mostram que há uma ligação entre as CSC e o processo de transição epitélio-mesenquimal (EMT, do inglês epithelial-mesenchymal transition), evento em que as células perdem a polaridade e a aderência célula-célula e exibem uma morfologia mesenquimal, o que as permite migrar além do tumor primário. Portanto, o objetivo deste estudo foi de avaliar, in vitro, a associação das propriedades biológicas relacionadas ao fenótipo tronco tumoral e de transição epitélio-mesenquimal, com o comportamento invasivo e metastático das linhagens SCC-9 de CEB primário e metastático correspondente. Para este fim, linhagens celulares parental (SCC-9 ZsGreen) e metastática (SCC-9 ZsGreen LN-1), obtidas após ensaios de tumorigênese in vivo, foram caracterizadas em relação à capacidade de proliferação e migração, bem como à presença e proporção da subpopulação de CSC, baseado na capacidade de formação de colônias tumorais, preferencialmente holoclones, e de esferas tumorais. Ensaios de expressão gênica (qRT-PCR) também foram conduzidos para se verificar os níveis de expressão diferencial dos marcadores de CSC (CD44, BMI1, ALDH1 e p75NTR), bem como de EMT (SNAIL1, TWIST1, AXL, vimentina, E-caderina e N-caderina) em ambas as linhagens tumorais, utilizando-se células epiteliais de palato humano (CEPH) como controle. Tanto a capacidade de proliferação e migração celular, quanto a quantidade de holoclones e esferas tumorais, foram significativamente maiores na linhagem metastática quando comparada com a parental. A linhagem metastática SCC-9 ZsGreen LN1 exibiu, ainda, superexpressão estatisticamente significante de CD44, BMI-1, AXL, vimentina e N-caderina e baixa expressão de E-caderina, quando comparadas com a linhagem parental. O potencial metastático de SCC-9 ZsGreen LN-1 parece ser uma consequência da sua maior quantidade de subpopulação com fenótipo de CSC que, ainda, passou pelo processo de EMT. Portanto, sugere-se que as propriedades biológicas relacionadas à capacidade metastática da linhagem SCC-9 ZsGreen LN-1 parecem estar relacionadas a ambos os fenótipos tronco tumoral e de transição epitélio-mesenquimal. / The presence of metastasis in cervical lymph nodes is the most significant prognostic factor for the oral squamous cell carcinoma (OSCC), one of the most common malignant neoplasms of the head and neck. Studies have associated the mechanisms of tumor progression, recurrence and metastasis with the presence and maintenance of cancer stem cells (CSC), which correspond to the most migratory and highly metastatic cellular subpopulation when compared to other cell subpopulations within the tumor. Moreover, recent evidence shows that there is a link between the CSC and the process of epithelial-mesenchymal transition (EMT), an event in which the cells lose their polarity and cell-cell adhesion and exhibit a mesenchymal morphology, which allows them to migrate beyond the primary tumor. Thus, the purpose of the present study was to evaluate, in vitro, the combination of the biological properties related to CSC and EMT phenotypes with the invasive and metastatic behavior of the corresponding primary and metastatic OSCC SCC-9 cell line. For this, parental (SCC-9 ZsGreen) and metastatic (SCC-9 ZsGreen LN-1) OSCC cell lines, obtained after in vivo tumorigenesis assays were characterized regarding the ability of proliferation and migration, as well as the presence and proportion of CSC subpopulation, based on the capacity of generating tumor colonies, preferably holoclones, and tumor spheres. Gene expression assays (qRTPCR) were also conducted to verify the differential expression levels of CSC markers (CD44, BMI-1, ALDH-1 and p75NTR) and EMT (SNAIL1, TWIST1, AXL, vimentin, Ecadherin and N-cadherin) markers in both tumor cell lines, using human palate epithelial cells (HPEC) as control. Both proliferation and cell migration capacity, as well as the numbers of holoclones and tumor spheres were significantly higher in metastatic cell line compared to the parental. Furthermore, the metastatic cell line SCC-9 ZsGreen LN-1 showed significantly higher expression of CD44, BMI-1, ALDH- 1, vimentin, and N-cadherin and lower expression of E-cadherin, when compared to parental cell line. The metastatic potential of SCC-9 ZsGreen LN-1 seems to be a consequence of the greater amount subpopulation with CSC phenotype that also underwent the EMT process. Therefore, it is suggested that the biological properties related to metastatic ability of SCC-9 ZsGreen LN-1 cell line are related to both CSC and EMT phenotypes.

Ph.D. / Molecular and Medical Genetics / The objective of this study is to examine, in light of the expression of multiple p53 family member isoforms, the specific role of p73 in malignant conversion, cellular response to DNA damage, and direct or indirect cooperation with other p53 family members in a clonal model of epidermal carcinogenesis. We first focused on the role of p73 in malignant conversion. Whether sporadic or siRNA induced, loss of p73 in initiated p53+/+ keratinocytes lead to conversion to squamous cell carcinoma (SCC) in vivo which was reversible upon reconstitution of TAp73α but not ΔNp73α. Second, we investigated the cellular response to ionizing radiation (IR) in the presence and absence of p73, showing that loss of p73 at malignant conversion was associated with resistance to IR in vitro. The loss of radiation sensitivity and malignant conversion was characterized by reduced steady state DNA binding levels of transcriptionally active p63 isoforms to the p21 promoter, failure to induce specific p53 family transcriptional targets, and failure to arrest in G1. Reconstitution of TAp73α, but not ΔNp73α, increased steady state DNA binding capabilities of TAp63β, TAp63γ, and ΔNp63γ, and steady state levels of p53 family target mRNA, but did not restore cellular sensitivity to IR. We thus uncovered a functional cooperation between TA isoforms of p73 and p63 and showed that p73-mediated DNA damage response was uncoupled from its tumor suppressive role. We observed preferential DNA binding of the inhibitory ΔNp63α isoform both in vitro and invivo in SCC suggesting that in the absence of TAp73α a balance is tipped toward DNA binding of the inhibitory isoforms. Third, we studied the role of the p53 family inkeratinocyte response to UVB. Tumorigenic cells lacking p73 that were resistant to IR remained sensitive to UVB, accompanied by DNA binding of the TAp63γ isoform, suggesting that keratinocyte response to UVB is not dependent upon p73 and suggesting a hierarchy of p53 family member responses to DNA damage. Finally, we examined TAp73α interaction with the p53 family inhibitor Mdm2. Mdm2 was in complex with DNA-bound p53 family members in malignant cells, but reconstitution of cells withTAp73α correlated with removal of Mdm2 from the complex, making them more like primary keratinocytes or initiated cells. Like the initiated cells, cells expressing TAp73α were refractory to treatment with the Mdm2-p53 inhibitor Nutlin-3 while cells lacking p73 expression or expressing ΔNp73α were sensitive. Thus, we suggest that p73 may be acting as a molecular shield to keep p53 family member inhibitors, such as ΔNp63α andMdm2, at bay. Further understanding of p53 family interplay in tumor development and DNA damage response could lead to new therapies or optimization of current therapeutic strategies in solid tumors of epithelium, particularly where deregulation or loss of p63 and p73 expression is associated with increased tumor invasiveness, treatment resistance, and poor patient prognosis.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 3 uppsatser.

Thesis (Ph. D.)--University of Virginia, 2008. / Includes bibliographical references. Also available online through Digital Dissertations.

Dissertation (Ph.D.)--University of South Florida, 2007. / Title from PDF of title page. Document formatted into pages; contains 82 pages. Includes vita. Includes bibliographical references.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2009. / Härtill 5 uppsatser.

Thesis (Ph.D. in Experimental Pathology, Program in Cancer Biology) -- University of Colorado Denver, 2007. / Typescript. Includes bibliographical references (leaves 144-158). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;