Death domain-associated protein 6 (DAXX) is a multifunctional protein involved in diverse cellular processes. It acts as a histone chaperone or regulator of transcription and apoptosis, in which is its role quite controversial. DAXX also participates in regulation of cell DNA damage response (DDR). DAXX co-creates and stabilizes complex with Mdm2, which negatively regulates the stability of p53, an important tumor suppressor, which is a part of signalling node in the DDR. If DNA damage is not lethal for the cell and unables it to proliferate, the irreversible state of cell cycle called cellular senescence takes place. Under physiological conditions, induction of senescence can prevent the development of tumorigenesis. Therefore, the description of mechanisms involved in the induction of senescence has potential clinical significance. In my thesis, I aimed to determine changes in the level of DAXX protein in senescent cells and to characterize the manner of its regulation. In tumor cells MCF-7 and primary BJ fibroblasts, I observed decrease in DAXX protein level and its regulation. I tested the hypothesis according to which an increase in DAXX level before DNA damage canprevent induction of cellular senescence, or increase in its expression during senescence can cause recovery of cell proliferation....

No description available.

Thesis advisor: Udayan Mohanty / The stabilization of particular conformations of protein and nucleic acid structure is believed to play an important role in many important biological functions. In chapter one, the α -helical conformation and structural stability of single and double stapled all- hydrocarbon cross-linked p53 peptides when bound and unbound to MDM2 are investigated. Our study provides a comprehensive rationalization of the relationship between peptide stapling strategy, the secondary structural stability, and the binding affinity of p53-MDM2 complex. In chapter two, we study counterion-mediated collapse of a strongly charged model polyelectrolyte chain by Group-II divalent metal cations using coarse-grained Brownian dynamics simulations. Polyelectrolyte effects govern the association of counterions with the chain. Large ions are less effective in counterion condensation than small ions. However, upon counterion condensation, the reduction of the backbone charge is independent of size of the metal cations. Above a threshold value of Coulomb strength parameter, counterion release entropy drives the formation of counterion-induced compact states. In chapter three, the nature of surface tension in the random first order theory of supercooled liquid is analyzed within the framework of Landau-Lifshitz fluctuation theory. We show that the surface tension of a droplet satisfies the differential equation 4πr2(dσ)+ 8πrσ(r)− Br1/2 = 0 , where B/ T = 12πkBcv , T is temperature, kB is dr Boltzmann constant, and cv is heat capacity. A consequence is that the slope of the relaxation time at the glass transition temperature, i.e., the fragility index, is expressed as the square of the ratio of heat capacity and configurational entropy of the supercooled liquid. When backbone extended nucleosides are incorporated into a double helix, a unique helical structure is formed. In chapter four, we find that the predicted stability of modified backbone DNA strands in aqueous solution is in good agreement with experimental melting temperature data. The incorporation of extended backbone nucleosides into a duplex results in elongation of the end-to-end chain distance due to the distortion of the B-DNA conformation at the mutated base-pair insertion. We also find that the modified backbone helical twist is approximately 40 degrees, larger than B-DNA helical twist and closer to the twist angle predicted for D-form DNA. The folding of RNA tertiary structure has been described as an equilibrium between partially folded I (intermediate) states, and the fully folded native conformation, or N state. RNA is highly sensitive to the ionic environment due to its negative charge, and tertiary structures tend to be strongly stabilized by Mg2+. There is a need for models capable of describing the ion atmosphere surrounding RNA with quantitative accuracy. In chapter 5, we present a generalized Manning condensation model of RNA electrostatics for studying the Mg2+-induced RNA folding of the 58mer ribosomal fragment. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Introdução: O carcinoma adenoide cístico (CAC) é uma das neoplasias de glândula salivar mais comuns para o qual não se encontra quimioterapia eficaz. Um conceito emergente na terapia do câncer é atingir proteínas especificas do tumor. MDM2 (murine double minute 2) é um importante inibidor do supressor tumoral p53, e sua expressão é aumentada em CAC. O objetivo do Artigo 1 foi avaliar o efeito de um novo inibidor da interação MDM2-p53 (MI-773) no CAC in vitro e in vivo. O Artigo 2 teve como objetivo entender o papel da combinação de MI-773 com cisplatina, além de avaliar a recorrência de CAC frente a regime neoadjuvante de MI-773. Materiais e Métodos: 3 modelos de xenoenxerto derivado de paciente (XEDP, UM-PDXHACC- 5; ACCx6; ACCx9) e 5 culturas primarias de CAC (UM-HACC-1, -2A, -2B, -5, -6) foram usados para experimentos in vitro e in vivo. Ensaio de Sulforrodamina B (SRB) foi realizado para avaliar o efeito dos agentes experimentais na viabilidade celular, além de determinar valores de IC50. Western blots revelaram a expressão de p53, fosfo-p53, MDM2, p21, PUMA, BAX, Bcl-2 e Bcl-xL. Lâminas histológicas (UMPDX- HACC-5) foram avaliadas por imunohistoquímica e imunofluorescência para determinar a localização de p53. Técnica de TUNEL in situ revelou o número de células de UM-PDX-HACC-5 no processo de apoptose. Citometria de fluxo foi realizada para determinar o efeito da terapia na proporção de células-tronco tumorais (ALDHhighCD44high) e para avaliar o ciclo celular. Para os estudos in vivo, animais transplantados com tumores (UM-PDX-HACC5, ACCx6, ou ACCx9) receberam protocolo terapêutico (MI-773 – gavagem; cisplatina – injeção intraperitoneal; ou veículo controle) conforme indicado. ANOVA, seguido de testes post-hoc (Tukey), Mann-Whitney U-test ou Student’s t-test foram usados para determinar as diferenças no crescimento tumoral, peso, volume, apoptose, viabilidade celular, expressão de TUNEL e p53. Significância estatística: p<0.05. Resultados: MI-773 causa regressão do tumor em todos os modelos préclínicos de CAC. Doses diárias de 100mg/kg de MI-773 reduziram significativamente o volume tumoral quando comparado com doses intermediárias (10 ou 50 mg/kg MI-773) ou veículo controle, em todos os modelos de CAC. Alternativamente, camundongos transplantados com tumores UM-PDX-HACC-5 receberam doses semanais de MI-773 (200 mg/kg) e/ou cisplatina (5 mg/kg) por 30 dias, a fim de se avaliar o efeito da combinação das drogas. MI-773, como agente único, causou regressão tumoral, sendo mais efetivo do que a cisplatina. Cisplatina, por outro lado, mostrou limitado efeito terapêutico, estabilizando o crescimento tumoral. Notavelmente, a combinação MI-773 + cisplatina foi mais efetiva do que os agentes isoladamente, e não foi verificada retomada do tumor no período pósoperatório. Importantemente, os protocolos experimentais não comprometeram a saúde geral dos animais. Coletivamente, estes resultados in vivo demonstram que MI-773 atua como mediador na regressão tumoral de CAC e sensibiliza os tumores à cisplatina. A inibição terapêutica da interação MDM2-p53 ativa p53 e induz apoptose. MI-773 potentemente induz expressão de p53, seu alvo p21 e proteínas relacionadas à apoptose, como PUMA, BAX, Bcl-2 e Bcl-xL in vitro e in vivo. Análise do ciclo celular mostrou que a inibição terapêutica da interação MDM2-p53 por MI- 773 causa parada no ciclo celular no primeiro ponto de checagem (G1). Marcação por TUNEL revelou número significativamente maior de células em apoptose quando tumores de UM-PDX-HACC-5 foram tratados com MI-773 em comparação com controle (p<0.05) Utilizando o mesmo modelo de xenoenxerto, a técnica de imunohistoquímica mostrou que MI-773 não somente aumentou a porcentagem de células p53-positivas (p<0.001), como causou uma translocação parcial de p53 ao citoplasma. MI-773 reduz a fração de células-tronco tumorais (CTT) e previne recorrência do CAC. Tratamento com MI-773 como agente único ou combinado com cisplatina reduziu a fração de CTT (p<0.05). Notavelmente, nenhum animal tratado com regime neoadjuvante de MI-773 apresentou recorrência tumoral mesmo após 300 dias de acompanhamento. Em contraste, em 62,5% dos animais do grupo controle houve recorrência (p=0.0097). Conclusões: Em resumo, os estudos demonstram que a inibição terapêutica da interação MDM2-p53 com MI-773 é uma estratégia antitumoral eficaz, é capaz de sensibilizar tumores à cisplatina e previne recorrência neste modelo pré-clínico de CAC. Coletivamente, os dados sugerem que pacientes com carcinoma adenoide cístico podem ser beneficiados através de terapias-alvo contra MDM2. / Introduction: Adenoid cystic carcinoma (ACC) is one of the most common salivary gland malignancies for which no effective chemotherapy is available. An emerging concept in cancer therapy is to target specific tumor-related proteins. Murine double minute 2 (MDM2) is an important inhibitor of the tumor suppressor p53 and has been found overexpressed in ACC. Paper #1 aimed to evaluate the effect of a novel small molecule inhibitor of the MDM2-p53 interaction (MI-773) on ACC in vitro and in vivo. Paper #2 aimed to understand the role of combining MI-773 with cisplatin, and to evaluated ACC recurrence using a neoadjuvant regimen of MI-773. Material and Methods: 3 patient-derived xenograft (PDX) models (UM-PDX-HACC-5; ACCx6; ACCx9) and 5 low passage primary human ACC cells pools (UM-HACC-1, -2A, -2B, - 5, -6) were used for in vivo and in vitro experiments. Sulforhodamine B (SRB) assay was performed to evaluate the effect of experimental agents on ACC cell viability and to determine IC50 values. Western blots revealed the expression of p53, phosphop53, MDM2, p21, PUMA, BAX, Bcl-2 and Bcl-xL. Histological sections from UM-PDXHACC- 5 tumors were stained using immunohistochemistry and immunofluorescence techniques to determine p53 status. In situ TUNEL staining revealed the number of UM-PDX-HACC-5 cells undergoing apoptosis. Flow cytometry was carried out to determine the effect of therapy on the proportion of cancer stem cells (ALDHhighCD44high) and for cell cycle analysis. For in vivo studies, mice harboring UM-PDX-HACC5, ACCx6, or ACCx9 tumors were treated following specific therapeutic protocol (MI-773 – gavage; cisplatin – intraperitoneal injection; or vehicle control), as opportunely indicated. One-way ANOVA, followed by post-hoc tests (Tukey), Mann-Whitney U-test or Student’s t-test were used to determine significant differences in tumor growth, weight, volume, apoptosis levels, cell viability, TUNEL and p53 expression. Significance was determined at p<0.05. Results: MI-773 caused tumor regression in all ACC PDX models. Daily doses of 100 mg/kg MI- 773 significantly reduced tumor volume when compared to intermediate doses (10 or 50 mg/kg MI-773) or vehicle-treated controls in all ACC xenograft models. Alternatively, mice harboring UM-PDX-HACC-5 tumors received either weekly doses of MI-773 (200 mg/kg) and/or cisplatin (5 mg/kg) for 30 days, in order to evaluate the effect of this drug combination. MI-773 as single agent caused tumor regression, being more effective than single agent cisplatin. Cisplatin showed limited therapeutic response stabilizing tumor growth. Notably, combination of MI-773 with cisplatin was more effective than single agent therapies and no tumor rebound was observed during the follow up period. Importantly, experimental protocols did not compromise the overall health status of mice. Collectively, these in vivo results demonstrate that MI-773 mediates ACC tumor regression, and sensitizes ACC xenograft tumors to cisplatin. Therapeutic inhibition of the MDM2-p53 interaction activates p53 and induces apoptosis. MI-773 potently induced the expression of p53, its downstream target p21 and apoptosis-related proteins PUMA, BAX, Bcl-2 and Bcl-xL in vitro and in vivo. Cell cycle analysis showed that therapeutic inhibition of the MDM2-p53 interaction by MI-773 causes cell cycle arrest at the first checkpoint (G1). In situ TUNEL revealed a significant higher number of cells undergoing apoptosis in UMPDX- HACC-5 tumors treated with MI-773 compared to vehicle control (p<0.05). Using the same xenograft model, immunohistochemistry assay showed that MI-773 not only increased the percentage of p53-positive cells (p<0.001), but also caused a partial translocation of p53 to the cytoplasm. MI-773 reduces the fraction of cancer stem cells (CSC) and prevents recurrence in ACC. Treatment with MI-773 as single agent or combined with cisplatin significantly reduced the fraction of CSC (p<0.05). Notably, not a single animal treated with neoadjuvant MI-773 presented recurrence even after 300 days of follow-up. In contrast, 62,5% of mice that received vehicle control experienced tumor reappearance within this time period (p=0.0097). Conclusions: In summary, these studies demonstrate that therapeutic inhibition of the MDM2-p53 interaction with MI-773 is an effective anti-tumor strategy that mediates tumor regression, sensitizes tumors to cisplatin and prevents recurrence in this pre-clinical model of ACC. Collectively, these data suggest that patients with adenoid cystic carcinoma might benefit from MDM2-targeted therapies.

Diffuse large B-cell lymphoma (DLBCL), which is the most common type of lymphoma, is characterised by its aggressiveness and poor outcome without adequate treatment and also for its biological and clinical heterogeneity. It is therefore highly desirable to gain a more profound understanding of the underlying biology of the disease, as well as predictive factors for the guidance of treatment. The studies presented here attempt to gain an overall grasp on DLBCL, from the epidemiological level down to the genomic level. The tumour microenvironment consists of both tumour cells and normal infiltrating cells in a delicate interplay. By assessing the number of infiltrating mast cells (MCs) in the microenvironment, a correlation between low numbers of MCs and poorer prognosis of DLBCL was found. However, malignant cells are not only affected by environmental conditions but also by intrinsic factors, such as small non-coding microRNAs. A low expression level of microRNA-129 was found to correlate with poor survival of DLBCL and the finding remained significant even for rituximab-treated patients. An even smaller intracellular genomic unit is one single nucleotide. The single nucleotide polymorphism 309 (SNP309) is a T to G change in the promotor region of MDM2, a regulatory protein in the p53 pathway, which results in increased transcription of MDM2 and thus decreased levels of p53. It was found that homozygous T allele patients had longer overall survival, as well as disease-specific survival and disease-free survival. However, treatment with rituximab eliminated the predictive value of the SNP309 polymorphism. In the last project presented in this thesis we used epidemiological methods to analyse all DLBCL cases diagnosed 2000-2013 in Sweden. Here it was possible to categorically show that higher age is an adverse prognostic factor, and most importantly, this starts from a young age. In conclusion, within this thesis I have applied different laboratory and analysis techniques to examine DLBCL biology in relation to the clinic. I have identified potential new prognostic markers, contributed to an enhanced understanding of DLBCL biology and described epidemiological data from one of the largest DLBCL cohorts ever presented. All of these aspects provide important information for a deeper understanding of the disease DLBCL.

The MDM2 protein regulates the tumour suppressor protein p53, acting as its chaperone, regulating its translation and targeting p53 for degradation by the 26s proteasome via its E3 ligase activity. The E3 ligase activity of MDM2 is dependent on its C-terminal RING domain. E3 ligases containing a RING domain are traditionally thought to catalyse the transfer of ubiquitin from their conjugating enzyme (E2) partner to the target protein, in the final step of the ubiquitination cascade. Various E2 enzymes have been shown to interact with their partner E3 ligases, yet evidence for the interaction between MDM2 and its partner E2, UbcH5α has not yet been shown. It has been reported that the reason for this lack of evidence is that the interaction between the two is highly unstable. Here I show that MDM2 forms a stable isolatable interaction with UbcH5α, the C-terminal tail of MDM2 is not necessary for this interaction. Although RING E3 ligases were not previously thought to interact with ubiquitin, preliminary evidence is emerging that suggests that this interaction is possible indeed I show that MDM2 and ubiquitin form a stable complex. I demonstrate that UbcH5α and ubiquitin both interact with the RING of MDM2, specifically the 20 most C-terminal amino acids of MDM2. My results show that both these proteins can bind this region of the RING simultaneously. I also highlight specific residues including tyrosine 489 and arginine 479 important for UbcH5α and ubiquitin binding respectively and the negative affect that these mutations have on the E3 ligase activity of MDM2 towards p53. Furthermore I show by limited proteolysis and hydrogen deuterium exchange that UbcH5α can be allosterically activated by MDM2. A novel peptide phage display technique linked to next generation sequencing was developed to further confirm an allosteric change and demonstrates that UbcH5α has different binding specificity for peptides when in a free or ligand bound conformation. MDM2 is a popular target for cancer therapeutics due to its dysregulation throughout many cancer types, including 30% of soft tissue sarcomas. Dissecting the mechanism of MDM2 function is an important step in identifying specific drugable interfaces on MDM2 and its interacting partners so that effective therapeutics can be designed.

Introdução: O carcinoma adenoide cístico (CAC) é uma das neoplasias de glândula salivar mais comuns para o qual não se encontra quimioterapia eficaz. Um conceito emergente na terapia do câncer é atingir proteínas especificas do tumor. MDM2 (murine double minute 2) é um importante inibidor do supressor tumoral p53, e sua expressão é aumentada em CAC. O objetivo do Artigo 1 foi avaliar o efeito de um novo inibidor da interação MDM2-p53 (MI-773) no CAC in vitro e in vivo. O Artigo 2 teve como objetivo entender o papel da combinação de MI-773 com cisplatina, além de avaliar a recorrência de CAC frente a regime neoadjuvante de MI-773. Materiais e Métodos: 3 modelos de xenoenxerto derivado de paciente (XEDP, UM-PDXHACC- 5; ACCx6; ACCx9) e 5 culturas primarias de CAC (UM-HACC-1, -2A, -2B, -5, -6) foram usados para experimentos in vitro e in vivo. Ensaio de Sulforrodamina B (SRB) foi realizado para avaliar o efeito dos agentes experimentais na viabilidade celular, além de determinar valores de IC50. Western blots revelaram a expressão de p53, fosfo-p53, MDM2, p21, PUMA, BAX, Bcl-2 e Bcl-xL. Lâminas histológicas (UMPDX- HACC-5) foram avaliadas por imunohistoquímica e imunofluorescência para determinar a localização de p53. Técnica de TUNEL in situ revelou o número de células de UM-PDX-HACC-5 no processo de apoptose. Citometria de fluxo foi realizada para determinar o efeito da terapia na proporção de células-tronco tumorais (ALDHhighCD44high) e para avaliar o ciclo celular. Para os estudos in vivo, animais transplantados com tumores (UM-PDX-HACC5, ACCx6, ou ACCx9) receberam protocolo terapêutico (MI-773 – gavagem; cisplatina – injeção intraperitoneal; ou veículo controle) conforme indicado. ANOVA, seguido de testes post-hoc (Tukey), Mann-Whitney U-test ou Student’s t-test foram usados para determinar as diferenças no crescimento tumoral, peso, volume, apoptose, viabilidade celular, expressão de TUNEL e p53. Significância estatística: p<0.05. Resultados: MI-773 causa regressão do tumor em todos os modelos préclínicos de CAC. Doses diárias de 100mg/kg de MI-773 reduziram significativamente o volume tumoral quando comparado com doses intermediárias (10 ou 50 mg/kg MI-773) ou veículo controle, em todos os modelos de CAC. Alternativamente, camundongos transplantados com tumores UM-PDX-HACC-5 receberam doses semanais de MI-773 (200 mg/kg) e/ou cisplatina (5 mg/kg) por 30 dias, a fim de se avaliar o efeito da combinação das drogas. MI-773, como agente único, causou regressão tumoral, sendo mais efetivo do que a cisplatina. Cisplatina, por outro lado, mostrou limitado efeito terapêutico, estabilizando o crescimento tumoral. Notavelmente, a combinação MI-773 + cisplatina foi mais efetiva do que os agentes isoladamente, e não foi verificada retomada do tumor no período pósoperatório. Importantemente, os protocolos experimentais não comprometeram a saúde geral dos animais. Coletivamente, estes resultados in vivo demonstram que MI-773 atua como mediador na regressão tumoral de CAC e sensibiliza os tumores à cisplatina. A inibição terapêutica da interação MDM2-p53 ativa p53 e induz apoptose. MI-773 potentemente induz expressão de p53, seu alvo p21 e proteínas relacionadas à apoptose, como PUMA, BAX, Bcl-2 e Bcl-xL in vitro e in vivo. Análise do ciclo celular mostrou que a inibição terapêutica da interação MDM2-p53 por MI- 773 causa parada no ciclo celular no primeiro ponto de checagem (G1). Marcação por TUNEL revelou número significativamente maior de células em apoptose quando tumores de UM-PDX-HACC-5 foram tratados com MI-773 em comparação com controle (p<0.05) Utilizando o mesmo modelo de xenoenxerto, a técnica de imunohistoquímica mostrou que MI-773 não somente aumentou a porcentagem de células p53-positivas (p<0.001), como causou uma translocação parcial de p53 ao citoplasma. MI-773 reduz a fração de células-tronco tumorais (CTT) e previne recorrência do CAC. Tratamento com MI-773 como agente único ou combinado com cisplatina reduziu a fração de CTT (p<0.05). Notavelmente, nenhum animal tratado com regime neoadjuvante de MI-773 apresentou recorrência tumoral mesmo após 300 dias de acompanhamento. Em contraste, em 62,5% dos animais do grupo controle houve recorrência (p=0.0097). Conclusões: Em resumo, os estudos demonstram que a inibição terapêutica da interação MDM2-p53 com MI-773 é uma estratégia antitumoral eficaz, é capaz de sensibilizar tumores à cisplatina e previne recorrência neste modelo pré-clínico de CAC. Coletivamente, os dados sugerem que pacientes com carcinoma adenoide cístico podem ser beneficiados através de terapias-alvo contra MDM2. / Introduction: Adenoid cystic carcinoma (ACC) is one of the most common salivary gland malignancies for which no effective chemotherapy is available. An emerging concept in cancer therapy is to target specific tumor-related proteins. Murine double minute 2 (MDM2) is an important inhibitor of the tumor suppressor p53 and has been found overexpressed in ACC. Paper #1 aimed to evaluate the effect of a novel small molecule inhibitor of the MDM2-p53 interaction (MI-773) on ACC in vitro and in vivo. Paper #2 aimed to understand the role of combining MI-773 with cisplatin, and to evaluated ACC recurrence using a neoadjuvant regimen of MI-773. Material and Methods: 3 patient-derived xenograft (PDX) models (UM-PDX-HACC-5; ACCx6; ACCx9) and 5 low passage primary human ACC cells pools (UM-HACC-1, -2A, -2B, - 5, -6) were used for in vivo and in vitro experiments. Sulforhodamine B (SRB) assay was performed to evaluate the effect of experimental agents on ACC cell viability and to determine IC50 values. Western blots revealed the expression of p53, phosphop53, MDM2, p21, PUMA, BAX, Bcl-2 and Bcl-xL. Histological sections from UM-PDXHACC- 5 tumors were stained using immunohistochemistry and immunofluorescence techniques to determine p53 status. In situ TUNEL staining revealed the number of UM-PDX-HACC-5 cells undergoing apoptosis. Flow cytometry was carried out to determine the effect of therapy on the proportion of cancer stem cells (ALDHhighCD44high) and for cell cycle analysis. For in vivo studies, mice harboring UM-PDX-HACC5, ACCx6, or ACCx9 tumors were treated following specific therapeutic protocol (MI-773 – gavage; cisplatin – intraperitoneal injection; or vehicle control), as opportunely indicated. One-way ANOVA, followed by post-hoc tests (Tukey), Mann-Whitney U-test or Student’s t-test were used to determine significant differences in tumor growth, weight, volume, apoptosis levels, cell viability, TUNEL and p53 expression. Significance was determined at p<0.05. Results: MI-773 caused tumor regression in all ACC PDX models. Daily doses of 100 mg/kg MI- 773 significantly reduced tumor volume when compared to intermediate doses (10 or 50 mg/kg MI-773) or vehicle-treated controls in all ACC xenograft models. Alternatively, mice harboring UM-PDX-HACC-5 tumors received either weekly doses of MI-773 (200 mg/kg) and/or cisplatin (5 mg/kg) for 30 days, in order to evaluate the effect of this drug combination. MI-773 as single agent caused tumor regression, being more effective than single agent cisplatin. Cisplatin showed limited therapeutic response stabilizing tumor growth. Notably, combination of MI-773 with cisplatin was more effective than single agent therapies and no tumor rebound was observed during the follow up period. Importantly, experimental protocols did not compromise the overall health status of mice. Collectively, these in vivo results demonstrate that MI-773 mediates ACC tumor regression, and sensitizes ACC xenograft tumors to cisplatin. Therapeutic inhibition of the MDM2-p53 interaction activates p53 and induces apoptosis. MI-773 potently induced the expression of p53, its downstream target p21 and apoptosis-related proteins PUMA, BAX, Bcl-2 and Bcl-xL in vitro and in vivo. Cell cycle analysis showed that therapeutic inhibition of the MDM2-p53 interaction by MI-773 causes cell cycle arrest at the first checkpoint (G1). In situ TUNEL revealed a significant higher number of cells undergoing apoptosis in UMPDX- HACC-5 tumors treated with MI-773 compared to vehicle control (p<0.05). Using the same xenograft model, immunohistochemistry assay showed that MI-773 not only increased the percentage of p53-positive cells (p<0.001), but also caused a partial translocation of p53 to the cytoplasm. MI-773 reduces the fraction of cancer stem cells (CSC) and prevents recurrence in ACC. Treatment with MI-773 as single agent or combined with cisplatin significantly reduced the fraction of CSC (p<0.05). Notably, not a single animal treated with neoadjuvant MI-773 presented recurrence even after 300 days of follow-up. In contrast, 62,5% of mice that received vehicle control experienced tumor reappearance within this time period (p=0.0097). Conclusions: In summary, these studies demonstrate that therapeutic inhibition of the MDM2-p53 interaction with MI-773 is an effective anti-tumor strategy that mediates tumor regression, sensitizes tumors to cisplatin and prevents recurrence in this pre-clinical model of ACC. Collectively, these data suggest that patients with adenoid cystic carcinoma might benefit from MDM2-targeted therapies.

Introdução: O carcinoma adenoide cístico (CAC) é uma das neoplasias de glândula salivar mais comuns para o qual não se encontra quimioterapia eficaz. Um conceito emergente na terapia do câncer é atingir proteínas especificas do tumor. MDM2 (murine double minute 2) é um importante inibidor do supressor tumoral p53, e sua expressão é aumentada em CAC. O objetivo do Artigo 1 foi avaliar o efeito de um novo inibidor da interação MDM2-p53 (MI-773) no CAC in vitro e in vivo. O Artigo 2 teve como objetivo entender o papel da combinação de MI-773 com cisplatina, além de avaliar a recorrência de CAC frente a regime neoadjuvante de MI-773. Materiais e Métodos: 3 modelos de xenoenxerto derivado de paciente (XEDP, UM-PDXHACC- 5; ACCx6; ACCx9) e 5 culturas primarias de CAC (UM-HACC-1, -2A, -2B, -5, -6) foram usados para experimentos in vitro e in vivo. Ensaio de Sulforrodamina B (SRB) foi realizado para avaliar o efeito dos agentes experimentais na viabilidade celular, além de determinar valores de IC50. Western blots revelaram a expressão de p53, fosfo-p53, MDM2, p21, PUMA, BAX, Bcl-2 e Bcl-xL. Lâminas histológicas (UMPDX- HACC-5) foram avaliadas por imunohistoquímica e imunofluorescência para determinar a localização de p53. Técnica de TUNEL in situ revelou o número de células de UM-PDX-HACC-5 no processo de apoptose. Citometria de fluxo foi realizada para determinar o efeito da terapia na proporção de células-tronco tumorais (ALDHhighCD44high) e para avaliar o ciclo celular. Para os estudos in vivo, animais transplantados com tumores (UM-PDX-HACC5, ACCx6, ou ACCx9) receberam protocolo terapêutico (MI-773 – gavagem; cisplatina – injeção intraperitoneal; ou veículo controle) conforme indicado. ANOVA, seguido de testes post-hoc (Tukey), Mann-Whitney U-test ou Student’s t-test foram usados para determinar as diferenças no crescimento tumoral, peso, volume, apoptose, viabilidade celular, expressão de TUNEL e p53. Significância estatística: p<0.05. Resultados: MI-773 causa regressão do tumor em todos os modelos préclínicos de CAC. Doses diárias de 100mg/kg de MI-773 reduziram significativamente o volume tumoral quando comparado com doses intermediárias (10 ou 50 mg/kg MI-773) ou veículo controle, em todos os modelos de CAC. Alternativamente, camundongos transplantados com tumores UM-PDX-HACC-5 receberam doses semanais de MI-773 (200 mg/kg) e/ou cisplatina (5 mg/kg) por 30 dias, a fim de se avaliar o efeito da combinação das drogas. MI-773, como agente único, causou regressão tumoral, sendo mais efetivo do que a cisplatina. Cisplatina, por outro lado, mostrou limitado efeito terapêutico, estabilizando o crescimento tumoral. Notavelmente, a combinação MI-773 + cisplatina foi mais efetiva do que os agentes isoladamente, e não foi verificada retomada do tumor no período pósoperatório. Importantemente, os protocolos experimentais não comprometeram a saúde geral dos animais. Coletivamente, estes resultados in vivo demonstram que MI-773 atua como mediador na regressão tumoral de CAC e sensibiliza os tumores à cisplatina. A inibição terapêutica da interação MDM2-p53 ativa p53 e induz apoptose. MI-773 potentemente induz expressão de p53, seu alvo p21 e proteínas relacionadas à apoptose, como PUMA, BAX, Bcl-2 e Bcl-xL in vitro e in vivo. Análise do ciclo celular mostrou que a inibição terapêutica da interação MDM2-p53 por MI- 773 causa parada no ciclo celular no primeiro ponto de checagem (G1). Marcação por TUNEL revelou número significativamente maior de células em apoptose quando tumores de UM-PDX-HACC-5 foram tratados com MI-773 em comparação com controle (p<0.05) Utilizando o mesmo modelo de xenoenxerto, a técnica de imunohistoquímica mostrou que MI-773 não somente aumentou a porcentagem de células p53-positivas (p<0.001), como causou uma translocação parcial de p53 ao citoplasma. MI-773 reduz a fração de células-tronco tumorais (CTT) e previne recorrência do CAC. Tratamento com MI-773 como agente único ou combinado com cisplatina reduziu a fração de CTT (p<0.05). Notavelmente, nenhum animal tratado com regime neoadjuvante de MI-773 apresentou recorrência tumoral mesmo após 300 dias de acompanhamento. Em contraste, em 62,5% dos animais do grupo controle houve recorrência (p=0.0097). Conclusões: Em resumo, os estudos demonstram que a inibição terapêutica da interação MDM2-p53 com MI-773 é uma estratégia antitumoral eficaz, é capaz de sensibilizar tumores à cisplatina e previne recorrência neste modelo pré-clínico de CAC. Coletivamente, os dados sugerem que pacientes com carcinoma adenoide cístico podem ser beneficiados através de terapias-alvo contra MDM2. / Introduction: Adenoid cystic carcinoma (ACC) is one of the most common salivary gland malignancies for which no effective chemotherapy is available. An emerging concept in cancer therapy is to target specific tumor-related proteins. Murine double minute 2 (MDM2) is an important inhibitor of the tumor suppressor p53 and has been found overexpressed in ACC. Paper #1 aimed to evaluate the effect of a novel small molecule inhibitor of the MDM2-p53 interaction (MI-773) on ACC in vitro and in vivo. Paper #2 aimed to understand the role of combining MI-773 with cisplatin, and to evaluated ACC recurrence using a neoadjuvant regimen of MI-773. Material and Methods: 3 patient-derived xenograft (PDX) models (UM-PDX-HACC-5; ACCx6; ACCx9) and 5 low passage primary human ACC cells pools (UM-HACC-1, -2A, -2B, - 5, -6) were used for in vivo and in vitro experiments. Sulforhodamine B (SRB) assay was performed to evaluate the effect of experimental agents on ACC cell viability and to determine IC50 values. Western blots revealed the expression of p53, phosphop53, MDM2, p21, PUMA, BAX, Bcl-2 and Bcl-xL. Histological sections from UM-PDXHACC- 5 tumors were stained using immunohistochemistry and immunofluorescence techniques to determine p53 status. In situ TUNEL staining revealed the number of UM-PDX-HACC-5 cells undergoing apoptosis. Flow cytometry was carried out to determine the effect of therapy on the proportion of cancer stem cells (ALDHhighCD44high) and for cell cycle analysis. For in vivo studies, mice harboring UM-PDX-HACC5, ACCx6, or ACCx9 tumors were treated following specific therapeutic protocol (MI-773 – gavage; cisplatin – intraperitoneal injection; or vehicle control), as opportunely indicated. One-way ANOVA, followed by post-hoc tests (Tukey), Mann-Whitney U-test or Student’s t-test were used to determine significant differences in tumor growth, weight, volume, apoptosis levels, cell viability, TUNEL and p53 expression. Significance was determined at p<0.05. Results: MI-773 caused tumor regression in all ACC PDX models. Daily doses of 100 mg/kg MI- 773 significantly reduced tumor volume when compared to intermediate doses (10 or 50 mg/kg MI-773) or vehicle-treated controls in all ACC xenograft models. Alternatively, mice harboring UM-PDX-HACC-5 tumors received either weekly doses of MI-773 (200 mg/kg) and/or cisplatin (5 mg/kg) for 30 days, in order to evaluate the effect of this drug combination. MI-773 as single agent caused tumor regression, being more effective than single agent cisplatin. Cisplatin showed limited therapeutic response stabilizing tumor growth. Notably, combination of MI-773 with cisplatin was more effective than single agent therapies and no tumor rebound was observed during the follow up period. Importantly, experimental protocols did not compromise the overall health status of mice. Collectively, these in vivo results demonstrate that MI-773 mediates ACC tumor regression, and sensitizes ACC xenograft tumors to cisplatin. Therapeutic inhibition of the MDM2-p53 interaction activates p53 and induces apoptosis. MI-773 potently induced the expression of p53, its downstream target p21 and apoptosis-related proteins PUMA, BAX, Bcl-2 and Bcl-xL in vitro and in vivo. Cell cycle analysis showed that therapeutic inhibition of the MDM2-p53 interaction by MI-773 causes cell cycle arrest at the first checkpoint (G1). In situ TUNEL revealed a significant higher number of cells undergoing apoptosis in UMPDX- HACC-5 tumors treated with MI-773 compared to vehicle control (p<0.05). Using the same xenograft model, immunohistochemistry assay showed that MI-773 not only increased the percentage of p53-positive cells (p<0.001), but also caused a partial translocation of p53 to the cytoplasm. MI-773 reduces the fraction of cancer stem cells (CSC) and prevents recurrence in ACC. Treatment with MI-773 as single agent or combined with cisplatin significantly reduced the fraction of CSC (p<0.05). Notably, not a single animal treated with neoadjuvant MI-773 presented recurrence even after 300 days of follow-up. In contrast, 62,5% of mice that received vehicle control experienced tumor reappearance within this time period (p=0.0097). Conclusions: In summary, these studies demonstrate that therapeutic inhibition of the MDM2-p53 interaction with MI-773 is an effective anti-tumor strategy that mediates tumor regression, sensitizes tumors to cisplatin and prevents recurrence in this pre-clinical model of ACC. Collectively, these data suggest that patients with adenoid cystic carcinoma might benefit from MDM2-targeted therapies.

Submitted by Chaylane Marques (chaylane.marques@ufpe.br) on 2015-03-12T19:05:14Z No. of bitstreams: 2 Dissertação - Biblioteca.pdf: 1309462 bytes, checksum: b4c445118f5bcfabe4bf07ca5de9ce8d (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-12T19:05:15Z (GMT). No. of bitstreams: 2 Dissertação - Biblioteca.pdf: 1309462 bytes, checksum: b4c445118f5bcfabe4bf07ca5de9ce8d (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2012-03-02 / Pequenos vírus de DNA, os Papilomavírus humano (HPV), são transmitidos por via sexual e infectam mucosas e epitélios levando ao desenvolvimento de tumores benignos, os quais podem evoluir para um processo carcinogênico. Este vírus apresenta seu genoma dividido em regiões de expressão precoce e tardia. Dentre as de expressão precoce, estão as regiões E6 e E7 as quais codificam para proteínas que interferem no ciclo celular do hospedeiro. A proteína viral E6 interage com a proteína celular p53 inibindo sua função supressora de tumor. Enquanto isso, a proteína E7 interage com a proteína pRb, também supressora de tumor, possibilitando a passagem do ciclo celular da fase G1 para a fase S. Dessa forma, o HPV é responsável pela transformação celular. Considerada o principal agente etiológico do câncer cervical, a infecção por HPV é necessária, porém não suficiente nesse processo. Fatores ambientais e genéticos têm sido apontados como co-fatores, sendo esse último responsável por 37% do risco total. Polimorfismos no gene TP53 bem como naqueles envolvidos na via da p53 têm sido relacionados com a susceptibilidade a lesões e câncer cervicais. Este trabalho teve como objetivo avaliar, em mulheres infectadas com HPV, a possível associação de polimorfismos em dois genes envolvidos na via da p53, MDM2 (SNPT309G) e WAF-1 (SNPC590T) com o aumento da susceptibilidade a lesões e câncer cervicais. Para tanto, foi utilizada a técnica de RFLP (Restriction Fragment Length Polymorphism). Os dados foram analisados através de testes estatísticos qui-quadrado de Pearson, teste G de aderência, equilibro de Hardy-Weinberg e teste exato de Fisher. Não se observou diferenças significativas entre as freqüências alélicas e genotípicas entre grupos de casos e de controles nos dois genes analisados. Os resultados obtidos nesse estudo sugerem que os polimorfismos MDM2 (SNPT309G) e WAF-1 (SNPC590T) não estão associados com lesões e câncer cervicais em pacientes da região nordeste do Brasil.

No description available.