Pancreatic cancer (PDAC) affects 4400 Canadians each year and with 5year survival rates <8%, there is clearly an unmet need for new therapeutic approaches for treating this deadly disease. Herein I report the development of a surgical model of PDAC that recapitulates many of the hallmarks of human disease and has an immune infiltrate consisting of T cells and suppressive regulatory T cells and myeloid derived suppressor cells. This model allows the exploration of new therapeutics that can be used in combination with surgical resection of primary tumours. Furthermore, I propose that the use of neoadjuvant administration of a prime-boost oncolytic vaccine targeting a pancreatic tumour associated antigen (TAA) - mesothelin - could potentiate pancreatic tumour specific immune responses to improve patient prognosis. We demonstrate that immune tolerance to this self antigen can be broken by the complete depletion of circulating Tregs at the time of vaccination, which leads to the activation of a population of CD8+ T cells responsive to mesothelin. We demonstrate that these T cells respond to mesothelin expressing tumour cells ex vivo, and that CD8+ T cells are recruited to the site of tumour challenge. However, despite the generated CD8+ T cell response, oncolytic vaccine strategies targeting mesothelin provide no protection against Pan02 tumours, or against other mesothelin expressing murine tumour lines. I demonstrate that this is not through common tumour escape mechanisms, nor through the upregulation of suppressive immune populations. Any efficacy observed was found to be provided solely by depletion of Tregs, as the depletion of CD8+ T cells did not reduce protection from tumour outgrowth in vaccinated mice. While mesothelin represents a promising target, it is not an ideal target for oncolytic vaccine platforms, potentially due to its nature as a self antigen.

Background and Objectives: Mesothelin, identified as a tumor-associated biomarker, is more often overexpressed in triple receptor-negative breast cancer (TNBC) than in common luminal breast tumor subtype or normal tissues. The objective of this systematic review is to determine the association between the expressions of mesothelin with survival outcomes in patients with TNBC. Methods We searched the following electronic databases: MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, PubMed, and Web of Science with no time or language restriction till May 19, 2016. Any prospective or retrospective longitudinal studies that investigate the prognosis of TNBC with mesothelin baseline measurement were selected. Two reviewers independently assessed every article for inclusion, extracted data, and assessed the methodological quality of every eligible trial. Pooled measures of associations were summarized with meta-analyses. Results and conclusions Among the 592 patients with TNBC included in the four eligible studies, 269 patients (45.4%) demonstrated mesothelin expression. For the primary outcome OS, we found the trend toward decreased survival for patients with mesothelin-positive TNBC than those without mesothelin expression. We also found that for long-term OS, the association was statistically significant (OR = 0.46; 95% CI= 0.30 to 0.73; P< 0.001). For the secondary outcomes, we found that mesothelin expression in patients with TNBC was associated with lower DFS and higher overall mortality than those without mesothelin expression. Despite the limitations of sample size, this present study shows a significant association between mesothelin expressions and survival outcomes in patients with TNBC. Patients with mesothelin-positive TNBC could benefit from mesothelin-targeted immunotherapies recently in the development. / Thesis / Master of Science (MSc) / It is unclear whether mesothelin expression in triple-negative breast cancer (TNBC) is an independent prognostic marker for survival. To the best of our knowledge, no systematic review or meta-analysis has ever been done on this topic. The present systematic review aims to evaluate the role of mesothelin as a prognostic marker for TNBC. The primary objective of this review is to synthesize available evidence on the association between the expression of mesothelin and overall survival (OS) of patients with TNBC. The secondary objectives include determining the relationship between the expression of mesothelin and disease-free survival (DFS), distant metastases, and mortality. Despite some limitations, this study shows a significant association between mesothelin expressions and long-term OS rate as well as DFS rate and mortality rate in patients with TNBC. Mesothelin has a prognostic significance for patients with mesothelin based on our findings. Patients with mesothelin-positive TNBC could benefit from mesothelin-targeted immunotherapies in development.

Orientador: João Alexandre Ribeiro Gonçalves Barbosa / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-14T15:40:05Z (GMT). No. of bitstreams: 1 Santos_CamilaRamosdos_D.pdf: 7751754 bytes, checksum: 779a2794a6dc213431c4264c43cc0af6 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho realizamos estudos estruturais com duas proteínas, a Q4DV70 de Trypanosoma cruzi e a mesotelina de Homo sapiens. O objetivo foi contribuir para a compreensão da função dessas proteínas, as quais possivelmente são importantes para a doença de Chagas e o câncer, respectivamente. A proteína Q4DV70 estava anotada no genoma de T. cruzi como hipotética conservada. Em nosso estudo, a proteína foi pela primeira vez detectada em amostras do parasita. Essa expressão ocorre na fase epimastigota, mas não na fase tripomastigota metacíclica, indicando que a proteína pode ter uma função importante no ciclo de vida do T. cruzi. A estrutura cristalográfica da Q4DV70 foi resolvida por substituição molecular e refinada com dados até 1,5 Å de resolução. Ela apresenta enovelamento tiorredoxina, formado por uma folha ß de 5 fitas cercada por duas hélices a de cada lado. As proteínas que apresentam maior identidade seqüencial e superposição estrutural com Q4DV70 são as tiorredoxinas e PDIs, oxidorredutases de pontes dissulfeto. Porém, as duas cisteínas do sítio ativo dessas proteínas estão substituídas por serinas em Q4DV70, o que impossibilita a função de formação, redução ou isomerização de pontes dissulfeto. Diversas tiorredoxina-like apresentam atividade chaperona independente da função oxidorredutase. Essa função está relacionada a regiões hidrofóbicas na superfície e/ou depende da presença de outro domínio. Q4DV70 é monomérica, composta apenas pelo domínio tiorredoxinalike, e não apresenta regiões hidrofóbicas em sua superfície. Além disso, não demonstrou capacidade de aumentar o enovelamento da GAPDH de T. cruzi. Esses resultados indicam que Q4DV70 não apresenta atividade chaperona. Mesotelina é uma proteína expressa em mesotélio normal e em diversos tipos de câncer, como mesotelioma, câncer de ovário e de pâncreas e leucemia mielóide aguda. Ela é considerada um marcador diagnóstico para esses cânceres e tem sido alvo para o desenvolvimento de drogas anti-tumor. Além disso, ela interage com MUC16, uma proteína presente na superfície de células de câncer de ovário. Apesar da reconhecida importância e uso da mesotelina, pouco se sabe sobre sua estrutura e função. A proteína foi purificada em condições desnaturantes e submetida ao re-enovelamento por diálise. Experimentos de dicroísmo circular, fluorescência e proteólise limitada comprovaram que a mesotelina foi corretamente re-enovelada. Essa amostra foi submetida a ensaios de cristalização, os quais resultaram em cristais que difrataram a baixa resolução. A estrutura de baixa resolução da mesotelina foi calculada a partir de dados de espalhamento de raios X a baixo ângulo e mostra que sua forma é alongada e curvada. O espectro de dicroísmo circular da mesotelina é típico de proteínas ricas em hélices a. Recentemente foi proposto que a estrutura da mesotelina é formada por uma estrutura em super-hélice, composta por repetições do tipo ARM, as quais apresentam 3 hélices a cada uma. Nossos resultados experimentais indicam que esse modelo teórico está correto. Proteólise limitada com quimotripsina resultou em um domínio estável de 20 kDa na região N-terminal da proteína. Esse domínio contém os 64 resíduos descritos como possível sítio de ligação a MUC16 e deve ser formado pelas 4 primeiras repetições do tipo ARM, de acordo com o modelo publicado. / Abstract: In this work we carried out studies with two proteins, Q4DV70 from Trypanosoma cruzi and mesothelin from Homo sapiens. The aim was to help the understanding of the function of these proteins which possibly are important to Chagas disease and cancer, respectively. Q4DV70 protein was annotated in T. cruzi genome as a conserved hypothetical protein. In our studies, the protein was detected for the first time in parasite samples. Its expression occurs in the epimastigote form but not in the metacyclic trypomastigote form indicating that Q4DV70 is important for the pathogen life cycle. Q4DV70 crystal structure was solved by molecular replacement and refined with data to 1.5 Å maximum resolution. It shows a thioredoxin fold, formed by a five stranded ß-sheet flanked by two a-helixes in each side. The proteins more sequentially identical and better structurally superposed to Q4DV70 are thioredoxins and protein disulfide isomerases, which are disulfide oxidoreductases. However, the cysteine residues from CXXC motif of the active site are replaced by serines in Q4DV70, what prevents the function of formation, reduction and isomerization of disulfide bonds. Different thioredoxin-like proteins show chaperone activity independent of oxidoreductase function. This function is related to hydrophobic regions on the surface and/or is dependent of another domain. Q4DV70 is monomeric, composed only by thioredoxin-like domain and does not show hydrophobic regions on its surface. Moreover the protein does not increase the refolding of GAPDH from T. cruzi. These results indicate that Q4DV70 does not present chaperone activity. Mesothelin is a protein expressed in normal mesothelium and in different types of cancer, such as mesothelioma, ovarian cancer, acute myeloid leukemia and cancer of pancreas. It is considered a diagnostic marker for these cancers and it has been used in the development of antitumor drugs. Besides that, it binds to MUC16, a protein present on the surface of ovarian cancer cells. In spite of its recognized significance and use in cancer, little is known about its structure and function. The protein was purified under denaturing conditions and submitted to refolding by dialysis. Circular dichroism, fluorescence and limited proteolysis experiments confirmed that mesothelin was correctly refolded. This sample was submitted to crystallization trials that resulted in crystals which diffracted at low resolution. The low resolution structure of mesothelin was calculated from small angle X-ray scattering data and it shows an elongated and curved shape. The circular dichroism spectrum for mesothelin is typical of proteins that are rich in a-helixes. Recently it was proposed that mesothelin has a superhelix structure made by ARM repeats which are composed by 3 a-helixes each one. Our experimental results indicate that this theoretical model is correct. Limited proteolysis with chymotrypsin resulted in a stable domain of 20 kDa in the Nterminal region of the protein. This domain has the 64 residues described as the possible binding site for MUC16 and should be composed by the first four ARM repeats according to the model. / Doutorado / Bioquimica / Doutor em Biologia Funcional e Molecular

Le trastuzumab est le traitement de référence des cancers du sein « HER2 amplifié ». Outre les limitations inhérentes à toute IgG, cet anticorps est inefficace pour traiter les tumeurs exprimant que modérément (cancers hormonaux) ou faiblement (triple négatif) HER2. L'objectif de ces travaux de thèse est de concevoir de nouveaux anticorps bispécifiques destinés au traitement de cancers du sein échappant à l'action du trastuzumab. Nous nous sommes appuyés sur des formats innovants, basés sur l'utilisation d'anticorps simple domaine de lama (sdAb) comme unité de reconnaissance antigénique. Deux anticorps bispécifiques Fab-like (bsFab) ont été développés, l'un dirigé contre HER2 (HER2bsFab) et l'autre ciblant la mésothéline (MesobsFab), un antigène surexprimé dans 30 à 70% des cancers du sein « triple négatif ». En liant spécifiquement et de façon efficace FcγRIII, ces deux bsFabs ne compètent pas avec les IgG endogènes, ne fixent pas FcγRIIB et activent fortement les NKs. In vitro, HER2bsFab induit de fortes sécrétions de cytokines pro-inflammatoires et de puissantes ADCCs contre des lignées de cancer du sein indépendamment du niveau d'expression d'HER2 et du polymorphisme FcγRIIIA-158. In vivo, HER2bsFab montre une nette supériorité comparé au trastuzumab contre des tumeurs ne surexprimant que modérément HER2. HER2bsFab et MesobsFab induisent in vitro de fortes cytotoxicités contre deux lignées de cancer du sein « triple négatif » et des résultats préliminaires réalisés chez la souris semblent confirmer ces observations. A termes, l'utilisation de ces anticorps permettrait d'étendre la proportion de patientes traitables de façon efficace par immunothérapie. / Trastuzumab is established as standard of care for the treatment of HER2high breast cancers. However, in addition to Fc-related limitations inherent to IgG antibodies, trastuzumab is inefficient to treat low- (triple-negative) or moderate-HER2-overexpressing (hormone-receptor-positive) breast cancers. Based on the unique structural and functional properties of llama single domain antibodies (sdAbs), we report the design of two Fab-like bispecific antibodies targeted to HER2 (HER2bsFab) and mesothelin (MesobsFab), an antigen overexpressed in several human tumors, including triple-negative breast cancers. The two bsFabs display a unique, specific and high affinity for FcγRIII. As a consequence, they do not bind the FcγRIIB inhibitor receptor and bypass competition with endogenous IgGs. HER2bsFab mediated ADCC at picomolar concentration against HER2high as well as HER2moderate cell lines. In vivo HER2bsFab potently inhibited HER2high tumor growth and more importantly, exhibited a net superiority over trastuzumab at inhibiting HER2moderate tumor growth. Moreover, FcγRIIIA-engagement by HER2bsFab was independent of FcγRIIIA-158 polymorphism and induced a stronger NK cells activation in response to target cell recognition. Such findings led us to investigating the efficacy of bsFabs in a context of low-HER2-overexpression displays by triple-negative breast cancers. In vitro characterization showed that both HER2bsFab and MesobsFab trigger efficient lysis of two different triple-negative breast cancer cell lines. Altogether, these findings would enable the treatment of a broader population of patients than that eligible with current HER2-targeted therapies.

Utilistions d'anticorps monoclonaux est une partie prometteuse de la thérapie du cancer. À ce jour, il existe plus de 30 anticorps monoclonaux approuvés pour la thérapie contre le cancer. Plus de 350 anticorps se situent également dans différentes phases du développement clinique. La mésothéline est l'une des cibles les plus prometteuses pour l'immunothérapie. La mésothéline est présente à des niveaux relativement faibles dans les cellules mésothéliales de la plèvre, du péritonéum et du péricarde normaux, mais est fortement exprimée dans un certain nombre de cancers différents, y compris les mésothéliomes, le cancer de l'estomac, les carcinomes à cellules squameuses, le cancer de la prostate, le cancer du pancréas, le cancer du poumon et le cancer de l'ovaire. La mésothéline est une glycoprotéine liée au glycosylphosphatidylinositol (GPI) synthétisée sous la forme d'un précurseur de 69 kDa et transformée de façon protéolytique en une forme sécrétée à 30 kDa (anciennement appelée Facteur de potentialisation des mégacaryocytes (MPF)) et une forme liée à la membrane de 40 kDa. Par ailleurs, il peut être clivé par une protéase et peut produire une forme de mésothéline soluble. Il a été déjà montré que cette forme soluble de mésothéline agit comme un ligand et neutralise les anticorps thérapeutiques ciblant la mésothéline. Par conséquent, les anticorps ne pouvaient pas atteindre les cellules cancéreuses et reste inefficaces. Dans notre travail, nous avons décidé de développer un anticorps discriminant spécifique à la forme associée à la membrane pour surmonter l'antagonisme produit par les formes solubles de mésothéline. Pour ce but, nous avons utilisé une nouvelle méthode d'immunisation de souris, que nous avons d'abord toléré la souris avec une mésothéline soluble et ensuite ré-immunisée avec des cellules exprimant la mésothéline. En utilisant la technologie de phage display, nous avons obtenu près de 150 clones de ciblant mésothéline dans 34 familles de VH-CDR3 parmi lesquelles nous avons identifié seulement 2 familles qui se lient à la mésothéline membranaire avec une affinité élevée et ne reconnaissent aucune autre forme soluble de mésothéline. Ici, nous proposons qu'ils puissent être des bons candidats pour être utilisés pour la thérapie contre le cancer de qui permet de passer à travers la barrière de mésothéline soluble. Pour démontrer leur efficacité pour une utilisation thérapeutique, nous avons construit une CAR avec le sc-Fv d'un anticorps discriminant de la forme membranaire. / Antibody based immune treatment is a promising component of cancer therapy. To date there are more than 30 approved monoclonal antibodies for cancer therapy. More than 350 antibodies are also in different phases of clinical development. Mesothelin is one of the most promising targets for immunotherapy. It is present at relatively low levels in mesothelial cells of the pleura, peritoneum and pericardium of healthy individuals, but is highly expressed in a number of different cancers, including mesotheliomas, stomach cancers, squamous cell carcinomas, as well as prostate, pancreatic, lung, and ovarian cancers. Mesothelin is a glycosylphosphatidylinositol (GPI)-linked glycoprotein synthesized as a 69 kDa precursor and proteolytically processed into a 30 kDa NH2-terminal secreted form (formerly referred to as Megakaryocyte Potentiating Factor (MPF)) and a 40 kDa membrane-bound form. Besides that it can be cleaved by a protease leading to the production of a soluble, shedded, form of mesothelin. It has already been shown that this soluble form of mesothelin acts as a ligand and neutralizes the mesothelin targeting therapeutic antibodies. Therefore antibodies could not reach cancer cells and remained inefficient. In our work we decided to develop discriminating antibodies specific to a membrane associated form so as to overcome the antagonism produced by soluble forms of mesothelin. To this aim we used a novel method of mouse immunization, in which we first tolerized the mouse with soluble mesothelin before immunization with mesothelin expressing cells. By using phage display technology we obtained nearly 150 mesothelin recognizing clones in 34 VH-CDR3 families, among which we identified only 2 families that bind membrane mesothelin with high affinity and do not recognize any other soluble form of mesothelin. Here we suggest that this Fab can be effective candidates to be used for mesothelin expressing cancer therapy being allowed to pass through the soluble mesothelin barrier. To show their efficacy for therapeutic use we constructed a CAR with the sc-Fv of a membrane-form discriminating antibody