Os receptores para a bombesina (BBN), especialmente o receptor para o peptídeo liberador de gastrina (GRPr), são massivamente expressos em vários tipos de câncer, dentre eles o câncer de próstata, e podem ser uma alternativa para seu diagnóstico e tratamento por terapia radioisotópica. Modificações moleculares na estrutura da BBN vêm sendo promovidas e os derivados produzidos têm apresentado bons resultados em estudos préclínicos. No entanto, todos os derivados estudados apresentaram alta captação abdominal e esta é a principal limitação do uso clínico da BBN, devido aos efeitos adversos aos pacientes. O objetivo deste trabalho foi radiomarcar uma nova série de derivados da bombesina com lutécio-177 e avaliar a relação entre sua estrutura e o potencial diagnóstico-terapêutico do câncer de próstata. Os peptídeos estudados apresentam estrutura genérica DOTA-Phe-(Gly)n-BBN(6-14), em que DOTA é o grupamento quelante, n é o número de aminoácidos glicina do espaçador Phe-(Gly)n e BBN(6-14) é a sequência original de aminoácidos da BBN do aminoácido 6 ao aminoácido 14. Estudos preliminares foram realizados a fim de avaliar a condição que conferia maior pureza radioquímica aos derivados radiomarcados, determinada por cromatografia em camada delgada (ITLC-SG) e cromatografia líquida de alta eficiência (CLAE). A estabilidade dos derivados radiomarcados foi avaliada após incubação à 2-8° C ou em soro humano à 37° C e o coeficiente de partição foi determinado em n-octanol:água. Estudos in vivo foram realizados em camundongos Balb-c sadios e Nude com tumor de células PC-3, a fim de caracterizar biologicamente os derivados da bombesina. Estudos in vitro envolveram a avaliação do efeito dos derivados não radiomarcados sobre a proliferação das células PC-3. A análise em ITLC-SG e CLAE revelou que todos os derivados da bombesina foram radiomarcados com alta pureza radioquímica. Os derivados radiomarcados apresentaram alta estabilidade à 2-8° C. A análise em soro humano indicou metabolismo tempodependente dos derivados pelas enzimas do soro e aumento da estabilidade com o acréscimo de aminoácidos glicina no espaçador após 4 horas de incubação, mas não após 24 horas. Os estudos em CLAE e de coeficiente de partição indicaram que os derivados da bombesina apresentam baixa lipossolubilidade, a qual decresce com o aumento do espaçador. Os derivados apresentaram rápido clareamento sanguíneo, rápida excreção, realizada primariamente por via renal, baixa retenção no organismo e baixo acúmulo abdominal nos estudos in vivo em camundongos Balb-c. Os estudos em camundongos Nude com tumor PC-3 mostraram a capacidade dos derivados de se ligar às células tumorais. Os dois peptídeos com maior espaçador apresentaram maior captação tumoral 1 hora após a administração endovenosa, mas o derivado com menor espaçador apresentou maior captação tumoral quatro e 24 horas após a administração. A ligação às células PC-3 in vivo mostrou ser específica e suficiente para a detecção do tumor por imagens cintilográficas, principalmente 30 minutos após a administração. Nos estudos in vitro, os derivados da bombesina estudados não apresentaram efeito proliferativo ou citotóxico sobre as células PC-3, o que os caracteriza como agonistas fracos ou antagonistas dos receptores para GRP. Os resultados deste trabalho mostraram, portanto, que todos os derivados estudados são promissores para aplicação in vivo. A maior captação tumoral dos derivados com maior espaçador na primeira hora após a administração indica que essas moléculas são os mais adequados para o diagnóstico por imagem de tumor de próstata. Já para aplicação em terapia radioisotópica, o derivado com menor espaçador é o mais adequado, devido à maior retenção tumoral. / Bombesin (BBN) receptors in particular, the gastrin-releasing peptide (GRP) receptor peptide have been shown to be massively overexpressed in several human tumors types, including prostate cancer, and could be an alternative as target for its treatment by radionuclide therapy (RNT). A large number of BBN analogs had already been synthesized for this purpose and have shown to reduce tumor growth in mice. Nevertheless, most of the studied analogs exhibit high abdominal accumulation, especially in pancreas. This abdominal accumulation may represent a problem in clinical use of radiolabeled bombesin analogs probably due to serious side effects to patients. The goal of the present work was to radiolabel a novel series of bombesin derivatives with lutetium-177 and to evaluate the relationship between their structure and diagnostic-therapeutic activity for prostate tumor. The generic structure of studied peptides is DOTA-Phe-(Gly)n-BBN(6-14), where DOTA is the chelator, n is the number of glycine amino acids of Phe-(Gly)n spacer and BBN(6-14) is the bombesin sequence from the amino acid 6 to the amino acid 14. Preliminary studies were done to establish the ideal labeling conditions for obtaining the highest yield of labeled bombesin derivatives, determined by instant thin layer chromatography (ITLC-SG) and high performance liquid chromatography (HPLC). The stability of the preparations was evaluated either after storing at 2-8º C or incubation in human serum at 37º C and the partition coefficient was determined in n:octanol:water. In vivo studies were performed in both healthy Balb-c and Nude mice bearing PC-3 xenografts, in order to characterize the biological properties of labeled peptides. In vitro studies involved the evaluation of cold bombesin derivatives effect in PC-3 cells proliferation. Bombesin derivatives were successfully labeled with high yield at optimized conditions and exhibited high stability at 4ºC. The analysis of the stability in human serum suggested a time-course metabolic degradation of labeled peptides by serum enzymes. The addition of four glycine amino acids in the spacer of bombesin derivatives resulted in slower degradation by human serum enzymes after 4 hours of incubation. HPLC and partition coefficient studies showed that bombesin derivatives present low lipophilicity and the increase of glycine amino acids number in peptides spacers slightly reduced their lipophilicity. The radiolabeled bombesin derivatives presented fast blood clearance, rapid excretion, performed mainly by renal pathway, and low abdominal accumulation in in vivo studies in Balb-c mice. Investigations in Nude mice bearing PC-3 tumor showed that the radiopeptides can target tumor cells. Higher tumor uptake was observed with the derivatives of larger spacers at 1 hour post injection, but higher tumor retention after 4 and 24 hours was observed with the derivative of smaller spacer. In addition, tumor uptake showed to be specific and allowed tumor detection by scintigraphy imaging, especially 30 minutes post injection. In addition, the studied bombesin derivatives did not present proliferative or cytotoxic effect to PC-3 cells in vitro and can be characterized as weak agonists or antagonists of bombesin receptors. The results of this work showed that phenyl-glycine extended bombesin derivatives are promising for in vivo applications. The higher tumor uptake of derivatives with larger spacer suggests that these molecules are more applicable in diagnostic procedures. The derivative with smaller spacer is more useful to be applied in radionuclide therapy, because of its higher tumor retention.

Têm sido estudadas novas modalidades para o diagnóstico e tratamento de câncer de próstata avançado baseado em peptídeos. Receptores para o peptídeo liberador de gastrina (GRPr) são superexpressos em vários tipos de células cancerígenas, incluindo câncer de mama e próstata. A bombesina é um análogo do peptídeo GRP de mamíferos que se liga com alta especificidade e afinidade a GRPr. Várias pesquisas têm sido realizadas para desenvolver e radiomarcar um análogo da bombesina com lutécio-177 com interesse para terapia de tumores pequenos ou metástases, devido às características físicas e viabilidade comercial do radionuclídeo. O objetivo deste trabalho foi estudar o processo de marcação e controle de qualidade de derivados da bombesina, usando como agente quelante DTPA e DOTA e espaçador aminoacídico Gly5, e realizar estudos de estabilidade e de biodistribuição de modo a avaliar o potencial de aplicação em estudos clínicos. Os estudos demonstraram que os análogos da bombesina estudados podem ser marcados com 177Lu com alto rendimento de marcação e alta atividade específica. Os estudos de estabilidade in vitro sugerem que os derivados DOTA-conjugados apresentam maior estabilidade que o DTPA-conjugados quando armazenados sob refrigeração e em soro humano. O coeficiente de partição do PG5N-DOTA-177Lu indicou maior lipofilicidade quando comparado com o derivado PG5M-DOTA-177Lu , porém sem influência sobre o clareamento sanguíneo ou captação hepática do composto. Os compostos DOTA-conjugados apresentam menor ligação às proteínas plasmáticas, corroborado pelo rápido clareamento sanguíneo observado nos estudos in vivo. Os estudos de biodistribuição com os compostos PG5M-DOTA-177Lu e PG5N-DOTA-177Lu mostraram o rápido clareamento sanguíneo dos compostos e excreção renal, e baixa captação óssea, indicando estabilidade in vivo dos derivados 177Lu-DOTA. O composto PG5M-DOTA-177Lu apresentou maior captação no pâncreas e intestinos, órgãos com maior porcentagem de receptores para bombesina. Entretanto, a ligação dos compostos às células tumorais (PC-3) in vitro foi similar para ambos os compostos. / New therapy modalities for the treatment of advanced prostate cancer based on peptide analogues are reviewed. It has been shown that gastrin releasing peptide receptors (GRPr) are overexpressed in various types of cancer cells including prostate and breast cancer. Bombesin is an analogue of the mammalian GRP that binds with high specificity and affinity to GRPr. Significant research efforts have been devoted to the design bombesin analogues labeled with 177Lu considering the excellent radiophysical properties and commercial availability of the radionuclide. The aim of this work was to study the labeling and the quality control of a bombesin analogues with Lu-177 using DOTA and DTPA as chelate group and an aminoacidic spacers Gly5 and study the stability and biodistribution properties in order to evaluate the potencial for clinical application. The studies showed that the bombesin analogs were labeled with 177Lu with high radiochemical yield and high specific activity. In vitro stability studies showed that DOTA-conjugated peptides were more stable than DTPA-conjugated, when stored under refrigeration or in human serum. The partition coefficient values showed that 177LuDOTA-PG5N was more lipophilic when compared with 177LuDOTA-PG5M but without influence on blood clearance and liver uptake. The DOTA-conjugated peptides presented low binding to plasma proteins, that contributes for fast blood clearance in vivo. Biodistribution studies of 177LuDOTA-PG5M and 177LuDOTA-PG5N, showed significant renal uptake, as a result of the urinary excretion and low bone uptake, that indicated the in vivo stability of the 177Lu-DOTA-complexes. The compound 177LuDOTA-PG5M showed higher uptake on pancreas and intestinses and these organs presents high density of BBN receptors. But the in vitro binding assays (PC-3 tumors cells) showed similar results for both compounds.

Os receptores para a bombesina (BBN), especialmente o receptor para o peptídeo liberador de gastrina (GRPr), são massivamente expressos em vários tipos de câncer, dentre eles o câncer de próstata, e podem ser uma alternativa para seu diagnóstico e tratamento por terapia radioisotópica. Modificações moleculares na estrutura da BBN vêm sendo promovidas e os derivados produzidos têm apresentado bons resultados em estudos préclínicos. No entanto, todos os derivados estudados apresentaram alta captação abdominal e esta é a principal limitação do uso clínico da BBN, devido aos efeitos adversos aos pacientes. O objetivo deste trabalho foi radiomarcar uma nova série de derivados da bombesina com lutécio-177 e avaliar a relação entre sua estrutura e o potencial diagnóstico-terapêutico do câncer de próstata. Os peptídeos estudados apresentam estrutura genérica DOTA-Phe-(Gly)n-BBN(6-14), em que DOTA é o grupamento quelante, n é o número de aminoácidos glicina do espaçador Phe-(Gly)n e BBN(6-14) é a sequência original de aminoácidos da BBN do aminoácido 6 ao aminoácido 14. Estudos preliminares foram realizados a fim de avaliar a condição que conferia maior pureza radioquímica aos derivados radiomarcados, determinada por cromatografia em camada delgada (ITLC-SG) e cromatografia líquida de alta eficiência (CLAE). A estabilidade dos derivados radiomarcados foi avaliada após incubação à 2-8° C ou em soro humano à 37° C e o coeficiente de partição foi determinado em n-octanol:água. Estudos in vivo foram realizados em camundongos Balb-c sadios e Nude com tumor de células PC-3, a fim de caracterizar biologicamente os derivados da bombesina. Estudos in vitro envolveram a avaliação do efeito dos derivados não radiomarcados sobre a proliferação das células PC-3. A análise em ITLC-SG e CLAE revelou que todos os derivados da bombesina foram radiomarcados com alta pureza radioquímica. Os derivados radiomarcados apresentaram alta estabilidade à 2-8° C. A análise em soro humano indicou metabolismo tempodependente dos derivados pelas enzimas do soro e aumento da estabilidade com o acréscimo de aminoácidos glicina no espaçador após 4 horas de incubação, mas não após 24 horas. Os estudos em CLAE e de coeficiente de partição indicaram que os derivados da bombesina apresentam baixa lipossolubilidade, a qual decresce com o aumento do espaçador. Os derivados apresentaram rápido clareamento sanguíneo, rápida excreção, realizada primariamente por via renal, baixa retenção no organismo e baixo acúmulo abdominal nos estudos in vivo em camundongos Balb-c. Os estudos em camundongos Nude com tumor PC-3 mostraram a capacidade dos derivados de se ligar às células tumorais. Os dois peptídeos com maior espaçador apresentaram maior captação tumoral 1 hora após a administração endovenosa, mas o derivado com menor espaçador apresentou maior captação tumoral quatro e 24 horas após a administração. A ligação às células PC-3 in vivo mostrou ser específica e suficiente para a detecção do tumor por imagens cintilográficas, principalmente 30 minutos após a administração. Nos estudos in vitro, os derivados da bombesina estudados não apresentaram efeito proliferativo ou citotóxico sobre as células PC-3, o que os caracteriza como agonistas fracos ou antagonistas dos receptores para GRP. Os resultados deste trabalho mostraram, portanto, que todos os derivados estudados são promissores para aplicação in vivo. A maior captação tumoral dos derivados com maior espaçador na primeira hora após a administração indica que essas moléculas são os mais adequados para o diagnóstico por imagem de tumor de próstata. Já para aplicação em terapia radioisotópica, o derivado com menor espaçador é o mais adequado, devido à maior retenção tumoral. / Bombesin (BBN) receptors in particular, the gastrin-releasing peptide (GRP) receptor peptide have been shown to be massively overexpressed in several human tumors types, including prostate cancer, and could be an alternative as target for its treatment by radionuclide therapy (RNT). A large number of BBN analogs had already been synthesized for this purpose and have shown to reduce tumor growth in mice. Nevertheless, most of the studied analogs exhibit high abdominal accumulation, especially in pancreas. This abdominal accumulation may represent a problem in clinical use of radiolabeled bombesin analogs probably due to serious side effects to patients. The goal of the present work was to radiolabel a novel series of bombesin derivatives with lutetium-177 and to evaluate the relationship between their structure and diagnostic-therapeutic activity for prostate tumor. The generic structure of studied peptides is DOTA-Phe-(Gly)n-BBN(6-14), where DOTA is the chelator, n is the number of glycine amino acids of Phe-(Gly)n spacer and BBN(6-14) is the bombesin sequence from the amino acid 6 to the amino acid 14. Preliminary studies were done to establish the ideal labeling conditions for obtaining the highest yield of labeled bombesin derivatives, determined by instant thin layer chromatography (ITLC-SG) and high performance liquid chromatography (HPLC). The stability of the preparations was evaluated either after storing at 2-8º C or incubation in human serum at 37º C and the partition coefficient was determined in n:octanol:water. In vivo studies were performed in both healthy Balb-c and Nude mice bearing PC-3 xenografts, in order to characterize the biological properties of labeled peptides. In vitro studies involved the evaluation of cold bombesin derivatives effect in PC-3 cells proliferation. Bombesin derivatives were successfully labeled with high yield at optimized conditions and exhibited high stability at 4ºC. The analysis of the stability in human serum suggested a time-course metabolic degradation of labeled peptides by serum enzymes. The addition of four glycine amino acids in the spacer of bombesin derivatives resulted in slower degradation by human serum enzymes after 4 hours of incubation. HPLC and partition coefficient studies showed that bombesin derivatives present low lipophilicity and the increase of glycine amino acids number in peptides spacers slightly reduced their lipophilicity. The radiolabeled bombesin derivatives presented fast blood clearance, rapid excretion, performed mainly by renal pathway, and low abdominal accumulation in in vivo studies in Balb-c mice. Investigations in Nude mice bearing PC-3 tumor showed that the radiopeptides can target tumor cells. Higher tumor uptake was observed with the derivatives of larger spacers at 1 hour post injection, but higher tumor retention after 4 and 24 hours was observed with the derivative of smaller spacer. In addition, tumor uptake showed to be specific and allowed tumor detection by scintigraphy imaging, especially 30 minutes post injection. In addition, the studied bombesin derivatives did not present proliferative or cytotoxic effect to PC-3 cells in vitro and can be characterized as weak agonists or antagonists of bombesin receptors. The results of this work showed that phenyl-glycine extended bombesin derivatives are promising for in vivo applications. The higher tumor uptake of derivatives with larger spacer suggests that these molecules are more applicable in diagnostic procedures. The derivative with smaller spacer is more useful to be applied in radionuclide therapy, because of its higher tumor retention.

Receptores para o peptídeo liberador de gastrina (GRPr) são super expressos em vários tipos de células cancerígenas, incluindo câncer de mama e próstata. A Bombesina é um análogo do peptídeo GRP de mamíferos que se liga com alta especificidade e afinidade aos receptores do peptídeo liberador de gastrina (GRPr). Significantes pesquisas têm sido realizadas para desenvolver e radiomarcar um análogo da bombesina para diagnóstico de tumores de próstata e mama, utilizando-se técnicas de SPECT e PET, com radionuclídeos como 111In e 68Ga. O objetivo deste trabalho foi estudar a marcação com 111In de uma série inédita de peptídeos derivados de bombesina e determinar o potencial de aplicação no diagnóstico de tumores de próstata em modelos animais. Vários estudos foram realizados para padronizar o procedimento de marcação, variando-se temperatura, tempo de marcação, massa do peptídeo e atividade do radionuclídeo. Os resultados demonstraram que os análogos da bombesina estudados podem ser marcados com índio-111 com alto rendimento de marcação e alta atividade específica. Os estudos de biodistribuição em animais normais demonstraram que o derivado de BBN com espaçador aminoacídico Gly5 apresentou captação pancreática e intestinal expressiva, sugerindo ser o melhor derivado. Dois derivados DOTA- conjugados, com espaçador Gly5 foram radiomarcados com gálio-68 e investigados em modelo animal com tumor de próstata humano, indicando o potencial para aplicação do peptídeo radiomarcado no diagnóstico por PET. / Gastrin releasing peptide receptors (GRPRs) are over expressed in various types of cancer cells including prostate and breast cancer. Bombesin is an analogue of the mammalian GRP that binds with high specificity and affinity to GRPRs. Significant research efforts have been devoted to the design and radiolabel bombesin peptides for the diagnostic of prostatic and breast cancer using SPECT e PET, with radionuclides like 111In e 68Ga. The objective of this work was to study the labeling with 111In of a new bombesin series and evaluate the potential for diagnostic application using animal model. Several studies were evaluated to optimize the labelling conditions of BBN derivatives with 111In using different temperature, time, mass of peptide and radionuclide activity. High radiochemical purity and high specific activity were obtained for all the peptides labeled with 111-indium. Biodistribution studies in normal mices showed that the BBN derivative with Gly5 as aminoacidic spacer presented high uptake on pancreas and intestines that suggests that is the best peptide. Two DOTA-derivatives with Gly5 as spacer were radiolabelled with 68-gallium and evaluated in tumor model animals of human prostatic cancer and showed high potential for clinical application in diagnostic procedures with PET.

Receptores para o peptídeo liberador de gastrina (GRPr) são super expressos em vários tipos de células cancerígenas, incluindo câncer de mama e próstata. A Bombesina é um análogo do peptídeo GRP de mamíferos que se liga com alta especificidade e afinidade aos receptores do peptídeo liberador de gastrina (GRPr). Significantes pesquisas têm sido realizadas para desenvolver e radiomarcar um análogo da bombesina para diagnóstico de tumores de próstata e mama, utilizando-se técnicas de SPECT e PET, com radionuclídeos como 111In e 68Ga. O objetivo deste trabalho foi estudar a marcação com 111In de uma série inédita de peptídeos derivados de bombesina e determinar o potencial de aplicação no diagnóstico de tumores de próstata em modelos animais. Vários estudos foram realizados para padronizar o procedimento de marcação, variando-se temperatura, tempo de marcação, massa do peptídeo e atividade do radionuclídeo. Os resultados demonstraram que os análogos da bombesina estudados podem ser marcados com índio-111 com alto rendimento de marcação e alta atividade específica. Os estudos de biodistribuição em animais normais demonstraram que o derivado de BBN com espaçador aminoacídico Gly5 apresentou captação pancreática e intestinal expressiva, sugerindo ser o melhor derivado. Dois derivados DOTA- conjugados, com espaçador Gly5 foram radiomarcados com gálio-68 e investigados em modelo animal com tumor de próstata humano, indicando o potencial para aplicação do peptídeo radiomarcado no diagnóstico por PET. / Gastrin releasing peptide receptors (GRPRs) are over expressed in various types of cancer cells including prostate and breast cancer. Bombesin is an analogue of the mammalian GRP that binds with high specificity and affinity to GRPRs. Significant research efforts have been devoted to the design and radiolabel bombesin peptides for the diagnostic of prostatic and breast cancer using SPECT e PET, with radionuclides like 111In e 68Ga. The objective of this work was to study the labeling with 111In of a new bombesin series and evaluate the potential for diagnostic application using animal model. Several studies were evaluated to optimize the labelling conditions of BBN derivatives with 111In using different temperature, time, mass of peptide and radionuclide activity. High radiochemical purity and high specific activity were obtained for all the peptides labeled with 111-indium. Biodistribution studies in normal mices showed that the BBN derivative with Gly5 as aminoacidic spacer presented high uptake on pancreas and intestines that suggests that is the best peptide. Two DOTA-derivatives with Gly5 as spacer were radiolabelled with 68-gallium and evaluated in tumor model animals of human prostatic cancer and showed high potential for clinical application in diagnostic procedures with PET.

Ces dernières années, le ciblage des RCPG avec des ligands radiomarqués est devenu très important en imagerie nucléaire, notamment avec le remplacement progressif d’analogues peptidiques de la somatostatine marqués à l’111In pour la TEMP par d’autres marqués au 68Ga pour l'imagerie TEP qui présente une meilleure efficacité diagnostique. Les récepteurs de haute affinité de la bombésine (GRPR) ou de la neurotensine (NTR1) sont eux aussi des RCPG surexprimés par les cellules tumorales par rapport au tissu sain. Le GRPR est surexprimé dans 83% des carcinomes mammaires canalaires estrogènes dépendants. Dans la première partie de ce travail, nous avons démontré qu’un agoniste du GRPR, l’AMBA marqué au 68Ga, permettait la détection en TEP d’un modèle murin de cancer du sein humain estrogène-dépendant et qu’il permettait de prédire la réponse tumorale à une hormonothérapie de manière plus sensible que le 18F-FDG.L’équipe du Dr. Gruaz-Guyon a développé de nouveaux radioligands analogues de la neurotensine pour le ciblage des tumeurs exprimant le NTR1 et a étudié les propriétés de ces peptides marqués à l'111In dans un modèle de tumeurs d’adénocarcinome colique surexprimant le NTR1. L’obtention d’images TEMP de contraste élevé, permettant une détection des greffes tumorales dans des temps courts après injection, a conduit cette équipe à envisager ce traceur peptidique pour l’imagerie TEP. Dans la seconde partie de ce travail, nous avons réalisé le radiomarquage au 68Ga du meilleur de ces dérivés (DOTA NT20.3) et évalué son potentiel pour l'imagerie TEP et la détection de tumeurs d’adénocarcinome colique. La surexpression de NTR1 a été démontrée dans plusieurs autres cancers comme l’adénocarcinome pancréatique (PDAC) (75-88%). Nous avons donc voulu étudier l'expression du NTR1 dans une tumorothèque locale de PDAC. Nous avons ensuite démontré le potentiel du 68Ga-DOTA-NT20.3 pour l’imagerie TEP dans deux modèles murins de PDAC humains. Nous avons caractérisé sa biodistribution, évalué sa spécificité in vivo et l’avons comparé au 18F-FDG, notamment pour valider sa capacité à discriminer in vivo la pancréatite de l’adénocarcinome pancréatique. / In recent years, the targeting of G protein-coupled membrane receptors (GPCRs) with radiolabeled ligands has become very important in nuclear imaging, particularly with the progressive replacement of somatostatin analogues labelled with 111In for SPECT by others labelled with 68Ga for PET imaging, which improves diagnostic efficacy. High-affinity bombesin receptors (GRPR) or neurotensin receptors (NTR1) are also GPCRs overexpressed in many cancers as compared with normal tissue. GRPR is overexpressed in 83% of estrogen-dependent ductal carcinomas. In the first part of this work, we demonstrated that 68Ga-AMBA, an agonist ligand of GRPR, allowed the PET detection of a mouse model of estrogen-dependent breast cancer and could be more sensitive than 18F-FDG to predict and monitor tumour response to hormone therapy.Dr. Gruaz-Guyon's team has developed new neurotensin radioanalogues for targeting NTR1-positive tumours. They studied the properties of these 111In-labeled peptides in a model of colon adenocarcinoma overexpressing NTR1. Obtaining high-contrast images allowing the detection of cancer within a short time after injection, this team subsequently developed this peptide radiotracer for PET imaging. In the second part of this work, we carried out the 68Ga radiolabeling of the best-performing of these derivatives and evaluated its potential for PET imaging of colon adenocarcinoma in a tumor model. Overexpression of NTR1 has been demonstrated in several human cancers such as PDAC (75-88%). We characterized the expression of NTR1 using specimens of human pancreatic cancer and then demonstrated the potential of this PET radiotracer to image two mouse models of human PDAC. We characterized its biodistribution, assessed its specificity in vivo in comparison with 18F-FDG, in particular its ability to discriminate in vivo pancreatitis from pancreatic adenocarcinoma.

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La surexpression des récepteurs GRP au niveau de différents types de cancers communs offre la possibilité d'utiliser des analogues radiomarqués de la bombésine pour leur diagnostic et leur traitement. Ce travail de thèse est consacré à la conception, la synthèse et l'évaluation biologique de nouveaux radiopharmaceutiques, contenant un antagoniste des récepteurs GRP, un bras espaceur et le chélatant cyclique DOTA. Nous avons tout d'abord déterminé la longueur du bras espaceur permettant une optimisation des propriétés biologiques. Puis en se basant sur les résultats de cette étude nous avons réalisé la synthèse et l'évaluation biologique de radio-ligands constitués d'antagonistes originaux des récepteurs GRP. Ces antagonistes ont été conçus en se basant sur le composé JMV 594, un antagoniste puissant de la bombésine synthétisé dans notre laboratoire. En plus de modifications réalisées sur ce peptide, des dimères ont également été synthétisés de façon à obtenir des antagonistes plus stables et plus affins pour les récepteurs GRP. / The abundant expression of the GRP receptor in many frequently occurring cancers that inflict humans provides the opportunity to use radiolabeled bombesin analogs for their diagnosis and treatment. This postgraduate work is dedicated to the design, synthesis and biological evaluation of new radiopharmaceuticals. These are made up of a GRP receptor antagonist, a spacer and the cyclic metal chelating agent DOTA. We first determined the spacer length which has optimal biological properties. Moving forward from this study, different radio-ligands containing new bombesin antagonists have been synthesized and biologically evaluated. Those antagonists are based on compound JMV 594, a powerful bombesin antagonist synthesized in our laboratory. Besides modifications of this peptide also dimers have been made to obtain more stable bombesin antagonist with more affinity to the GRP receptor.

Meduloblastoma é o tumor intracranial mais comum em crianças, provavelmente derivado de células precursoras da camada granular externa do cerebelo durante seu desenvolvimento. O tratamento padrão consiste em cirurgia, radioterapia e quimioterapia, que produzem graves sequelas nos pacientes e garantem uma sobrevida baixa, o que demonstra a necessidade de novas alternativas terapêuticas para a doença. Evidências demonstram que o receptor do peptídeo liberador de gastrina (GRPR) está superexpresso em diversos tumores humanos, assim como seu agonista (GRP) pode atuar como um fator de crescimento autócrino em tumores cerebrais. No presente estudo, avaliamos a expressão de GRPR e o efeito de seus agonistas, bombesina (BB) e GRP, além do antagonista RC-3095, sobre a viabilidade celular de linhagens de meduloblastoma humano DAOY, D283 e ONS76. Mostramos que meduloblastomas, apesar de expressarem GRPR, não têm sua viabilidade celular afetada por agonistas e antagonista desse receptor. Uma vez que há evidências de que BDNF (fator neurotrófico derivado de cérebro) esteja relacionado à diferenciação celular em meduloblastomas, também avaliamos o efeito de BDNF sobre a viabilidade celular das linhagens de meduloblastoma humano. As linhagens DAOY e D283 tiveram sua viabilidade celular reduzida pela presença de BDNF. Uma vez que a via da PKA tem sido implicada na iniciação e progressão de vários tumores, também avaliamos o efeito de rolipram, um inibidor de fosfodiesterase tipo IV, sobre a viabilidade celular das linhagens de meduloblastoma humano, sendo que rolipram reduziu a viabilidade celular de todas as linhagens estudadas. Os receptores de BDNF e a via da PKA podem, portanto, ser alvos moleculares promissores para o desenvolvimento de novas terapias para meduloblastomas. / Medulloblastoma is the most common intracranial tumor in children and is believed to arise from the precursor cells of the external granule layer of the developing cerebellum. The standard treatment, consisting of surgery, craniospinal radiotherapy and chemotherapy, produces severe sequelae in patients and provides a poor overall survival, indicating the need for new therapeutic alternatives for treating this disease. Evidences show that the gastrin releasing peptide receptor (GRPR) is overexpressed in various human tumors and its agonist (GRP) can act as an autocrine growth factor in brain tumors. In the present study, we evaluated GRPR expression, as well as the effect of its agonists, bombesin (BB) and GRP, and its antagonist RC-3095, over cell viability of the human medulloblastoma cell lines DAOY, D283 and ONS76. We found that medulloblastomas, in spite of expressing GRPR, do not have its viability affected by the presence of agonists and antagonist of this receptor. Since there are evidences that BDNF (brain-derived neurotrophic factor) is related to cell differentiation in medulloblastomas, we also evaluated the effect of BDNF over the viability of medulloblastoma cell lines. The viability of the cell lines DAOY and D283 was reduced by the presence of BDNF. Since the PKA pathway has been implicated in the initiation and progression of various tumors, we also evaluated the effect of rolipram, a phosphodiesterase IV inhibitor, over the viability of the same medulloblastoma cell lines and we found that rolipram inhibited the viability of all the cell lines studied. BDNF receptors, as well as the PKA pathway, may be therefore promising molecular targets for the development of new therapies for treating medulloblastomas.

Neuropeptides, such as substance P (SP) and bombesin/gastrin-releasing peptide (BN/GRP), and neurotrophins are involved in neuro-immunomodulatory processes and have marked trophic, growth-promoting and inflammation-modulating properties. The impact of these modulators in rheumatoid arthritis (RA) is, however, unclear. An involvement of the innervation, including the peptidergic innervation, is frequently proposed as an important factor for arthritic disease. Many patients with RA, but not all, benefit from treatment with anti-TNF medications. The studies presented here aimed to investigate the roles of neuropeptides, with an emphasis on BN/GRP and SP, and neurotrophins, especially with attention to brain-derived neurotrophic factor (BDNF), in human and murine knee joint tissue. The expression patterns of these substances and their receptors in synovial tissue from patients with either RA or osteoarthritis (OA) were studied in parallel with the levels of these factors in blood and synovial fluid from patients with RA and from healthy controls. Correlation studies were also performed comparing the levels of neuropeptides with those of pro-inflammatory cytokines [tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6)]. Furthermore, the impact of anti-TNF treatment on the levels of BDNF in blood was investigated. In a murine model of RA, the expression of these substances on articular chondrocytes along with their expression in synovial tissue was investigated. The expression of BN/GRP in human synovial tissue was confined to fibroblast-like and mononuclear-like cells whereas SP was detected in nerve-related structures. Receptors for these neuropeptides (GRP-R and NK-1R) were frequently present in blood vessel walls, and on fibroblast-like and mononuclear-like cells. The expression of BDNF and its receptors, p75 neurotrophin receptor and TrkB, was mainly confined to nerve structures. The levels of SP, and particularly those of BN/GRP, in synovial fluid and peripheral blood correlated with the levels of pro-inflammatory cytokines. There were clearly more correlations between SP-BN/GRP and inflammatory parameters than between BDNF and these factors. Plasma levels of BDNF were decreased following anti-TNF-treatment. In the joints of the murine model, there was a marked expression of neurotrophins, neurotrophin receptors and NK-1R/GRP-R in the articular chondrocytes. The expression was down-regulated in the arthritic animals. A neurotrophin system was found to develop in the inflammatory infiltrates of the synovium in the arthritic mice. The results presented suggest that there is a local, and not nerve-related, supply of BN/GRP in the human synovial tissue. Furthermore, BN/GRP and SP have marked effects in the synovial tissue of patients with RA, i.e., there were abundant receptor expressions, and these neuropeptides are, together with cytokines, likely to be involved in the neuro-immunomodulation that occurs in arthritis. The observations do on the whole suggest that the neuropeptides, rather than BDNF, are related to inflammatory processes in the human knee joint. A new effect of anti-TNF treatment; i.e., lowering plasma levels of BDNF, was observed. Severe arthritis, as in the murine model, lead to a decrease in the levels of neurotrophin, and neurotrophin and neuropeptide receptor expressions in the articular cartilage. This fact might be a drawback for the function of the chondrocytes. Certain differences between the expression patterns in the synovial tissue of the murine model and those of human arthritic synovial tissue were noted. It is obvious that local productions in the synovial tissue, nerve-related supply in this tissue and productions in chondrocytes to different extents occur for the investigated substances.