No Brasil, o Sistema de Saúde é Universalista, com o tratamento integral gratuito ao paciente com câncer, cujo direito é assegurado por Lei e regulamentado pelo Ministério da Saúde / Instituto Nacional de Câncer José Alencar Gomes da Silva (INCA), por meio de Decreto Presidencial e Portarias. A habilitação e credenciamento de Hospitais em Unidades ou Centros de Alta Complexidade em Oncologia segue critérios rígidos, que determina como sendo obrigatória a presença do Cirurgião-Dentista na equipe multiprofissional e multidisciplinar na oncoterapia. O tratamento odontológico é compulsório e imprescindível na terapia antineoplásica, para prevenir e tratar as complicações orais: hemorragia, infecção, mucosite oral, xerostomia, cárie de radiação, trismo, alterações periodontais, osteonecrose avascular, osteorradionecrose; que podem levar à interrupção da oncoterapia, acarretando um aumento considerável nos custos da terapia implementada, a piora da qualidade de vida, e em alguns casos, podendo levar o paciente a óbito. O protocolo de cuidados orais na oncoterapia é normatizado e padronizado pelo INCA. Desta forma, foi realizado estudo do tratamento odontológico em pacientes com diagnóstico de câncer atendidos no Serviço de Odontologia Oncológica do UNACON do Hospital Geral de Palmas/Tocantins, no período de abril de 2011 a dezembro de 2016. Os dados foram obtidos de forma individualizada e estruturados segundo Variáveis Demográficas (VD), Procedimento Odontológico (PO), Procedimento Odontológico por Dente (POD) e Outras Variáveis de Interesse (OVI). O impacto financeiro de PO e POD foi avaliado pela comparação entre a tabela SIGTAP do Sistema Único de Saúde (SUS) e a tabela VRPO/SOESP (Valores Referenciais para Procedimentos Odontológicos/Sindicato dos Odontologistas do Estado de São Paulo). A maior incidência de pacientes foi observada na 5ª década de vida, com tendência à proporção homem/mulher de 1:1. Foram realizados 910 procedimentos preventivos/profilaxia/atividade educativa; 1826 raspagens supra e subgengival e aplicação tópica de flúor por hemiarcada; 932 restaurações de uma e duas faces com resina fotopolimerizável; 909 exodontias; 2746 sessões de laserterapia de baixa potência. O impacto financeiro mostrou uma defasagem significativa da Tabela SIGTAP/SUS. O estudo realizado revela a importância de uma base de dados estruturada para o registro do tratamento odontológico realizado em pacientes com diagnóstico de câncer atendidos no Sistema Único de Saúde; para que com isso seja possível fomentar, nos Sistemas de Saúde no Mundo, a elaboração e padronização de protocolo de cuidados orais na terapia antineoplásica, e o planejamento dos recursos humanos e financeiros destinados ao tratamento odontológico nos pacientes oncológicos. / In Brazil, the Health System is Universalist, with free comprehensive treatment for the cancer patient, whose right is guaranteed by Law and regulated by the Ministry of Health / National Cancer Institute José Alencar Gomes da Silva (INCA), through a Presidential Decree and Ordinances. The accreditation of Hospitals in Units or Centers of High Complexity in Oncology follows rigid criteria, which determines as mandatory the presence of the Dentist in the multiprofessional and multidisciplinary team in oncotherapy. Dental treatment is compulsory and essential in antineoplastic therapy to prevent and treat oral complications: hemorrhage, infection, oral mucositis, xerostomia, radiation caries, trismus, periodontal changes, avascular osteonecrosis, osteorradionecrosis; which can lead to interruption of oncotherapy, leading to a considerable increase in the costs of the therapy implemented, worsening of quality of life, and in some cases, leading to death. The protocol of oral care in oncotherapy is standardized by INCA. In this way, a study of the dental treatment was carried out in patients diagnosed with cancer attended at the UNACON Oncological Dentistry Service of the General Hospital of Palmas / Tocantins, from april 2011 to december 2016. Data were obtained individually and structured according to Demographics Variables (VD), Dental Procedure (PO), Dental Procedure by Tooth (POD) and Other Variables of Interest (OVI). The financial impact of PO and POD was evaluated by comparing the SIGTAP table of the Unified Health System (SUS) and the VRPO / SOESP table (Reference Values for Dental Procedures / Union of Dental Practitioners of the State of São Paulo). The highest incidence of patients was observed in the 5th decade of life, with a tendency to male to female ratios of 1: 1. Nine hundred and ten (910) preventive procedures / prophylaxis / educational activity were carried out; 1826 supra and subgingival scaling and topical application of fluoride by hemiarcate; 932 single and double sided restorations with photopolymerizable resin; 909 exodontia; 2746 sessions of low power laser therapy. The financial impact showed a significant lag in the SIGTAP / SUS Table. The study reveals the importance of a structured database for the registry of dental treatment performed in patients diagnosed with cancer treated in the Unified Health System; so that it is possible to promote, in the World Health Systems, the elaboration and standardization of oral care protocol in antineoplastic therapy, and the planning of human and financial resources for dental treatment in cancer patients.

My research was focused on understanding the importance of mammalian RAD51 paralogs in genome maintenance and suppression of tumorigenesis. The investigation carried out during this study has been addressed toward gaining more insights into the involvement of RAD51 paralogs in DNA damage signalling, repair of various types of lesions including double stranded breaks (DSBs), daughter strand gaps (DSGs), interstrand crosslinks (ICLs), and in the protection of stalled replication forks. My study highlights the molecular functions of RAD51 paralogs in Fanconi anemia (FA) pathway of ICL repair, in the ATM and ATR mediated DNA damage responses, in homologous recombination (HR), and in the recovery from replication associated lesions. My research also focused on the development of a novel photoinducible ICL agent for targeted cancer therapy. The thesis has been divided into following sections as follows: Chapter I: General introduction that describes about DNA damage responses and the known functions of RAD51 paralogs across species in DNA repair and checkpoint The genome of every living organism is susceptible to various types of DNA damage and mammalian cells are evolved with various DNA damage surveillance mechanisms in response to DNA damages. In response to DNA damage, activated checkpoints arrest the cell cycle progression transiently and allow the repair of damaged DNA. Upon completion of DNA repair, checkpoints are deactivated to resume the normal cell cycle progression. Defective DNA damage responses may lead to chromosome instability and tumorigenesis. Indeed, genome instability is associated with several genetic disorders, premature ageing and various types of cancer in humans. The major cause of chromosome instability is the formation of DSBs and DSGs. Both DSBs and DSGs are the most dangerous type of DNA lesions that arise endogenously as well as through exogenous sources such as radiations and chemicals. Spontaneous DNA damage is due to generation of reactive oxygen species (ROS) through normal cellular metabolism. Replication across ROS induced modified bases and single strand breaks (SSBs) leads to DSGs and DSBs, respectively. Such DNA lesions need to be accurately repaired to maintain the integrity of the genome. To understand the various cellular responses that are triggered after different types of DNA damage and the possible roles of RAD51 paralogs in these processes, chapter I of the thesis has been distributed in to multiple sections as follows: Briefly, the initial portion of the chapter provides a glimpse of various types of DNA damage responses and repair pathways to deal with the lesions arising from both endogenous as well as exogenous sources. Owing to the vast range of cellular responses and pathways, the following section provides the detailed description and mechanisms of various pathways involved in taking care of wide range of DNA lesions from SSBs to DSBs. Subsequent section of chapter I provides a comprehensive description of maintenance of genome stability at the replication fork and telomeres. Germline mutations in the genes that regulate genome integrity cause various genetic disorders and cancer. Mutations in ATM, ATR, MRE11, NBS1, BLM and FANC (1-16), BRCA1 and BRCA2 that are known to regulate DNA damage signaling, DNA repair and genome integrity lead to chromosome instability disorders such as ataxia-telangiectasia, ATR-Seckel syndrome, AT-like disorder, Nijmegen breakage syndrome, Bloom syndrome, FA, and breast and ovarian cancers respectively. Interestingly, RAD51 paralog mutations are reported in patients with FA-like disorder and various types of cancers including breast and ovarian cancers. Mono-allelic germline mutations in all RAD51 paralogs are reported to cause cancer in addition to the reported cases of FA-like disorder with bi-allelic germline mutations in RAD51C and XRCC2. In accordance, the last section of the chapter has been dedicated to describe the genetics of breast and ovarian cancers and the known functions of tumor suppressors such as BRCA1, BRCA2 and RAD51 paralogs in the protection of genome. Despite the identification of five RAD51 paralogs nearly two decades ago, the molecular mechanism(s) by which RAD51 paralogs regulate HR and genome maintenance remain obscure. To gain insights into the molecular mechanisms of RAD51 paralogs in DNA damage responses and their link with genetic diseases and cancer, the following objectives were laid for my PhD thesis: 1) To understand the functional role of RAD51 paralog RAD51C in FA pathway of ICL repair and DNA damage signalling. 2) To dissect the ATM/ATR mediated targeting of RAD51 paralog XRCC3 in the repair of DSBs and intra S-phase checkpoint. 3) To uncover the replication restart pathway after transient replication pause and the involvement of distinct complexes of RAD51 paralogs in the protection of replication forks. 4) To design photoinducible ICL agent that can be activated by visible light for targeted cancer therapy. Chapter II: Distinct roles of FANCO/RAD51C protein in DNA damage signaling and repair: Implications for Fanconi anemia and breast cancer susceptibility RAD51C, a RAD51 paralog has been implicated in HR. However, the underlying mechanism by which RAD51C regulates HR mediated DNA repair is elusive. In 2010, a study identified biallelic mutation in RAD51C leading to FA-like disorder, whereas a second study reported monoallelic mutations in RAD51C associated with increased risk of breast and ovarian cancers. However, the role of RAD51C in the FA pathway of DNA cross-link repair and as a tumor suppressor remained obscure. To understand the role of RAD51C in FA pathway of ICL repair and DNA damage response, we employed genetic, biochemical and cell biological approaches to dissect out the functions of RAD51C in genome maintenance. In our study, we observed that RAD51C deficiency leads to ICL sensitivity, chromatid-type errors, and G2/M accumulation, which are hallmarks of the FA phenotype. We found that RAD51C is dispensable for ICL unhooking and FANCD2 monoubiquitination but is essential for HR, confirming the downstream role of RAD51C in ICL repair. Furthermore, we demonstrated that RAD51C plays a vital role in the HR-mediated repair of DSBs associated with replication. Finally, we showed that RAD51C participates in ICL and DSB induced DNA damage signaling and controls intra-S-phase checkpoint through CHK2 activation. Our analyses with pathological mutants of RAD51C displayed that RAD51C regulates HR and DNA damage signaling distinctly. Together, these results unravel the critical role of RAD51C in the FA pathway of ICL repair and as a tumor suppressor. Chapter III: ATM-and ATR-mediated phosphorylation of XRCC3 regulates DNA double-strand break-induced checkpoint activation and repair The RAD51 paralogs XRCC3 and RAD51C have been implicated in HR and DNA damage responses, but the molecular mechanism of their participation in these pathways remained obscured. In our study, we showed that an SQ motif serine 225 in XRCC3 is phosphorylated by ATR kinase in an ATM signaling pathway. We found that RAD51C in CX3 complex but not in BCDX2 complex is essential for XRCC3 phosphorylation, and this modification follows end resection and is specific to S and G2 phases. XRCC3 phosphorylation was found to be required for chromatin loading and stabilization of RAD51 and HR-mediated repair of DSBs. Notably, in response to DSBs, XRCC3 participates in the intra-S-phase checkpoint following its phosphorylation and in the G2/M checkpoint independently of its phosphorylation. Strikingly, we found that XRCC3 distinctly regulates recovery of stalled and collapsed replication forks such that phosphorylation was required for the HR-mediated recovery of collapsed replication forks but is dispensable for the recovery of stalled replication forks. Together, our findings suggest that XRCC3 is a new player in the ATM/ATR-induced DNA damage responses to control checkpoint and HR-mediated repair. Chapter IV: RAD51 paralogs protect stalled forks and mediate replication restart in an FA-BRCA independent manner Mammalian RAD51 paralogs RAD51 B, C, D, XRCC2 and XRCC3 are critical for genome maintenance. To understand the crucial roles of RAD51 paralogs during spontaneously arising DNA damage, we have studied the RAD51 paralogs assembly during replication and examined the replication fork stability and its restart. We found that RAD51 paralogs are enriched onto the S-phase chromatin spontaneously. Interestingly, the number of 53BP1 nuclear bodies in G1-phase and micro-nucleation which serve as markers for under replicated lesions increases after genetic ablation of RAD51C, XRCC2 and XRCC3. Furthermore, we showed that RAD51 paralogs are specifically enriched at two major fragile sites FRA3B and FRA16D after replication fork stalling. We found that all five RAD51 paralogs bind to nascent DNA strands after replication fork stalling and protect the fork. Nascent replication tracts created before fork stalling with hydroxyurea degrade in the absence of RAD51 paralogs but remain stable in wild-type cells. This function was dependent on ATP binding at the walker A motif of RAD51 paralogs. Our results also suggested that RAD51 paralogs assemble into BCDX2 complex to prevent generation of DSBs at stalled replication forks, thereby safeguarding the pre-assembled replisome from the action of nucleases. Strikingly, we showed that RAD51C and XRCC3 in complex with FANCM promote the restart of stalled replication forks in an ATP hydrolysis dependent manner. Moreover, RAD51C R258H mutation that was identified in FA-like disorder abrogates the interaction of RAD51C with FANCM and XRCC3, and prevents fork restart. Thus, assembly of RAD51 paralogs in different complexes prevents nucleolytic degradation of stalled replication forks and promotes restart to maintain genomic integrity. Chapter V: Trans-dichlorooxovandium(IV) complex as a potent photoinducible DNA interstrand crosslinker for targeted cancer therapy Although DNA ICL agents such as MMC, cisplatin and psoralen are known to serve as anticancer drugs, these agents affect normal cells as well. Moreover, tumor resistance to these agents has been reported. We have designed and synthesized a novel photoinducible DNA crosslinking agent (ICL-2) which is a derivative of oxovanadiumterpyridine complex with two chlorides in trans position. We found that ICL-2 can be activated by UV-A and visible light to enable DNA ICLs. ICL-2 efficiently activated FA pathway of ICL repair. Strikingly, photoinduction of ICL-2 induces prolonged activation of cell cycle checkpoint and high degree of cell death in FA pathway defective cells. Moreover, we showed that ICL-2 specifically targets cells that express pathological RAD51C mutants. Our findings suggest that ICL-2 can be potentially used for targeted cancer therapy in patients with gene mutations in FA and HR pathway.

La recherche contre le cancer est aujourd’hui tournée vers les thérapies ciblées. Dans ce contexte, la nucléoline et la nucléophosmine sont fortement impliquées dans la croissance tumorale et l’angiogenèse associée et surexprimées dans les cellules tumorales et endothéliales activées. Elles apparaissent donc comme des cibles de choix. Le pseudopeptide HB-19 lie la nucléoline de surface, inhibe la croissance cellulaire de nombreuses lignées de cellules tumorales et induit la mort de ces cellules tumorales par apoptose. D’autre part, il inhibe, in vitro et in vivo, plusieurs étapes de l’angiogenèse tumorale. Ces deux activités mènent, in vivo, à l’inhibition de la croissance tumorale dans de nombreux modèles de croissance tumorale chez la souris. Dans le but d’améliorer les activités observées avec HB- 19, des pseudopeptides dérivés de ce dernier ont été synthétisés. Ainsi le NucAnt 6L (N6L) montre une activité 5 à 10 fois supérieure à celle de HB-19 selon les modèles. Son activité anti-métastatique a également été démontrée. L’étude du mécanisme d’action des pseudopeptides a permis d’identifier deux nouveaux récepteurs: les héparanes sulfates et la nucléophosmine. L’importance du TIMP-3 dans son activité anti-métastatique a également été soulignée. Enfin, aucune toxicité n’a été observée chez les souris aux doses employées et la synthèse de N6L peut être effectuée à l’échelle industrielle. N6L apparaît donc comme un composé prometteur pour une thérapie anti-cancéreuse / The cancer research is nowadays interested in targeting therapies. In this context, nucleolin and nucleophosmin are proteins highly involved in tumor growth and angiogenesis and over-expressed in activated endothelial and tumor cells. So, they appear as very promising targets. The pseudopeptide HB-19 binds to cell surface-expressed nucleolin, inhibits different tumor cell growth and induces cell death by apoptosis. Furthermore, it inhibits, in vitro and in vivo, several steps of angiogenesis. These two activities lead, in vivo, to the suppression of tumor growth and angiogenesis in several mice models. In order to improve the activities observed with HB-19, new compounds derived from HB-19 were synthesized. So, NucAnt 6L (N6L) show 5 to 10 fold stronger anti-tumoral activity than HB- 19 depending of the model. Study of their action mechanism allowed us to identify two new receptors: nucleophosmin and heparan sulfates. The importance of TIMP-3 in anti-metastatic activity has also been highlighted. Finally, no toxicity has been observed in mice treated with N6L which can easily industrially be synthesized. N6L appears to be a promising compound for anti-cancer therapies

No description available.

<p>Cerebral radiation necrosis as a consequence of radiation therapy is often observed in patients several months to years after treatment. Complications include painful headaches, seizures, and in the worst-case death. Radiation necrosis is an irreversible condition with the options available to manage it all having noticeable downsides. As such, there is a critical need for better ways of either preventing the onset of necrosis and/or managing its symptoms. As radiation necrosis cannot be induced in humans for ethical reasons, a mouse model that mirrors the features of radiation necrosis observed in patients would allow for new techniques to be tested before being used in human clinical trials. This thesis will explain how our lab designed a murine model of cerebral radiation necrosis that uses a 320 keV cabinet irradiator to produce radiation necrosis and MRI and histology to evaluate the development of radiation necrosis at multiple time points.</p><p><br></p> <p> </p> <p>Our model required the development of a mouse positioning apparatus that could be used in the cabinet irradiator used as well as the machining of lead shields so that focal semi-hemispheric irradiations could be conducted with other critical structures spared. The MRI scans used as well as the algorithm used to draw radiation necrosis lesions were based off what has been used in previous Gamma Knife models of radiation necrosis. Our initial work showed that since the cabinet irradiator has a relatively flat dose distribution unlike the Gamma Knife, the radiation lesion volumes produced in the former either plateaued or decreased, unlike in the case of the latter where lesion volumes tended to decrease over time. Further work analyzed the effects of fractionation and found minimal sparing using four different fractionation schemes. The effects of strain and sex on the development of radiation necrosis were also analyzed, with strain being found to be a statistically significant parameter while sex was not. Future research should focus on testing the effects of new drugs and techniques for better dealing with radiation necrosis.<b></b></p>

No description available.

Mutations in the hereditary breast/ovarian cancer genes BRCA1/2 were shown to be synthetic lethal with poly(ADP-ribose) polymerase inhibitors (PARPi). This toxicity is assumed to derive from PARPi-induced DNA double strand breaks (DSBs) that necessitate BRCA function in homologous recombination (HR) and/or fork protection (FP). However, PARPi accelerates replication forks. While high-speed replication could cause DSBs, the finding that PARPi leads to single-stranded DNA (ssDNA) gaps/nicks suggests replication gaps could also or alone be the cause of synthetic lethality. Here, we demonstrate that PARPi toxicity derives from replication gaps. Isogenic cells deficient in BRCA1 or the BRCA1-associated FANCJ, with common DNA repair defects in HR and FP, exhibit opposite responses to PARPi. Deficiency in FANCJ, a helicase also mutated in hereditary breast/ovarian cancer and Fanconi anemia, causes aberrant accumulation of fork remodeling factor HLTF and limits unrestrained DNA synthesis with ssDNA gaps. Thus, we predict replication gaps as a distinguishing factor and further uncouple HR, FP and fork speed from PARPi response. BRCA-deficient cells display excessive gaps that are diminished upon resistance, restored upon re-sensitization and when targeted augment synthetic lethality with PARPi. Furthermore, we define the source of gaps to defects in Okazaki fragment processing (OFP). Unchallenged BRCA1-deficient cells have elevated poly(ADP-ribose) and chromatin-associated PARP1 but aberrantly low XRCC1 indicating a defective backup OFP pathway. Remarkably, 53BP1 loss resuscitates OFP by restoring XRCC1-LIG3 that suppresses the sensitivity of BRCA1-deficient cells to drugs targeting OFP or generating gaps. Collectively, our study highlights unprotected lagging strand gaps as a determinant of synthetic lethality, providing a new paradigm and biomarker for PARPi toxicity.

Dysregulation of PI3K-AKT-mTOR pathway has been reported in various pathologies, such as cancer and insulin resistance. The proline-rich AKT substrate of 40-kDa (PRAS40), also known as AKT substrate 1 (AKT1S1), lies at the crossroads of these cascades and inhibits the activity of the mTOR complex 1 (mTORC1) kinase. Firstly, our findings showed that disruption of PRAS40, a substrate of AKT and component of mTORC1, alters glucose homeostasis and prevent hyperglycemia in the streptozotocin (STZ)-induced diabetes mouse model. PRAS40 ablation resulted in a mild lowering of blood glucose levels and glycated hemoglobin (HbA1C), a lowered insulin requirement, and improved glucose tolerance in untreated PRAS40 gene knockout (PRAS40 (-/-)) as compared to wild-type (PRAS40 (+/+)) mice. PRAS40 deletion significantly attenuates hyperglycemia in STZ-induced PRAS40 (-/-) mice through increased hepatic AKT and mTORC1 signaling, a lowered serum insulin requirement, and altered hepatic GLUT4 levels. Furthermore, we investigated the role of PRAS40 in possible feedback mechanisms, and altered AKT/PRAS40/mTOR signaling in the pathogenesis of tumor progression. For this we probed new datasets extracted from Oncomine, a cancer microarray database containing datasets derived from patient samples, to further understand the role of PRAS40 (AKT1S1). These data strongly supports the previous findings that PRAS40 may serve as a potential therapeutic target for various cancers. Elevated levels of HER2 and PRAS40 are found in some human breast cancers. To directly test the importance of these genetic events in mammary tumorigenesis, we assessed whether disruption of PRAS40 could alter mammary tumor occurrence in HER2 overexpressing mice. HER2 overexpressing mice expressing the activated rat Erbb2 (c-neu) oncogene under the direction of the MMTV promoter was bred with Cre-recombined homozygous (PRAS40-/-) mice. We examined mammary tumor development in the presence (PRAS40+/+) or absence (PRAS40-/-) of PRAS40 using this double transgenic mouse mammary tumor model. Loss of PRAS40 resulted in a delayed mammary tumor onset, improved tumor-free survival, and reduced mammary pre-cancerous lesions in PRAS40-/- versus PRAS40+/+ HER2 overexpressing mice. These results suggest that PRAS40 knockdown could be an attractive target and adjuvant therapy in HER2-positive breast cancers.

For any drug candidate to be approved by the U.S. Food and Drug Administration, it must meet strict standards for safety and efficacy. While the field of nuclear medicine is over 100 years old, traditional methods such as external beams or systematic administration have rarely met these standards or have limited application. Ligand-targeted therapy and diagnostics, or “theranostics,” has emerged in the past several decades as an exciting field that offers new possibilities to design drugs that are both safe and effective. When applied to nuclear medicine, the field of ligand-targeted radioactive theranostics is younger still, with many critical lessons being discovered and applied currently. This dissertation outlines the necessary principles of radioactive theranostic drug design, then demonstrates the application of several more recent techniques to improve both the efficacy and safety of radioactive theranostics targeting two high priority oncological targets: fibroblast activation protein alpha and folate receptor.

Die Entwicklung von enzymfreien, isothermen Nachweisverfahren für Nukleinsäuren, die mit der PCR konkurrieren können, ist seit langem ein Ziel. Eine potenzielle Strategie besteht darin, Nukleinsäure-templierte Reaktionen zu verwenden, bei denen das Templat (Analyt) als Katalysator fungiert und das Signal verstärkt. Die derzeitig verwendeten Strategien, wie Ligations- oder Transferreaktionen, sind jedoch in ihrer Empfindlichkeit aufgrund des Effekts der Produktinhibierung begrenzt. Um dies zu überwinden, müssen die Reaktanten nicht nur sequenzspezifisch an die DNA oder RNA binden, sondern die Produkte müssen sich auch von der DNA oder RNA wieder lösen können. Diese Arbeit stellt ein neues Paradigma für Nukleinsäure templierte Reaktionen vor: Das Loss-of-Affinity Prinzip. In diesem Prinzip werden Produkte generiert, die eine geringere Affinität zum Templat aufweisen als die Reaktanten. Dadurch wird die Produktinhibierung verhindert. Im ersten Teil dieser Arbeit wurde das Loss-of-Affinity Prinzip mit triplexbildenden, spaltbaren bis-PNA Sonden untersucht. Diese erfuhren eine C-O-Bindungsspaltung, ausgelöst durch die katalytische Photoreduktion eines Rutheniumkomplexes. Nach mehreren Optimierungsrunden zeigte eine 10-mer bis-PNA Sonde eine beeindruckende katalytische Effizienz. Diese Ergebnisse zeigen, dass das Loss-of-Affinity Prinzip zur Überwindung der Produktinhibierung genutzt werden kann. Die verwendeten bis-PNAs zeigten jedoch eine stark unspezifische Bindung. Im zweiten Teil dieser Arbeit wurden die bis-PNA Sonden gegen PNA- und GPNA-Spermin Sonden ausgetauscht, um das Problem der unspezifischen Bindung zu überwinden. Die PNA- und GPNA Spermin Sonden zeigten die wahrscheinlich effizientesten, bisher bekannten Nukleinsäure templierten Reaktionen, welchee die meisten natürlichen Enzyme übertrafen. Darüber hinaus zeigten sie eine ausgezeichnete Sequenzspezifität. / Developing enzyme-free isothermal detection methods of nucleic acids that can challenge PCR has been a long-standing goal. One potential strategy revolves around nucleic acid-templated reactions, in which the template (analyte) can act as a catalyst and amplify the signal. However, current strategies such as ligation reactions or functional group interconversions are plagued by product inhibition, which limits the sensitivity. To overcome this, the reactants must not only bind to DNA or RNA in a sequence-specific manner, but the products must also be able to detach from the DNA or RNA. This work introduces a new paradigm to nucleic acid-templated reactions, the loss-of-affinity principle, which yields products that have a lower template affinity than the reactants. This prevents product inhibition. In the first part of this work, the loss-of-affinity principle was explored with triplex-forming immolative bis-PNA probes that underwent a C-O bond cleavage upon catalytic photoreduction using a ruthenium complex. After several rounds of optimization, a 10-mer bis-PNA demonstrated an impressive catalytic efficiency. These results demonstrate that the loss-of-affinity principle can be used to overcome product inhibition. However, the bis-PNAs demonstrated highly non-specific binding. In the second part of this work, the bis-PNAs were replaced with PNA- and GPNA-spermine probes to address the issue of non-specific binding. The PNA- and GPNA-spermine probes exhibited probably the most efficient nucleic acid-templated reactions to date, outperforming most natural enzymes. In addition, they demonstrated excellent sequence specificity.