Defects within the DNA damage response (DDR) pathways are common in human malignancies. This is especially true in high-grade serous ovarian cancer (HGSOC) where defects within the Homologous Recombination (HR) pathway may be present in up to 50% of tumours. Oncolytic adenovirus is a potential novel therapy for human malignancies. These viruses infect malignant cells and multiply selectively within them causing cell death and release of mature virions. Here, I have investigated the role of the DDR in determining the efficacy of the E1A-CR2 deleted adenovirus type 5 (Ad5) vector, dl922-947, in ovarian cancer. I show that infection with dl922-947 stimulates a robust DDR within the host cell, which the virus manipulates in order to ensure optimal viral replication. In a panel of HGSOC cell lines, the extent of overreplication of genomic DNA and the degree of genomic damage following infection with dl922-947 was shown to correlate closely with viral efficacy. Functional HR, however, promoted viral DNA replication and augmented overall anti-cancer efficacy. Mechanistically, both BRCA2 and RAD51 localised to viral replication centres within the infected cell nucleus. RAD51 co-localisation was also demonstrated in cells with defective HR and occurred independently of BRCA2. In addition, a direct interaction was identified between RAD51 and adenovirus E2 DNA binding protein. Using functional assays of HR competence, I show that Ad5 infection does not alter cellular ability to repair DNA double-strand break damage via HR. These data suggest that oncolytic adenoviral therapy may be most clinically relevant in tumours with intact HR function. Using a high-throughput siRNA DNA repair screen, potential novel targets have been identified that can increase the efficacy of dl922-947 (for example: NONO) and also result in increased resistance (RPA). These results highlight the complex interplay between adenovirus and host cell. Further understanding of these pathways is vital to increase efficacy, develop biomarkers and improve patient selection into clinical trials for these therapies.

Activated Heat Shock Transcription Factor 1 (HSF1) has received attention in recent literature as a therapeutic effector in diseases of protein misfolding, as an immune modulating adjuvant in tumor regression, and as a trigger for gene therapy transcription. In its normal function, activated HSF1 enhances heat shock protein (Hsp) expression when additional molecular chaperoning is required (i.e., in situations of proteotoxic stress, including thermal stress) in a process known as the heat shock (HS) response. Thus, HSF1 acts as an environmental sensor, and a harness based on the biology of this capability enables transcription of genes for engineered purposes. The hypothesis of this thesis is that a harness of the heat shock response, when paired with a therapeutic mechanism, will refine novel therapies. Extensions to the concept of deliberately activating HSF1's normal functions for therapeutic purposes are examined through in vitro trials and in vivo preliminary studies that feature the use of HSF1 as a regulator of therapy. Successful in vitro work translated to pioneering preclinical studies, launched at the University of Florida's Center for Environmental and Human Toxicology. Collaboration supported the development of an innovative project to treat solid tumors using a recombinant virus system. The system was designed to facilitate intratumoral delivery of a previously characterized molecular switch, which was newly engineered to control cytotoxic gene transcription that produced dramatic consequences in cells of human origin. Central to the targeting of the in vivo therapy, is a transient, initial trigger: a thermal dose, delivered to solid tumors, which localizes HSF1 activation (a constitutively active mouse HSF1 construct was also produced to aid clarification of physiological consequences associated with deliberately upregulating HSF1 activity in vivo). Gene transcription was expected to ensue to both cause and sustain tumor regression through other regulatory elements of the molecular switch. Results demonstrated practical potential to achieve a therapeutic outcome of solid tumor regression and define contemporary challenges that continuing research directions (e.g.: production of additional viral vectors, an improved animal model, and a refined heat system) now confront in order to target and safely regulate even more potent, novel therapeutic agents.

MicroRNAs are small non-coding RNA molecules that regulate mRNA translation by binding to complementary sequences usually within the 3’ un-translated region (UTR). By inserting four perfectly complementary binding sites for the hepatic specific microRNA mir122 into the 3’ UTR of adenovirus wild type 5 (Ad5 WT) E1A mRNA I show that the acute liver toxicity caused by Ad5 WT in mice can be significantly reduced. This virus, termed Ad5-mir122, is a promising virotherapy candidate and causes no obvious liver pathology whilst maintaining Ad5 WT replication in mir122 negative cells. Data shows that repeat intravenous administration of Ad5-mir122 (2x1010vp) to HepG2 tumour bearing mice mediated significant anti-cancer efficacy. RT-QPCR for E1A mRNA demonstrated a 29-fold reduction when compared to Ad5 WT in murine liver whilst western blot confirmed that all E1A protein variants were knocked down. Viral genomic replication was also reduced in mouse liver by 25-fold compared to Ad5 WT. This control of virus activity reduced alanine and aspartate transaminase release by >15-fold and histological analysis showed little to no pathology in Ad5-mir122 infected livers. Measurement of mature mir122 levels in Ad5-mir122 infected livers by RT-QPCR showed that the quantity of mir122 remained unaffected at therapeutic doses. Complete genome mRNA array profiling of infected livers showed that the transcript levels of >3900 different mRNAs were changed more than 2-fold following Ad5 WT infection whilst less than 600 were changed by Ad5-mir122. A non-replicating control adenovirus vector altered >550 mRNAs. No known mir122 target mRNAs were affected following infection with Ad5-mir122. Western blot analysis of a known mir122 regulated target (Aldolase A) confirmed these results, demonstrating no change in protein level despite infection with Ad5-mir122. These data combined demonstrate that the exploitation of microRNA mir122 regulation to control adenovirus replication is a safe method of control and does not alter the endogenous level or activity of the microRNA or its endogenous mRNA targets. Ad5-mir122 is a potent anti-cancer agent that replicates to wild-type levels in microRNA mir122 negative cells but is specifically and safely attenuated in hepatocytes.

Nous avons mis en place au cours de ce travail de thèse différentes stratégies permettant d’améliorer l’efficacité thérapeutique des adénovirus (Ad) oncolytiques contre différents types de tumeurs. Une première stratégie a été de combiner un inhibiteur d’histone-désacétylase, l’acide valproique (VPA) avec un Ad oncolytique à capside sauvage E1Δ24 (CRAd) dans le traitement de carcinomes côliques. Nous avons dans un premier temps démontré que la combinaison du CRAd et du VPA permettait une diminution plus importante de la survie des cellules cancéreuses côliques comparé au simple traitement basé sur le CRAd ou le VPA in vitro mais aussi in vivo.De plus, nous avons observé que cet effet n’était pas lié à une meilleure réplication du CRAd par le VPA. En effet, le VPA provoquait un ralentissement de la réplication virale à des temps précoces mais ne modifiait pas la production virale. Nous avons également découvert que le co-traitement CRAd+VPA conduisait à une forte inhibition de la croissance cellulaire mais aussi à une mort cellulaire non apoptotique. Par ailleurs, nous avons mis en évidence que les cellules co-traitées par le CRAd et le VPA affichaient une forte polyploïdie accompagnée d’une augmentation de la phosphorylation de l’histone H2AX, un marqueur de dommages à l’ADN. Une deuxième stratégie a été de fournir aux Ad oncolytiques de nouvelles voies d’entrée afin d’infecter et de détruire plus efficacement des cellules de carcinomes rénaux réfractaires à l’infection adénovirale. Nous avons démontré que les CRAd à hexon modifié porteurs d’un ligand CKS-17 (Ad-HCKS-17-E1Δ24) ou à fibre modifiée de sérotype 3 (AdF3-E1Δ24) étaient capables d’infecter et de tuer plus efficacement ces cellules qu’un CRAd à capside sauvage in vitro. Malheureusement in vivo, les modifications de capside n’ont permis ni d’améliorer l’entrée des CRAd dans les tumeurs rénales, ni d’améliorer leur efficacité anti-tumorale. Cependant, nous avons observé qu’après administration intra-tumorale, les Ad à capside modifiée présentaient un plus faible tropisme hépatique comparé à un Ad à capside sauvage. / During this thesis, we investigated different strategies to increase the therapeutic effects of oncolytic adenovirus (CRAd) to fight several kinds of tumors.The first strategy seeks to evaluate in human colon carcinomas the association of a CRAd bearing Δ24 deletion in E1A with valproic acid (VPA), a histone deacetylase inhibitor. Interestingly, this combination led to a dramatic reduction of cell survival both in vitro and in vivo compared to single treatment with CRAd or VPA. This effect did not stem from a better CRAd replication and production in the presence of VPA. Inhibition of cell proliferation and a non-apoptotic cell death were shown to be two mechanisms mediating the effects of the combined treatment. Interestingly, whereas cells treated only with CRAd displayed a > 4N population and polyploidy, this phenotype was strongly increased in cells treated with both CRAd and VPA. In addition, the increase in polyploidy triggered by a combined treatment with CRAd and VPA was associated with the enhancement of H2AX phosphorylation (γH2AX), a hallmark of DNA damage. The second strategy developed aimed to find new entry pathways allowing CRAd to better infect and kill renal tumor cells, known to be refractory of Ad infection. We demonstrated that CRAd with capsid modified (Ad-HCKS-17-E1Δ24 and AdF3-E1Δ24), containing respectively a ligand CKS-17 in hexon or a fiber of serotype 3, were more efficient to infect different renal cell carcinomas in vitro compared to a CRAd with a wild type capsid. However, these capsid-modified oncolytic adenovirus provoked, neither increase of the infection level, nor a better efficacy of growth inhibition in renal tumor xenografts bearing by nude mice. Nevertheless, both types of modifications reduce Ad ability to transduce hepatocytes after intratumoral injection.

Poor drug penetration through tumor tissue has emerged as a fundamental obstacle to cancer therapy. The solid tumor microenvironment presents several physiological abnormalities which reduce the uptake of intravenously administered therapeutics, including leaky, irregularly spaced blood vessels, and a pressure gradient which resists transport of therapeutics from the bloodstream into the tumor. Because of these factors, a systemically administered anti-cancer agent is unlikely to reach 100% of cancer cells at therapeutic dosages, which is the efficacy required for curative treatment. The goal of this project is to use high-intensity focused ultrasound (HIFU) to enhance drug delivery via phenomena associated with acoustic cavitation. ‘Cavitation’ is the formation, oscillation, and collapse of bubbles in a sound field, and can be broadly divided into two types: ‘inertial’ and ‘stable’. Inertial cavitation involves violent bubble collapse and is associated with phenomena such as heating, fluid jetting, and broadband noise emission. Stable cavitation occurs at lower pressure amplitudes, and can generate liquid microstreaming in the bubble vicinity. It is the combination of fluid jetting and microstreaming which it is attempted to explore, control, and apply to the drug delivery problem in solid tumors. First, the potential for cavitation to enhance the convective transport of a model therapeutic into obstructed vasculature in a cell-free in vitro tumor model is evaluated. Transport is quantified using post-treatment image analysis of the distribution of a dye-labeled macromolecule, while cavitation activity is quantified by analyzing passively recorded acoustic emissions. The introduction of exogenous cavitation nuclei into the acoustic field is found to dramatically enhance both cavitation activity and convective transport. The strong correlation between inertial cavitation activity and drug delivery in this study suggested both a mechanism of action and the clinical potential for non-invasive treatment monitoring. Next, a flexible and efficient method to simulate numerically the microstreaming fields instigated by cavitating microbubbles is developed. The technique is applied to the problem of quantifying convective transport of a scalar quantity in the vicinity of acoustically cavitating microbubbles of various initial radii subject to a range of sonication parameters, yielding insight regarding treatment parameter choice. Finally, in vitro and in vivo models are used to explore the effect of HIFU on delivery and expression of a biologically active adenovirus. The role of cavitation in improving the distribution of adenovirus in porous media is established, as well as the critical role of certain sonication parameters in sustaining cavitation activity in vivo. It is shown that following intratumoral or intravenous co-injection of ultrasound contrast agents and adenovirus, both the distribution and expression of viral transgenes are enhanced in the presence of inertial cavitation. This ultrasound-based drug delivery system has the potential to be applied in conjunction with a broad range of macromolecular therapeutics to augment their bioavailability for cancer treatment. In order to reach this objective, further developmental work is recommended, directed towards improving therapeutic transducer design, using transducer arrays for treatment monitoring and mapping, and continuing the development of functionalized monodisperse cavitation nuclei.