Sir Peter MacCallum Department of Oncology - Theses
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ItemDefining functional drivers of oesophageal tumourigenesis( 2019)The incidence of oesophageal adenocarcinoma (OAC) has risen rapidly over the last four decades and has a high overall mortality rate that has shown only incremental improvements over the same duration. OAC develops from the precursor intestinal metaplasia of the oesophageal mucosa known as Barrett’s oesophagus. However, limited knowledge of the molecular mechanisms driving disease progression makes effective clinical management of OAC challenging. One of the common genetic events associated with the progression from Barrett’s oesophagus to OAC is loss of the tumour suppressor, SMAD4 (mutated in 13% or loss of function in 34% of OAC cases). Herein, this thesis firstly investigated the effect of SMAD4 inactivation in Barrett’s carcinogenesis. Genetic knockdown or knockout of SMAD4 was sufficient to initiate tumourigenesis of dysplastic Barrett’s oesophagus cell line, CP-B, in vivo, establishing SMAD4 loss as a crucial event driving progression to OAC. Further, low coverage whole genome sequencing (LC-WGS) analysis revealed that tumourigenic SMAD4 knockdown/knockout CP-B cell lines exhibited distinctive and consistent copy number alterations (CNAs) compared to non-tumourigenic SMAD4 wild-type parental cells. Amongst the alterations we observed were loss of chromosome arm 14q, while amplified regions include chromosome arms 6q and 12p, consistent with common CNAs found in patient tumours. This high genomic instability, characterized by structural chromosomal rearrangements within the tumours following SMAD4 loss, implicates SMAD4 as a protector of genome integrity in OAC development and progression. Moreover, initial in vitro data shows that SMAD4 knockout in CP-B cell line, results in differential expression of transforming growth factor-beta (TGF-beta) pathway target genes (such as ACTA2, CRYAB, PTK2B, ATF3 and CDC6) and loss of cell cycle arrest in response to TGF-beta1 cytokine compared to SMAD4 wild-type parental cells. Furthermore, SMAD4 knockout negatively regulated transcript expression of the multifunctional tumour suppressor INK4/ARF locus, demonstrating the novel and complex network of SMAD4 tumour suppressive activity. This thesis also focused on deciphering the functional role of growth factor receptor bound protein 7 (GRB7) amplification and overexpression in OAC and its potential targeting. GRB7 gene is positioned within known 17q12 amplicon, together with HER2 gene encoding for human epidermal growth factor receptor 2 (HER2). GRB7 is an adaptor molecule that mediates networking of multiple cell surface receptors with downstream signalling pathways. GRB7 high expression was found to be associated with worse survival in OAC patient cohort. Further, genetic GRB7 knockdown (siRNA) inhibited cell proliferation and clonogenic survival and induced apoptosis in GRB7 amplified and overexpressing OAC cell lines (OE19 and Eso26), without altering proliferation of the cells with normal GRB7 expression. Furthermore, whilst HER2 amplification and overexpression was also observed in OE19 and Eso26 cells, they were not uniquely sensitive to trastuzumab (HER2 inhibitor), with Eso26 cells exhibiting resistance in vitro. Taken together, initial findings raise the possibility that GRB7 may be a better molecular therapeutic target than HER2 in OAC with the 17q12 amplicon. To address this possibility, OE19 and Eso26 cell line xenograft models with inducible expression of shRNA targeting GRB7 were used. Consistent with in vitro findings, HER2 expression did not predict sensitivity to trastuzumab, with Eso26 xenografts remaining refractory to trastuzumab treatment. Of high importance, mimicking GRB7 inhibition with inducible-shRNA significantly inhibited tumour growth in both OE19 and Eso26 xenografts. Thus, this part of the thesis demonstrates the functional role of GRB7 overexpression as an oncogenic driver independent of HER2. In summary, the identification of functional genetic drivers and a deeper understanding of the mechanisms that underlie tumour progression in Barrett’s carcinogenesis will lead to improved strategies for the clinical management of OAC patients. To this end, SMAD4 loss was sufficient for progression from dysplasia to OAC. Tumours driven by SMAD4 loss exhibit distinctive CNAs consistent with OAC and metastatic potential. In addition, GRB7 high expression predicts poor outcome in patients with OAC and as such, GRB7 represents an oncogenic driver that could be used as a therapeutic target. Crucially, this thesis provides in vitro and in vivo preclinical and molecular biology evidence for the potential therapeutic benefit of targeting GRB7 in cancer.
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ItemExploration of novel regulators of mutant p53 in cancer cells: a role for NDFIP1( 2019)Mutations in the tumour suppressor gene, TP53 occur in more than 50% of human cancers. Mutant p53 proteins not only lose their tumour suppressive capacities, but also gain oncogenic functions, broadly referred to as gain of function (GOF). Cancer cells frequently accumulate mutant p53 and may become addicted to this protein for their survival. During development, mutant p53, like its wild-type counterpart, is inherently labile, however in cancer cells mutant p53 frequently accumulates. In part, this is due to the interrupted auto-regulatory loop with MDM2. However, MDM2 alone cannot explain the stability of mutant p53 in many cancer contexts. We therefore argued that additional factors are responsible for its stability in cancer cells. In order to identify the major players in the regulation of mutant p53, we performed a high-throughput RNAi screen through which we evaluated 18,120 genes for their effects on mutant p53 levels in two different mutant p53 expressing cell lines. Based on network analyses, pathway analyses and extensive literature mining, we selected 37 candidate genes to be validated through p53 immunoblotting. From the validated genes, we have selected one candidate for further studies. The results described in this thesis highlight a previously unknown mode of mutant p53 regulation in cancer cells. Future studies will explore in greater depth the functional consequences of this new interaction with mutant p53. Excitingly, these studies expose new vulnerabilities for therapeutic intervention and these opportunities for targeting aggressive cancers with mutant p53 will also be the focus of ongoing research.
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ItemThe evolutionary history of genes and transcriptional networks reveals fundamental properties of cancer associated with the breakdown of multicellularity( 2018)All biological systems follow the rules and constraints imposed during their evolution. Current-day gene phenotypes such as gene expression, gene essentiality, gene function and protein localization are linked with the time of evolutionary emergence of genes. In cancer, tumours rely on cellular processes that date back to unicellular ancestors (e.g., cell replication, glycolysis), while dysregulating key pathways linked to the emergence of multicellularity, suggesting that the transition from unicellularity to multicellularity left vulnerabilities in cells that act as guiding principles during cancer development. Therefore, in this thesis I integrate genomics, systems biology and evolutionary biology to investigate fundamental principles of tumourigenesis related to the evolutionary history of genes using gene expression and somatic mutation information across multiple tumour types. First, I coupled the evolutionary age of genes and cellular processes with their expression levels in tumour and normal samples, and found that tumours consistently activate genes from unicellular ancestors while switching off genes related to multicellularity. These consistent patterns were supported by a mutual exclusivity between the activity of genes and transcriptional networks of unicellular and multicellular ancestors, which promoted convergent evolution towards a state of loss of multicellularity. Second, I investigated how somatic mutations disrupted gene regulatory networks. Genes that emerged together with early metazoans were enriched in point mutations and copy- number alterations, indicating that gene innovations that took place at the onset of multicellularity play a fundamental role in cancer development. Importantly, the uncoupling of regulatory networks of unicellular and multicellular ancestors was mostly due to point mutations in gene regulators linking these networks. On the other hand, copy-number aberrations were directly involved in the activation and inactivation of unicellular and multicellular genes, suggesting point mutations and copy-number aberrations play complementary roles in the loss of regulation between unicellular and multicellular transcriptional networks in cancer. Third, I focused on novel transcriptional associations formed during tumourigenesis using gene co-expression module analysis. Significant levels of rewiring between unicellular and multicellular genes were found across tumours. This rewiring was mostly driven by gene amplifications, which promoted the formation of tumour-specific modules composed of novel transcriptional associations between unicellular and multicellular genes, once more linking the genes and regulatory associations evolved at the onset of multicellularity to cancer development. The findings of this work reveal fundamental principles driving cancer development associated with genes and transcriptional networks evolved during the transition from unicellularity to multicellularity. I propose a model whereby activation of programs that date back to unicellular ancestors and the deactivation of multicellular programs is driven by an inherent mutual exclusivity of these genes together with the breakage of regulation between unicellular and multicellular genes by point mutations, whereas the formation of novel transcriptional associations between these genes in tumours is driven by copy-number changes. Finally, I identify potential novel drivers based on their key role in uncoupling unicellular and multicellular transcriptional networks across tumours and suggest novel treatment strategies derived from this evolutionary approach. The results presented in this thesis contribute to our understanding of how past evolutionary events led to vulnerabilities in transcriptional networks that influence cancer development, and highlight the benefits of the integration of evolutionary concepts with genomics and network biology to identify fundamental principles of cancer.
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ItemHow information technology improves the quality and efficiency of medical care and research( 2018)In 2007, the concept of rapid learning healthcare was proposed in the United States of America health system in a response to increasing healthcare costs. Its aim was to accelerate knowledge discovery through a systematic approach to integrating electronic medical records design with analysis infrastructure to rapidly and continuously assess health system performance. The delivery of healthcare is becoming increasingly performed and documented within the electronic domain, and large databases of healthcare-related information being created as a by-product. This has led to an unprecedented level of access to detailed and structured clinical data that could be used to accelerate research. In a rapid learning healthcare system, the high level of integration from electronic record to policy would ensure that each patient and each click of the mouse would drive innovation. The attraction of rapid learning was not to supplant the traditional clinical trial paradigm, but to augment its effectiveness with accelerated analysis of real-world outcomes. The rapid learning concept relied heavily on electronic medical records, administrative systems and disease registries as data sources to power analyses. Electronic health record penetrance in Australia has lagged that achieved in the USA, primarily because of financial assistance provided as part of the HITECH act in the USA. However, one exception is seen in oncology, where radiotherapy is exclusively prescribed electronically. Additionally, there has been a significant shift toward electronic chemotherapy prescribing due to the clinical risk associated with manual systems. Perhaps in oncology there is an opportunity to replicate the successes of data-driven health research achieved elsewhere. The objective of the work contained in this thesis is to develop practical methods to expand and discover the infrastructure required to implement rapid learning health care in the Australian oncology context. Ultimately, the aim is to increase the quality and efficiency of medical care and research by harnessing novel information technology (IT) methods. In addition to leveraging existing secondary databases for health services research and creating high impact linkages with state-level cancer registries, advanced IT methods could also be used to automate manual data extraction tasks in a timely and cost-effective fashion. The integration of these methods into routine clinical practice has enormous implications for tracking patient care quality, and accelerating research by utilising all data by-products of health care.
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ItemInvestigating acquired resistance to Pol I transcription inhibitors for the treatment of haematologic malignancies( 2018)Previous work from our group and others has demonstrated that CX-5461 (Senhwa Biosciences), a first-in-class small molecule inhibitor of RNA Polymerase I transcription of the ribosomal RNA genes, is effective at treating a range of different cancers both in vitro and in vivo, and is currently in clinical trials for haematologic and solid tumours. However, despite initial tumour clearance in response to CX-5461 treatment in preclinical murine models of cancer, mice eventually relapse with tumours that are resistant to further CX-5461 treatment. This thesis investigates the mechanisms via which the tumours can develop resistance to CX-5461 treatment and extrapolates this research to better understand: 1) how CX-5461 functions as an anti-tumour agent; 2) which pathways are required to mediate resistance to CX-5461; and 3) how resistance can be overcome with combination therapy. Using DNA exome sequencing, we found that Top2α is frequently mutated in tumours that have acquired resistance to CX-5461 treatment in vivo. Functional characterization of a Top2α mutant cell line demonstrated that Top2α expression and activity were reduced in these cells. Indeed, we found that knockdown of Top2α was sufficient to cause resistance to CX-5461. This implies that Top2α could provide a novel biomarker for CX-5461 response in clinical trials. Further investigation of the CX-5461 resistance mechanism uncovered that CX-5461 also acts as a Top2 inhibitor in addition to its ability to inhibit rDNA transcription. However, unlike common chemotherapeutic Top2 inhibitors which kill cells by causing genome-wide DNA damage thereby initiating a DNA damage response, CX-5461 treatment causes comparatively fewer DNA breaks enriched at the ribosomal DNA promoter loci. Thus, CX-5461 is able to kill tumour cells via the DNA damage response in the absence of extensive DNA damage thereby potentially limiting the cytotoxicity of drug treatment. Together, the work presented in this thesis identifies novel mechanisms of action and resistance to CX-5461. We propose that CX-5461 and other second-generation inhibitors of RNA Polymerase I and Top2α may provide a viable, less genotoxic alternative to classic Top2 inhibitors.
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ItemFever and neutropenia in children with cancer: optimising clinical research and the delivery of care in Australia( 2017)Fever and neutropenia (FN) is the most common complication of childhood cancer treatment. Management traditionally involves hospital admission for antibiotics until resolution of fever and recovery of neutrophil count. However, children with FN are a heterogeneous group with varying risk of severe infection, and this approach over treats up to half of all episodes where risk of serious complications is low. Unlike FN management for adults, formal low-risk treatment strategies for children are not routinely employed. In Australia, little is known about the aetiology and management of FN in children and clinical decision rules (CDRs), designed to predict infection, have not been validated. These factors remain a critical barrier to implementing ambulatory-care programs for children with low-risk FN in this country. Such programs are safe, improve quality of life (QoL) and reduce healthcare expenditures. The overall aims of this thesis were to optimise clinical paediatric FN research; to advance our understanding of the assessment and management of FN in children with cancer in Australia; and to facilitate treatment that is tailored to the patient’s risk of infection. Each project addresses important evidence gaps, namely the absence of standardised paediatric FN research outcomes and definitions, the lack of a contemporary evaluation of FN management in Australia and the limited use of risk-based treatment algorithms. To optimise clinical paediatric FN research, Delphi survey methodology was used to achieve consensus on a set of core variables and outcomes that should be reported in all FN studies. This is the first time a paediatric-specific FN research framework has been developed and is the result of an international collaboration. Standardised FN research outcomes will reduce heterogeneity between studies, minimise reporting bias and enable research results to be compared, contrasted and combined. To advance our understanding of the management of FN in Australia, a national practice survey was conducted. There was clear evidence of heterogeneity in assessment, risk stratification and treatment of children with FN. The survey identified critical knowledge gaps and deviations from best practice, and the results will be used to inform guidelines, education and low-risk program implementation strategies. It also highlighted the necessity for validation studies to determine which CDRs are most appropriate for use in Australia. A series of studies were conducted to facilitate FN treatment that is tailored to the risk of infection. In a retrospective study, seven CDRs were validated, of which two exhibited the most clinically meaningful results. The accompanying economic evaluation highlights opportunities for substantial healthcare savings by reducing length of stay (LOS) for low-risk patients. The systematic review and meta-analysis of the predictive ability of novel biomarkers found that marked heterogeneity between studies limits firm conclusions, and further research is required. This thesis has addressed key evidence gaps and contributed new knowledge that will optimise clinical FN research and the delivery of FN care to children with cancer. It has informed the national Australian Predicting Infectious ComplicatioNs in Children with Cancer (PICNICC) project that will prospectively validate CDRs, identify novel biomarkers and evaluate the cost and QoL associated with standard FN treatment. It has also established a collaborative network that will ensure FN research continues in this country and results are translated into practice.
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ItemPragmatic, consensus-based minimum standards and structured interview to guide the selection and development of cancer support group leaders( 2018)Across the globe, peer support groups have emerged as a community-led approach to connecting people with cancer experiences and accessing support. Members of cancer support groups seek to help themselves and each other to reduce the negative or disabling effect that cancer may have on general health, relationships, coping, and daily functioning. With no centralised registry, the number of cancer support groups is unknown but thought to be considerable. Peak cancer agencies have established relationships with support groups, in an effort to strengthen and sustain delivery of peer support. Agency funding, training, resources, and support staff are extended to groups, with the group leader being the primary recipient and point of contact. Group leadership is usually provided voluntarily by people with a personal experience of cancer. Challenges have been reported in maintaining group leaders’ quality of life and preventing burn-out. The ability of an individual to function in the role and maintain this role over a period of time is important for group sustainability. However, little is known about the essential qualities required to lead a cancer support group, or how to determine a person’s suitability for the role. Initial scoping of the literature revealed the lack of a relevant role analysis and no accurate synopsis of the basic knowledge, skills, and attributes required for the group leader role. There are no published guidelines, standards, or tools to guide selection and development of peer support group leaders. This project aimed to generate pragmatic, consensus-based minimum standards for the cancer support peer group leader role, and to develop a structured interview and user manual to guide the selection and development of cancer support group leaders. The interview was anchored in a comprehensive role analysis and validities were maximised by increasing structure in process and use of the interview data. Following a systematic review of research relevant to the desirable qualities for support group leaders, an online Delphi study was used to reach expert-consensus on the 52 knowledge, skills, and attributes considered essential for cancer support group leaders. These 52 requisite knowledge, skills, and attributes describe the minimum standards for the role, and were used to develop the structured interview. The structured interview and accompanying user manual were piloted for aspects of clinical utility and determined to be appropriate, accessible, practical, and acceptable for use by cancer agency workers. The structured interview was field tested with 63 current support group leaders to determine a potential cut-off score for selection of group leader’s suitability. However, a more comprehensive pool of participants and scores are required to determine reasonable cut-off scores. This PhD project used pragmatic, novel, and robust methods to respond to a real-world problem. Our study outputs are a first in the field, with scope for future research and development to apply the structured interview more broadly.
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ItemThe role of nature in cancer patients' experiences of health and recovery( 2017)This thesis explores the role of nature in cancer patients’ experiences of health and recovery. Using a 2-Phase mixed-method approach, the investigation aimed to generate new theoretical understanding about cancer patients’ use of nature and how they find nature engagement helpful or not when confronting cancer diagnosis. The project’s translational focus was to produce expert recommendations for nature-based care opportunities in oncology contexts based on patient-reported data. First, a systematic literature review and meta-synthesis was conducted to describe the existing qualitative research evidence base relating to nature experiences and nature-based interventions for cancer populations specifically. The aim was to describe current knowledge about the role of nature in cancer patients’ lives. From eleven eligible publications, seven inter-related core themes were identified as follows: connecting with what is valued; being elsewhere, seeing and feeling differently; exploration, inner and outer excursions; home and safe; symbolism, understanding and communicating differently; benefitting from old and new physical activities; and, enriching aesthetic experiences. Next, an in-depth investigation of cancer patients’ own experiences with nature used primary data to develop a new Grounded Theory describing the underlying and intrapsychic mechanisms of cancer patients’ phenomenal nature experiences. Based on qualitative data collected from semi-structured interviews with 20 cancer patients (9 female), the resulting theory model explores the unique role nature plays when diagnosed with cancer. It constitutes a core category and two inter-related themes, which explain a normalization process in which patients moved towards a state of 'new-normal' (Core Category). Nature functioned in this process as a support structure that repositioned patients and nurtured their inner and outer capacities to respond and connect more effectively (Theme A). Once enabled and comforted, participants could engage survival and reconstructive manoeuvres and explore the consequences of cancer in their present lives and possible futures (Theme B). A dynamic relationship was shown between moving away while, simultaneously, advancing towards the cancer reality in order for patients to incorporate their cancer experiences into a shifting normality. From a place of comfort and safety, patients felt supported to deal differently and more creatively with the threat and demands of cancer diagnosis, treatment, and outlook. The descriptively rich interview data provided further insights into patients’ own recommendations for nature engagement in the oncology context, which were extracted from the transcriptions using deductive content analysis and were consolidated into patient recommendations for nature-based care opportunities. These incorporated using nature for vital sensory stimulation and engagement, using nature for personal space and freedom to enable private and social exploration, using views of nature for distraction and comfort, and accessing nature for physical activity and movement. Three critical factors were determined to avoid adverse experiences: determining appropriate health-care expenditure and resourcing on nature-based interventions, selection of appropriate nature-based design materials, and exercising caution around demanding nature engagement and harsh weather conditions. A questionnaire survey study was conducted following an environmental intervention in an oncology waiting room to assess patient, visitor, and staff responses to design changes, which included the addition of artificial plant materials. Based on 143 returned survey questionnaires consisting of 73 cancer patients, 13 staff, 52 carers, and five ‘other’, it was found that the environmental intervention positively impacted patients, staff, and carers’ perceptions of the oncology waiting room environment. Patients, staff, and carers mostly accepted artificial plants as an alternative design solution to real plants. Comments included positive appraisals and occasional adverse reactions to artificial plants. No significant differences were found between patient, staff, and carer reactions. Insights gleaned from the initial, exploratory phase formed the basis for a second phase investigation comprising an international online Delphi study. The aim was to solicit knowledge from relevant experts drawn from a range of healthcare practitioners, management, designers, and researchers to determine feasible opportunities for, and barriers to, providing helpful nature engagement in oncology settings. Two hundred potential panellists were identified and sent an invitation to participate. Thirty-eight experts were recruited who represented 7 countries: Australia (19), USA (8), UK (3), New Zealand (2), Canada (2), Denmark (3), and Sweden (1). This study followed a structured, iterative feedback process that queried and synthesized expert opinion. Cancer patients’ own recommendations, extracted from phase 1, were used as a starting point for the Delphi panel to brainstorm and develop their own ideas about appropriate nature-based opportunities in oncology settings and the barriers to their provision. In total, 250 separate suggestions for opportunities and 205 suggestions for barriers were collected. Further analysis condensed these into 55 unique items (35 opportunities, 20 barriers). The Delphi panel’s list of recommendations included “Window views from clinical areas onto nature […]” as the highest rated opportunity, and “Building design and site constraints […]” as the highest rated barrier to providing nature-based supports for oncology care. Finally, a synthesis of findings from the overall investigation, which constitutes six publications, is provided to summarize and outline the salient findings and discern the study’s limitations in order to suggest pathways for future research. This synthesis produced a conceptual framework consolidating new theoretical understanding and empirical content from patient and expert-reported data about nature-based care opportunities in the oncology setting. The thesis findings provide evidence for multiple uses of nature as a supportive aid in the cancer care context. Concrete recommendations have resulted to guide the application of nature based concepts in future oncology setting design and may be considered when developing additional supportive care services. The findings may assist healthcare practitioners, designers, researchers, and patients themselves to creatively and practically participate in future oncology care practice and design.
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ItemBET bromodomain inhibition as combined apoptotic and immunomodulatory therapy for the treatment of MYC-driven lymphoma( 2017)Bromodomain and Extra-Terminal (BET) proteins are a conserved family of ‘epigenetic readers’ that bind to acetylated lysine residues on histone and non-histone proteins to modulate transcription. BET proteins are enriched at promoter and enhancer regions and recruit the positive transcription elongation factor b (P-TEFb) complex to activate RNA polymerase II. Anti-tumour responses elicited by BET inhibitors have been associated with the suppression of genes required for cellular proliferation and survival, including oncogenic transcription factors. Suppression of the proto-oncogene MYC was initially reported as a key mechanistic property of BET inhibitors, however more recent evidence suggests that additional target genes are mechanistically implicated. In this thesis, the Eμ-Myc model of aggressive B-cell lymphoma was utilized to investigate the full repertoire of genes modulated by JQ1 and their functional significance in mediating therapeutic responses. JQ1 did not suppress the expression of transgenic Myc in this model, allowing the determinants of apoptosis induction to be assessed, independently of changes in Myc expression. This apoptotic response was p53-independent and associated with modulation in the ratio of pro- and antiapoptotic Bcl-2 family members to favor activation of the intrinsic mitochondrial apoptotic pathway. Therapeutic administration of JQ1 to mice bearing Eμ-Myc lymphomas led to robust clinical responses, however, universal treatment failure was observed despite ongoing therapy. Using RNA-Seq, disease progression and secondary JQ1 resistance was found to be associated with RAS pathway activation and Bcl-2 upregulation. In addition, the efficacy of JQ1 was found to be dependent on an intact host immune system, where a 50% reduction in the survival advantage was observed upon transplantation into immune-deficient mice. Using RNA-Seq, the immune checkpoint ligand Cd274 (Pd-l1) was found to be potently suppressed by JQ1. Mechanistically, BET inhibition decreased Brd4 occupancy at the Cd274 promoter, leading to promoter-proximal pausing of RNA polymerase II, and loss of Cd274 mRNA production. Rapid epigenetic remodeling of the Cd274 locus in response to interferon gamma (IFN-γ) stimulation led to recruitment of Irf1, Brd4, RNA polymerase II, as well as increased local histone acetylation. Accordingly, BET inhibition suppressed constitutive and IFN-γ-induced PD-L1 expression in genetically diverse tumour models. Ectopic expression of PD-L1 in Eμ-Myc lymphomas was sufficient to reduce the efficacy of JQ1, demonstrating the significance of PD-L1 suppression to the observed therapeutic responses associated with BET inhibition. Finally, treatment of mice bearing Eμ-Myc lymphomas with JQ1 in combination with a checkpoint inhibitor (anti-PD-1) or immune stimulating antibody (anti-4-1BB/CD137) led to improved therapeutic responses. The results presented herein demonstrate the importance of MYC-independent apoptotic signaling to therapeutic responses associated with BET inhibition, as well as acquired drug resistance. In addition, these results demonstrated the ability of BET inhibitors to directly engage the host immune response during anti-cancer therapy. Finally, BET inhibitors can suppress oncogenic PD-L1 transcription for therapeutic gain, leading to augmented anti-tumour immunity. These studies establish a strong rationale for clinical investigation of BET inhibitors in combination with immune modulating therapies.
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ItemThe role of Pim-1 in breast cancer metastasis( 2017)Breast cancer is the most common cancer in women. Despite advances in treatment options, the spread of breast cancer to distant organs (metastasis) remains the major cause of morbidity and mortality in breast cancer patients. This is attributed primarily to the impairment of function in affected organs. Thus, there remains a vital need for better-targeted treatments that more effectively inhibit the development or progression of metastases. Pim-1 is a serine/threonine survival kinase that has been implicated in the development of metastasis in several haematological and solid cancers. However, little is known about its role in breast cancer. In our laboratory, we previously identified Pim-1 as upregulated in brain metastatic 4T1Br4 syngeneic mouse cells and tumours compared to parental 4T1 cells. This led us to propose that Pim-1 may play a role in mediating breast cancer brain metastasis. Therefore, the overall objective of this project was to examine the expression and functional role of Pim-1 in breast cancer metastasis, with a focus on organ-specific metastasis. We interrogated public databases to show that Pim-1 expression is low to absent in normal breast tissue and increased in breast tumour tissue. Furthermore we show that the murine (4T1Br4) and human (MDA-MB-231Br) brain metastatic breast cancer cell lines and tumours demonstrate the highest expression of Pim-1 mRNA and protein. To investigate the function of Pim-1 in breast cancer metastasis we tested the impact of inhibiting Pim-1, either by gene knock down using short hairpin RNAs or the pharmacological inhibitor SGI-1776, on the ability of 4T1Br4 and MDA-MB-231Br cells to migrate and invade in vitro. 4T1Br4 cells displayed increased migration and invasion propensity after Pim-1 knock down and this was coupled with a decrease in β4 integrin expression. Conversely, MDA-MB-231Br cells showed a decreased ability to migrate and invade after Pim-1 KD, as well as decreased cell surface expression of β1 and β3 integrins. Treatment with SGI-1776 dose-dependently decreased the ability of both 4T1Br4 and MDA-MB-231Br cells to migrate and invade, decreased cell surface expression of β3 integrin in 4T1Br4 cells, and both β1 and β3 integrins in MDA-MB-231Br cells. To examine the effect of Pim-1 inhibition in vivo, we assessed the metastatic spread of Pim-1 knock down MDA-MB-231Br cells in an experimental metastasis assay. After intracardiac injection of Pim-1 knock down cells, we observed a reduction in the number of circulating tumour cells and decreased bone metastasis, indicating a functional role for Pim-1 in breast cancer metastasis to the bone. Data from brain metastasis in this model were inconclusive. In summary, results from this project highlight the importance of Pim-1 in breast cancer metastasis and provide evidence that Pim-1 contributes to the migration and invasion of breast cancer cells both in vitro and in vivo, possibly via regulation of integrin expression, and indicate that Pim-1 is a relevant therapeutic target for the treatment of metastatic breast cancer.