Metabolic reprogramming in cancer cells provides energy and important metabolites required to sustain tumour proliferation. Hypoxia represents a hostile environment that can encourage these transformations and other adaptive responses that contribute to poor prognosis and resistance to radiation and chemotherapy. Hypoxic signatures associated with worse prognosis were previously derived in different cancer types, and led to the selection of two candidates with potential metabolic implications, namely the mir210-putuative target iron-sulfur scaffold protein ISCU and glycogen phosphorylase (PYGL). Firstly, it was verified that the hypoxia-induced miR-210 targets ISCU. Iron-sulfur clusters represent cofactors for key enzymes involved in Krebs cycle and electron transport chain. Downregulation of ISCU was associated with the induction of reactive oxygen species (ROS) and reduced mitochondrial complex I and aconitase activity, caused a shift to glycolysis in normoxia and enhanced cell survival. This indicates that the induction of a single microRNA, miR-210, can mediate a new mechanism of adaptation to hypoxia, by regulating mitochondrial function via iron-sulfur cluster metabolism and free radical generation. Secondly, it was found that changes in PYGL expression reflect a characteristic upregulation of glycogen metabolism in hypoxia in both tumour xenografts and in cancer cell lines. More specifically, hypoxia stimulates glycogen accumulation and its utilisation, as well as the concurrent upregulation of several glycogen-metabolizing enzymes such as glycogen synthase (GYS1) and PYGL. PYGL depletion led to glycogen accumulation in hypoxic cells, increased intracellular levels of ROS, and a reduction in proliferation due to a p53-dependent induction of senescence. Furthermore, depletion of PYGL was associated with markedly impaired tumorigenesis in vivo. Finally, metabolic analyses indicated that glycogen degradation by PYGL is important for the optimal functioning of the pentose phosphate pathway. Collectively, this study shows the contribution of two important pathways to the metabolic adaptations induced by hypoxia.

No description available.

Several research groups have applied elevated hydrostatic pressure to ONH astrocytes cultured on a rigid substrate as an in vitro model for glaucoma. These studies have shown significant biological effects and this hydrostatic pressure model is now becoming generally accepted in the ophthalmic community. However, since the applied pressures were modest the finding of significant biological effects due to pressure alone is surprising. We hypothesized that the application of hydrostatic pressure as described in these studies also altered gas tensions in the culture media. Our goal was to design equipment and carry out experiments to separate the biologic effects of pressure from those of hypoxia on cultured astrocytes. We designed equipment and carried out experiments to subject cultures of DITNC1 astrocytes to the four combinations of two levels of each parameter. We explored the morphology and migration rates of astrocytes, but observed no significant change in any of these properties.

Cytochrome c oxidase (COX) is complex IV of the electron transport system, and catalyzes the reduction of molecular oxygen to water. It possesses ten nuclear-encoded subunits, the largest of which is COX4. Bayesian analysis suggests the isoform pair for this subunit arose early in vertebrate evolution, and tissue distribution of the COX4 paralogs is similar in mammals and teleosts: COX4-1 is ubiquitously transcribed while COX4-2 is present in large amounts only in brain and respiratory tissue. This subunit is of interest due to its apparent sensitivity to oxygen. During hypoxia, transcription switches from COX4-1 to COX4-2 in some mammalian tissues. However, questions remain about the regulation of this response as well as its pervasiveness across vertebrates. I investigated these uncertainties by measuring the transcriptional response of the COX4 paralogs to hypoxia in a variety of vertebrate models, and assessing the hypoxic induction of putative oxygen-responsive elements (HRE1, HRE2, and ORE) from candidate vertebrate species in a transfection experiment. I also examined the conservation of key elements of the COX4-2 gene and polypeptide in vertebrates. It was found that the hypoxia-responsiveness of COX4-2 may not be vital to the cellular response to hypoxia. COX4-1 transcripts remained in excess during hypoxia in all of the vertebrate models used with the exception of western painted turtle (Chrysemys picta), where COX4-2 transcripts remained in excess during control and hypoxic treatments. Only the HRE2 element from human COX4-2 was activated with hypoxic exposure, yet this along with the other features of the gene and polypeptide were not well conserved across mammals, and nearly absent outside of this lineage. These results provide evidence that COX4-2 may respond to hypoxia in only select few mammalian tissues, or that the function of this gene is not related to the cellular hypoxic response. / Thesis (Master, Biology) -- Queen's University, 2012-11-25 20:51:59.419

Cancer develops in many organs and tissues in the body through genetic and environmental modifications to acquire the hallmarks of cancer. The hallmarks of cancer allow the cells to become malignant and progress to a tumorigenic state. It has previously been shown in various carcinomas that HIF-2a, a key component in hypoxia adaptation, has a role in autonomous growth, the first hallmark of cancer. Ovarian cancer is the most lethal of the gynecological malignancies and accounts for 3% of new cases in women annually but is the fifth most common cause of death due to cancer. Here, it is shown in two ovarian carcinoma cell lines that HIF-2a is involved in in vitro and in vivo growth. It is also shown that the effect of HIF-2a is due to its role in autonomous growth and not vascularization with the use of in vitro spheroids. From recent findings in the laboratory the oxygen-stimulated translation initiation complex was discovered and HIF-2a is one of its components. In the absence of HIF-2a there is a downregulation in translation in hypoxia in ovarian carcinoma. This is also seen in a HIF-2a translational target, IGF1R and its downstream signaling pathway, which may be involved in autonomous growth as well as other hallmarks of cancer. Taken together, the data in this thesis presents the importance of HIF-2a in autonomous growth and cancer progression in ovarian carcinoma, as well as verifying its role in translation.

During stress conditions, glucocorticoids are secreted and exert most of their physiological responses by binding to and modulating the transcriptional activity of the glucocorticoid receptor (GR). Once activated, GR can regulate numerous cellular processes including inflammation, development, growth, metabolism and apoptosis. Although glucocorticoids have been used in the treatment of leukaemia for over 50 years, with the molecular mechanisms by which steroids exert their pro-apoptotic effect, the pathways responsible for the development of resistance to glucocorticoid treatment, as well as their role in the programmed cell death in other tissue types have not been precisely defined. Research has demonstrated that glucocorticoid-induced apoptosis requires a transcriptionally active form of GR and is executed by the induction of the intrinsic pathway of apoptosis. In addition, GR is regulated by diverse types of cytotoxic stress; including UV irradiation and hypoxia, which alter the receptor’s transcriptional activity through multiple mechanisms. These include post-translational modifications, subcellular localisation and interaction of the receptor with co-regulator proteins. The aims of this study are to identify novel members of the Bcl-2 family that are regulated at the transcriptional level by GR in both leukaemia and other tissue types where glucocorticoids promote cell survival. In addition, the molecular crosstalk between signalling pathways activated by cytotoxic stress conditions and the mechanisms by which they differentially modulate the apoptotic response will be investigated. Results obtained in this study have identified putative glucocorticoid response elements in the promoters of the BH3-only pro-apoptotic gene NOXA and the anti-apoptotic gene Mcl-1 and confirmed that both NOXA and Mcl-1 are direct GR transcriptional targets. The glucocorticoid-mediated expression of NOXA and Mcl-1 alters their protein-protein interaction pattern, leading to the subsequent destabilisation of Mcl-1 in cell lines that undergo glucocorticoid-induced apoptosis. Investigation into the effects that other cytotoxic stress pathways have on GR function have revealed that serine 226 phosphorylation of GR by JNK occurs in a rapid and transient manner. Phosphorylation has inhibitory effects on the transcription of GR targets in a gene-specific manner, including the differential regulation of NOXA gene expression. During hypoxia, glucocorticoids differentially regulate the GR and HIF-1 target genes, NOXA and Mcl-1, altering the apoptotic response. This study has provided additional insight into the molecular mechanisms that govern glucocorticoid-induced programmed cell death and revealed mechanisms by which glucocorticoids and cytotoxic stress pathways crosstalk, regulating apoptosis.

Studies were undertaken to determine toxicological effects in a model species, Cyprinus carpio L. following hypoxic exposure either alone or in combination with representative heavy metal (i.e. copper; Cu) via a dietary route, at different levels of biological organisation (viz. biochemical, histological and individual level effects). Initially, the validation study of biological responses using a range of concentrations of dietary Cu as a relevant environmental contaminant was carried out (Chapter 3). The results showed a range of biological responses in exposed fish including significant genotoxic response as determined by induction of DNA strand breaks (i.e. the Comet assay) with bacterial enzymes Fpg and Endo-III (for detection of oxidative DNA damage) and reduction in growth rate suggesting the robustness of selected biomarkers. Subsequently, this approach was used initially to determine the biological responses following chronic hypoxic and hyperoxic exposure (Chapter 4). The results suggested that both hypoxic and hyperoxic conditions lead to a range of comparable biological responses. Following relative evaluation of chronic hypoxic and hyperoxic exposures, experiments were carried out to elucidate potential interactive effect of hypoxia in combination with dietary Cu (Chapter 5). The combined exposure of hypoxia and Cu induced a significantly higher level of DNA damage suggesting that DNA damage in fish can serve as a sensitive biomarker for changes in water quality as well as presence of genotoxic chemicals. The final sets of experiment were carried out to determine the biological responses in C. carpio following exposure to chronic hypoxic stress and subsequent recovery in normoxic condition for 7 days. Real-time PCR (qPCR) technology was used to examine the hypoxia inducible Factor-1 α (HIF-1α) gene expression pattern (Chapter 6). The results suggested that the expression levels of HIF-1α in response to hypoxia were significantly higher compared to normoxic controls, a high level of oxidative DNA damage under hypoxia and re-exposure to normoxic condition (i.e. recovery period). This will shed lights for development of adaptive response in higher vertebrates, which could also have significant clinical implications in human health.

Tumour hypoxia has been demonstrated to cause development of an aggressive tumour phenotype and is associated with increased patient mortality and poorer response to treatments such as chemotherapy and radiotherapy. Previous studies have established that hypoxia exists within a nidus of prostate cancer. Based on the importance of the tumour microenvironment, especially hypoxia, in prostate cancer, the major aims of this thesis were to establish: (a) the role of a novel putative survival factor, dermcidin, in prostate cancer survival under hypoxia/oxidative stress; and (b) the effect of nitric oxide-donating non-steroidal anti-inflammatory drugs (NO-NSAIDS), a new class of drugs, on the killing of prostate cancer cells subjected to hypoxia. A wide-range of confirmatory, cellular and molecular biology techniques were employed in this thesis. The PC-3 hormone-insensitive prostate cancer cell line was used for the majority of studies as this cell line represents hormone-independent prostate cancer, treatment of which is currently palliative. Cell incubation at 0.2% oxygen for 48 hours was established as suitable conditions to stimulate the development of the hypoxia response. Upregulation of nuclear hypoxia-inducible factor-1α protein was the main marker used to assess the hypoxia response. Dermcidin messenger RNA production was found to occur in a range of prostate cancer cell lines; was upregulated in cell lines by both hypoxic and oxidative stress; and found to act as a proliferation, survival and pro-invasion factor under hypoxia and oxidative stress in immortalised prostate cancer cell lines. Furthermore, the portion of the dermcidin molecule responsible for the survival advantage was localised to the proteolysis-inducing factor core peptide subunit. However, subsequent analysis of primary cancer samples from prostate cancer patients revealed that dermcidin was not expressed in these tumours, although dermcidin mRNA was identified in analysis of other primary tumours. As such, the role of dermcidin in prostate cancer was not evaluated further in this thesis. Investigation of NO-sulindac (a NO-NSAID drug) in hypoxic PC-3 cells showed that these agents were significantly more pro-necrotic, pro-apoptotic and anti-invasive than traditional, unnitrated sulindac. NO-sulindac was found to downregulate the hypoxia response mounted by PC-3 cells under hypoxia via the Akt signalling pathway. Finally, analysis of the role of NO-sulindac in radiosensitising hypoxic PC-3 cells showed that NO-sulindac caused significant radiosensitisation under normoxia, but particularly in hypoxic conditions. As such, NO-NSAIDs show great promise as neoadjuvant, concurrent and adjuvant treatments for patients with hypoxic prostate cancer. The findings of this thesis illustrate several potential novel strategies for treatment of hormone-independent prostate cancer.

In this study we found that tumour cells can be radiosensitised by targeting the DNA damage response kinases, ATM and ATR. Furthermore, we highlight that Wee1 inhibitors, which are already under the clinical trials need to be further investigated in combination with radiation in the context of tumour hypoxia. In addition, we observed that induction of autophagy using STF-62247 can lead to radiosensitisation of VHL deficient RCC cells. Our studies with the rapamycin analogue temsirolimus, already in the clinic for the treatment of various cancers, can be a potential candidate as a radiosensitiser for RCC cells. Overall, these finding led us to investigate further whether autophagy inducing compounds, which are either in clinic or in clinical trials, can effect the response to radiation. From a panel of candidate drugs which are known to induce autophagy we identified an aminopeptidase inhibitor, CHR-2797. CHR-2797 induces autophagy in the oesophageal cancer cell lines FLO-1 and OE21. Although, our results with CHR-2797 demonstrate it as a potential radiosensitiser, the mechanism of its radiosensitisation needs to be established. Our results from CHR-2797-induced radiosensitisation, further led us to investigate if other aminopeptidase inhibitors have a role in radiosensitisation. Therefore, we selectively screened candidate aminopeptidase inhibitors and identified some promising effects on radiosensitivity.

Several human diseases have been associated with mitochondria! voltage-dependent anion channel-1 (VDAC1) due to its role in calcium ion transportation and apoptosis. Recent studies suggest that VDAC1 may interact with endothelium-dependent nitric oxide synthase (eNOS). Decreased VDAC1 expression may limit the physical interaction between VDAC1 and eNOS and thus impair nitric oxide production, leading to cardiovascular diseases, including pulmonary arterial hypertension (PAH). In this report, we conducted meta-analysis of genome-wide expression data to identify VDAC1 influenced genes implicated in PAH pathobiology. First, we identified the genes differentially expressed between wild-type and Vdac1 knockout mouse embryonic fibroblasts in hypoxic conditions. These genes were deemed to be influenced by VDAC1 deficiency. Gene ontology analysis indicates that the VDAC1 influenced genes are significantly associated with PAH pathobiology. Second, a molecular signature derived from the VDAC1 influenced genes was developed. We suggest that, VDAC1 has a protective role in PAH and the gene expression signature of VDAC1 influenced genes can be used to i) predict severity of pulmonary hypertension secondary to pulmonary diseases, ii) differentiate idiopathic pulmonary artery hypertension (IPAH) patients from controls, and iii) differentiate IPAH from connective tissue disease associated PAH.