Glioma, an infrequent form of cancer, continues to confer poor prognosis despite advances in current therapeutic techniques. This research identified the presence of hsp90a in glioma and investigated its potential as a diagnostic or therapeutic marker. l-Isp90ct is emerging as an encouraging target for cancer therapy attributed to the integral role it plays in the stabilisation and folding of proteins crucial for normal cellular homeostasis and its subsequent involvement in tumorigenesis. Modulation of Hsp90 as a drug target offers the possibility of simultaneously impeding numerous signaling pathways implicated in the development and progression of glioma and has thus far shown evidence of clinical activity in patients with melanoma, breast and prostate cancer. With this in mind, the primary focus of this thesis was to evaluate the association between hsp90a expression in glioma versus the normal brain cell lines and tissues. Results from this study showed that hsp90a was transcribed at a higher level in glioma cell lines and tissues and absent in normal brain cell lines and tissues. This suggests that the expression level of hsp90a may be a distinguishing marker between glioma and normal brain tissue and furthermore, in the subset of glioma cell lines examined, an increase in expression of hsp90cz appeared to correlate with a decrease in malignancy. As modulation of a single target is likely to be insufficient due to the development of resistance, emphasis of research has focused on a combinational attack for optimal therapy. Simultaneous silencing of hsp90a, at transcriptional (siRNA) or post-translational level (RA), and subsequent subjection to a chemotherapeutic drug appeared to be more effective than chemotherapy alone. This increase in chemosensitivity could be attributed to the downregulation of hTERT caused by inhibition of l-Isp90c&. The research has led to two novel findings; 1) The identification of hsp90a in glioma 2) Silencing hsp90a led to approximately 13-fold reduction of TMZ in tissues for the achievement of the same effect with TMZ alone 3) Has led to the following two publications: a). Shervington, A., Cruickshanks, N., Wright, H., Atkinson-Dell, R., Lea, R., Roberts, (3 and Shervington, L. (2006) Glioma: What is the role of c-Myc, Hsp90 and telomerase? MoL celL Biochem. 283, 1-9. b). Shervington, A., Cruickshanks, N., Lea, R., Roberts, (3., Dawson, T and Shervington, L. (2008) Can the lack of Hsp90a protein in brain normal tissue and cell lines, rationalise it as a possible therapeutic target for gtiomas. Cancer Invest. 16, 900-904. As silencing of hsp90a and the subsequent downregulation of /ITERT exhibited a correlation with chemosensitivity, it has further emphasised the need for individual characterisation of tumours to highlight the most effective therapeutic option and improve patient survival rates for glioma.

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The growth of bacteriophage HK75 is inhibited by specific mutations in the zinc binding domain of the host RNA polymerase beta prime subunit. It shares this rare property with bacteriophage HK022 and other phages that use RNA mediated antitermination to promote early gene expression. Recent genomic analysis of HK75 and HK022 has confirmed the relatedness of these two phages and place HK75 in the lambdoid family of bacteriophages. Lambdoid phages are temperate and can adopt a lytic or lysogenic lifestyle upon infection of a suitable host. However, HK75 only forms clear plaques and thus appears to be defective in its ability to form lysogens. Based on published analyses of other lambdoid phages, a clear plaque phenotype is commonly due to a mutation in one of 5 phage genes: cI, cII, cIII, int, xis or the phage repressor DNA binding sites. To determine which mutation is responsible for the clear plaque phenotype of HK75, we cloned the cI and cIII genes and assayed their activities. The HK75 cI gene clone prevented super-infection by HK75. This result demonstrated repressor functionality and thus the clear plaque phenotype cannot be due to a mutation in the HK75 cI gene. Several amino acid differences were noted between the HK022 and HK75 CIII proteins. To determine if the clear plaque phenotype was due to mutations in the HK75 cIII gene, we cloned it into an expression vector. Only under conditions of cIII gene overexpression were lysogens of HK75 recovered. The phage CIII protein normally protects CII from proteolysis. Stabilization of CII by mutations in specific host proteases has been shown to suppress a clear plaque phenotype caused by mutations in the cIII gene. When HK75 was plated on a protease deficient strain of E. coli, turbid plaques were formed and lysogens were recovered. These results support the idea that the clear plaque phenotype of HK75 is due to a defect in the expression of the phage cIII gene.