The photophysical properties of porphyrin and phthalocyanine photosensitisers for the photodynamic therapy of cancer (PDT), sterically hindered porphyrins and a novel chemotherapeutic agent (Mitoxantrone), have been investigated using the time resolved techniques of laser flash photolysis, pulse radiolysis, fluorescence and near infrared luminescence. Current topics of interest in PDT and phototherapy of neonatal jaundice are the use. of 5-aminolaevulinic acid to stimulate the formation of protoporphyrin IX for treatment of tumour and skin lesion, and the formation of the potentially cytotoxic species, lumirubin, by green light irradiation of infants with hyperbilirubinemia. Continuous irradiation, and steady state techniques have been used to study the photoproduct, and singlet oxygen formation, by these systems. The effect of environment on the photophysical properties of haematoporphyrin has been studied. It was found that under certain conditions the triplet state lifetime and relative quantum yield are enhanced. The results of this have been used to suggest an explanation for enhanced singlet oxygen yields in such environments. A novel water soluble phthalocyanine with no peripheral substitution, but the axial ligands conferring the desired property, has been studied and found to have a triplet state lifetime in aqueous solution of approximately O.7J.1s, and a singlet oxygen yield of zero. Yet this phthalocyanine has been reported to be efficient sensitizer for the photodynamic therapy of cancer. This supports current discussions that mechanisms other than type II (singlet oxygen) could be of significance in the destruction of tumours.

No description available.

The effect of heat on the phosphoinositide signalling pathway was investigated in CHO-K1 cells and WRK-1 cells. Heat caused a decrease in 1,2-diacylglycerol (1,2- DAG) levels but did not have any effect on monoacylglycerol (MAG) levels in both cell types. On the other hand, an increase in triacylglycerol (TAG) level was observed in both cell lines. This heat-induced decrease in 1,2-DAG level in WRK-1 cells was not due to an increase in turnover rate of 1,2-DAG to phosphatidic acid (PA) since the decrease in 1,2-DAG was not affected when cells were heated in the presence of die DAG kinase inhibitor, dioctanoylethylene glycol (diC(_8)EG). The increase in TAG level may be due to a rapid, he at-induced increase in TAG synthesis from 1,2-DAG, thus leading to decreased levels of 1,2-DAG. Heat also led to an increase in inositol bisphosphate (InsP(_2)) and inositol trisphosphate (InsP(_3)) but not inositol monophosphate (InsP(_1)) or higher inositol phosphate (InsP(_4/5/6)) levels in WRK-1 cells. The increase in InsP(_2) and InsP(_3) was both temperature and heating time-dependent. A transient increase in InsP(_3) was observed at 11 min, and did not require extracellular calcium nor did it depend on the heat-induced increase in cytosolic free calcium ([Ca(^2+)]i). The magnitude of the heat- induced increase in InsP(_3) was comparable to that obtained upon incubation in AIF(_4). Stimulation of WRK-1 cells with vasopressin at 45ºC distorted the pattern of inositol phosphate metabolism. However, the vasopressin-sensitive phosphoinositide signalling pathway remained intact after a severe heat shock, sufficient to lead to the death of greater than 95% of the cells. Heat also led to an increase in [Ca(^2+)]i in WRK-1 cells which came primarily (solely?) from calcium influx from the extracellular medium. This influx was unlikely to occur through voltage-gated calcium channels because calcium channel blockers, such as La(^3+) and nifedipine, did not inhibit the heat-induced elevation in [Ca(^2+)]i. This heat-induced increase in [Ca(^2+)]i may have a protective role in hyperthermic cell death.

No description available.

The aim of this study was to investigate the DNA damaging abilities of SR 4233 (Tirapazamine) and a range of congeners. These are novel benzotriazine-N-oxide compounds of potential clinical importance in the treatment of hypoxic tumours. The studies used a viral double transfection assay which involved exposing purified $X174 DNA to the compounds under oxic, hypoxic and hypoxic reductive conditions and subsequently transfecting the DNA into E. coli AB1157 and E. coli C. Experiments under reductive hypoxia were carried out between pH 4-7 to establish if a reduction product required protonation for the DNA damage process. The biologically relevant druginduced DNA damage was assessed by utilising a range of E. coli mutants deficient in specific DNA repair genes, the products of which are involved in excision, recombination and SOS repair. Viscometry was used to assess the effects of various druginucleotide ratios and the ionic strength of the buffer on the DNA damage caused. DNA has been confirmed as a target for the action of the benzotriazine-N-oxides. SR 4233, the lead compound, was found to be the most active of all the compounds tested. Damage was only induced upon reduction of the compounds and there was no significant damage to DNA under oxic or hypoxic conditions. SR 4233 exhibited increased DNA damage at acid pH indicating that the radical anion responsible for DNA damage has a requirement for protonation. The damaging species is probably the 1-electron reduction product of SR 4233 as SR 4317 and SR 4330, the 2-electron and 4-electron reduction products respectively, caused significantly less DNA damage under hypoxic reductive conditions. There is also evidence that the disproportionation reaction, which can lead to radical production without DNA damage, may not be an important reaction for SR 4233 bioactivation. Studies with repair-deficient mutants of E. coli indicated that SR 4233 is capable of inducing DNA damage which is recognised and repaired by the ABC excinuclease complex. However, the major damage caused is recognised and repaired by the gene products of the xth and nth mutants. This indicates that reduced SR 4233 induces primarily pyrimidine based oxidative damage in DNA.

Oncolytic viruses (OVs) are an emerging cancer therapy that use an oncotropic virus to selectively infect and kill cancer cells, as well as stimulate long-lasting anti-tumor immune responses. In order to achieve high therapeutic efficacy, OVs need sufficient replication within the tumor tissue to mediate these effects. However, OV’s infectivity varies between different tumors and the host’s immune system can rapidly clear the virus, hampering treatment efficiency. Oncolytic virus sensitizers are chemical compounds that specifically enhance OV’s infectivity and efficacy. In our lab, I found that treatment of various cancer cell lines with BI-D1870, a pan-RSK (ribosomal S6 kinase) inhibitor, resulted in augmented Herpes Simplex Virus-1 (HSV1) and Vesicular Stomatitis Virus (VSVΔ51) infectivity. I also demonstrated that the effects of BI-D1870 on viral infection are virus-specific, and that RSK inhibition is not the primary target causing the enhancement of HSV1 and VSVΔ51 infection. Finally, BI-D1870 structural analogs were generated in an attempt to enhance the efficacy and selectivity of BI-D1870-based OV sensitizers. One of the analogs synthesized, KA-019, showed an improvement in the augmentation of OV infection over BI-D1870. As a genetically engineered strain of HSV1 has been approved by FDA for treatment of melanoma, the results of my project propose a novel viral sensitizer to improve viral replication within tumour cells with the hope of improving therapeutic efficacy.

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No description available.

No description available.

Poly (adenine diphosphate-ribosyl)ation of a variety of nuclear proteins is the immediate response in most eukaryotic cells to DNA strand breaks. This modification is catalysed' by the chromatin bound enzyme Poly (ADP-ribose) polymerase (PADPRP). The enzyme is thought to be intimately involved in several cellular processes including cell differentiation, gene expression, transformation of oncogenes and repair of DNA damage. As a consequence, inhibitors of PADPRP are able to potentiate the cytotoxicity of many anti-tumour agents whose actions include DNA damage, and as such these inhibitors are potential resistance-modifying agents for use in cancer therapy. In order to probe the active site of the enzyme a series of potential mimics (i) of NAD' were synthesised from readily available 3-hydroxybenzamide. The conformation of the amide bond is considered to be important and for increased potency the amide carbonyl should be anti with respect to the nicotinamide C2-C3 bond. Based on this reported observation a series of novel inhibitors were synthesised, which include a series of benzoxazole-4-carboxamide analogues( ii) and 8-hydroxy-2- (substituted)quinazolin-4-one analogues (iii). The structure of the benzoxazole analogues are such that the amide is anchored into the required conformation by an intramolecular hydrogen bond between the carboxamide N-H and the benzoxazole nitrogen. The benzyloxybenzamide analogues had comparable potency to 3-hydroxybenzamide against PADPRP. However, both the benzoxazole-4-carboxamide and 8-hydroxy quinazolin-4-one series of analogues exhibited outstanding inhibitory activity against PADPRP. The most potent of the benzoxazole-4-carboxamide analogues (ii, R= phenyl) had an IC50 value of 2.1 p. M. Exceptional PADPRP inhibitory activity was observed in the 8-hydroxyquinazolin-4-one (iii) series, where R= CH3 (IC50 = 0.4 μ M) and R= 4-nitrophenyl (IC50 = 0.2 μM). Further in vitro evaluation has shown that 8-hydroxy-2-methylquinazolin-4[3H]-one potentiates cytotoxicity in temozolomide treated cells.