Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 144-158). Available also in a digital version from Dissertation Abstracts.

Misonidazole (Ro 07-0582) is a nitroheterocyclic drug which sensitizes hypoxic (oxygen-deficient) cells to the lethal action of ionising radiation. Tumours contain radioresistant hypoxic cells which may limit the usefulness of radiotherapy as a modality of cancer treatment. The use of misonidazole as an adjunct to radiotherapy may improve the local control of such tumours, and clinical trials are in progress. Misonidazole is selectively toxic to hypoxic cells, even in the absence of radiation. This effect may be related to the clinical toxicity of the drug, which limits the dose of misonidazole which may be delivered safely, and, thus, limits the effectiveness of the radiosensitizer. The selective toxicity of misonidazole is believed to be related to its metabolism in hypoxic cells. Reduction of nitroaromatic compounds, such as nitrobenzene, is inhibited by oxygen; thus, reductive activation of misonidazole to a toxic species may explain the selective action of the drug against hypoxic cells. We have studied the reductive chemistry of misonidazole, and its metabolism, using a variety of chemical and in vitro biological techniques. Ascorbic acid (vitamin C) enhances the toxicity of misonidazole to hypoxic Chinese hamster ovary (CHO) cells. This marked enhancement appears to be caused by accelerated drug metabolism in the presence of ascorbate. Chemical reduction of misonidazole by zinc dust yields a mixture of azo-misonidazole and azoxy-misonidazole. These compounds were separated by preparative reversed-phase liquid chromatography, char- acterized chemically, and tested for in vitro biological activity. Azo-misonidazole is almost non-toxic, but azoxy-misonidazole is more toxic than misonidazole itself. Misonidazole was reduced by the xanthine/xanthine oxidase (XO) system, under hypoxia. This enzymatic reduction yielded a single major product, which appears to be hydroxylamino-misonidazole. The same enzyme system also reduces azo- and azoxy-misonidazole. The metabolic transformation of ¹⁴C-misonidazole was studied, using dense suspensions of CHO cells in hypoxia. Misonidazole is converted into several polar products, and binding to acid-insoluble material (presumably macromolecules) was observed. The organic-soluble metabolite fraction contains a compound with identical chromatographic properties to the xanthine/XO product, believed to be hydroxylamino-misonidazole. The significance of these results is discussed in the context of the clinical potential of misonidazole and related drugs as radiosensitizers. The possibility of exploiting hypoxic cytotoxicity as a selective chemotherapy for hypoxic tumour cells is considered. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (M.S.)--University of Toledo, 2007. / Typescript. "Submitted as partial fulfillment of the requirements for The Master of Pharmaceutical Sciences." "A thesis entitled"--at head of title. Bibliography: leaves 53-55.

Local control of tumours by radiotherapy may fail due to the presence of regions of hypoxic cells. Radiosensitizers, such as nitroimidazoles, enhance killing of the resistant cells by ionizing radiation. However, dose limiting side-effects have prevented the attainment of maximum sensitization. The successful chemotherapeutic drug, cis-diamminedichloroplatinum(II) (cis-DDP), and analogues show moderate radiosensitizing effects, possibly because of binding to DNA. A rationale is then to use the DNA binding property of a metal to carry a sensitizer to the target of radiation damage, DNA, thereby improving the radiosensitizing effect while reducing the toxic side-effects of nitroimidazoles. The complex cis-RuCI₂(dmso)₄ was used as a precursor for synthesis of Ru(II)-nitroimidazole complexes because of its anti-tumour and DNA binding activities. A series of Ru(II) complexes of formulation RuCI₂(dmso)₂Ln, where dmso is S-bonded dimethyl sulphoxide, L = a nitroimidazole, and n=1 or 2, has been synthesized and characterized, and their toxicities and radiosensitizing abilities examined in vitro. When L = 2-nitroimidazole or a substituted-2-nitroimidazole, n = 2, but the nitroimidazole ligands dissociate in aqueous medium. With L = the 5-nitroimidazole, metronidazole, n=2, the sensitizing ability of the six-coordinate cis complex was disappointing with sensitizer enhancement ratio (SER) of 1.2 in hypoxic Chinese hamster ovary (CHO) cells. A series of 4-nitroimidazoles ligands was then studied. With L = 4-nitroimidazole (4-NO₂-Im), 1-(1' -aziridinyl-2' -propanol)-2-methyl-4-nitroimidazole (RSU-1170), 2-(1,2-dimethyl-4-nitroimidazolyl)-2-aminoethanol (RSU-3083), and 1-methyl-4-nitro-5-phenoxyimidazole (RSU-3100), n=2 and the six coordinate complexes appear to be of all cis geometry. The NMe-4-NO₂-Im ligand (n=1) chelates through the imidazole-N and the oxygen of NO₂ group as evidenced from spectroscopic data. Coordination via the nitrito group is uncommon and other examples involving nitroimidazole ligands have not been reported. For the 1-methyl-5-(2'-thioimidazolyl)-4-nitroimidazole (RSU-3159) ligand (n=1), binding to Ru occurs through the thioether and chelation may occur through the imidazole-NCH₃. In this series of Ru(II)-4-nitroimidazole complexes studied, RuC1₂(dmso)₂-NO₂-Im)₂, 5, was the most effective radiosensitizer (SER = 1.6 at 200 ,μM) and is better than the clinically used misonidazole (SER = 1.3 at 200 μM). In addition, 5 did not sensitize oxic CHO cells. Other Ru-N-substituted-4-nitroimidazole complexes gave SER values of 1.1-1.4 at 100-200 μM. Complex 5 also produced a dose-dependent increase in genotoxic activity (as measured by the in vitro induction of chromosome aberrations in CHO cells), which is similar to that of misonidazole but much less than that of c/s-DDP. Two changes in ancillary ligands and geometry of complexes were also examined: replacement of (i) dmso by tmso (tetramethylene sulphoxide), (ii) C1⁻ by Br⁻. The Ru-nitroimidazole complexes were synthesized from the precursors RuCl₂(tmso)₄ and trans-RuBr₂(dmso)₄. In this series of complexes, only RuCl₂(tmso)₂(4-NO₂-Im)₂, 15, and RuCl₂(tmso)₂(SR-2508), 18, have significantly higher SER values (1.6 and 1.5, respectively) than their corresponding nitroimidazole ligands. The tmso complexes of 2-NO₂-Im derivatives were more stable than the dmso series in aqueous solution with respect to the dissociation of the nitroimidazole ligands, which might be due to the improved lipophilicity of tmso complexes. Complex 18. is suggested to be penta-coordinated from XPS and ir data. The RuBr₂(dmso)₂(4-NO₂-Im)₂ was a less effective sensitizer (SER = 1.3 at 200 μM) than the dichloro analogue which may result from different geometrical structures or different behaviour in aqueous solution chemistry. The enhanced radiosensitizing effect over the corresponding free nitroimidazole ligand observed for complexes 5, 15 and 18 may depend on: (a) the metal's ability to target the sensitizer to DNA; complex 5 does bind to DNA, dissociation of C1⁻ perhaps facilitating the reaction; (b) the increase in reduction potential or (c) an increase in lipophilicity of the nitroimidazole ligand on coordination. However, the enhanced radiosensitization does not result from depletion of non-protein thiols. In the present study, the Ru complexes are less toxic than their corresponding nitroimiazole ligands in vitro. The radiosensitization and toxicity of the complexes 5, 15 and 18 are better than those of the free nitroimidazole ligands and the clinically used radiosensitizer, misonidazole. The data encourage further investigations of the use of transition metal complexes as radiosensitizers to combat the hypoxic tumour cells. [Formula Omitted] / Science, Faculty of / Chemistry, Department of / Graduate

Thesis (Ph. D.)--University of Chicago, Dept. of Radiology, August 2000. / Includes bibliographical references. Also available on the Internet.

It is well established that many solid tumours are heterogeneous with respect to oxygenation, and contain regions of hypoxic cells, which due to their inherent resistance to ionizing radiation, limit the success of radiotherapy. Numerous chemicals and drugs have been investigated over the past few decades as potential radiosensitizers. The most notable of these being the organometallic compound, cis-diammine dichloroplatinum(II). The clinical success of this drug led to the synthesis of other types of organic cytotoxic metal-containing drugs. Prof. J.C. Swart from the University of the Orange Free State supplied seventeen novel iridium, ferrecenium and rhodium complexes, which I screened for cytotoxic activity against the CHO cell line. The two most cytotoxic complexes namely, [Rh(fctca)(cod)] and [Rh(fctfa)(cod)], were tested for radiosensitizing potential against aerobic and hypoxic CHO cells in the presence of an 8 MV photon beam by the MTT assay adapted to our laboratory conditions. The ferrocene betadiketones co-ordinated to them, Hfctca and Hfctfa and the Ir compliment of [Rh(fctfa)(cod)] namely, [Ir(fctfa)(cod)] were also assessed by the MTT assay. Interestingly, neither the ferrocene nor the iridium complexes showed noteworthy sensitization, which suggests that the rhodium is responsible for the efficacy observed. The radiosensitizing potential of the most active complex, [Rh(fctfa)(cod)] and cisplatin were also confirmed by the use of the more traditional clonogenic assay. Not only did the MTT assay deliver results comparable to the clonogenic technique, but one of the complexes [Rh(fctfa)(cod)] showed radiosensitizing potential against hypoxic CHO cells, equal to that of cisplatin. The rhodium complex, [Rh(fctfa)(cod)] was also tested for radiosensitization properties against the CHO cell line in the presence of a p(66)/Be neutron beam. Results indicated that [Rh(fctfa)(cod)] sensitizes cells to radiation possibly by inhibition of cell inactivation mechanisms that are normally associated with repairable damage. Consequent work done on the flow cytometer where direct DNA damage after irradiation (8 MV photon beam) and drug treatment, was assessed on aerobic CHO cells by a technique adapted to our laboratory showed no significant increase in the forward angle scattered light (FSC) parameter which is an indication of radiation induced strand breaks. Furthermore, [Rh(fctfa)(cod)] showed a significantly greater increase in the side angle scattered light (SSC) parameter, which is an indication of the binding ability of the complex, compared to cisplatin, after treatment with different concentrations of the drugs. Results obtained from enumerating micronuclei frequencies after drug treatment and radiation confirmed that both cisplatin and [Rh(fctfa)(cod)] are more active under hypoxic conditions, with [Rh(fctfa)(cod)] responsible for more micronuclei per binucleated cell. In conclusion, I have established that [Rh(fctfa)(cod)] has a cytotoxic activity comparable to that of cisplatin and that it sensitizes preferentially hypoxic CHO cells to radiation in the clinically relevant dose range. I have also identified the probable action by which [Rh(fctfa)(cod)] sensitizes CHO cells to radiation as being inhibition of repair capacity. Furthermore, results suggest that this complex binds covalently to DNA base pairs. The complex [Rh (fctfa) (cod)] , has so far proven to possess interesting radiosensitizing potential which must be exploited for eventual therapeutic benefit. / Dissertation (MSc (Medical Physics))--University of Pretoria, 2007. / Medical Oncology / unrestricted

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Breast Cancer remains one of the world’s leading causes of cancer related deaths amongst women. Its treatment has evolved from invasive, highly toxic therapies to treatments that possess a higher specificity and a lower toxicity. Despite improvements in overall survival, many patients do not benefit from these agents because of acquired and/or inherent tumour resistance, which could hinder treatment efficacy. Novel treatment strategies are, therefore, warranted to address these challenges and to significantly improve patient responses. Inhibiting components of the HER-2 signalling pathway can significantly sensitise breast cancer cells to low doses of ionising radiation. The objective of this study was to inhibit key molecular targets of the human epidermal growth factor receptor 2 (HER-2) signalling pathway and expose breast cancer cell lines to doses of radiation, so as to establish potential therapeutic targets that may be amenable to combined modality therapy, and formulate a cocktail of inhibitors to evaluate its radiosensitising capability. This study found that pre-treatment of two breast cancer cell lines (MDA-MB-231 and MCF-7) with a HER-2 inhibitor (TAK-165) had little or no effect on radiosensitivity. However, a radiation enhancement was observed when these cells were pre-treated either with BEZ235, a dual inhibitor of phosphoinositide 3-kinase (PI3K) and mammalian target for rapamycin (mTOR), or a cocktail of TAK-165 and BEZ235. These findings suggest that concurrent inhibition of HER-2, PI3K and mTOR during radiotherapy might improve treatment response of breast cancer patients. / AFRIKAANSE OPSOMMING: Borskanker bly steeds een van die leidende oorsake van sterftes aan kanker in vrouens. Behandeling het vanaf ‘n ingrypende, hoogs toksiese terapie verander na ‘n regimen wat hoogs spesifiek met ‘n laer toksisiteit is. Nogtans trek baie pasiënte geen voordeel uit hierdie nuwe benadering nie, omdat inherente en/of verworwe tumorweerstand daarteen suksesvolle uitkomste verhoed. Nuwe behandelingstrategieë is dus nodig om hierdie uitdagings te bekamp en om resultate in pasiënte aansienlik te verbeter. Inhibisie van komponente van die HER-2-seinoordragkaskade kan borskankerselle gevoelig maak vir lae dosisse van geïoniseerde bestraling. Die doelwit van hierdie studie was om sleutelteikens in die HER-2- seinoordragkaskade te inhibeer en om borskankerselle daarna aan bestralings dosisse bloot te stel. Sodoende word potensiële terapeutiese teikens wat vatbaar is vir gekombineerde modaliteitsterapie geïdentifiseer, waarna ‘n kombinasie van inhibitore geformuleer en geëvalueer kan word ten opsigte van hulle kapasiteit om gevoeligheid vir bestraling te verhoog. Die studie bevind dat voorbehandeling met ‘n HER-2-inhibitor (TAK-165) van borskankersellyne (MDA-MB-231 en MCF-7) min of geen invloed gehad het op stralingsensitiwiteit nie. ‘n Stralingsversterking is egter geïdentifiseer toe die selle vooraf behandel is met óf BEZ-235, ‘n tweevoudige inhibitor van fosforinositied 3-kinase (PI3K) en soogdierteiken vir rapamisien (mTOR), óf ‘n mengsel van TAK-165 en BEZ-235. Hierdie bevindinge suggereer dat gelyktydige inhibisie van die HER-2- seinoordragkaskade, PI3K en mTOR gedurende stralingsterapie moontlik die uitkoms in borskankerpasiënte kan verbeter.

Thesis (Ph. D.)--Ohio State University, 2006. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2007 Apr 14

Radiotherapy is second only to surgery in the curative management of patients with cancer, and yet the molecular mechanisms that determine the sensitivity of tumours to radiation remain largely unclear. A high-throughput radiosensitivity screening method based on clonogenicity was developed and a siRNA library against kinase targets was screened. The gold standard colony formation endpoint was chosen for determining reproductive cell death after radiation treatment, since effects on proliferation often do not reflect survival. Thiamine pyrophosphokinase-1 (TPK1), a key component of Vitamin B1/thiamine metabolism, was identified as a target for radiosensitisation. TPK1 knockdown caused significant radiosensitisation in cancer but not normal tissue cell lines. Other means of blocking this pathway such as knockdown of thiamine transporter-1 (THTR1) or treatment with the thiamine analogue pyrithiamine hydrobromide (PyrH) caused significant tumour specific radiosensitisation. There was persistent DNA damage in cells irradiated after TPK1 and THTR1 knockdown or PyrH treatment. Thus this screen allowed the identification of thiamine metabolism as a novel radiosensitisation target that affects DNA repair. Short-term modulation of thiamine metabolism could be a clinically exploitable strategy to achieve tumour specific radiosensitisation. Three additional genes, signal recognition particle-72 kDa (SRP72), glycogen synthase 3-beta (GSK3β) and MAP/Microtubule Affinity-Regulating Kinase 2 (MARK2) were also investigated. Knockdown of these genes radiosensitised both tumour and normal tissue cell lines and expression of two of them, GSK3β and SRP72 were found to be associated with poor recurrence-free survival in early breast cancer patients.

Radiotherapy is a major treatment modality used to treat muscle-invasive bladder cancer, with patient outcomes similar to surgery. However, radioresistance is a significant factor in treatment failure. Cell-free extracts of muscle-invasive bladder tumors are defective in nonhomologous end-joining (NHEJ), and this phenotype may be used clinically by combining radiotherapy with a radiosensitizing drug that targets homologous recombination, thereby sparing normal tissues with intact NHEJ. The response of the homologous recombination protein RAD51 to radiation is inhibited by the small-molecule tyrosine kinase inhibitor imatinib. Stable RT112 bladder cancer Ku knockdown (Ku80KD) cells were generated using short hairpin RNA technology to mimic the invasive tumor phenotype and also RAD51 knockdown (RAD51KD) cells to show imatinib's pathway selectivity. Ku80KD, RAD51KD, nonsilencing vector control, and parental RT112 cells were treated with radiation in combination with either imatinib or lapatinib, which inhibits NHEJ and cell survival assessed by clonogenic assay. Drug doses were chosen at approximately IC40 and IC10 (nontoxic) levels. Imatinib radiosensitized Ku80KD cells to a greater extent than RAD51KD or RT112 cells. In contrast, lapatinib radiosensitized RAD51KD and RT112 cells but not Ku80KD cells. Taken together, our findings suggest a new application for imatinib in concurrent use with radiotherapy to treat muscle-invasive bladder cancer. Cancer Res; 73(5); 1611-20. (c)2012 AACR.