Thesis (doctoral)--München, 1983.

Cervical cancer (CECA) and ovarian cancer (OVCA) rank first and third in the number of new cases diagnosed among gynecologic cancers，and chemoresistance severely limits their treatment success. The underlying mechanism of chemoresistance is multi-factorial and partly due to defects in drug-induced apoptosis. Cisplatinum (CDDP) -induced, p53-mediated mitochondrial cell death is controlled by Akt and is a determinant of chemosensitivity in gynecologic cancer cells. Mitochondria dynamics (fusion and fission) are involved in the regulation of mitochondria-mediated apoptosis. The tumor suppressor prohibitin 1 (Phb1) is involved in long from Opa1 (L-Opa1) processing and p53-regulated apoptosis. Whether mitochondrial fusion protein Opa1 and its protease Oma1 as well as Phb1 are involved in the regulation of chemoresistance in CECA and OVCA cells are not known. The overall objective of my research is to increase the current understanding on the regulation of mitochondrial dynamics and on its role in chemoresistance in gynecologic cancer cells. We hypothesize that CDDP induces Phb1 binding to phosphorylated p53 (p-p53) and Bak, resulting in Bak activation and mitochondrial outer membrane permeabilization (MOMP). These responses also induce Oma1-mediated Opa1 processing, mitochondrial fragmentation and apoptosis but are inhibited by high Akt level in chemoresistant cells. Here we present evidence that CDDP induces Oma1 activation, L-Opa1 processing and mitochondrial fragmentation in chemosensitive but not in chemoresistant cells. Silencing p53 expression attenuated CDDP-induced L-Opa1 loss, mitochondrial fragmentation and apoptosis in chemosensitive cells, while reconstitution of p53 in p53-deficient (mutant or null) chemoresistant cells induced Oma1 activation, L-Opa1 processing and changes in mitochondrial dynamics irrespective of the presence of CDDP. In response to CDDP, p-p53 (ser15) dissociates Phb1 from Opa1-Phb1 complex and binds to Bak in chemosensitive but not chemoresistant cells. Inhibition of Akt is required for CDDP to induce L-Opa1 processing, mitochondrial fragmentation and apoptosis in chemoresistant cells. Our study suggests a mechanism that p53 regulates L-Opa1 processing and mitochondrial fragmentation in chemosensitive cells induced by CDDP, while this pathway is suppressed in chemoresistant cells. Dysregulated mitochondrial dynamics may in part be involved in the pathophysiology of CDDP resistance. Inhibiting Akt activity and inducing Opa1 processing may serve as novel therapeutic strategies for these gynecologic cancers.

Thesis (M.Psych.Clin.) - University of Queensland, 2003. / Includes bibliography.

A major challenge in cancer therapy is the emergence of acquired resistance to a wide range of chemotherapeutic drugs with unrelated structures and activities. Possible mechanisms to explain drug resistance are induction of efflux pumps, activation of scavenging pathways and/or changes in the oncogene status of a cell. A number of studies have shown that overexpression of Bcl-2 confers resistance by preventing drug induced apoptosis. In this thesis, Madin Darby canine kidney epithelial (MOCK) cells were used to investigate the relationship between cisplatin resistance and Bcl-2 expression. In our studies overexpression of Bcl-2 was sufficient in preventing apoptosis induced by serum deprivation. However, treatment with varying cisplatin doses did not induce an apoptotic response. Electron microscopy and in situ DNA end labelling experiments show changes distinct from those associated with serum deprivationinduced apoptosis. Survival as assessed by DNA fluorometry and clonogenic assays clearly demonstrate that the overexpression of Bcl-2 fails to protect against the cytotoxic effects of cisplatin in MOCK cells. Our results show that cisplatin induces a form of cell death distinct from apoptosis and suggests that multiple pathways to cell death exist which are differentially regulated in a cell type-specific and stimuli-specific fashion. / Thesis / Master of Science (MS)

No description available.

The aim of this thesis was to develop biodegradable devices loaded with chemotherapy drug. The system is targeted for advanced ovarian cancer treatment through the intraperitoneal (IP) route of administration. Polylactide-co-glycolide (PLGA) was selected as the model biodegradable polymer to produce drug-loaded microsphere, hollow and solid fibres. Copolymer PLGA with three different lactic:glycolic acids ratios; 50:50, 65:35 and 75:25 were used in order to compare their drug loading capacities and in vitro drug release profiles. Cisplatin, a cytotoxic drug with proven activity against ovarian cancer was selected as the model chemotherapy drug. Intraperitoneal administration is often associated with abdominal pain therefore a local anaesthetic, lidocaine, was selected for the purpose of pain relief.

Radio- und/oder Chemotherapie-induzierte Ototoxizität bei Kindern mit Medulloblastom im Alter von 4 bis 21 Jahren, die im Rahmen der Studie HIT 2000 – AB 4 mit postoperativer normofraktionierter bzw. hyperfraktionierter Bestrahlung und anschließender Erhaltungschemotherapie behandelt wurden. / Radiation and/or chemotherapy induced ototoxicity in children with medulloblastoma aged 4 to 21 years treated within the study HIT 2000 - AB 4 with postoperative normofractionated or hyperfractionated radiation and following maintenance chemotherapy.

The DNA-damaging compound, cisplatin (cis-diamminedichloridoplatinum (II)), is a highly successful anti-tumour agent widely used in the treatment of a range of human cancers. Despite the clinical efficacy of cisplatin, its curative potential is largely restricted by the occurrence of drug resistance and several dose-limiting toxic side effects. Attempts to ameliorate these deficiencies have met with limited success. However, it is ultimately hoped that such efforts will benefit from a more comprehensive understanding of the mechanism by which cisplatin elicits tumourspecific cytotoxicity. The overall aim of this project was to further elucidate the mechanism of action of cisplatin. For this purpose, different experimental approaches were employed to examine the interaction of cisplatin with DNA, and the drug???s effect on human gene expression. Firstly, chromatin structures native to DNA in human cells were simulated in vitro via reconstitution techniques. Their effect on cisplatin-mediated DNA damage could then be evaluated. Various cisplatin analogues and other DNA-damaging compounds were also investigated in this model system. Secondly, the transcriptional response of human cells to cisplatin treatment was analysed using microarrays and gene expression profiling techniques. Transcript profiles compiled for cisplatin and its clinically ineffective isomer, transplatin, were compared to establish a possible relationship between compound-specific responses and therapeutic efficiency. To assess the relative influence of individual chromatin elements on cisplatin- DNA interactions, the first part of this study employed the octamer transfer method of nucleosome reconstitution to create a defined experimental construct. Standard footprinting techniques allowed the precise location of two positioned nucleosomes to be established with respect to the DNA sequence. The construct was then subjected to drug treatment and the resulting DNA damage was quantitatively analysed using a Taq DNA polymerase stop assay. At sites of damage, densitometric comparisons between purified and reconstituted DNA were used to evaluate the influence of nucleosomal core proteins on specific drug-DNA interactions. For cisplatin and most of the other DNAdamaging agents studied, this method revealed regions of the construct that were relatively protected from drug-induced damage. These regions corresponded to the sites of the positioned nucleosome cores and indicated that the preferred site of DNA binding for these compounds was in the linker region of the construct. Statistical analyses confirmed the significant level of damage protection conferred by the nucleosome cores and exposed subtle differences between the agents examined. Most prominent among the trends observed, was the negative correlation between compound size and the relative propensity for damaging nucleosomal core DNA. Larger compounds generally displayed a greater tendency to target the linker region of the nucleosomal DNA. In contrast, the access of smaller molecules was not impeded as significantly. In the second stage of the project, the effect of cisplatin on human gene expression levels was described using 19000-gene microarrays and transcription profiling methods. In cultured human cells, cisplatin treatment was shown to significantly up- and down-regulate consistent subsets of genes. Many of these genes responded similarly to treatment with transplatin, the therapeutically inactive isomer of cisplatin. However, a smaller proportion of these transcripts underwent differential expression changes in response to the two isomers. Some of these genes may constitute part of the DNA damage response induced by cisplatin that is critical for its anti-tumour activity. Ultimately, the identification of gene expression responses unique to clinically active compounds, like cisplatin, could thus greatly benefit the design and development of improved chemotherapeutics.

Thesis (Ph.D.) - University of Queensland, 2007. / Includes bibliography.

Being currently the second and potentially becoming the first cause of death in North America, cancer has been the focus of researchers from various areas of science. Chemotherapy is one of the leading treatment options for treating various types of cancer, particularly advanced cancers. Among different chemotherapeutic drugs currently used against cancer, cisplatin (CDDP) is considered as one of the most effective and widely used. Despite being the most successful drug in cancer chemotherapy, cisplatin has some shortcomings that restrict it from being more widely used. More than three decades of intensive research has not yet clearly explained why these shortcomings are associated with cisplatin treatment. Using the advanced “Pump-Probe Femtosecond Time-Resolved Transient Absorption Laser Spectroscopy” technique to study the reaction dynamics of cisplatin at the molecular level, we discovered new findings that make a profound contribution to our understanding of the mechanism of activity of CDDP as a very widely used and effective anticancer drug. By observing the reaction dynamics of cisplatin both in its reaction with electrons in water, and with all four DNA bases, in real time, we shed new light on the issues that have long been elusive for the last three decades. In addition to these two main research goals, we utilized the same methodology to examine the reaction dynamics of transplatin, which currently is not a clinically effective drug, despite being an isomer of cisplatin. In this part we mainly focused on examining the molecular reaction dynamics of transplatin photoactivation caused by UV irradiation. Here, we studied the transplatin reaction with electrons in water as well as with four DNA bases. Results obtained in this thesis work clearly reveal the mechanism underlying the cytotoxicity enhancement of this molecule after it is irradiated by UV radiation. The data obtained by our experiments provide a mechanistic understanding of this cytotoxicity enhancement at the molecular level. As the last goal in our research, we compared the explored reaction dynamics of cisplatin with its clinically ineffective trans isomer, transplatin. We believe that our understanding of one of these isomers, would also contribute to understanding of the other. The methodology we used to examine transplatin was the same as what we used for cisplatin. First, we monitored the possible reactions of transplatin with prehydrated electrons in water. After this, the dynamics of transplatin’s reactions with DNA bases were examined. For the first time, we directly observed the reactions of cisplatin and discovered that its extremely high reactivity with prehydrated electrons happens in an ultrafast process. We also showed the order of reactivity of all four DNA bases with cisplatin and transplatin to be G > A > C > T. Finally, in comparing cis and trans isomers of DDP, we discovered cisplatin to be about 50% more reactive, suggesting why it is much more cytotoxic. In all of these investigations we obtained promising results that revolutionize our understanding of the mechanism of action of cisplatin as a very important drug in current cancer chemotherapy.