京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第17820号 / 医博第3818号 / 新制||医||999(附属図書館) / 30635 / 京都大学大学院医学研究科医学専攻 / (主査)教授 富樫 かおり, 教授 伊藤 壽一, 教授 楠見 明弘 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18152号 / 医博第3872号 / 新制||医||1002(附属図書館) / 31010 / 京都大学大学院医学研究科医学専攻 / (主査)教授 小川 誠司, 教授 武藤 学, 教授 戸井 雅和 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Cancer, a global epidemic, is a major cause of morbidity and mortality affecting populations in all nations and regions. Breast cancer (BC) is the second most common cancer in the world and the most fatal malignancy affecting women both in the developed and developing countries. Even with the improvement in overall survival of BC patients due to early detection and advancement with systematic therapy, triple negative breast cancer (TNBC), an aggressive subtype of BC still remains a major challenge as it lacks targetable receptors. Chemotherapy is the main treatment for TNBC. However, de novo and acquired resistance to conventional anticancer drugs is a major limitation and cause of therapeutic failure. Cancer stem cells (CSCs) are believed to be responsible for chemoresistance and tumour relapse. My study demonstrates that hypoxia is involved in the development and maintenance of these CSCs traits in TNBC, as cells grown in hypoxia are significantly resistant to several first line anti-BC drugs. Hypoxia-induced activation of nuclear factor kappa B (NFB) and hypoxia inducible factors (HIFs) also play pivotal roles in chemoresistance. Forced expression of NFB and HIFs by transfection with p65 subunits of NFB and HIF1α and 2α subunits induced CSCs characters and resistance to a range of anticancer drugs in TNBC cell lines. My study also indicated a positive loop between the activation of NFB and HIFs. Therefore development of novel medicine to interfere the pathways of hypoxia and NFB may efficaciously target CSCs and reverse chemoresistance which will be of clinical significance for TNBC treatment. iv Disulfiram (DS) is a commercially available anti-alcoholism drug. Recent studies demonstrate that it is highly cytotoxic in a wide range of cancer types and potentially repurposed as an anticancer drug. The anticancer mechanisms of DS were investigated in this study. The results from my study indicate that the cytotoxicity of DS is copper (Cu) dependent with a biphasic manner. The instant cytotoxic phase is induced by the extracellular reactive oxygen species (ROS) generated by the reaction between DS and Cu. The delayed killing is caused by the complex diethyldithiocarbamate (DDC) and Cu (DDC-Cu), the final product of the reaction. The cytotoxicity of both phases needs the intact DS. However, due to the extremely short half-life of DS in the bloodstream, the anticancer efficacy of DS has been severely hampered in vivo and in patients. Nanotechnology-based drug delivery system is a rapidly evolving and expanding interdisciplinary field involving in an amalgamation of chemistry, engineering, biology and medicine. In the last part of my study, I have successfully encapsulated DS into polymeric micelle (PM) nanoparticles. The half-life of PM encapsulated DS (PM-DS) was extended to over 3 hours in horse serum. The PM-DS showed strong anticancer efficacy. Therefore this nano-enabled DS may be able to translate DS into cancer therapeutics in the future.

The primary focus of this research is the mechanisms of cell death in head and neck squamous cell carcinoma (HNSCC) treatment. These cancers typically originate in squamous cells that line the moist mucosal surfaces of head and neck. HNSCC is commonly treated with a platinum based agent, cisplatin. While the drug does offer strong antitumor effects, its prolonged use often results in tumor-acquired resistance, which limits treatment effectiveness. We have shown that cisplatin treatment induces the expression of a pro-apoptotic BCL-2 family member Noxa, which then initiates caspase- dependent apoptosis through its binding and sequestration of pro-survival protein MCL-1 for its inactivation. Without Noxa induction, cell death is significantly reduced when treating HNSCCs with cisplatin. The objectives of this study are (1) to determine the molecular mechanisms by which Noxa induces cell death in HNSCC cells; (2) to determine the molecular mechanisms of cisplatin-resistance in isogenic HNSCC cell lines. We observed an increase of apoptosis by ectopic expression of Noxa in all HNSCC cell lines tested, but not in immortalized human normal oral keratinocytes (NOK), suggesting that Noxa overexpression is sufficient to induce tumor-specific cell death. Noxa-induced cell death was mediated by BAX and BAK activation. BAK activation was mediated through Noxa binding to MCL-1, but not BCL-XL. Cisplatin- resistant cells induced less Noxa and apoptosis, supporting that Noxa induction is prerequisite for apoptosis induced by cisplatin. Taken together, Noxa induces tumor- specific cell death in HNSCC cells primarily through BAX and BAK activation, which suggests the therapeutic potential of this protein.