TRAIL has been widely investigated as an anti-cancer agent due to its high efficacy in vitro and its safety to normal cells. However, TRAIL-based agents only showed modest effect in clinical studies because of TRAIL resistance. In addition to apoptosis, TRAIL has also been reported to promote pro-survival signalings, cell migration and metastasis. One of the current strategies in the development of TRAIL-based therapeutics focuses on the search of sensitizing agents that help overcome TRAIL resistance without increasing harm to normal cells. / This study reports a novel combination of TRAIL and 4-methylumbelliferone (4-MU) which can kill HeLa cells and HepG2 cells synergistically without cytotoxicity to Hs68 non-tumorigenic cells. This combination also effectively inhibited cancer cell proliferation and potentiated apoptosis by accumulation of tBid, down-regulation of anti-apoptotic proteins and inhibition of Akt. More importantly, 4-MU could suppress the recovery of HeLa cells from TRAIL-induced apoptosis, a process previously implicated to be associated with cancer relapse and tumor heterogeneity. This study has provided solid evidences substantiating further research on TRAIL-4-MU combination. / 腫瘤壞死因子相關凋亡誘導配體 (TRAIL) 在體外實驗中有良好抗癌作用，且不會傷害正常細胞，使之得到廣泛研究，成為近年熱門的新抗癌分子。然而TRAIL 在臨床實驗中並沒有顯著抗癌功效，一般認為人體腫瘤細胞對TRAIL 具有耐藥性。研究文獻亦指出，除了細胞凋亡外，TRAIL亦會誘發細胞存活機制、促進細胞移行及癌細胞轉移。目前，對於TRAIL相關藥品抗癌作用的研究有幾個大方向，其中之一就是尋找良好的增敏分子。良好的增敏分子應能夠增力癌細胞對TRAIL的敏感性，對抗癌細胞對TRAIL的耐藥性，同時不能殺傷正常細胞。 / 本研究揭示了一個全新的抗癌藥物聯合。當TRAIL聯合4-甲基伞形酮(4-MU)能產生協同作用，殺傷HeLa癌細胞和HepG2癌細胞而不會傷害Hs68正常細胞。此組合能有效抑制癌細胞生長，並透過增加tBid蛋白表達、減少抗凋亡蛋白表達及抑制Akt來促進細胞凋亡。更為重要的是，4-MU能抑制HeLa癌細胞自TRAIL誘導凋亡的恢復和逆轉。而癌細胞凋亡逆轉一般被視為與癌症復發及腫瘤多樣性有關。本研究提供了實質證據，支持對TRAIL-4-MU組合的後續研究。 / Wu, Hoi Yan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2015. / Includes bibliographical references (leaves 90-107). / Abstracts also in Chinese. / Title from PDF title page (viewed on 05, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

[Truncated abstract] The pro-inflammatory cytokine tumour necrosis factor (TNF) has a critical role in skeletal muscle atrophy. The catabolic effect of TNF is partially due to abrogation of the anabolic insulin-like growth factor 1 (IGF-1) signalling pathway. However, the precise signalling events that lead to the loss of myofibrillar protein following activation of TNF receptor are unknown. The over arching aim of the study is to determine the mechanisms of by which TNF induces atrophy in differentiated muscles cells. To achieve this aim a series of experiments were performed to: 1) investigate the molecular events that lead to TNF mediated myofibre atrophy, 2) determine to what extent c-Jun N-terminal Kinase (JNK) signalling plays a part in TNF induced myotube atrophy, and in TNF-mediated inhibition of IGF-1 induced hypertrophy, and 3) use inhibitors of JNK to block the catabolic effects of TNF. 1) To investigate the molecular events that lead to TNF mediated myofibre atrophy, the experiments were conducted using C2C12 mouse myotube cultures and primary myotube cultures derived from FVB mice, and transgenic mice which over-express Class 2 IGF-1 Ea in skeletal muscles (IGF:C2). The treatment of mature C2C12 and FVB primary myotubes (respectively at 7 and 4 days after fusion medium) with 10 ng/mL of TNF for 3 days resulted in statistically significant myotube atrophy (decreased mean width). The observed TNF-mediated atrophy has not previously been demonstrated in tissue cultured myotubes. In contrast, addition of IGF-1 (20 ng/ml) to 7 day C2C12 myotubes for 3 days resulted in significant hypertrophy. ... The most suitable inhibitor was TAT-TIJIP and was thus used in subsequent studies. Inhibition of JNK activity by TAT-TIJIP was confirmed indirectly by detecting nuclear translocation of c- Jun, which is a downstream target of phosphorylated JNK. Immunohistochemical analyses showed nuclear localisation and phosphorylation of c-Jun in TNF treated myotubes. Nuclear localisation and phosphorylation of c-Jun was not observed in cultures pre-treated with TAT-TIJIP before TNF treatment, nor in the untreated control myotubes. 3) The use of JNK inhibitors to block the catabolic effects of TNF was tested using C2C12 and primary myotube cultures. Pre-treatment of C2C12 and primary FVB myotubes with the JNK inhibitor TAT-TIJIP, 30 min before TNF administration (for 3 days) prevented myotube atrophy. The mean width of myotubes pre-treated with TATTIJIP prior to TNF treatment closely resembled that of the control myotubes. Administration of TNF in combination with TAT-TIJIP for 3 days to C2C12 myotubes prevented myotube atrophy and unexpectedly resulted in hypertrophy when compared to the mean widths of untreated and TAT-TIJIP treated myotubes. This trend was also demonstrated in the FVB primary cultures. These combined results strongly support the role of JNK in TNF-mediated atrophy. Preliminary studies were carried out in vivo using the mdx mouse model of muscular dystrophy, TAT-TIJIP was administered via intraperitoneal injection to the mice for 3 days at a dose of 10 mg/ml, however the results form this study are inconclusive. These novel observations are of considerable interest to the field of muscle wasting because they demonstrate for the first time TNF-mediated myotube atrophy, the role of JNK in situations of TNF induced muscle atrophy, and explore the use of JNK inhibitors to prevent muscle atrophy.