| Melanoma is an aggressive form of cancer, with an increasing incidence rate and high mortality rate for patients with advanced disease. As advances made in melanoma treatment remain unsatisfactory, better drug treatment is being sought. In 1995, betulinic acid, isolated from the stem bark of Ziziphus mauritiana Lam. (Rhamnaceae), demonstrated selective cytotoxicity for melanoma. Potential chemotherapeutic properties are currently being assessed pre-clinically under the Rapid Access to Intervention in Development (RAID) program of the National Cancer Institute. A molecular understanding of the mechanisms of action of betulinic acid will aid its development as a drug to combat melanoma. Betulinic acid induced apoptosis in UISO-Mel-1, cultured human melanoma cells. Investigations conducted to elucidate the apoptotic signaling mechanisms demonstrated the critical role played by reactive oxygen species in activating the MAP kinase pathway and modulating essential apoptotic mitochondrial events, such as Bax dimerization. In addition, signaling cascade was unusual in that it was independent of cytochrome c and caspases.; The second part of the dissertation discusses the development of a high-throughput bioassay using the luciferase reporter gene. Four stably transfected cell lines (ARE-, ERE-, NF-κB-, and PPRE-luciferase) demonstrated satisfactory responses toward their respective stimulants. Further optimization of the bioassay will hopefully yield positive hits when screened for natural products that target specific molecular pathways involved in the carcinogenic process. |
