Molecular mechanisms of the anti-cancer action of schweinfurthins

ii ACKNOWLEDGEMENTS First of all, I wish to express my great gratitude to my graduate mentor, Dr. Raymond J. Hohl, for his encouragement, understanding, support and guidance throughout my graduate career. I would also like to thank all my committee members: for their invaluable discussions, comments and suggestions. In addition, I wish thank the Molecular and Cellular Program for providing a supporting environment and giving me the chance to pursue my scientific goals. Thanks to Paulette Villhauer and Joshua Lobb for their administrative help. discussion, help and support throughout my research career. I am grateful to Dr. Wiemer's lab and Dr. Jeffery D. Neighbors for their design and providing the schweinfurthin analogues for my research. I wish to thank all my friends here who have been together with me through the ups and downs during my life in Iowa. Their help and encouragement keep me moving on along my way of my life. I won't forget our friendship forever. Finally, I want to thank my mother and family members for their endless love and continuous support. They are always by my side, raising me up to make me more than I can be. iii ABSTRACT Schweinfurthins are a family of natural products with significant anti-cancer activities. They were originally identified in the National Cancer Institute (NCI) human 60 cancer cell line screening. The growth inhibition profile of schweinfurthins is distinct from other clinically used anti-cancer agents, indicating that they have a novel mechanism of action or have a previously unrecognized protein target. Previous studies showed that schweinfurthins affect multiple cellular processes in cancer cells. For example, schweinfurthins can alter cytoskeleton organization, induce ER stress and apoptosis, and inhibit the mevalonate pathway. The mevalonate pathway is responsible for the production of isoprenoids and cholesterol, which have been shown to play regulatory roles in the Hedgehog (Hh) signaling pathway. In this study, we found that the Hh signaling pathway in NIH-3T3 and SF-295 cells was inhibited by schweinfurthins. The supplementation of mevalonate and cholesterol partially restored Hh signaling, indicating that schweinfurthins inhibit Hh signaling partially by down-regulating the products from the mevalonate pathway. Interestingly, schweinfurthins in combination with cyclopamine, an inhibitor of the Hh singaling pathway, synergistically decreased cell viability. In order to better understand the underlying mechanism of the anti-cancer action of schweinfurthins, we attempted to identify the protein target of schweifnurthins. Affinity chromatography was performed to pull down the protein …