Advisory Committee Chair
Jay McDonald
Advisory Committee Members
Susan Bellis
Michael Fallon
John Mountz
Selvarangan Ponnaazhagan
Kevin Roth
Document Type
Dissertation
Date of Award
2008
Degree Name by School
Doctor of Philosophy (PhD) Heersink School of Medicine
Abstract
Cholangiocarcinoma, a fatal tumor arising from biliary epithelium, has very poor 5-year survival rate due to lack of early diagnosis and effective therapies. Induction of the Fas-mediated apoptosis is a promising therapeutic target in this tumor. Studies from our group and others have indicated that Fas-expression correlates inversely with disease progression and that CaM-antagonists induce apoptosis in cholangiocarcinoma cells in a Fas related manner. Further, we reported a direct and dynamic interaction of CaM and Fas and that CaM is recruited into the Fas-stimulated death inducing signaling complex (DISC), suggesting a cross talk between Fas and CaM pathways. The studies presented in this dissertation were designed to characterize the role of CaM in Fas-induced signaling and identify potential therapies for cholangiocarcinoma. Fas-mediated apoptosis typically involves the recruitment of an adapter protein, FADD, caspase-8 and/or c-FLIP to form the DISC. Screening for the CaM binding proteins in the DISC, we demonstrated a Ca++-dependent direct interaction between CaM and FLIPL, but not the other DISC components, FADD, caspase-8 and FLIPS. Fas activation induced a Ca++ dependent increase in CaM-FLIP binding which was inhibited by CaM-antagonist, trifluoperazine (TFP), with concurrent inhibition of ERK ii phosphorylation and increased FLIP binding with ubiquitin. The CaM binding region was identified between aa 197-213 on FLIPL. Over expression of FLIPL decreased the sensitivity of cholangiocarcinoma cells to Fas and CaM-antagonist-induced apoptosis and increased their tumorigenicity in nude mice. Deletion of the CaM binding region from FLIPL restored the sensitivity of cholangiocarcinoma cells to Fas and CaM-antagonist-induced apoptosis and decreased their tumorigenicity in nude mice. The CaM-antagonist, tamoxifen (TMX), induced apoptosis in caspase dependent and independent manners with concurrent inhibition of pAKT and FLIP expression in cholangiocarcinoma cells. A combination of TMX and Gemcitabine, a currently used therapy for cholangiocarcinoma, induced more apoptosis than treatment with either agent alone. Thus the results of this dissertation support the concept that the CaM-FLIP binding is an important regulator of Fas- and CaM-antagonist-induced apoptosis and that it may provide a novel therapeutic target for cholangiocarcinoma. Further the CaMantagonist, TMX, may be used alone or in combination with Gemcitabine or other antineoplastic compounds as a therapy for cholangiocarcinoma.
Recommended Citation
Pawar, Pritish Subhash, "Calmodulin Binding To Cellular Flice Like Inhibitory Protein Modulates Fas-Induced Signaling And Tumorigenesis In Cholangiocarcinoma" (2008). All ETDs from UAB. 3781.
https://digitalcommons.library.uab.edu/etd-collection/3781