Advisor(s)
Jay McDonald
Committee Member(s)
Susan Bellis
Michael Fallon
John Mountz
Selvarangan Ponnaazhagan
Kevin Roth
Document Type
Dissertation
Date of Award
2008
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.
ProQuest Publication Number
ISBN
978-0-549-69735-0
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
