creator Zhang, Honghong advisor Xiang, Jialing Bax is a pro-death tumor suppressor in the Bcl-2 family, and is frequently mutated in microsatellite instable tumors, especially Hereditary Non-Polyposis Colorectal Cancer (HNPCC). The loss of apoptotic Bax contributes to tumor development and chemoresistance. We recently uncovered that the combination of a Bax microsatellite mutation with a specific alternative splicing generated a unique Bax isoform (BaxΔ2) in Bax-negative cells. Similar to the prototype Baxα, BaxΔ2 is a potent pro-apoptotic molecule. However, the pro-apoptotic mechanism, therapeutic implication, and tumor tissue distribution of BaxΔ2 protein remain elusive. In this thesis research, we isolated and analyzed isogenic sub-cell lines that represent different Bax microsatellite statuses from colorectal cancer cells. We found that the colon cancer cells harboring Bax microsatellite G7/G7 alleles produced low levels of endogenous BaxΔ2 transcripts and proteins. BaxΔ2-positive cells were selectively sensitive to a subgroup of chemotherapeutics in comparison with BaxΔ2-negative cells. Different from other Bax isoforms, which mostly act through targeting mitochondria, BaxΔ2 recruited caspase-8 into the aggregates for activation, and consequently induced cell death independent of the mitochondrial pathway. Furthermore, the distribution of BaxΔ2 protein was mostly found in well-differentiated epithelial cells in primary colon tumor tissues or in primary squamous buccal cells, which contain Bax G7 mutation. However, not all cells harboring the Bax G7 mutation had a detectable level of BaxΔ2 proteins. These data suggest that, similar to Baxα, BaxΔ2 protein is pro-apoptotic, but not toxic to normal cells; expression of BaxΔ2 protein restores apoptotic program in Bax negative cells via a non-classical signaling pathway. Importantly, BaxΔ2 may provide a selective chemotherapeutic advantage for certain Bax-negative colon tumors. Submitted by Erma Thomas (thomase@iit.edu) on 2015-05-14T17:20:43Z No. of bitstreams: 2 Thesis-Honghong Zhang.pdf: 3150177 bytes, checksum: c77ede7e927834163e5f9bba33ab22ff (MD5) Signed Cover Page-Honghong Zhang.pdf: 215453 bytes, checksum: ccab8e5003a6c232a0bb83187d919142 (MD5) Made available in DSpace on 2015-05-14T17:20:43Z (GMT). No. of bitstreams: 2 Thesis-Honghong Zhang.pdf: 3150177 bytes, checksum: c77ede7e927834163e5f9bba33ab22ff (MD5) Signed Cover Page-Honghong Zhang.pdf: 215453 bytes, checksum: ccab8e5003a6c232a0bb83187d919142 (MD5) Previous issue date: 2014-07 Ph.D. in Biology, July 2014 2014 2014-07 http://hdl.handle.net/10560/3411 en Dissertation born digital application/pdf In Copyright http://rightsstatements.org/page/InC/1.0/ Restricted Access BIOL / Biology Illinois Institute of Technology Affiliated department