Most human cancer cells are resistant to apoptosis. Among the major regulators of apoptosis are the Bcl-2 family of proteins. An emerging cancer therapeutic strategy is directly activating the apoptotic pathways by inhibiting the activity of ani-apoptotic Bcl-2 proteins or promoting the function of pro-apoptotic Bcl-2 proteins. However, many of these strategies target the interaction among various Bcl-2 proteins, particularly the interaction between pro- apoptotic and anti-apoptotic Bcl-2 proteins. Due to functional redundancy among Bcl-2 proteins, these approaches are likely effective only on limited tumor types or display non-specific killing activities. As an important pro-apoptotic Bcl-2 protein, Bax s involved in the development of tumors, and Bax activation has been linked to apoptosis in lung tumors. Given that Bax alone is sufficient to initiate apoptosis in almost all apoptotic paradigms, direct activation of Bax by small molecule compounds could induce death of Bax-expressing tumor cells. Our preliminary studies using in silico screening of large chemical libraries identifid a small molecule predicted to bind to the Bax hydrophobic groove. This compound is able to activate Bax, leading to Bax-dependent tumor cell apoptosis and inhibition of mouse tumor growth. The following specific aims are proposed: 1) Examine the mechanisms by which the Bax activator inhibits tumor growth in mice. We will test the ability of the Bax activator to inhibt the growth of transplanted human tumors in mice as well as spontaneous mouse lung tumors. Furthermore, we will investigate whether the active compound acts synergistically with other therapeutic drugs to inhibit the growth of tumors. 2) Improve the ability of Bax activators to activate Bax, induce apoptosis and inhibit tumor growth. Ligand-based analyses will be used to identify potential compounds with greater biological activities and the compounds will be experimentally examined. 3) Investigate the mechanism of Bax activation on biological membranes by the Bax activators. We will use a novel patch-clamp technique combined with biochemical and cell biology approaches to investigate how the Bax activators induce Bax permeation channels on native biological membranes in vitro. We will also study how Bax permeation pore formation is regulated by the anti-apoptotic Bcl-2 protein Bcl-XL. As dysregulation of Bax expression has been implicated in lung tumor development, inducing apoptosis in tumor cells by directly activating Bax holds promise as a novel therapeutic strategy to treat lung cancer patients.
This project is designed to address the question of whether inducing apoptosis by direct activation of the pro- apoptotic protein Bax will be an effective chemotherapeutic treatment for cancer. By carrying out the experiments proposed in this study, we hope to develop agents for the selective activation of Bax as a novel anti-neoplastic strategy.
|Zhao, Guoping; Neely, Aaron M; Schwarzer, Christian et al. (2016) N-(3-oxo-acyl) homoserine lactone inhibits tumor growth independent of Bcl-2 proteins. Oncotarget 7:5924-42|
|FouquÃ©, A; Lepvrier, E; Debure, L et al. (2016) The apoptotic members CD95, BclxL, and Bcl-2 cooperate to promote cell migration by inducing Ca(2+) flux from the endoplasmic reticulum to mitochondria. Cell Death Differ 23:1702-16|
|Rajan, Sreekanth; Choi, Minjoo; Nguyen, Quoc Toan et al. (2015) Structural transition in Bcl-xL and its potential association with mitochondrial calcium ion transport. Sci Rep 5:10609|
|Lanceta, Lilibeth; Mattingly, Jacob M; Li, Chi et al. (2015) How Heme Oxygenase-1 Prevents Heme-Induced Cell Death. PLoS One 10:e0134144|
|Zhao, Guoping; Lu, Huayi; Li, Chi (2015) Proapoptotic activities of protein disulfide isomerase (PDI) and PDIA3 protein, a role of the Bcl-2 protein Bak. J Biol Chem 290:8949-63|
|Schwarzer, Christian; Fu, Zhu; Morita, Takeshi et al. (2015) Paraoxonase 2 serves a proapopotic function in mouse and human cells in response to the Pseudomonas aeruginosa quorum-sensing molecule N-(3-Oxododecanoyl)-homoserine lactone. J Biol Chem 290:7247-58|
|Zhao, Guoping; Zhu, Yanglong; Eno, Colins O et al. (2014) Activation of the proapoptotic Bcl-2 protein Bax by a small molecule induces tumor cell apoptosis. Mol Cell Biol 34:1198-207|
|Huang, H; Shah, K; Bradbury, N A et al. (2014) Mcl-1 promotes lung cancer cell migration by directly interacting with VDAC to increase mitochondrial Ca2+ uptake and reactive oxygen species generation. Cell Death Dis 5:e1482|
|Schwarzer, Christian; Fu, Zhu; Shuai, Stacey et al. (2014) Pseudomonas aeruginosa homoserine lactone triggers apoptosis and Bak/Bax-independent release of mitochondrial cytochrome C in fibroblasts. Cell Microbiol 16:1094-104|