Discovery of Small Molecule Bak Activator for Lung Cancer Therapy

• Type of Material: Article
• Authors: Dongkyoo Park, Emory University; Abu Syed M Anisuzzaman, Emory University; Andrew T Magis, Emory University; Guo Chen, Emory University; Maohua Xie, Emory University; Guojing Zhang, Emory University; Madhusmita Behera, Emory University; Gabriel Sica, Emory University; Suresh Ramalingam, Emory University; Taofeek Owonikoko, Emory University; Xingming Deng, Emory University
• Language: English
• Date: 2021-01-01
• Publisher: IVYSPRING INT PUBL
• Publication Version: Final Published Version
• Copyright Statement: © The author(s)
• Final Published Version (URL): http://dx.doi.org/10.7150/thno.60349
• Title of Journal or Parent Work: THERANOSTICS
• Volume: 11
• Issue: 17
• Start Page: 8500
• End Page: 8516
• Grant/Funding Information: This work was supported by NIH/NCI grants R01CA200905, R01 CA255257-01A1, R01CA136534, and P50CA217691 (to X. Deng); by the Winship Research Informatics, Pathology and Integrated Cellular Imaging shared resource, the cores supported by the Winship Cancer Institute of Emory University (P30CAJ38292), by the Winship Fashion a Cure Research Scholar Award (to X. Deng), a philanthropic award provided by the Winship Cancer Institute of Emory University, and by Winship Endowment Fund (to X. Deng).
• Keywords: therapy; DUAL INHIBITORS; RESISTANCE; lung cancer; Research & Experimental Medicine; apoptosis; STATISTICS; BCL-XL; small molecule activator; Science & Technology; VENETOCLAX; CELL-DEATH; BH3 domain; SENSITIVITY; Bak; Life Sciences & Biomedicine; APOPTOSIS; Medicine, Research & Experimental; PROTEIN; EXPRESSION
• Research Categories: Health Sciences, Oncology; Health Sciences, Pathology

Abstract

Rationale: Bak is a major proapoptotic Bcl2 family member and a required molecule for apoptotic cell death. High levels of endogenous Bak were observed in both small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) cell lines. Increased Bak expression was correlated with poor prognosis of NSCLC patients, suggesting that Bak protein is an attractive target for lung cancer therapy. The BH3 domain functions as death domain and is required for Bak to initiate apoptotic cell death. Thus, the BH3 domain is attractive target for discovery of Bak agonist. Methods: The BH3 death domain binding pocket (aa75-88) of Bak was chosen as a docking site for screening of small molecule Bak activators using the UCSF DOCK 6.1 program suite and the NCI chemical library (300,000 small molecules) database. The top 500 compounds determined to have the highest affinity for the BH3 domain were obtained from the NCI and tested for cytotoxicity for further screening. We identified a small molecule Bak activator BKA-073 as the lead compound. The binding affinity of BKA-073 with Bak protein was analyzed by isothermal titration calorimetry (ITC) assay. BKA-073-mediated Bak activation via oligomerization was analyzed by a cross-linking with Bis (maleimido) hexane (BMH). Sensitivity of BKA-073 to lung cancer cells in vitro was evaluated by dynamic BH3 profiling (DBP) and apoptotic cell death assay. The potency of BKA-073 alone or in combination with radiotherapy or Bcl2 inhibitor was evaluated in animal models. Results: We found that BKA-073 binds Bak at BH3 domain with high affinity and selectivity. BKA-073/Bak binding promotes Bak oligomerization and mitochondrial priming that activates its proapoptotic function. BKA-073 potently suppresses tumor growth without significant normal tissue toxicity in small cell lung cancer (SCLC) and NSCLC xenografts, patient-derived xenografts, and genetically engineered mouse models of mutant KRAS-driven cancer. Bak accumulates in radioresistant lung cancer cells and BKA-073 reverses radioresistance. Combination of BKA-073 with Bcl-2 inhibitor venetoclax exhibits strong synergy against lung cancer in vivo. Conclusions: Development of small molecule Bak activator may provide a new class of anticancer agents to treat lung cancer.