title: Obatoclax, a Pan-BCL-2 Inhibitor, Targets Cyclin D1 for Degradation to Induce Antiproliferation in Human Colorectal Carcinoma Cells.
abstract: Colorectal cancer is the third most common cancer worldwide. Aberrant overexpression of antiapoptotic BCL-2 (B-cell lymphoma 2) family proteins is closely linked to tumorigenesis and poor prognosis in colorectal cancer. Obatoclax is an inhibitor targeting all antiapoptotic BCL-2 proteins. A previous study has described the antiproliferative action of obatoclax in one human colorectal cancer cell line without elucidating the underlying mechanisms. We herein reported that, in a panel of human colorectal cancer cell lines, obatoclax inhibits cell proliferation, suppresses clonogenicity, and induces G₁-phase cell cycle arrest, along with cyclin D1 downregulation. Notably, ectopic cyclin D1 overexpression abrogated clonogenicity suppression but also G₁-phase arrest elicited by obatoclax. Mechanistically, pre-treatment with the proteasome inhibitor MG-132 restored cyclin D1 levels in all obatoclax-treated cell lines. Cycloheximide chase analyses further revealed an evident reduction in the half-life of cyclin D1 protein by obatoclax, confirming that obatoclax downregulates cyclin D1 through induction of cyclin D1 proteasomal degradation. Lastly, threonine 286 phosphorylation of cyclin D1, which is essential for initiating cyclin D1 proteasomal degradation, was induced by obatoclax in one cell line but not others. Collectively, we reveal a novel anticancer mechanism of obatoclax by validating that obatoclax targets cyclin D1 for proteasomal degradation to downregulate cyclin D1 for inducing antiproliferation.
authors.affiliation: Department of Life Science, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. richardor92@yahoo.com.tw.|Department of Anesthesiology, Kuang Tien General Hospital, Dajia Branch, 321 Jingguo Road, Taichung 43761, Taiwan. richardor92@yahoo.com.tw.
authors.forename: Chi-Hung R
authors.initials: CR
authors.lastname: Or
authors.affiliation: Institute of Biomedical Sciences, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. yachu_0712@hotmail.com.
authors.forename: Yachu
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Institute of Biomedical Sciences, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. pa6153680@gmail.com.
authors.forename: Wei-Cheng
authors.initials: WC
authors.lastname: Lin
authors.affiliation: Institute of Biomedical Sciences, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. chyan_9@hotmail.com.
authors.forename: Wee-Chyan
authors.initials: WC
authors.lastname: Lee
authors.affiliation: Department of Life Science, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. suhonglin@gmail.com.|Ph.D. Program in Translational Medicine, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. suhonglin@gmail.com.|Agricultural Biotechnology Center, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. suhonglin@gmail.com.|Rong Hsing Research Center for Translational Medicine, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. suhonglin@gmail.com.
authors.forename: Hong-Lin
authors.initials: HL
authors.lastname: Su
authors.affiliation: Department of Anesthesiology, Kuang Tien General Hospital, Dajia Branch, 321 Jingguo Road, Taichung 43761, Taiwan. garrettc1957@yahoo.com.tw.
authors.forename: Muk-Wing
authors.initials: MW
authors.lastname: Cheung
authors.affiliation: Department of Anesthesiology, Kuang Tien General Hospital, Dajia Branch, 321 Jingguo Road, Taichung 43761, Taiwan. vincent520330@yahoo.com.tw.
authors.forename: Chang-Po
authors.initials: CP
authors.lastname: Huang
authors.affiliation: Department of Anesthesiology, Kuang Tien General Hospital, Dajia Branch, 321 Jingguo Road, Taichung 43761, Taiwan. b611071@tmu.edu.tw.
authors.forename: Cheesang
authors.initials: C
authors.lastname: Ho
authors.affiliation: Institute of Biomedical Sciences, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. chia_che@dragon.nchu.edu.tw.|Department of Life Science, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. chia_che@dragon.nchu.edu.tw.|Ph.D. Program in Translational Medicine, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. chia_che@dragon.nchu.edu.tw.|Agricultural Biotechnology Center, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. chia_che@dragon.nchu.edu.tw.|Rong Hsing Research Center for Translational Medicine, National Chung Hsing University, 145 Xingda Road, Taichung 40227, Taiwan. chia_che@dragon.nchu.edu.tw.|Department of Medical Research, China Medical University Hospital, 2 Yude Road, Taichung 40447, Taiwan. chia_che@dragon.nchu.edu.tw.|Department of Biotechnology, Asia University, 500 Liufeng Road, Taichung 41354, Taiwan. chia_che@dragon.nchu.edu.tw.
authors.forename: Chia-Che
authors.initials: CC
authors.lastname: Chang
mesh_terms: D002277:Carcinoma / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects*; D015179:Colorectal Neoplasms / Q000378:metabolism*; D019938:Cyclin D1 / Q000378:metabolism*; D015536:Down-Regulation; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D007211:Indoles; D059748:Proteolysis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors*; D011758:Pyrroles / Q000494:pharmacology* / Q000633:toxicity
chemical_list: D007211:Indoles; D019253:Proto-Oncogene Proteins c-bcl-2; D011758:Pyrroles; D019938:Cyclin D1; C520962:obatoclax
keywords: BH3 (BCL-2 homology 3) mimetics; G1-phase arrest; antiproliferation; colorectal cancer; cyclin D1; obatoclax; proteasomal degradation