Data from A Synthetic Cell-Penetrating Dominant-Negative ATF5 Peptide Exerts Anticancer Activity against a Broad Spectrum of Treatment-Resistant Cancers

Abstract

<div>Abstract<p><b>Purpose:</b> Despite significant progress in cancer research, many tumor entities still have an unfavorable prognosis. Activating transcription factor 5 (ATF5) is upregulated in various malignancies and promotes apoptotic resistance. We evaluated the efficacy and mechanisms of the first described synthetic cell-penetrating inhibitor of ATF5 function, CP-d/n-ATF5-S1.</p><p><b>Experimental Design:</b> Preclinical drug testing was performed in various treatment-resistant cancer cells and <i>in vivo</i> xenograft models.</p><p><b>Results:</b> CP-d/n-ATF5-S1 reduced the transcript levels of several known direct ATF5 targets. It depleted endogenous ATF5 and induced apoptosis across a broad panel of treatment-refractory cancer cell lines, sparing non-neoplastic cells. CP-d/n-ATF5-S1 promoted tumor cell apoptotic susceptibility in part by reducing expression of the deubiquitinase Usp9X and led to diminished levels of antiapoptotic Bcl-2 family members Mcl-1 and Bcl-2. In line with this, CP-d/n-ATF5-S1 synergistically enhanced tumor cell apoptosis induced by the BH3-mimetic ABT263 and the death ligand TRAIL. <i>In vivo</i>, CP-d/n-ATF5-S1 attenuated tumor growth as a single compound in glioblastoma, melanoma, prostate cancer, and triple receptor–negative breast cancer xenograft models. Finally, the combination treatment of CP-d/n-ATF5-S1 and ABT263 significantly reduced tumor growth <i>in vivo</i> more efficiently than each reagent on its own.</p><p><b>Conclusions:</b> Our data support the idea that CP-d/n-ATF5-S1, administered as a single reagent or in combination with other drugs, holds promise as an innovative, safe, and efficient antineoplastic agent against treatment-resistant cancers. <i>Clin Cancer Res; 22(18); 4698–711. ©2016 AACR</i>.</p></div>