Abstract 2670: Natural compound tetrocarcin-A downregulates junctional adhesion molecule-A in conjunction with erα, her2 and inhibitor of apoptosis proteins and inhibits tumor cell growth

Overexpression of the tight junction protein Junctional Adhesion Molecule-A (JAM-A) has been linked to aggressive disease in breast and several other cancers, but JAM-targeting drugs remain elusive. Screening of a natural compound library identified the cytotoxic antibiotic Tetrocarcin-A as a novel downregulator of JAM-A protein expression in breast cancer cells. Specifically, Tetrocarcin-A-induced cytotoxicity was accompanied by downregulation of JAM-A protein expression in conjunction with that of estrogen receptor alpha (ERα) and human epidermal growth factor receptor 2 (HER2) in MCF7-HER2-overexpressing breast cells. Lysosomal inhibition partially rescued the downregulation of JAM-A, HER2 and ERα caused by Tetrocarcin-A, and attenuated its cytotoxicity. Interestingly, Tetrocarcin-A repressed the transcriptional activity of c-FOS by inhibiting ERK1/2-mediated phosphorylation at Threonine-232, and downregulated protein expression of the inhibitor of apoptosis proteins (IAP). Investigation of cell death pathways revealed that Tetrocarcin-A induced caspase-dependent apoptosis. To begin testing the potential clinical relevance of our findings, we extended our studies into various other models. Encouragingly, Tetrocarcin-A downregulated JAM-A expression and caused cytotoxicity in primary breast cancer and lung cancer stem cells, and inhibited the growth of model human breast tumors in an in vivo model involving invasion across the chicken egg chorioallantoic membrane. Taken together, our data suggest that Tetrocarcin-A merits future evaluation as a novel cancer therapeutic by virtue of its ability to downregulate JAM-A expression, induce apoptosis and reduce tumorigenic signalling. This work was financially supported by Science Foundation Ireland (grant 13/IA/1994 to AMH). Tetrocarcin-A was provided by the NCI/DTP Open Chemical Repository https://dtp.cancer.gov. (NSC 333856) Citation Format: Sri Harikrishna Vellanki, Lance Hudson, Hanne Jahns, Rodrigo G.B. Cruz, Giovanni Sette, Adriana Eramo, Ann M. Hopkins. Natural compound tetrocarcin-A downregulates junctional adhesion molecule-A in conjunction with erα, her2 and inhibitor of apoptosis proteins and inhibits tumor cell growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2670.