Abstract 2117: TRAIL-induced apoptosis in TRAIL-resistant breast carcinoma

Abstract

Abstract Recombinant human tumor necrosis factor-related apoptosis-inducing ligand (rhTRAIL), the optimized form of the endogenous death ligand TRAIL, shows therapeutic potential for cancer due to its ability to induce apoptosis in cancer cells independent of p53, while exhibiting minimal toxicity to normal cells. Despite this, a majority of breast cancers display resistance to rhTRAIL treatment due to up-regulation of pro-apoptotic proteins, down-regulation of anti-apoptotic proteins, and/or up-regulation of death receptors (DR) 4 and 5. To overcome rhTRAIL resistance, natural compounds have been investigated as sensitizing agents. This study considered the application of the naturally occurring flavonol Quercetin (Q). Q has been shown to have the ability to up-regulate DR5 and down-regulate anti-apoptotic proteins in cancer cells, and thereby, making Q a favorable choice to be employed as a sensitizing agent. The intention of this study was to ascertain the capacity of Q to sensitize rhTRAIL-resistant triple negative breast cancer BT-20 cells and hormone-dependent breast cancer MCF-7 cells to rhTRAIL-induced apoptosis and elucidate the underlying mechanism for Q’s sensitization. Q demonstrated the ability to intensify rhTRAIL’s pro-apoptotic effects in the breast cancer BT-20 and MCF-7 cell lines as detected through Annexin V/PI assays followed by FACS analysis. In comparison to single agent treatments, the cotreatment of Q and rhTRAIL enhanced the induction of the extrinsic pathway of apoptosis as marked by PARP cleavage (a hallmark of apoptosis), activation of caspase 8, and activation of the executioner caspases 3 and 7. The mechanism for Q’s augmentation in breast cancer was determined to be through the down-regulation of c-FLIPL (caspase 8 inhibitor) in a dose-dependent manner. Furthermore, Q promoted the ubiquitination of c-FLIPL facilitating the proteasome-mediated degradation of c-FLIPL in breast cancer. An additional mechanism for Q’s sensitization was displayed in breast cancer BT-20 cells. Q up-regulated DR5 membrane and protein expression in breast cancer BT-20 cells in a dose-dependent manner. RT-PCR analysis revealed that Q’s influence on DR5 expression occurred at the transcriptional level in those breast cancer cells. Thus, these data suggest that the cotreatment of Q and rhTRAIL possesses the therapeutic potential to be an effective anti-breast carcinoma regimen. Citation Format: Jasmine M. Manouchehri, Michael Kalafatis. TRAIL-induced apoptosis in TRAIL-resistant breast carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2117. doi:10.1158/1538-7445.AM2017-2117