Abstract B115: Use of a genome-wide loss-of-function screen to identify novel mechanisms of resistance to TRAIL induced apoptosis.

Abstract

Abstract A biological approach to combat cancer is to define and specifically target signaling pathways involved in tumor progression and metastasis. One such target is the TNF-Related Apoptosis Inducing Ligand (TRAIL) signaling pathway. Importantly, TRAIL kills tumor cells selectively without inducing apoptosis in normal tissue. Recombinant TRAIL and agonistic antibodies against the receptors DR4 and DR5 are in early-phase clinical trials as an anti-cancer treatment in breast cancer. However, since cancer cells must evade tumor surveillance, it is not surprising that many tumors are TRAIL-resistant. We are interested in the molecular basis of acquired resistance to TRAIL induced apoptosis as a result of long-term exposure to the drug. Our goal is to gain an increased understanding of how cancer cells can become resistant to TRAIL and how this resistance can be predicted and circumvented, ultimately leading to more efficient TRAIL-based therapy. To this end, we utilized the Burkitt's lymphoma cell line BJAB-LexR that has been made naturally resistant to TRAIL through long-term culture in the presence of increasing concentrations of the drug Lexatumumab, an anti-DR5 antibody. We performed a genome wide loss-of-function screen using the GeneNet lentiviral shRNA library containing 200 000 shRNAs with sequencing tags, allowing for high throughput deep sequencing. After selection for a particular phenotype, in this case TRAIL resistance, the shRNAs that promote or prevent this phenotype can be deduced from the frequency in which the shRNA is present in the selected (TRAIL-treated) population versus the unselected population. Bioinformatic analysis yielded a list of putative resistance genes that were validated in the BJAB system and also in other cell lines that have been made resistant to TRAIL in a similar fashion. With this unbiased approach, we have identified novel genes associated with TRAIL resistance that may provide targets for combination therapy that could improve the response to TRAIL. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B115. Citation Format: Lina Y. Dimberg, Joshua Cabrera, Christina Menke, Jihye Kim, Christopher C. Porter, Aik-Choon Tan, Kian Behbakht, Andrew Thorburn, Heide L. Ford. Use of a genome-wide loss-of-function screen to identify novel mechanisms of resistance to TRAIL induced apoptosis. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B115.