TNF-related apoptosis inducing ligand (TRAIL) induces apoptosis through its death receptors (DRs) 4 and/or 5 expressed on the surface of target cells. Despite its selectivity in killing cancer cells over most normal cells, recombinant human TRAIL or its receptor agonists (monoclonal antibodies against DR4 or DR5) encountered resistance in many tumor cells while the underlying mechanisms remain partially understood. Here, we show that wild-type H-Ras GTPase is systemically upregulated in TRAIL-resistant cells compared to TRAIL-sensitive cells. The elevated H-Ras expression correlated with a deficiency of DR4 and DR5 on plasma membrane in TRAIL-resistant cell lines. Notably, knockdown of H-Ras in TRAIL-resistant cells successfully restored the surface expression of DR4 and DR5, thereby sensitizing the cells to TRAIL-induced apoptosis. Consistently, ectopic expression of H-Ras in TRAIL-sensitive cells reduced surface DR4 and DR5 which was associated with a loss of TRAIL sensitivity. By contrast, the status of K-Ras or its mutations was not casually linked to TRAIL receptor expression or TRAIL sensitivity across the panel of cancer cell lines tested. These data suggest that H-Ras may play a distinct role to negatively regulate TRAIL receptors and apoptosis. The upregulated H-Ras could be a predictor of tumor resistance to DR-targeted agents and a potential therapeutic target for combinational therapy to achieve better treatment outcomes.

Citation Format: Su-Ryun Kim. Elevated H-Ras suppresses death receptor-mediated apoptosis in cancer cells [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 2316. doi:10.1158/1538-7445.AM2017-2316