Carbon nanotubes induce apoptosis resistance of human lung epithelial cells through FLICE-inhibitory protein.

Chronic exposure to single-walled carbon nanotubes (SWCNT) has been reported to induce apoptosis resistance of human lung epithelial cells. As resistance to apoptosis is a foundation of neoplastic transformation and cancer development, we evaluated the apoptosis resistance characteristic of the exposed lung cells to understand the pathogenesis mechanism. Passage control and SWCNT-transformed human lung epithelial cells were treated with known inducers of apoptosis via the intrinsic (antimycin A and CDDP) or extrinsic (FasL and TNF-α) pathway and analyzed for apoptosis by DNA fragmentation, annexin-V expression, and caspase activation assays. Whole-genome microarray was performed to aid the analysis of apoptotic gene signaling network. The SWCNT-transformed cells exhibited defective death receptor pathway in association with cellular FLICE-inhibitory protein (c-FLIP) overexpression. Knockdown or chemical inhibition of c-FLIP abrogated the apoptosis resistance of SWCNT-transformed cells. Whole-genome expression signature analysis confirmed these findings. This study is the first to demonstrate carbon nanotube-induced defective death receptor pathway and the role of c-FLIP in the process. Published by Oxford University Press on behalf of the Society of Toxicology 2014. This work is written by US Government employees and is in the public domain in the US.