NANOG, a stemness-associated
transcription factor, is highly expressed in many
cancers and plays a critical role in regulating tumorigenicity.
Transformation/transcription domain-associated protein (TRRAP) has been reported to stimulate the tumorigenic potential of
cancer cells and induce the gene transcription of NANOG. This study aimed to investigate the role of the TRRAP-NANOG signaling pathway in the tumorigenicity of cancer stem cells. We found that TRRAP overexpression specifically increases
NANOG protein stability by interfering with NANOG ubiquitination mediated by FBXW8, an
E3 ubiquitin ligase. Mapping of NANOG-binding sites using deletion mutants of TRRAP revealed that a domain of TRRAP (
amino acids 1898-2400) is responsible for binding to NANOG and that the overexpression of this TRRAP domain abrogated the FBXW8-mediated ubiquitination of NANOG. TRRAP knockdown decreased the expression of CD44, a cancer stem cell marker, and increased the expression of P53, a tumor suppressor gene, in HCT-15
colon cancer cells. TRRAP depletion attenuated spheroid-forming ability and
cisplatin resistance in HCT-15 cells, which could be rescued by NANOG overexpression. Furthermore, TRRAP knockdown significantly reduced
tumor growth in a murine
xenograft transplantation model, which could be reversed by NANOG overexpression. Together, these results suggest that TRRAP plays a pivotal role in the regulation of the tumorigenic potential of
colon cancer cells by modulating
NANOG protein stability.