Abstract

Background The aim of this study was to explore the expression levels and biological significance of TDO2 in colorectal cancer (CRC). Methods First, we explored the potential oncogenic roles of TDO2 across 33 tumors based on data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). Second, we evaluated TDO2 protein expression in 55 CRC tissue samples and 30 cDNA samples by immunohistochemistry and qPCR. Third, we investigated the effect of TDO2 on CRC cells by cell proliferation, wound healing, invasion, and colony formation assays. Finally, we determined the protein that is most closely associated with TDO2 via bioinformatics analysis, enriched the key pathways, and verified them. Results The expression level of TDO2 was found to be associated with the tumor clinical stage in CRC. A high expression of TDO2 was associated with a poor outcome in CRC patients. Inhibition of TDO2 expression by RNAi in LoVo and HCT116 cell lines significantly reduced the proliferation, migration, and invasion abilities as well as colony formation abilities of cells. Further, knockdown of TDO2 expression induced inactivation of the TDO2–KYNU–AhR signaling pathway. Conclusion The results suggest that TDO2 plays an important role in the progression of CRC. Accordingly, TDO2 is a potential therapeutic target in CRC.