Sox9 mediated transcriptional activation of FOXK2 is critical for colorectal cancer cells proliferation.

FOXK2, which belongs to the fork head DNA binding protein family, has been shown to play a critical role in tumorigenesis. Here, we detected FOXK2 expression and its clinical significance in colorectal cancer, which has not been fully investigated before. Results from public database and our cohort indicated that FOXK2 was transcriptionally activated in colorectal cancer tissues compared to non-cancer tissues. High expression of FOXK2 was significantly correlated with poor survival. In vitro cell experiments suggested that FOXK2 promoted cell proliferation. Furthermore, we found that oncogene SOX9 was responsible for the up-regulation of FOXK2 by directly binding on its promoter. Depletion of FOXK2 attenuated SOX9 induced cell growth. In addition, we observed that the expression of FOXK2 was significantly associated with the expression of SOX9 both in the public database and our colorectal cancer tissues. The patients with SOX9+FOXK2+ had a poor overall survival (p = 0.0084). In conclusion, our data suggested that SOX9 transcriptionally activated FOXK2 was involved in the pathogenesis of colorectal cancer and might be a novel target for colorectal cancer therapy.