β-Catenin/TCF4 Complex-Mediated Induction of the NRF3 (NFE2L3) Gene in Cancer Cells

Abstract

Remarkable upregulation of the NRF2 (NFE2L2)-related transcription factor NRF3 (NFE2L3) in several cancer tissues and its correlation with poor prognosis strongly suggest the physiological function of NRF3 in tumors. Indeed, we had recently uncovered the function of NRF3, which promotes cancer cell proliferation by p53 degradation via the 20S proteasome. Nevertheless, the molecular mechanism underlying the induction of <i>NRF3</i> gene expression in cancer cells is highly elusive. We herein describe that <i>NRF3</i> upregulation is induced by the β-catenin/TCF4 complex in colon cancer cells. We first confirmed high <i>NRF3</i> mRNA expression in human colon cancer specimens. The genome database indicated that the human <i>NRF3</i> gene possesses a species-conserved WRE sequence (TCF/LEF consensus element), implying that the β-catenin/TCF complex activates <i>NRF3</i> expression in colon cancer. Consistently, we observed that the β-catenin/TCF4 complex mediates <i>NRF3</i> expression by binding directly to the WRE site. Furthermore, inducing NRF3 activates cell proliferation and the expression of the glucose transporter <i>GLUT1</i>. The existence of the β-catenin/TCF4-NRF3 axis was also validated in the intestine and organoids of <i>Apc</i>-deficient mice. Finally, the positive correlation between <i>NRF3</i> and β-catenin target gene expression strongly supports our conclusion. Our findings clearly demonstrate that NRF3 induction in cancer cells is controlled by the Wnt/β-catenin pathway.