NRN1 and nonpapillary renal cell carcinoma: As a potential NRN1-activated transcriptional factor, nuclear factor of activated T-cells (NFAT) c4 may activate CXCR4 transcription in ccRCC based on previous literature describing that NRN1 activates NFATc4 via binding to insulin receptor in neuronal cells (19), and that NFATc4-binding on the CXCR4 promoter increases CXCR4 expression in 3D spheroid culture of ovarian cancer cells (20).