The upstream stimulating factor 1 (USF1), an evolutionarily conserved basic-helix-loop-helix leucine zipper transcription factor, stimulates basal activation by interacting with the E-box element, as supported by decreased MVP expression in human colon carcinoma (SW620) and human renal adenocarcinoma (ACHN) following USF1 siRNA silencing [113]. Here, USF1 is linked to papillary renal cell carcinoma.