YB-1 (Y-box binding protein-1) contains a highly conserved cold shock domain and is a transcription factor that binds to a CCAAT box. It has been reported that P-glycoprotein is highly expressed in cisplatin-resistant cancer cell lines since the sequence of CCAAT box is located in the promoter region of the drug-resistance gene MDR1, and YB-1 is involved in transcription of P-glycoprotein, the product of the MDR1 gene.