Kru¨ppel-like factor 4 (KLF4) is an evolutionarily conserved zinc finger-containing transcription factor. In the present study, peripheral blood mononuclear cells and phorbol 12-myristate 13-acetate-differentiated THP-1 cells were treated with oxidized low-density lipoproteins and high-density lipoproteins to determine the expression of KLF4 and scavenger receptor class B type I (SR-BI).