KLF9 and lung cancer: Based on the roles in lung cancers, the KLFs were divided into four classifications with promotion (KLF5, KLF7, KLF8 and KLF15), inhibition (KLF2, KLF3, KLF9 ∼ KLF12 and KLF17), dual functions (KLF4 and KLF6) and unknown (KLF1, KLF13, KLF14 and KLF16), indicated that abnormal KLFs be derived from tissues with different biological function during lung cancer progression.