KLF5 and pulmonary arterial hypertension: Previous studies have shown that IL-6 can induce apoptosis resistance in PASMCs through different signal transduction pathways, thereby promoting vascular remodeling in PAH, such as IL-6/STAT3/Kruppel-like factor 5 (KLF5) [187] and IL-6/bromodomain protein 4 (BRD4) [188].