IL6 and pulmonary arterial hypertension: Although numerous proteins or signaling pathways have been implicated in the development and progression of PAH [6], such as STAT3 (signal transducer and activator of transcription 3) [7], hypoxia-inducible factors (HIFs) [8] and interleukin-6 (IL6) [9], studies focusing on individual protein or pathway have limitations due to the high complexity of PAH and potential bias.