CDK4 and pulmonary arterial hypertension: IRF1 is downregulated in lung cancer, IPF and PAH datasets, probably because it represses the expression of genes involved in anti-proliferative response, such as BIRC5/survivin, CCNB1, CCNE1, CDK1, CDK2 and CDK4 (Armstrong et al., 2012) and in immune response, such as FOXP3, IL4, ANXA2 and TLR4 (Fragale et al., 2014).