This analysis revealed that some pentastatin target genes which are involved in early immediate gene response and endothelial cell activation, namely JUNB, FOS, EGR1 and ZFP36 (as identified in Fig. 3, A–C), were upregulated in the endothelial cell compartment of end-stage PAH-PAs (Fig. 3, F and G), while transcription factors that are known to be crucial for maintaining endothelial cell barrier integrity [ETS1, SOX7, LEF1, LMO2, SOX18, FOXF2, KLF11, FOXC1, TAL1, (40)] were downregulated (Fig. 3H). The gene discussed is FOS; the disease is pulmonary arterial hypertension.