Recently we found that CXCR4 was expressed in pulmonary artery smooth muscle cells and that hypoxia increased CXCR4 expression in the lungs from mice with pulmonary hypertension and that a CXCR4 inhibitor AMD3100 significantly inhibited pulmonary artery smooth muscle cell proliferation (unpublished data). This evidence concerns the gene CXCR4 and pulmonary hypertension.