1. Division of Pulmonary, Allergy & Critical Care Medicine, Department of Medicine, and
2. Vera Moulton Wall Center for Pulmonary Vascular Disease, Stanford University School of Medicine, Stanford, California;
3. VA Palo Alto Health Care System, Palo Alto, California; and
4. The Cancer Research Institute, Hengyang Medical School, University of South China, Hengyang, China