Thus, we have investigated whether the fibrocytes of COPD patients, with exercise-induced hypoxemia, may be increased in the peripheral blood through up-regulation of CXCR4, and exhibit higher proliferation and myofibroblast transformation through up-regulation of EGFR, HIF-1α, and CTGF. The gene discussed is CXCR4; the disease is chronic obstructive pulmonary disease.