Having reported that HIF-1α and VEGF operate as lung structure maintenance factors [9], [11], [13], [19], in particular that HIF-1α protein expression was suppressed in the lungs from patients with COPD/emphysema, we next investigated whether the expression of HIF-1α and VEGF was affected by fenretinide treatment. Here, HIF1A is linked to chronic obstructive pulmonary disease.