This hypothesis is supported by the finding of Kranenburg and colleagues [44] that increased VEGF expression and their receptors (VEGFR-1, also called FLT-1, and VEGFR-2 also called KDR/Flk-1) were demonstrated in ex-smoking patients with COPD in comparison with ex-smoking healthy control subjects. Here, KDR is linked to chronic obstructive pulmonary disease.