EDN1 and lung cancer: In the present studies, we observed that the decreases of the PWMT and hind limb use score in LLC bearing mice without treatment (BCP mice), treated with morphine (BCP-morphine mice), or morphine + ET-1 (BTcP mice) were associated with the infiltration of lung cancer cells in the hind paw of mice by immunohistochemical analysis (data not shown), suggesting the mouse model of metastatic BCP was established.