Although the role of bombesins in modulating mucus secretion or muc5AC/muc5B regulation in COPD is unknown, given that bombesins are increased in COPD [193] and muc5B is also increased [188], then it is possible that either a direct or indirect relationship between bombesin signaling and muc5B expression exists. This evidence concerns the gene MUC5AC and chronic obstructive pulmonary disease.