MMP9 and Cowden syndrome 1: These data suggest that neutrophilic chemokines play a significant role in the migration of neutrophils into the lungs in younger and older mice exposed to CS, thereby mediating alveolar destruction as a result of releasing a number of damaging factors (serine proteases, elastase, cathepsin-G, proteinase-3, matrix metalloproteinases [e.g. MMP-8 and MMP-9]), and reactive oxygen species25,46,47.