Since it has been reported that IL-1β acts as a trigger when MMP-9 induction occurs through the activation of the mitogen-activated protein kinase (MAPK) pathway and the translocation of nuclear factor-κB (NF-κB) in cancer cells [40,41] and fibroblasts [42], we next assessed the expression of IL-1β in each region of the lung. Here, MMP9 is linked to cancer.