MMP9 and neoplasm: The results showed that 1 week after adenovirus inhalation, pulmonary IL-17 expression (150-fold difference) and the incidence of lung cancer were significantly higher in the experimental group than in the control group; moreover, high IL-17 expression was associated with upregulated expression of matrix metallopeptidase 9 (MMP-9) and higher invasiveness of tumour cells.