MMP9 and neoplasm: Several MMPs have been found to take part in lung metastases [79]: MMP-1 overexpression has been found to significantly promote lung metastasis [80]; adenovirus-mediated knockdown of MMP-2 decreased tumor growth and prevented formation of lung nodules [81] while, in a previous study, an increased expression of MMP9 in the premetastatic lung niche derived from a distant primary tumor was found to be induced by VEGFR-1 and to promote lung metastasis [82].