MMP9 and infectious otitis media: While genetic deficiency of MMP9 decreased Apc-mutation-mediated intestinal tumorigenesis in mice (60), deletion of MMP9 in AOM/DSS-treated mice instead enhanced CAC development (61), suggesting that while MMP9 has oncogenic roles in Apc-mutation-mediated sporadic CRC, it may elicit tumor suppressive effects during CAC.