MMP9 and infectious otitis media: Garg and colleagues demonstrated that MMP9, which is a mediator of pro-inflammatory response, plays a protective role in the AOM/DSS mouse model of colitis-associate colorectal cancer, by activating p21WAF1/Cip1, which in turn modulates Notch1 and suppresses β-catenin.66 Intriguingly, in a different model of intestinal inflammation the role of MMP9 has also been related to an oncogenic function of Notch signaling.