Basically, while CD44 recruits MMP-9 at the protrusions of migrating cells, thereby spatially directing MMP-9 proteolytic activity, CD151 facilitates MMP-9-mediated cancer cell motility by mediating integrin endocytosis at the rear or basal-lateral front of migrating cells (Table 1) [68,78,79]. The gene discussed is CD44; the disease is cancer.