However, since OPN has additional functions as both a promoter of cellular division and mediator of innate immune responses (Cui et al., 2007; Denhardt et al., 2001; Liaw et al., 1998; Likui et al., 2011; Midwood et al., 2004; Zhang et al., 2014; Zhivkova‐Galunska et al., 2010), persistent OPN production by tubular epithelial cells could have detrimental effects in PKD by promoting cyst epithelial cell proliferation, cyst growth, or fibrosis. This evidence concerns the gene SPP1 and cyst.