SPP1 and cancer: Cancer biology researchers have long been interested in OPN given its observed functions to accelerate cellular division, inhibit apoptosis, and drive tumor propagation (Cui et al., 2007; Denhardt et al., 2001; Liaw et al., 1998; Likui et al., 2011; Midwood et al., 2004; Shevde & Samant, 2014; Zhang et al., 2014; Zhivkova‐Galunska et al., 2010).