PTENP1 and renal cell carcinoma: Moreover, PTENP1, too, acts as a tumor-suppressive factor in RCC by acting as a competing endogenous RNA for miR-21, which would otherwise promote cell proliferation, migration, and invasion by the suppression of PTEN, an important tumor suppressor (Zhang A. et al., 2011; Song et al., 2012; Yu et al., 2014).