Of note, the expression of previously well-established in vitro targets of miR-21 having tumor-suppressive activity, i.e., Ppara [21], Pdcd4 [64], Timp3 [64], Spry2 [62,65], Pten [66], and Hbp1 [23], was unchanged with miR-21 deficiency in vivo in mice again highlighting a cell/organ context-dependent action of miR-21. The gene discussed is PDCD4; the disease is neoplasm.