Dillhoff et al. (2008) demonstrated that miR-21 was significantly over-expressed in PC. Although we could not find any direct evidence to support an important role of PDGFD in PC, we found that PDGFD could regulate many cellular processes, including cell proliferation, apoptosis, transformation, migration, invasion, angiogenesis and metastasis (Wang et al., 2010). Recent studies (Walters et al., 2013; Ogawa et al., 2015) have also shown that PDGFD is closely related to various cancers. The gene discussed is PDGFD; the disease is pachyonychia congenita.