DROSHA and pachyonychia congenita: This prominent downregulation of miRNAs in PC bone metastases was in line with results previously reported for PC [14,15,16,18,31], and might be the result of a hypoxic bone environment as hypoxia has been shown to globally reduce miRNA expression due to the downregulation and/or inactivation of Drosha, Dicer and Ago2 (reviewed in [7]).