MiR-21is overexpressed in ICC cell lines [29], and many tumor suppressor mRNAs have been identified as direct targets of this mRNA, including programmed cell death 4 (PDCD4) [30], phosphatase and tension homolog (PTEN) on chromosome 10 [31], tissue inhibitor of metalloproteinase 3 (TIMP3) [30], and reversion-inducing cysteine-rich protein with kazal motifs (RECK) [32]. This evidence concerns the gene PDCD4 and intrahepatic cholangiocarcinoma.