Besides, shuttling of exosomal microRNA (e.g. miR-21 [70] and miR-181a [71]) might mediate liver metastases of CRC by suppressing their target genes phosphatase and tensin homolog (PTEN), programmed cell death 4(PDCD4) or Wnt inhibitor factor(WIF)-1 in hepatocytes. The gene discussed is PDCD4; the disease is colorectal carcinoma.