Overexpression of miR-21 can regulate the expression of invasion- and metastasis-related target genes in the hepatocellular carcinoma (HCC) cell line HepG2 and the lung cancer cell line A549 by inhibiting the expression of programmed cell death 4 and PTEN, which are involved in apoptosis.84 The gene discussed is PDCD4; the disease is hepatocellular carcinoma.