These results indicate that the miR21 targets PDCD4 mRNA and post-transcriptionally down-regulates PDCD4 expression, resulting in the increased transformation, invasion, and metastasis of cancer cells [56], Besides miR21, many other kinds of microRNA such as miR182, miR16, miR150, miR499 and other microRNAs has been shown to target the PDCD4 mRNA down-regulating PDCD4 expression in different cellular systems [58,59,60,61]. Here, PDCD4 is linked to cancer.