PDCD4 and neoplasm: MiR-21 has also been linked to human tumor invasion and metastasis by negatively regulating targets that are adversely associated with metastatic capacity, such as PTEN, PDCD4, von Hippel-Lindau (VHL), TIMP3, Tropomyosin 1 (TPM1), and Serpin Family B Member 1 (SEPINB1) [40,47,56,57,58,59,60].