PTEN and cancer: miR-21 negatively regulates reversion-inducing-cysteine-rich protein with kazal motifs (RECK), a molecule that represses GC metastasis and angiogenesis, and miR-21 is also involved in cancer tissue invasion and lymph node metastasis via reducing the protein levels of phosphatase and tensin homolog (PTEN), a tumor-suppressor gene (41,42).