As miR-21-5p overexpression increased cell growth, invasion and migration, and reduced apoptosis [21, 22], through downregulation of several tumor suppressor genes such as PTEN, TPM1, and PDCD4 [23–25], miR-21-5p is likely to be a true prognostic factor for breast cancer and other cancers. The gene discussed is PDCD4; the disease is breast cancer.