For instance, the research conducted by Anwar and colleagues demonstrated that upregulation of miR-21 was associated with poor PFS in BC patients (Anwar et al., 2019), and it refers to its potential role in targeting the genes including TIMP3, PDCD4, PTEN, TPM1, and RECK that are involved in BC promotion and progression, especially invasion, angiogenesis, and metastasis (Petrović, 2016). The gene discussed is PDCD4; the disease is breast cancer.