PTEN and neoplasm: Another widely expressed miRNA in hematopoietic and solid tumors is miRNA-21 [17, 28, 31, 33–35] miR-21 targets several tumor suppressor genes such as phosphatase and tensin homolog (PTEN) [34], programmed cell death 4 (PDCD4) [36], and tropomyosin 1 (TPM1) [37].