Among the three micro-RNAs that we selected, miR-21 is known to function in cell proliferation and relate to cancers [18, 33, 34]; miR-221 is known to regulate the cell cycle [18, 19, 35]; miR-141 is known to affect the expression of androgen receptor [7, 34] and progress of metastatic cancer. The gene discussed is AR; the disease is cancer.