miR-34 suppressed the expression of target genes: BCL2/CCND1, which is leading to the resistance of MCF-7 to docetaxel. The overexpression of miR-34 suppress the expression of MAGE-A, then increasing the expression of P53, and upregulate the expression of miR-34 by positive feedback regulation mechanism, which increases the sensitivity of tumor cells to mitomycin and cisplatin. The overexpression of miR-34 could downregulate the expression of SIRT1 and BCL2 directly or by suppressing the expression of HuR, and weaken the resistance hormone-independent prostate cancer PC3 cells to paclitaxel. The gene discussed is SIRT1; the disease is prostate cancer.