**3. The application of RNAi for silencing of tumor-related genes**

RNAi has a standard procedure in intracellular gene knockout and can be used to identify gene functions by inhibiting specific genes and analyzing the change of gene appearance. As such, by analyzing gene functions, the signal pathway of tumor development could be identified. This further provides the feasibility to assess the medical or RNAi therapeutic target(Devi,2006). In addition, systemic treatment approaches with cancer-related miRNA or miRNA offer opportunities for tumor therapy. There have been a few overexpressed target genes for RNAi study *in vivo*. The section is a retrospective review of these targets.
