Double-stranded Let-7 mimics, potential candidates for cancer gene therapy.

MicroRNAs (miRNAs), a class of small, single-stranded endogenous RNAs, act as post-transcriptional regulators of gene expression. The ability of one single miRNA regulating multiple functionally related mRNAs makes it a new potential candidate for cancer gene therapy. Let-7s miRNAs have been demonstrated as tumor-suppressor genes in various types of cancers, providing one choice of gene therapy by replenishing this miRNA. In the present studies, we demonstrate that the chemically synthesized, double-stranded Let-7 mimics can inhibit the growth and migration and induce the cell cycle arrest of lung cancer cell lines in vitro. Let-7 mimics silence gene expression by binding to the 3' UTR of targeting mRNAs. Mutation of seed sequence significantly depresses the gene silencing activity of Let-7 mimics. Our results also demonstrate that it is possible to increase the activity of Let-7s through mutating the sequence within the 3'end of the antisense strand. Directly, co-transfection Let-7 mimics with active siRNAs impairs the anti-cancer activities of Let-7 mimics. However, a 3-h interval between the introduction of Let-7 mimics and a kind of siRNA avoids the competition and enhances the anti-cancer activities of Let-7 mimics. Taken together, these results have revealed that Let-7s mimics are potential candidates for cancer gene therapy.

The design of vectors for RNAi delivery system.

RNA interference (RNAi) is a process of double-stranded RNA-dependent post-transciptional gene silencing that occurs mainly in the mRNA processing bodies (P-bodies) of cells. It has become the most powerful and widely used gene strategy for genetic analysis and molecular therapeutics, based on the highly specific and efficient silencing of target genes. The key challenge for achieving effective RNAi in vitro and in vivo is its delivery to the desired organs and into the target cells. The RNAi delivery systems can be either non-viral or viral vectors. The main candidate for RNAi as a therapeutical tool is the viral-based vectors, including retroviruses, adenoviruses, adeno-associated viruses (AAV), lentiviruses and herpes simplex virus-1 (HSV-1). There is a high potential for clinical use of RNAi in treatment of a wide variety of human diseases, including genetic disorders, infectious diseases and cancer. This paper reviews the designs of inducible, tissue specific, hybrid, oncolytic and high-throughput RNAi vectors based on plasmids or viruses, and discusses their specificity, efficiency and safety.

Preparation and blood coagulation evaluation of chitosan microspheres.

Cross-linked chitosan microspheres (40-100 microm) with smooth surface were prepared by the methods of emulsification and ethanol coagulant. FTIR results showed that the cross-linking reaction occurred on the amino groups of chitosan molecules. The swelling characteristic of chitosan microspheres was influenced by the environment pH, being generally greater at low rather than higher pH values. The coagulation properties of chitosan microspheres were evaluated by dynamic blood clotting, platelet adhesion and activation, erythrocyte adhesion, hemolysis, and protein absorption assays. Chitosan microspheres can shorten the clotting time and induce the adhesion and activation of platelets. But the shortening of clotting time by chitosan microspheres may be related to not only platelet aggregation, but also erythrocyte aggregation. Take together, chitosan microspheres may be potential use as thrombospheres.