Silencing Bag-1 gene via magnetic gold nanoparticle-delivered siRNA plasmid for colorectal cancer therapy in vivo and in vitro

Apoptosis disorder is generally regarded as an important mechanism of carcinogenesis. Inducement of tumor cell apoptosis can be an effectual way to treat cancer. Bcl-2-associated athanogene 1 (Bag-1) is a positive regulator of Bcl-2 which is an anti-apoptotic gene. Bag-1 is highly expressed in colorectal cancer, which plays a critical role in promoting metastasis, poor prognosis, especially in anti-apoptotic function, and is perhaps a valuable gene target for colorectal cancer therapy. Recently, we applied a novel non-viral gene carrier, magnetic gold nanoparticle, and mediated plasmid pGPH1/GFP/Neo-Bag-1-homo-825 silencing Bag-1 gene for treating colorectal cancer in vivo and in vitro. By mediating with magnetic gold nanoparticle, siRNA plasmid was successfully transfected into cell. In 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, magnetic gold nanoparticle had no significant cytotoxicity and by which delivered RNA plasmid inhibited cell viability significantly (P < 0.05). Downregulation of Bag-1 promoted cell apoptosis (similar to 47.0 %) in vitro and significantly decreased tumor growth when the cells were injected into nude mice. Based on the studies in vivo, the relative expression of Bag-1 was 0.165 +/- 0.072 at mRNA level and similar to 60 % at protein level. In further study, C-myc and beta-catenin, mainly molecules of Wnt/beta-catenin pathway, were decreased notably when Bag-1 were silenced in nanoparticle plasmid complex-transfected Balb c/nude tumor xenograft. In conclusion, Bag-1 is confirmed an anti-apoptosis gene that functioned in colorectal cancer, and the mechanism of Bag-1 gene causing colorectal cancer may be related to Wnt/beta-catenin signaling pathway abnormality and suggested that magnetic gold nanoparticle-delivered siRNA plasmid silencing Bag-1 is an effective gene therapy method for colorectal cancer.