OBJECTIVETo investigate the effect of small interfering RNA (siRNA) targeting human vascular endothelial growth factor (hVEGF) on A549 cell growth in nude mice and angiogenesis on chorioallantoic membrane (CAM) assay.

METHODSThree pairs of hVEGF siRNA-plasmid and non-silencing-plasmid were constructed, and transfected into A549 cells through lipofectamine 2000, respectively. The most effective pair of hVEGF siRNA-plasmid was selected by ELISA and real-time RT-PCR. A549 cells transfected with selected hVEGF siRNA- plasmid, A549 cells transfected with non-silencing-plasmid and A549 cells without transfection were inoculated into nude mice, respectively. Chick embryos were randomly divided into four groups and CAM was treated by different solutions for 48 h: culture media DMEM as negative control group,un-transfected A549 cell culture supernatants as positive control group, hVEGF siRNA A549 cell culture supernatants as hVEGF siRNA group and nonsilencing siRNA A549 cell culture supernatants as non-silencing siRNA group. The CAMs were harvested on d12 for microscopic assays.

RESULTCompared with control group, hVEGF siRNA-plasmid induced 48% reduction in hVEGF secretion by A549 cells accompanied by 70% reduction in hVEGF mRNA. Compared with non-silencing siRNA group, the mean tumor volume of murine xenograft was reduced by 58% in hVEGF siRNA group; time for xenografts growing to 50 mm(3)was delayed by 5.4 d. hVEGF contents in xenograft were reduced by 54%; but mean doubling time of tumors and the growth rate of tumors were not significantly reduced. In CAM assays, hVEGF content was zero in negative group, and in hVEGF siRNA group that was 40%-44% of non-silencing siRNA group or positive group; vessels branch points of CAM in hVEGF siRNA group or non-silencing siRNA group or positive group were increased by 45%-55% compared with negative group; total vessel length of CAM in hVEGF siRNA group was increased by 53% compared with negative group, while in non-silencing siRNA group or positive group that was increased by 97% or 99%. Compared with negative control group, the proliferation of microvessels was increased when cell culture supernatant with hVEGF was added in hVEGF siRNA group, significant proliferated vessels were observed in non-silencing siRNA group or positive group.

CONCLUSIONA plasmid-mediated hVEGF siRNA has been constructed and verified, which can effectively downregulate the expression of hVEGF in human A549 cells, resulting in the inhibition of angiogenesis. hVEGF siRNA can delay initial growth of A549 tumor xenograft but not reduce the growth rate.