Effect of blocking VEGF, hTERT and Bcl-xl by multiple shRNA expression vectors on the human laryngeal squamous carcinoma xenograft in nude mice

Background: In our previous work, we constructed short hairpin RNA (shRNA) expression plasmids that targeted human telomerase reverse transcriptase (hTERT) messenger RNA, and we demonstrated that these vectors could inhibit the growth of cancer cells by 76.5% in vivo. In order to maximize the efficiency and versatility of the vector-based siRNA approach, here we have constructed multiple shRNA expression vectors that simultaneously targeted 3 different genes in cancer cells, and then investigated their effect on human laryngeal squamous carcinoma (Hep-2) in vivo. Results: We found that expression of multiple shRNAs led to a significant reduction in VEGF, hTERT and Bcl-xl mRNA and protein expression. Tumor growth curves showed that those tumors treated with the shRNAs were obviously smaller than control, non-transfected tumors. Analysis at 14 days following the final injection showed a tumor inhibition ratio of 91.2%. However, the control shRNA vectors showed none of these effects. Materials and methods: Short hairpin RNA expression vectors targeting the mRNA of VEGF, hTERT and Bcl-xl were constructed and subsequently transfected by direct injections into the tumors formed by Hep-2 cells implanted in nude mice. The expression of targeted genes as well as apoptosis of tumor cells were evaluated after treatment with multiple shRNA vectors or control vectors. Conclusions: Our results demonstrate that the application of vector-based RNAi technology that involves blocking multiple targets will be a promising therapeutic modality in the gene therapy of human cancers. The data strongly suggest that simultaneously blocking multiple genes in human cancers using an RNAi approach should be considered in cancer therapy.