Ribozyme approach to study functions of vascular endothelial growth factor isoforms on the progression of non-small cell lung cancer

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The specific role of the cell-associated isoform of vascular endothelial growth factor (VEGF189) has not been clarified, while five isoforms of VEGF which have different biological activities (VEGF121, VEGF145, VEGF165, VEGF189, VEGF206) are generated by alternative splicing. We used a hammerhead-type ribozyme (V189Rz) to suppress VEGF189 mRNA.The V189Rz specifically cleaved exon 6 of VEGF189 mRNA, but showed no activity against VEGF121 or VEGF165 isoforms. The V189Rz was introduced into the human non-small cell lung cancer cell line (OZ-6/VR). The expression level of VEGF189 mRNA was decreased in the OZ-6/VR, while VEGF121 and 165 expression were preserved. The OZ-6/VR xenotransplanted into nude mice showed markedly reduced vascularisation and growth, whereas the cell line did not show any decreased growth under tissue culture conditions. The OZ-6/VR cells (1×10^5/mouse) formed no tumours, whereas the parental OZ-6 cells formed huge tumours within 8 weeks. The specific suppression of VEGF189 by the ribozyme decreased vascularity and xenotranplantability of the lung cancer cell line. The cell-associated isoform of VEGF (VEGF189) might have key roles on stromal vascularisation and growth of non-small cell lung cancer xenografts in vivo.