[Construction of adenovirus expressing anti-vascular endothelial growth factor hairpin ribozyme and its inhibition of growth of colorectal cancer HT-29 cells].

Background And Objective: Oversexpression of vascular endothelial growth factor (VEGF) is correlated to poor prognosis of colorectal cancer. This study was to construct replication deficient adenovirus carrying anti-VEGF hairpin ribozyme and investigate its inhibitory effects on VEGF expression and growth of colorectal cancer HT-29 cells.

Methods: Anti-VEGF hairpin ribozyme was cloned into the transfer vector pAdTrack-CMV, and recombined with adenoviral backbone vector pAdEasy-1 in BJ5183 bacteria. The recombinant plasmids were packaged and amplified in 293 cells (named Ad-Rz). The expression of anti-VEGF ribozyme in HT-29 cells was examined by RT-PCR. Inhibition of Ad-RZ on VEGF mRNA and protein expressions were detected by real-time PCR and ELISA, respectively. Inhibition of cell growth was measured by MTT assay. HT-29 cell xenografts were established in nude mice and the microvessel density (MVD) was determined by CD34 staining.

Results: The anti-VEGF ribozyme was successfully inserted into the adenoviral vector. Anti-VEGF ribozyme was effectively expressed in HT-29 cells. After infection by Ad-RZ, the relative expression of VEGF mRNA was decreased to about(45+/-0.01)% of that of PBS control group in HT-29 cells (P<0.05); the amount of VEGF protein in the supernatant of Ad-Rz treated cells [(OD=(0.46+/-0.35)/million cells] was lower than that of PBS treated cells [(OD=(0.80+/-0.35)/million cells] (P<0.05). Although Ad-Rz did not significantly inhibit cell growth of HT-29 cells (P>0.05), it significantly inhibited tumor angiogenesis of HT-29 cell xenografts in nude mice, compared with PBS group (P<0.05). The proliferation rate of xenografts treated by Ad-Rz was lower than that treated by PBS, but the difference was not significant (P>0.05).

Conclusion: Anti-VEGF hairpin ribozyme mediated by adenovirus could inhibit the expression of VEGF and the tumor angiogenesis in colorectal cancer HT-29 cells.