Objectives: To search for a new clinical application of melittin (Mel): treating hepatocellular carcinoma with Mel gene.
Methods: Recombinant adenoviruses carrying the Mel gene and alpha-fetoprotein (AFP) promoter (Ad-rAFP-Mel) were constructed through a bacterial homologous recombinant system. The efficiency of adenovirus-mediated gene transfer and the inhibitory effect of Ad-rAFP-Mel on the proliferation of hepatocarcinoma cells were determined by X-gal stain and MTT assay, respectively. The tumorigenicity of hepatocarcinoma cells transfected by Ad-rAFP-Mel and the antitumor effect of Ad-rAFP-Mel on transplanted tumor in nude mice were detected in vivo.
Results: The Mel mRNA was transcribed in BEL-7402 hepatocellular carcinoma cells transducted by Ad-rAFP-Mel. The efficiency of adenovirus-mediated gene transferred to BEL-7402 cells was 100% when the multiplicity of infection of Ad-rAFP-Mel was 10 in vitro, and was also high in vivo. The inhibitive rates of Ad-rAFP-Mel and Ad-rAFP for BEL7402 cells were 66.2 +/- 2.7% and 2.9 +/- 2.3% (t=30.83, P=6.6 x 10(-6)) by MTT assay. The inhibitive rates of Ad-CMV-Mel for BEL7402, SMMC7721 and L02 cells were 58.9 +/- 9.6%, 65.9 +/- 3.8% and 31.7 +/- 1.2%, respectively, and of Ad-rAFP-Mel were 66.2 +/- 2.7%, 16.1 +/- 6.6% and 7.5 +/- 3.3%, respectively (t=1.27, P=0.27; t=11.31, P=3.5 x 10(-4); and t=12.12, P=2.7 x 10(-4) versus the Ad-CMV-Mel group in the same cells). The tumorigenicity rates of hepatocarcinoma cells transfected by Ad-rAFP-Mel were decreased. A significant antineoplastic effect was detected on transplanted tumor in nude mice by intratumoral injection of Ad-rAFP-Mel.
Conclusions: Ad-rAFP-Mel can inhibit specifically proliferation of AFP-producing human hepatocarcinoma cells in vitro and in vivo. This suggests that animal toxin gene can be used as an antitumor gene.