Suppression of tumor growth by intratumoral injection of short hairpin RNA-expressing plasmid DNA targeting β-catenin or hypoxia-inducible factor 1α

To inhibit the growth of murine melanoma B16 cells in mice, we downregulated the gene expression of β-catenin and hypoxia-inducible factor 1α (HIF1α) in the tumor cells by delivering short hairpin RNA (shRNA)-expressing plasmid DNA (pDNA) targeting one of these genes. Transfection of any of the shRNA-expressing pDNAs to B16 cells resulted in the reduction of the corresponding mRNA, which was associated with a reduced number of viable cells. A flow cytometric analysis of annexin V labeling assay was also performed to count the number of apoptotic cells. A flow cytometric analysis showed that the suppression of the expression of β-catenin or HIF1α in B16 cells increased the number of apoptotic cells. An intratumoral injection of pshβ-catenin (shRNA-expressing pDNA targeting β-catenin) or pshHIF1α (shRNA-expressing pDNA targeting HIF1α) followed by electroporation greatly suppressed the expression of the corresponding target mRNA in the intradermal tumor tissue. The growth of the intradermal tumor was significantly (P < 0.05) suppressed by the treatment. In conclusion, tumor growth was successfully inhibited by the intratumoral delivery of pshβ-catenin or pshHIF1α.