DNAzymes are a novel class of gene suppressors that selectively bind to an
RNA substrate by Watson-Crick base pairing and cleave phosphodiester bonds. To explore the potential for
therapeutic use of
catalytic DNA molecules, active
DNAzymes targeting the bcl-xL gene were generated through a multiplex in vitro selection. The
DNAzyme-mediated down-regulation of the bcl-xL expression was demonstrated in various
cancer cell lines by Western blots. Treatment of the cells with the active
DNAzyme led to increases in percentage of apoptotic cells and
cytochrome c release from mitochondria, a hall marker of apoptosis. When combined with chemotherapeutics such as
Taxol, the
DNAzyme significantly sensitised a panel of
cancer cells to apoptosis as measured by cell survival assay. In
Taxol-resistant cells, down-regulation of bcl-xL expression by the
DNAzyme reversed the chemo-resistant phenotype of the
cancer cells. In a xenograft mouse model, the
DNAzyme was delivered into the
tumors via an ALZET osmotic pump and shown to chemosensitize PC3
tumor when treating with
Taxol. The results from the present study demonstrate that bcl-xL
DNAzyme treatment facilitates apoptosis in solid
tumors and suggest the potential use of bcl-xL
DNAzyme in combination with chemotherapeutics for
cancer therapy.