Abstract
In the area of gene-directed enzyme prodrug therapy (GDEPT), using herpes simplex virus thymidine kinase (HSV-tk) paired with prodrug ganciclovir (GCV) for cancer treatment has been extensively studied. It is a process involved with two steps whereby the gene (HSV-tk) is first delivered to malignant cells. Afterward, non-toxic GCV is administered to that site and activated to cytotoxic ganciclovir triphosphate by HSV-tk enzyme expressed exogenously. In this study, we presented a one-step approach that both gene and prodrug were delivered at the same time by incorporating them with polymeric micellar nanovectors. GCV was employed as an initiator in the ring-opening polymerization of ε-caprolactone (ε-CL) to synthesize hydrophobic GCV-poly(caprolactone) (GCV–PCL), which was furthered grafted with hydrophilic chitosan to obtain amphiphilic polymer (GCV–PCL–chitosan) for the fabrication of self-assembled micellar nanoparticles. The synthesized amphiphilic polymer was characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Micellar prodrug nanoparticles were analyzed by dynamic light scattering, zeta potential, critical micelle concentration, and transmission electron microscopy. Polymeric prodrug micelles with optimal features incorporated with HSV-tk encoding plasmids were cultivated with HT29 colorectal cancer cells and anticancer effectiveness was determined. Our results showed that prodrug GCV and HSV-tk cDNA encoded plasmid incorporated in GCV–PCL–chitosan polymeric nanocarriers could be delivered in a one-step manner to HT-29 cells and triggered high cytotoxicity.
Highlights
Our results indicate that GCV–PCL–chitosan/herpes simplex virus thymidine kinase (HSV-tk) nanovectors are potent carriers for one-step gene-directed enzyme prodrug therapy (GDEPT)
Fetal bovine serum (FBS), mouse IgG1 horseradish peroxidase (HRP)-conjugated antibody, and MTT cell proliferation/viability assay kits were all purchased from R&D Systems (Minneapolis, MN)
To expand the range of tumors susceptible to cytotoxic drugs converted from enzymecatalyzed prodrug, gene-directed enzyme prodrug therapy (GDEPT) has been developed
Summary
To facilitate tumors susceptible to enzyme-prodrug cancer therapy, prodrug-activating exogenous enzymes can be delivered to tumor cells using genes. This approach is so-called gene-directed enzyme prodrug therapy (GDEPT) [1]. It is a two-step treatment for cancer therapy. Enzymes are delivered to and expressed in target cells where they can activate subsequently administered non-toxic prodrugs to cytotoxic drugs. A gene expressing the enzyme is delivered. A prodrug is administered that can be activated to a toxic drug by the enzyme that has been expressed in the tumor.
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