Abstract
BACKGROUND AND OBJECTIVE: One of many limitations for cancer gene therapy is the inability of the therapeutic gene to transfect a sufficient number of tumor cells. Photochemical internalization (PCI) is a photodynamic therapy-based approach for improving the delivery of macromolecules and genes into the cell cytosol. The utility of PCI for the delivery of the GFP reporter gene on the same plasmid as a tumor suppressor gene (PTEN) was investigated in monolayers of U251 human glioma cells and muticell U87 glioma spheroids. MATERIALS AND METHODS: U251 monolayers or U87 spheroids were incubated in AlPcS(2a) and non-viral vector polyplexes for 18 hours. In all cases, light treatment was performed with a diode laser at a wavelength of 670 nm. The non-viral transfection agents, branched polyethylenimine (bPEI), or protamine sulfate (PS), were used with the plasmid constructs GFP/PTEN or GFP. RESULTS: PS/GFP polyplexes were much less toxic to the glioma cells compared to bPEI/GFP polyplexes but were highly inefficient at gene transfection if used alone. PCI resulted in a 5- to 10-fold increase in GFP protein expression compared to controls. PCI-bPEI/PTEN or PCI-PS/PTEN transfection of either U251 monolayers or U87 spheroids significantly inhibited their growth. but had no effect on MCF-7 cells containing a wild-type PTEN gene. In addition PCI-GFP transfection of gliomas cells had no effect on their growth pattern. CONCLUSIONS: Collectively, the results suggest that AlPcS(2a) -mediated PCI can be used to enhance cell growth inhibition via transfection of tumor suppressor genes in glioma cells containing mutant PTEN genes.