Eradication of p53-mutated head and neck squamous cell carcinoma (HNSCC) xenografts using nonviral p53 gene therapy and photochemical internalisation (PCI)

Abstract

3155 Background: p53 gene therapy trials have been initiated using viral vectors in p53-mutated HNSCC. Alternatively, using nonviral vectors for gene therapy is limited because of their low transfection rate. Our in vitro results using PCI demonstrated that PCI enhances the transfection efficiency of polyethylenimine-mediated p53 gene transfer and justify in vivo evaluation. Methods: Tetraglucosylated polyethylenimine (PEIGlu4)-mediated gene transfer was performed alone or in conjunction with PCI, in mice bearing HNSCC xenograft. Using luciferase as reporter, we evaluate the influence of PCI on the transgene expression kinetics. Then, p53 gene transfer was performed by weekly injection of p53/PEIGlu4 complexes during five (Group A) or seven (Group B) consecutive weeks. Efficiency of the gene therapy was evaluated by following tumor growth and by analysis of P53, P21, mdm2, Bax and Bcl2 proteins expression. Results: Using PCI, the expression of luciferase was significantly (P < 0.01) enhanced. Enhancement was maximal (20-fold) at 48h and remained significant during 7 days after completion of the transfection protocol. Applying PCI to p53 gene transfer, tumor growth inhibition was observed in all transfected animals. One week after the last PCI-mediated p53 gene transfer, complete tumor regression was achieved in 4/6 mice (Group A) and in 6/6 mice (Group B). Three weeks after the transfection tumor regrowth was observed in 3/4 mice (Group A) and in 1/6 mice (Group B). Successful tumor cure was achieved in 1 mouse (Group A) and in 5/6 mice (Group B) that were still tumor-free 8 weeks after the last transfection. The use of PCI led to higher P53 protein expression and was correlated with subsequent induction of Bax, P21 and MDM2 proteins and with repression of Bcl2 protein. Conclusions: PCI enhances the in vivo efficiency of PEIGlu4-mediated p53 nonviral gene transfer and can be proposed as a potent alternative for p53 gene therapy in HNSCC. No significant financial relationships to disclose.