Introduction: Abnormalities in the p53 and p16 tumor suppressor genes are one of the most common occurrences associated with human neoplasia. Consequently, restoration of wild-type p53 or p16 functions is seen as a particularly promising approach for cancer gene therapy. In vitro and in vivo data have demonstrated that virus-mediated p53 gene transfer can induce active cell death and ovarian tumor regression.
Aim: To evaluate the efficiency of intratumoral injection of naked DNA in tumor growth inhibition in an ovarian xenograft model. For that purpose, plasmid vectors encoding wild-type p53 (wt-p53) or p16 alone or in combination were used.
Methods: Nude mice were injected subcutaneously with the human ovarian adenocarcinoma cell line SKOV3. Three weeks after xenograft, tumor-bearing mice were injected twice a week with plasmid vectors carrying WT-p53 and/or WT-p16 cDNA. Empty plasmids and saline buffer were used as control. Tumor growth was monitored to evaluate the inhibition potential with p53 and/or p16 restoration.
Results: When compared to the control, intratumoral repeated injections of naked plasmid DNA encoding wt-p53 were inhibiting tumor growth. This inhibition was not observed with p16 and no synergy could be obtained between p53 and p16. p53 expression was restored in 84% of mice injected with plasmid encoding wt-p53. p16 expression was restored in 63% of mice injected with plasmid encoding p16.
Conclusions: In this report we demonstrated that: (i) naked DNA represents an efficient gene transfer in the SKOV3 xenograft model; (ii) restoration of wt-p53 gene allows tumor growth inhibition; and (iii) this inhibition could be correlated with p53 expression as seen in 84% of treated mice after repeated naked DNA injections. These results allow us to envisage naked DNA as a therapeutic adjuvant in ovarian cancer treatment, concomitantly with tumor resection and chemotherapy.