Intracerebral adenovirus-mediated p53 tumor suppressor gene therapy for experimental human glioma

Malignant gliomas of astrocytic origin are good candidates for gene therapy because they have proven incurable with conventional treatments. Although mutation or inactivation of the p53 tumor suppressor gene occurs at early stages in gliomas and is associated with tumor progression, many tumors including high-grade glioblastoma multiforme carry a functionally intact p53 gene. To evaluate the effectiveness of p53-based therapy in glioma cells that contain endogenous wild-type p53, a clinically relevant model of malignant human glioma was established in athymic nu/nu mice. Intracerebral, rapidly growing tumors were produced by stereotactic injection of the human U87 MG glioma cell line that had been genetically modified for tracking purposes to express the Escherichia coli lacZ gene encoding beta-galactosidase. Overexpression of the p53 gene by adenovirus-mediated delivery into the tumor mass resulted in rapid cell death with the eradication of beta-galactosidase-expressing glioma cells through apoptosis. In long-term experiments, the survival of mice treated with the p53 adenoviral recombinant was significantly longer than that of mice that had received control adenoviral recombinant. During the observation period of 1 year, a complete cure was achieved in 27% of animals after a single injection of p53 adenoviral recombinant, and 38% of the animals were tumor free in the group receiving multiple injections of p53 adenoviral recombinant into a larger tumor mass. These experiments demonstrate that overexpression of p53 in gliomas, even in the presence of endogenous functional wildtype p53. leads to efficient elimination of tumor cells. These results point to the potential therapeutic usefulness of this approach for all astrocytic brain tumors.