) Derangements of p53 function are common in malignant gliomas and may be responsible for the genetic instability and resistance tot ionizing radiation (IR) that contribute to the poor prognosis of these tumors. The relationship between p53 and apoptosis suggests that viral transduction of wild-type (wt) p53 could be used to impair proliferation and enhance the sensitivity of glioma cells to IR. Preliminary studies demonstrate that rat malignant glioma cells when transduced with wt p53 in vitro exhibit decreased clonogenic survival and increased apoptosis after IR exposure. Implanted in syngeneic rats, p53 transduced cells form intracerebral tumors similar to control cells but animals receiving the p53 transduced cells survive significantly longer than those with control cells. IR appears to further prolong survival in this group. Preliminary evidence indicates the feasibility of viral transgene expression in brain and brain tumors by direct intraparenchymal controlled-rate infusion. It is hypothesized that viral particle concentrations and interrelated parameters of infusion volume, rate and pressure will have optima for maximum distribution of transduction while minimizing tissue disruption. In four Specific Aims, this project will test the hypothesis that adenoviral transduction of rodent and human glioma cells with vt p53 can enhance their radiosensitivity both in vitro and in vivo; (1) the p53 status (wt versus mutant) and susceptibility to adenoviral transduction will be studied in glioma cell lines to facilitate interpretation of their responses to IR exposure after p53 transduction. Variability in transduction efficiency will be determined in a selection of primary human tumor cell cultures. (2) In vitro studies will determine the ability of transduced wt p53 to impair proliferation and enhance apoptosis after IR exposure in rodent and human glial tumor cells. (3) Controlled-rate positive pressure infusion of adenoviral vector into rat brain and intracerebral gliomas will determine parameters critical for delivery and transduction of tumor cells in vivo. Volume of distribution and per cent transduction will be examined while monitoring behavioral or histological evidence of toxicity. (4) The effects of p53 transduction on the radiosensitivity of glioma cells in vivo will be studied with respect to histology, apoptosis, tumor growth and animal survival. Human cell lines will be studied after transduction in vivo by positive pressure infusion prior to irradiation.
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