A novel approach for examining the anti-proliferative effect of protein kinase C inhibitors against human astrocytoma cells.

Prognosis for astroglial brain tumors that are not amenable to surgical resection remains poor and even successful treatment with current chemoradiotherapy is associated with debilitating sequelae. Consequently, a need to identify novel therapeutics for the treatment of brain tumors remains. Regulation of protein kinase C (PKC) whose activity regulates many cellular functions is crucial for maintaining normal cellular proliferation. Recent reports indicate that malignant glioma cell lines express 100 to 1000-fold higher PKC activity when compared to non-neoplastic astrocytes. In this study we used a novel approach for the evaluation of known PKC inhibitors (CGP 41251, Go 6976, and tamoxifen) as chemotherapeutic agents for the inhibition of growth of an astroglial derived cell line. For this purpose, we constructed a model cell system based on the measurement of light production in cells transfected with the luciferase reporter gene whose expression was quantitated by a highly sensitive, rapid, and easy to perform assay. We isolated U-373MG/MEK1C clone whose highly increased luciferase activity was independent of external stimuli and directly proportional to cell number, and therefore, was used as a measure of cell proliferation to quantitate the effects of several PKC inhibitors on growth of astrocytoma cells in vitro. In conclusion, we have constructed a novel cell system that can be utilized for high throughput screening and identification of potential anti-cancer drugs active against astrocytoma cells in culture.