ABSTRACT
OBJECTIVE: It has been suggested that protein kinase C(PKC) may be one of a number of important regulatory enzymes influencing the tumor cell proliferation and intracellular sensitivity to irradiation. In this study, authors investigate the role of PKC in the growth and radiosensitization of glial brain tumors. METHODS: Human glioblastoma cell line U-87 was stably transfected with sense and antisense complementary deoxyribonucleic acid(cDNA) encoding PKCalpha. The effect of sense and antisense PKCalpha cDNA transfection on PKCalpha expression, PKC activity, cell proliferation, and radiosensitivity of tumor cells was determined. RESULTS: There was no significant difference in cell proliferation between control cells and cDNA(sense and antisense) transfected cells on thiazolyl blue(microculture tetrazolium, MTT) assay. PKC activity was increased by 68% in cells transfected with the sense PKCalpha cDNA(U-87/sPKCalpha), and was reduced by 32% in cells transfected with the antisense PKCalpha cDNA(U-87/aPKCalpha) compared to control cells(p<0.05). Western blotting with a polyclonal antibody against PKCalpha and scanning densitometric analysis of autoradiograms revealed that PKCalpha expression was enhanced by about 5 times of that of control cells in U-87/sPKCalpha cells and was suppressed by more than 30% of that of control cells in U-87/aPKCalpha cells. After exposure to 6 Gy irradiation, cell viability on MTT assay was increased by 43.7% in U-87/sPKCalpha cells and was reduced by 24.3% in U-87/aPKCalpha cells compared to control cells(p<0.001). CONCLUSION: The results of this study demonstrate that PKCalpha overexpression confers a relative radior-esistance and PKCalpha suppression enhances a radiosensitivity on U-87 cells. These observations suggest that PKCalpha plays an important role in regulating cell response to irradiation and a specific modulation of PKCalpha expression in malignant gliomas may influence the radiosensitivity of them.