Human malignant gliomas are among the most intractable of human tumors to therapy. There is, therefore, a continued urgent need for a better understanding of the molecular mechanisms underlying the malignant growth, progression and therapeutic failure in these tumors. Among the most common molecular alteration in brain and other human tumors is the over-expression of the glutathione S-transferase P1 (GSTP1) gene. This application is based on several important findings on the GSTP1 gene in human gliomas that have been made in our laboratory. These include the discovery of allelopolymorphism of the GSTP1 gene locus and the demonstration that GSTP1 gene expression in gliomas is highly heterogeneous and is a strong prognostic indicator of patient survival and response to therapy. Our goal in this application is to better understand the molecular mechanisms that regulate differential GST-pi expression among malignant gliomas. We will test the hypothesis that the heterogeneity in GSTP1 expression among gliomas results from differential transcriptional activity of the GSTP1 gene and that differences in methylation of CpGs in the 5'-region of the GSTP1 gene results in altered chromatin structure and altered transcription factor binding to the GSTP1 promoter, which ultimately accounts for the differences in GSTP1 expression between gliomas. Using both primary specimens and cell lines of human malignant gliomas, we will a) Determine be extent to which differential GSTP1 expression among malignant gliomas is regulated at the transcriptional level; b) Determine the relationship between methylation status of CpGs in the 5?-region of the GSTP1 gene and the transcriptional activity and expression of the GSTP1 gene in gliomas, and examine whether different GSTP1 alleles are differentially methylated and expressed, and whether GSTP1 gene methylation status is associated with drug resistance in gliomas; c) Investigate the effects of the methylation of CpGs in the GSTP1 5'-region on transcription factor binding to the GSTP1 promoter region and on GSTP1 promoter function; d) Examine whether methylation of the GSTP1 gene is associated with altered histone acetylation/deacetylation and chromatin structure at the GSTP1 gene locus, and whether these together determine GSTP1 expression in gliomas. The proposed studies represent a well-focused innovative research effort. The results should yield important new information on DNA methylation-related mechanisms involved in the over-expression of the GSTP1 gene in human gliomas and will contribute to efforts in the rational development of more effective agents and treatment strategies for these tumors. The results should also lead to a better understanding of the malignant process, not only in gliomas, but also in many other human cancer characterized be GSTP1 over-expression.
| Singh, Simendra; Okamura, Tatsunori; Ali-Osman, Francis (2010) Serine phosphorylation of glutathione S-transferase P1 (GSTP1) by PKC? enhances GSTP1-dependent cisplatin metabolism and resistance in human glioma cells. Biochem Pharmacol 80:1343-55 |
| Lo, Hui-Wen; Ali-Osman, Francis (2007) Genetic polymorphism and function of glutathione S-transferases in tumor drug resistance. Curr Opin Pharmacol 7:367-74 |
| Lo, Hui-Wen; Antoun, Gamil R; Ali-Osman, Francis (2004) The human glutathione S-transferase P1 protein is phosphorylated and its metabolic function enhanced by the Ser/Thr protein kinases, cAMP-dependent protein kinase and protein kinase C, in glioblastoma cells. Cancer Res 64:9131-8 |
