Detection Aberrant Promoter Methylation Of GSTP1 Gene In Hepatocellular Carcinoma

Objective To examine the methylation status of GSTP1 promoter region in hepatocellular carcinoma(HCC) , and to explore the possibility of using this assay in early detection.Methods (1) Methylation-specific PCR (MSP) was used to detect GSTP1 methylation in DNA extracted from 25 HCC tissues and 47 serum samples. The serum sample was obtained from 25 HCC patients, 14 cirrhosis patients and 8 healthy volunteers. The association of GSTP1 methylation with clinicopathological characteristics was analyzed. (2) GSTP1 protein expression was also examined by immunohistochemical staining in HCC tumor and corresponding nontumor tissue. (3) GSTP1 methylation in the HepG2 cell lines was determined by MSP and correlated with expression of the gene using reverse-transcription PCR and immunoblotting, Results (1) GSTP1 methylation was detected in 12 of 25 (48.0%) HCC tissues, and a significant correlation was found between methylation and loss of GSTP1 protein expression(P=0.001). (2) Similarly, DNA from HepG2 cell lines displayed complete GSTP1 methylation, and they failed to express GSTP1 mRNA and the corresponding protein product. Treatment of the celllines with the DNA memyltransferase inhibitor reversed the methylation, andrestored GSTPl rnRNA and protein expression. (3) In these primary tumors with GSTPl methylation, 7 of 12(58.3%) samples also had abnormal methylated DNA in the mached serum samples, moreover, none of the sera from patients with tumors not demonstrating methylation and all healthy control subjects. (4) A significant correlation was not found between abnormal promoter methylation and clinicopathological characteristics of HCC.Conclusions (1) Promoter methylation of GSTPl gene is a common event in HCC and may play an important role in hepatocarcinogenesis. (2) Detection of aberrant promoter methylation of GSTPl gene in serum may be useful for cancer diagnosis or detection of recurrence.