Relationship between promoter methylation and protein expression of glutathione S-transferase gene class P1 in breast cancer

Publish : December 15, 2012
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Supparit Pakdeethai, BSc**, Valla Fongchaiya, BSc**, Tanett Pongtheerat, PhD***, Kroon- pong Iampenkhae, MD**, Pichet Sampatanukul, MD, MSc***

This paper was supported by the CU.GRADUATE SCHOOL THESIS GRANT of Chulalongkorn University.
**Department of Pathology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
*** Unit of Biochemistry, Department of Medical Science, Faculty of Science, Rangsit University, Patumthani, Thailand
Correspondence :   Pichet Sampatanukul, MD, MSc, Email: fmedpst@gmail.com


ABSTRACT

 

Background: Glutathione S-transferase gene class P1 (GSTP1) encodes glutathione S-transferase P1 (GSTP1) that catalyses detoxifying metabolism of glutathione. The lack of GSTP1 expression is linked to carcinogen-esis and is related to promoter methylation. The previous studies of GSTP1 hypermethylation in breast cancer reveal diverse results and suspicious correlation with GSTP1 expression. Objective: To investigate the correlation between promoter methylation and protein expression of GSTP1 in breast cancer.

Methods: One hundred breast cancer samples were used. The study of promoter methylation employed meth- ylation specifi c assay (MSP) on fresh tissues while the assessment of protein expression was done with im- munohistochemistry (IHC) on formalin fi xed paraffi n embedded tissues. The results were correlated each other and with clinicopathologic parameters using Chi Square statistics.

Results: The rate of hypermethylation of GSTP1 was 28%. Of which, 8 cases showed double-band signal indicating either heterozygous tumors or contamination with normal tissues. Another case was found in a non- invasive carcinoma. Of the remaining 19 cases with hypermethylation status, 12.5% contradictorily revealed protein expressions.
The correlation of the results from MSP and IHC methods yielding the Chi Square test,
p-value= 0.04. The correlations with clinicopathological parameters showed that progesterone receptor corre- lated with MSP-methylation status (p-value= 0.05) and estrogen receptor correlated with GSPTP1 expression (p-value= 0.001). The other parameters – tumor size, tumor grade, lymph node status, HER2-IHC score, Ki67 index were not correlated.

Conclusion: The results between hypermethylation of GSTP1 by MSP and GSTP1 expression by IHC cor- relate, however, some unclear technical problems exist.

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Address of editorial Corresponce
✎  Vorachai Sirikulchayanonta, MD, Editor-in-Chief: Asian Archives of Pathology, Faculty of Science, Rangsit University, Pathumthani 12000, Thailand.
✉  Email address: asianarchpath@gmail.com, vorachai7@gmail.com