Promoter Methylation Status of PTEN Tumor Suppressor Gene among Palestinian Breast Cancer Patients

Abstract

Background: The phosphatase and tensin homolog (PTEN) gene, is a tumor suppressor gene located on chromosome 10q23. Several studies showed that 30-40% of sporadic breast cancer cases show a loss of PTEN protein levels due to mutations, loss of heterozygosity, or promoter hypermethylation. The PTEN promoter methylation is a major epigenetic silencing mechanism leading to the development of tumors. Purpose: The purpose of this study was to explore PTEN gene promoter methylation status in Palestinian breast cancer patients and to investigate if the methylation status in PTEN gene related to breast cancers has been correlated with a triple-negative phenotype. Methods: In this study, DNA samples extracted from formalin fixed paraffin embedded (FFPE) blocks after characterizing the PTEN expression by immunohistochemical staining, for 38 patients diagnosed with breast cancer were analyzed, and DNA methylation in the 5' CPG island spanning the PTEN transcription start site was determined using methylation specific polymerase chain reaction (MSP) assay. Results: Promoter methylation of PTEN was detected in three (8%) out of 38 specimens, all the methylated tumors had loss of PTEN expression. The Promoter methylation of PTEN gene was not correlated with the clinicopathological parameters including the loss of PTEN expression and the triple negative breast cancer. Conclusion: We reported here for the first time the status of PTEN methylation among Palestinian breast cancer patients. Our data show that methylation of the PTEN promoter in 38 breast cancer women is not associated with the loss of PTEN protein expression, and triple negative breast cancer subtype (TNBC) in these samples. Although, the methylated cases are rare among the Palestinian patients, but further studies using large sample size and high throughput analysis is highly recommended