Promoter hypermethylation of estrogen receptor alpha gene is correlated to estrogen receptor negativity in Iranian patients with sporadic breast cancer

Breast Cancer is the most common cancer in Iranian women. Breast tumors are classified based on the estrogen receptor alpha [ER alpha] expression status into ER negative and ER positive tumors. ER negative tumors tend to have worse prognosis and less likely to respond to endocrine therapy. Aberrant methylation of gene promoter is one of the mechanisms for gene silencing in breast tumors. Because of its reversible nature, promoter methylation is a good target for new therapeutic strategies. We aimed to evaluate the frequency of this epigenetic event in ER alpha gene and its association to clinicopathological features in Iranian breast cancer patients. In this case control study the patient series consisted of 100 sporadic primary breast cancer cases [51 ER negative and 49 ER positive tumors]. None of the participants had chemo or radiotherapy before surgery. In breast tumors ER alpha promoter methylation were assessed with methylation specific polymerase chain reaction [MSP]. Data was collected on clinicopathological features of the patients. Correlation between ER alpha methylation and clinicopathological characteristics of the patients was investigated by Pearson Chi-Square and Fisher's exact test. ER alpha methylation was detected in 98% of ER negative and 65% of ER positive breast tumors. A strong correlation was found between ER alpha methylation and ER negativity in tumors [p<0.0001]. Also, ER alpha methylation has associated to progesterone receptor negativity [p<0.008] and double receptor negative status [p<0.0001] in breast tumors. ER alpha methylation occurs with high frequency in the breast tumors of Iranian breast cancer patients and may play a considerable role in pathogenesis of ER alpha negative tumors as a poor prognosis and more aggressive category. The reversible nature of DNA methylation may provide new therapeutic possibilities in ER negative breast tumors

[Study of the association between estrogen receptor alpha gene expression in the levels of RNA and protein in primary breast tumors]

Estrogen receptor alpha protein status is determined by routine immunohistochemistry analysis in all malignant breast tumors. This assay has its limitations. RNA based techniques are potential complements for immunohistochemistry but it must be noticed that gene silencing may occur at different levels from RNA to protein. The aim of this study was the comparison of the results from these two assays and characterizing the tumors subgroup in which gene expression occurs at RNA level but the target protein is absent. 92 primary breast tumors including their clinical and IHC results were collected before treatment. Estrogen receptor gene expression of tumors was studied by Reverse Transcription Polymerase Chain Reaction [RT PCR]. In this assay, GAPDH was used as a reference gene. 36.6% of tumors with negative estrogen receptor protein showed gene expression at mRNA level. In this subgroup most of the patient were older than 50 years and in stages 3 or 4 of breast cancer and had poor prognosis according to Nottingham prognostic index. Most cases of the perineural invasion have been seen in this subgroup. It seems that RT-PCR assay would enable us to recognize a subgroup of breast tumors with poor prognosis which expresses RNA but not protein