Detection of Estrogen Receptor Alpha and Beta Gene Mutations in Iraqi Women with Breast Cancer

   This study was aimed to determine the mutations and single nucleotide polymorphisms (SNPs) in exon 4 and 6 of estrogen receptor alpha (ESR1) gene as well as exon 3 and 7 of estrogen receptor beta (ESR2) gene in Iraqi women with breast cancer. Different group of samples (25 of blood with FFPE from the same patient, 15 of fresh tissue with blood and FFPE from the same patient, and formalin fixed
paraffin embedded) were collected from women with breast cancer during 1  of April to 1 st  of September, 2014. Immunoexpression of estrogen receptor (ER) protein was examined in 50 samples of FFPE by using immunohistochemistry technique. A specific positive immune staining of estrogen receptor was detected in 35 (70%) women with breast cancer. Moreover, a correlation between expression of estrogen protein and risk factors such as age, familiar history, and metastasis to lymph node was studied. A significant difference was noticed between expression of estrogen protein and age, familiar history, and metastasis lymph node while nonsignificant differences were found between estrogen expression and menopause. On the other hand, the molecular analysis of exon 4 and 6 in ESR1 and exon 3 and 7 in ESR2 has been studied by using PCR. It was found that exon 4 and 6 in ESR1were appeared as a single band with size 370 and 300 bp respectively, while exon 3 and 7 in ESR2 were revealed as a single band with size 151 and 157 bp, respectively.  Moreover, single nucleotide polymorphisms (SNPs) were determined in exon 4 and 6 of ESR1 and in exon3 and 7 of ESR2 using DNA sequence. Then,nucleotide sequences of these exons were aligned with the control group (healthy women) and with NCBI. Seven polymorphisms (AAG, AAA, TTT,AAA, CCG, AAA, and AAC)  were detected in exon 4 of ESR1, six of them (AAG, AAA, TTT, AAA, AAA, and AAC) were novel SNPs while CCG was notified as a common polymorphism in comparison with variants recorded in different population, all types of polymorphism in exon 4 of ESR1were substitution.  Whereas no SNPs were detected in exon 6 of ESR, nevertheless two polymorphisms, A 375455 C and G 375718 T, in intronic flaking region around this exon were determined. Regarding ESR2, there was no SNP in exon 3 has been identified. While three novel polymorphisms (ACT, AGG and GCA) were detected in exon 7, the type of those polymorphisms was deletion for ACT and AGG while substitution for GCA.  From this study, it can be concluded that some single nucleotide polymorphism in ESR1 and ESR2 may effect gene expression.
 



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