Human estrogen receptor (ESR) gene locus: PssI dimorphism

ESR1 promoter polymorphism is not associated with nonsyndromic cryptorchidism

The ESR1 promoter microsatellite (TA)n was reported as a potential functional polymorphism. In a case-control study, we were unable to demonstrate any association between (TA)n and nonsyndromic cryptorchidism in Italian and Spanish study populations.

Association of the estrogen receptor alpha gene polymorphisms with osteoporosis in the Mexican population

The estrogen receptor gene (ER alpha) has been implicated in the development of osteoporosis. In this study, the association of two ER alpha gene polymorphic markers (a TA dinucleotide repeat and a single nucleotide polymorphism, G2014A) with osteoporosis was tested in 70 osteoporotic women, 70 non-osteoporotic women and 500 subjects from the Mexican population. According to the genetic analysis of the Mexican population using eight unlinked polymorphic markers, we found that our population is structured into three subpopulations; therefore, the allele-phenotype relationship was analyzed with a statistical method that considered population stratification. We found that the G2014A polymorphism is associated with the presence of osteoporosis while the TA dinucleotide repeat is not. The G allele and the GG genotype frequencies of the G2014A marker were significantly higher in osteoporotic than in non-osteoporotic women. Likewise, subjects bearing the G allele in heterozygous or homozygous displayed lower values for lumbar bone mineral density and T score than those who did not present any G allele. The effect of confounders for osteoporosis on the association of G allele-osteoporosis was ruled out. In summary, we conclude that the G2014 polymorphism may become a useful marker for genetic studies of osteoporosis in the Mexican population.

Association of estrogen receptor alpha polymorphisms with breast cancer risk in older Caucasian women

Estrogens exert their effect on the breast through the estrogen receptor. We prospectively investigated breast cancer risk associated with 2 polymorphic sites in the estrogen receptor alpha gene (ESR1). A total of 4,248 Caucasian women from the Study of Osteoporotic Fractures were genotyped for the -401 T/C and -354 A/G polymorphisms in ESR1. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the associations between genotypes and breast cancer. During a mean follow-up of 12.4 years, 252 (5.9%) women developed breast cancer. The HR (95% CI) for breast cancer were 0.928 (0.708, 1.22) and 0.834 (0.538, 1.29) for the -354 A/G and A/A genotypes, respectively. Interactions with -354 variant were observed for smoking (HR = 1.52 and 1.56 for A/G and A/A smokers, respectively; HR = 0.74 and 0.60 for A/G and A/A non-smokers, respectively; interaction p = 0.03) and walking (HR = 0.75 and 1.15 for A/G and A/A walkers, respectively; HR = 0.18 and 0.49 for A/G and A/A non-walkers, respectively; interaction p = 0.01). There were no differences in the HR for the -401 T/C genotypes. An interaction between parity and carriage of the T allele was found (HR = 0.60 vs. 1.12 for nulliparous vs. parous women; interaction p = 0.03). ESR1 polymorphisms in combination with lifestyle factors may be associated with breast cancer risk in older Caucasian women.

Genetics of osteoporosis: role of steroid hormone receptor gene polymorphisms

Osteoporosis is a common skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. In the past years, twin and family study have shown that this disease recognizes a strong genetic component and that genetic factors play an important role in regulating bone mineral density (BMD). While in few isolate conditions osteoporosis can be inherited in a simple Mendelian pattern, due to single gene mutations, in the majority of cases has to be considered a multifactorial polygenic disease in which genetic determinants are modulated by hormonal, environmental and nutritional factors. Given the important role that steroid hormones play in bone cell development and in the maintenance of normal bone architecture, polymorphisms at receptor of the steroid/thyroid hormone receptor superfamily, such as estrogen receptor alpha (ERalpha) and Vitamin D receptor (VDR) have been thoroughly investigated in the last years and appeared to represent important candidate genes. The individual contribution of these genetic polymorphisms to the pathogenesis of osteoporosis remains to be universally confirmed and an important aim in future work will be to define their functional molecular consequences and how these polymorphisms interact with each other and with the environment to cause the osteoporotic phenotype. A further promising application of genetic studies in osteoporosis comes from their pharmacogenomic implications, with the possibility to give a better guidance for therapeutic agents commonly used to treat this invalidating disorder or to identify target molecules for new therapeutic agents.

Association of bone mineral density with polymorphism of the estrogen receptor gene

PvuII and XbaI restriction fragment length polymorphisms (RFLPs) of the estrogen receptor (ER) gene and its relation to bone mineral density (BMD) were examined in 238 postmenopausal healthy women aged 45-91 years (66.3 +/- 0.6 years, mean +/- standard error of the mean [SEM]) in Japan. The RFLPs were represented as Pp (PvuII) and Xx (XbaI), with capital letters signifying the absence of and small letters the presence of restriction sites. In the PPxx genotype (n = 18), Z score values of BMD were significantly lower than those for other genotypes (n = 220) (lumbar spine, -0.746 vs. -0.065 [p = 0.022]; total body, -0.482 vs. 0.308 [p = 0.002]). We classified the subjects into three genotypes with allelic haplotype: homozygote of the Px haplotype was expressed as the 11 genotype, heterozygote of the Px haplotype as the 10 genotype, and the one lacking the Px haplotype as the 00 genotype. The PpXx genotype was not included in this analysis because the allelic haplotypes are uncertain. The Px haplotype was associated with a low BMD in postmenopausal women (Z score for the lumbar spine, -0.746 vs. -0.279 vs. 0.083, for the 11, 10, 00 genotypes, respectively [p = 0.029]; Z score for the total body, -0.482 vs. 0.164 vs. 0.427, respectively [p = 0.003]). We suggest that some variation of the ER gene linked to these RFLPs is associated with low BMD and that this at least partly explains the cause of postmenopausal osteoporosis in Japanese women.

Characterization of estrogen receptor cDNAs from human uterus: identification of a novel PvuII polymorphism

Using reverse transcription and the polymerase chain reaction, we have cloned estrogen receptor complementary DNAs from normal human uterine tissue. Restriction endonuclease analysis identified a polymorphic PvuII recognition site within half of the receptor cDNAs. Sequence analysis revealed a number of differences with the sequence previously reported for the ER cDNA isolated from MCF7 cells and confirmed that the codon for amino acid 400 was erroneously assigned as valine (GTG) rather than glycine (GGG). Sequencing also defined the nature of the PvuII polymorphism, with allele A coding for Glu22 and allele B (with an additional PvuII site) coding for Gln22. We demonstrate that both alleles of this receptor activate transcription of an estrogen-responsive gene to the same extent. This selective cloning method should have wide application in the investigation of naturally occurring cDNA variants from diseased tissues, such as breast cancer cell lines and primary tumor specimens.

Exon skipping gives rise to alternatively spliced forms of the estrogen receptor in breast tumor cells

We have previously described three messenger RNA variants coding for the human estrogen receptor (ER) [1]. These variants were identified using the polymerase chain reaction to perform directed cloning of ER cDNAs synthesized from polyadenylated RNA extracted from the human breast cancer cell line T47D. Each of the variants is characterized by the precise deletion of a single exon within the protein coding region of this message and was presumably derived by inaccurate or promiscuous splicing of primary estrogen receptor transcripts. We report here the results of RNAse protection experiments which independently confirm the existence of these splicing variants in T47D cells. Similar analysis of RNA from MCF-7 cells also revealed the presence of variant ER transcripts, suggesting that they may be a common finding in tumor cell lines which express the estrogen receptor. However, attempts to identify splicing variants in a number of nominally ER-negative cell lines using either RNAse protection or PCR amplification were without success.

Oestrogen receptor gene structure and function in breast cancer

The mechanisms underlying loss of oestrogen responsiveness in breast cancer are not well-defined. Potential mechanisms include loss of receptor expression, alterations in the oestrogen receptor (ER) gene producing proteins with abnormal function, or changes to receptor-dependent or -independent pathways controlling cell proliferation. Examination by Southern analysis of the ER gene in a series of ER-negative and -positive breast tumour biopsies failed to provide evidence of gross rearrangements and in only one of thirty seven tumour DNA samples was significant gene amplification observed. No restriction fragment length polymorphisms were detected for the restriction enzymes EcoR I, Pst I or Hind III. Methylation of the ER gene as assessed by Hpa II and Msp I restriction enzyme digests varied between tumours but the degree of methylation was not correlated with levels of expression of the receptor protein. Similar findings applied in a series of ER-negative and -positive breast cancer cell lines and clonal lines of MCF-7 cells, which were developed as an in vitro model for the acquisition of oestrogen and antioestrogen resistance. In this model there was no evidence that changes to ER receptor function and/or structure at the level of the ER gene, mRNA, ligand binding, and ability to induce progesterone receptor might account for the development of hormone resistance. However, the ability of ER to interact with a DNA sequence containing the vitellogenin promoter oestrogen response element, as assessed by gel retardation assay, was impaired in the clone showing the greatest degree of oestrogen and antioestrogen resistance.

Immunocytochemical identification of nuclear estrogen-receptors in human acute myeloid leukemia

The peripheral and bone marrow blast cells of twenty patients newly-diagnosed as acute myeloid leukemia (AML), subtypes M1-M5, were analysed for the presence of estrogen-receptors by ER-ICA immunocytochemistry and dextran-coated charcoal cytosolic (DCC) assay. Two patients demonstrated myeloblasts with nuclear staining patterns consistent with the presence of estrogen-receptors. The positive immuno-staining results were confirmed by DCC in one patient with AML, subtype M4. This patient demonstrated an unusual myeloblast karyotype with a reciprocal translocation t(6;11)(q27;q23.3) involving the designated locus of the ESR gene on chromosome 6 (6q24-qter). The abnormal juxtaposition of DNA control elements close to the promoter of the ESR gene may be one mechanism by which aberrant synthesis of estrogen-receptor protein can occur to provide a growth advantage for leukemia cell clones.