Perinatal exposure to estradiol and bisphenol A alters the prostate epigenome and increases susceptibility to carcinogenesis

An important and controversial health concern is whether low-dose exposures to hormonally active environmental oestrogens such as bisphenol A can promote human diseases including prostate cancer. Our studies in rats have shown that pharmacological doses of oestradiol administered during the critical window of prostate development result in marked prostate pathology in adulthood that progress to neoplastic lesions with ageing. Our recent studies have also demonstrated that transient developmental exposure of rats to low, environmentally relevant doses of bisphenol A or oestradiol increases prostate gland susceptibility to adult-onset precancerous lesions and hormonal carcinogenesis. These findings indicate that a wide range of oestrogenic exposures during development can predispose to prostatic neoplasia that suggests a potential developmental basis for this adult disease. To identify a molecular basis for oestrogen imprinting, we screened for DNA methylation changes over time in the exposed prostate glands. We found permanent alterations in DNA methylation patterns of multiple cell signalling genes suggesting an epigenetic mechanism of action. For phosphodiesterase type 4 variant 4 (PDE4D4), an enzyme responsible for intracellular cyclic adenosine monophosphate breakdown, a specific methylation cluster was identified in the 5'-flanking CpG island that was gradually hypermethylated with ageing in normal prostates resulting in loss of gene expression. However, in prostates exposed to neonatal oestradiol or bisphenol A, this region became hypomethylated with ageing resulting in persistent and elevated PDE4D4 expression. In total, these findings indicate that low-dose exposures to ubiquitous environmental oestrogens impact the prostate epigenome during development and in so doing, promote prostate disease with ageing

School to School collaboration: improvement and collaboration?

Baseline characteristics according to tertiles of plasma fluorescent oxidation products in the Health Professional Follow-up Study in prostate cancer cases (N = 457), 1993–1995. (DOCX 14 kb

The DEK Oncogene Is a Target of Steroid Hormone Receptor Signaling in Breast Cancer

<div><p>Expression of estrogen and progesterone hormone receptors indicates a favorable prognosis due to the successful use of hormonal therapies such as tamoxifen and aromatase inhibitors. Unfortunately, 15–20% of patients will experience breast cancer recurrence despite continued use of tamoxifen. Drug resistance to hormonal therapies is of great clinical concern so it is imperative to identify novel molecular factors that contribute to tumorigenesis in hormone receptor positive cancers and/or mediate drug sensitivity. The hope is that targeted therapies, in combination with hormonal therapies, will improve survival and prevent recurrence. We have previously shown that the DEK oncogene, which is a chromatin remodeling protein, supports breast cancer cell proliferation, invasion and the maintenance of the breast cancer stem cell population. In this report, we demonstrate that DEK expression is associated with positive hormone receptor status in primary breast cancers and is up-regulated <em>in vitro</em> following exposure to the hormones estrogen, progesterone, and androgen. Chromatin immunoprecipitation experiments identify <em>DEK</em> as a novel estrogen receptor α (ERα) target gene whose expression promotes estrogen-induced proliferation. Finally, we report for the first time that DEK depletion enhances tamoxifen-induced cell death in ER+ breast cancer cell lines. Together, our data suggest that DEK promotes the pathogenesis of ER+ breast cancer and that the targeted inhibition of DEK may enhance the efficacy of conventional hormone therapies.</p> </div

Association of DEK expression with clinical and pathological variables in invasive adenocarcinomas of the breast.

*<p>Chi-Squared statistic.</p

Model for DEK transcriptional up-regulation following 17β-estradiol exposure.

<p>Upon 17β-estradiol exposure, ERα is activated and binds to the <i>DEK</i> promoter at least at two locations – an ERE half site at −716 bp and at ERα/Sp1 binding sites more proximal to the transcriptional start site. A second potential mechanism of up-regulation is the ERα-mediated up-regulation of E2F proteins (particularly E2F3) that also increase <i>DEK</i> transcription. Increased levels of DEK then promote proliferation. DEK expression can be targeted with the anti-estrogen tamoxifen to inhibit cell proliferation. The knockdown of DEK by RNAi can increase tamoxifen sensitivity of ER+ cell lines by synergistically inducing an apoptotic response.</p

DEK is necessary for 17β-estradiol stimulated cell proliferation and modulates sensitivity to tamoxifen.

<p>(A) DEK expression is required for 17β-estradiol stimulated cellular proliferation. Hormone starved MCF7 cells transduced with non-targeting shRNA (NTsh) or DEK shRNA (DEKsh2) were untreated (CS-FBS) or exposed to 10 nM 17β-estradiol, then cultured in BrdU. The percentage of BrdU positive cells was determined by flow cytometry. Asterisk (*) denotes p<0.05 using Student’s t-test. (B and C) DEK depletion by shRNA (DEKsh2) works synergistically with tamoxifen to induce apoptosis in breast cancer cell lines. (B) Bright field images (100× magnification) of MCF7 cells expressing either NTsh or DEKsh2 were cultured in low serum media and either untreated or treated with tamoxifen for 18 hours. (C) DEK depletion by shRNA (DEKsh2) enhances the cytotoxic effect of tamoxifen. DEK proficient and deficient MCF7 (left) and T47D (right) cells were grown in low serum media then treated with 3 µg/ml tamoxifen for 22 hours. Cells were labeled with 7AAD then analyzed for sub-G1 content by flow cytometry as a measure of apoptosis. Results shown are the average of triplicate experiments. Two asterisks (**) indicate p<0.01 as determined using a 2-way ANOVA test for significance. For MCF7 cells, p = 0.08. (A and B insets) DEK shRNA knockdown is shown by western blot analysis for normally cultured cells that were transduced with lentivirus carrying either non-targeting shRNA (NTsh) or DEK specific shRNA (DEKsh2).</p

Summary of baseline characteristics (n = 60).

<p>*Numerical variables are summarized using mean ± standard deviation (SD). Categorical variables are summarized using frequency (in %).</p>†<p><i>p</i> values are calculated from t-tests.</p><p>#Serum PSA significantly rose during follow-up.</p

Fold change in the percentage of cells with centrosomal amplification in presence of 100

<p>*Fold change is defined as % of cells with abnormal centrosomes at 0.1 nM BPA/% cells with abnormal centrosomes in untreated cells.</p>†<p><i>Post hoc</i> comparisons were performed under a fixed effect model and adjusted using Bonferroni's methods. Only the p-values of comparing NPrEC-1 to other cell lines are presented. Other comparisons between the cell lines were not statistically different.</p

Cells grown in the absence and presence of 0.1-independent growth.

<p>Representative pictures of colonies after 2 weeks of incubation in agar. C4-2 cells in the presence of 0.1 nM BPA formed larger colonies (B, B′, 100–1200 µm diameter) compared with those grown in the absence of BPA (A, A′, 50–400 µm diameter).</p

Scatter plots of LnBPA.

<p>Urine BPA levels are associated with PCa. The log-transformed BPA is referred to as LnBPA. Values in graph are mean ± SD of LnBPA. (A) Urine BPA levels are higher in PCa patients than in non-PCa patients. Means of LnBPA  = 1.75±1.97 in PCa (blue, n = 27) vs. 0.35±2.14 in non-PCa (red, n = 33), <i>p</i> = 0.012. (B) LnBPA in PCa vs. LnBPA in non-PCa, stratified by age = 65. Urine BPA levels are significantly higher in young PCa patients than in the respective non-PCa patients only in the age group <65 years old; <i>p</i> = 0.006. (C) Linear regression analyses of Serum PSA vs. LnBPA in patients <65 years old only (n = 30). Blue solid squares represent PCa patients; red inverse-circles represent non-PCa patients. Blue and red solid lines represent their regression lines, respectively. (D) Comparison of the geometric mean of BPA in PCa and non-PCa groups. The geometric mean (Geo) is defined as the exponential of the mean of LnBPA. Values are geometric means (95% CI) of BPA in unit of µg/g creatinine.</p