Sublethal toxicant effects with dynamic energy budget theory: model formulation

We develop and test a general modeling framework to describe the sublethal effects of pollutants by adding toxicity modules to an established dynamic energy budget (DEB) model. The DEB model describes the rates of energy acquisition and expenditure by individual organisms; the toxicity modules describe how toxicants affect these rates by changing the value of one or more DEB parameters, notably the parameters quantifying the rates of feeding and maintenance. We investigate four toxicity modules that assume: (1) effects on feeding only; (2) effects on maintenance only; (3) effects on feeding and maintenance with similar values for the toxicity parameters; and (4) effects on feeding and maintenance with different values for the toxicity parameters. We test the toxicity modules by fitting each to published data on feeding, respiration, growth and reproduction. Among the pollutants tested are metals (mercury and copper) and various organic compounds (chlorophenols, toluene, polycyclic aromatic hydrocarbons, tetradifon and pyridine); organisms include mussels, oysters, earthworms, water fleas and zebrafish. In most cases, the data sets could be adequately described with any of the toxicity modules, and no single module gave superior fits to all data sets. We therefore propose that for many applications, it is reasonable to use the most general and parameter sparse module, i.e. module 3 that assumes similar effects on feeding and maintenance, as a default. For one example (water fleas), we use parameter estimates to calculate the impact of food availability and toxicant levels on the long term population growth rate

The role of the androgen receptor and hydroxysteroid 17β dehydrogenase in breast cancer : Impact on tamoxifen treatment

The healthy breast is a tissue composed of centrally located milk producing glands connected to the nipple by ducts, surrounded by fat tissue and connective tissue. The growth of the breast is primarily mediated by the estrogens, while the androgens mediate tissue homeostasis and protect against growth signals. In breast cancer, the cells of the glands or ducts undergo malignant transformation, and start proliferating in an uncontrollable fashion. Breast cancer is the most common malignancy in women, and it is estimated that 10% of all women will be diagnosed with breast cancer during their life-time. The primary classification of breast cancer is based mainly on the expression of the estrogen receptor, and 70-80% of breast cancers are estrogen receptor positive, and are classified as luminal. The remaining breast cancers are classified into HER2 positive or triple negative breast cancer. Out of all breast cancers, ~80% are androgen receptor positive. This varies in different subtypes, however, with the highest expression in luminal and lowest expression in triple negative breast cancers. The role of androgen receptor varies depending on subtype. It is considered tissue-protective in luminal breast cancer, while it’s role in HER2 positive and triple negative breast cancers is less defined, but is generally considered to be associated with worse outcome. The primary treatment for breast cancer is surgery, followed by chemotherapy and/or radiotherapy to reduce the risk of recurrence. Treatment is also subtype specific, and luminal breast cancers in premenopausalwomen are treated using the estrogen receptor blocker (antagonist) tamoxifen, which blocks estrogen signaling. In postmenopausal women, luminal breast  cancers are treated using tamoxifen or aromatase inhibitors, which prevent the formation of estrogen. The knowledge of which patient will respond and who will develop treatment resistance is of great importance, and the development of markers which can be analyzed prior to treatment in order to reduce the risk of unwanted side effects or complications is the focus of a large body of research. One of the primary goals of this thesis was to establish biomarkers for prognosis and tamoxifen treatment in breast cancer, and paper I, paper II and paper III address this aim. Steroid hormones, including estrogens and androgens, are normally synthesized from cholesterol in the adrenal gland, as well as in gender specific tissues such as ovaries in women or the testis or prostate in men. This synthesis takes place as a number of enzymatic conversions, mediated by several different enzymes, and the expression of these enzymes determines the final product of this conversion. In the adrenal gland, testis and prostate, androgens are the end-product, while the ovaries synthesize estrogens. These hormones are transported through the circulation, and upon reaching their target tissues, they mediate their effect. The impact of the steroids on their destination tissue is dependent on their relative concentration and exposure time, which in turn is dependent on the amount in the circulation, but also on the presence of local steroid converting enzymes, which are present in most tissues. The enzymes of the hydroxysteroid 17β dehydrogenase family are present in most tissues, primarily the oxidative member hydroxysteroid 17β dehydrogenase type 2, which facilitate the conversion of estrogens and androgens to the less active forms, thus protecting the tissues from their effect. In breast cancer, the reductive form, hydroxysteroid 17β dehydrogenase type 1 is often up-regulated, and mediates increased activation of estrogens, resulting in increased estrogen signaling, which results in increased proliferation and growth. The second goal of this thesis was to further study the role of hydroxysteroid 17β dehydrogenase enzymes in breast cancer, and paper I and paper IV address different  aspects of their role in breast cancer. Following reduction of the expression of hydroxysteroid 17β dehydrogenase type 14, an oxidative member of the family, in breast cancer, the expression of C-X-C ligand 10 was found to be altered. In paper I, in order to determine the role of C-X-C ligand 10 and C-X-C receptor 3 in breast cancer, their expression was quantified using immunohistochemistry in breast cancer patients randomized to tamoxifen or no endocrine treatment irrespectively of estrogen receptor status. The expression of C-XC ligand 10 and C-X-C receptor 3 was found to be associated with increased tamoxifen treatment benefit in the estrogen receptor positive group of patients, indicating that they could be useful markers for determining which patient would respond well to this treatment. Further, C-X-C receptor 3 expression was associated with worse outcome in patients who did not receive tamoxifen, and could be a potential target for inhibitors in order to improve patient outcome. The role of the androgen receptor in breast cancer was evaluated. In paper II the expression was quantified using immunohistochemistry in the same cohort as in paper I. We show that in patients with estrogen receptor negative tumors, the androgen receptor is associated with worse outcome. In patients with high tumoral androgen receptor expression, tamoxifen signaling results in significant improvement in outcome, despite lack of the estrogen receptor. The opposite was observed in patients without tumoral androgen receptor expression, and tamoxifen treatment was associated with adverse outcome. Similar findings were made in the triple negative cases. In the luminal cases, the androgen receptor does not provide further information pertaining to outcome. In paper III we evaluated the role of mutations in the androgen receptor in the cohort of estrogen receptor-negative and androgen receptorpositive cases from paper II. The role of mutations in the androgen receptor appear to have a modest role in regard to patient outcome, but rs17302090 appear associated with tamoxifen treatment benefit. The modulation of the members of the hydroxysteroid 17β dehydrogenase in breast cancer is associated with changes in the local steroid balance, and has been associated with worse outcome and changes in the response to tamoxifen. Further, the inhibition of hydroxysteroid 17β dehydrogenase type 1 has been proposed as an alternate treatment for breast cancer, but no inhibitors are currently used in the clinic. In paper IV, we evaluated several different mechanisms by which the expression of hydroxysteroid 17β dehydrogenase type 1 and type 2 are modulated in breast cancer. We show that the most potent estrogen estradiol, in an estrogen receptor dependent fashion, can result in decreased hydroxysteroid 17β dehydrogenase type 1 expression, and a short term reduction in type 2 expression or long term increased type 2 expression. We also show that the most potent androgen, dihydrotestosterone, can increase hydroxysteroid 17β dehydrogenase type 2 expression, but has limited impact on hydroxysteroid 17β dehydrogenase type 1. Further, we show that a number of genes involved in breast cancer, and microRNA are involved in modulating the expression of the hydroxysteroid 17β dehydrogenase type 1 and type 2 in breast cancer. These findings could potentially be used as an alternative to inhibitors, and help modulate the steroidal balance in target tissue

Estrogen and androgen-converting enzymes 17 beta-hydroxysteroid dehydrogenase and their involvement in cancer: with a special focus on 17 beta-hydroxysteroid dehydrogenase type 1, 2, and breast cancer

Sex steroid hormones such as estrogens and androgens are involved in the development and differentiation of the breast tissue. The activity and concentration of sex steroids is determined by the availability from the circulation, and on local conversion. This conversion is primarily mediated by aromatase, steroid sulfatase, and 17 beta-hydroxysteroid dehydrogenases. In postmenopausal women, this is the primary source of estrogens in the breast. Up to 70-80% of all breast cancers express the estrogen receptor-a, responsible for promoting the growth of the tissue. Further, 60-80% express the androgen receptor, which has been shown to have tissue protective effects in estrogen receptor positive breast cancer, and a more ambiguous response in estrogen receptor negative breast cancers. In this review, we summarize the function and clinical relevance in cancer for 17 beta-hydroxysteroid dehydrogenases 1, which facilitates the reduction of estrone to estradiol, dehydroepiandrosterone to androstendiol and dihydrotestosterone to 3 alpha- and 3 beta-diol as well as 17 beta-hydroxysteroid dehydrogenases 2 which mediates the oxidation of estradiol to estrone, testosterone to androstenedione and androstendiol to dehydroepiandrosterone. The expression of 17 beta-hydroxysteroid dehydrogenases 1 and 2 alone and in combination has been shown to predict patient outcome, and inhibition of 17 beta-hydroxysteroid dehydrogenases 1 has been proposed to be a prime candidate for inhibition in patients who develop aromatase inhibitor resistance or in combination with aromatase inhibitors as a first line treatment. Here we review the status of inhibitors against 17 beta-hydroxysteroid dehydrogenases 1. In addition, we review the involvement of 17 beta-hydroxysteroid dehydrogenases 4, 5, 7, and 14 in breast cancer.Funding Agencies|Swedish Cancer Society [150349]</p

The regulation of hydroxysteroid 17 beta-dehydrogenase type 1 and 2 gene expression in breast cancer cell lines by estradiol, dihydrotestosterone, microRNAs, and genes related to breast cancer

Aim. To investigate the influence of estrogen, androgen, microRNAs, and genes implicated in breast cancer on the expression of HSD17B1 and HSD17B2. Materials. Breast cancer cell lines ZR-75-1, MCF7, T47D, SK-BR-3, and the immortalized epithelial cell line MCF10A were used. Cells were treated either with estradiol or dihydrotestosterone for 6, 24, 48 hours, or 7 days or treated with miRNAs or siRNAs predicted to influence HSD17B expression Results and discussion. Estradiol treatment decreased HSD17B1 expression and had a time-dependent effect on HSD17B2 expression. This effect was lost in estrogen receptor-alpha down-regulated or negative cell lines. Dihydrotestosterone treatment increased HSD17B2 expression, with limited effect on HSD17B1 expression. No effect was seen in cells without AR or in combination with the AR inhibitor hydroxyflutamide. The miRNA-17 up-regulated HSD17B1, while miRNA-210 and miRNA-7-5p had up- and down-regulatory effect and miRNA-1304-3p reduced HSD17B1 expression. The miRNA-204-5p, 498, 205-3p and 579-3p reduced HSD17B2 expression. Downregulation of CX3CL1, EPHB6, and TP63 increased HSD17B1 and HSD17B2 expression, while GREB1 downregulation suppressed HSD17B1 and promoted HSD17B2 expression. Conclusion. We show that HSD17B1 and HSD17B2 are controlled by estradiol, dihydrotestosterone, and miRNAs, as well as modulated by several breast cancer-related genes, which could have future clinical applications.Funding Agencies|Swedish Research Council [A0346701]; Swedish Cancer Foundation [150349]; Stiftelsen Onkologiska Klinikernas i Linkoping Forskningsfond</p

C-X-C ligand 10 and C-X-C receptor 3 status can predict tamoxifen treatment response in breast cancer patients

To investigate the expression levels of CXCL10 and CXCR3 in tumors from breast cancer patients randomized to adjuvant tamoxifen treatment or no endocrine treatment, in order to further study the connection to prognosis and prediction of tamoxifen treatment outcome. Immunohistochemistry on tissue microarrays from 912 breast cancer patients randomized to tamoxifen or no endocrine treatment. CXCR3 status was found to be a prognostic tool in predicting distant recurrence, as well as reduced breast cancer-specific survival. In patients with estrogen receptor (ER)-positive tumors, tumors with strong CXCL10 levels had improved effect of tamoxifen treatment in terms of local recurrence-free survival [risk ratio (RR) 0.46 (95 % CI 0.25-0.85, P = 0.01)] compared with patients with tumors expressing weak CXCL10 expression. Further, patients with ER-positive tumors with strong CXCR3 expression had an improved effect of tamoxifen in terms of breast cancer-specific survival [RR 0.34 (95 % CI 0.19-0.62, P less than 0.001)] compared with the group with weak CXCR3 levels [RR 1.33 (95 % CI 0.38-4.79, P = 0.65)]. We show here for the first time that CXCL10 and CXCR3 expression are both predictors of favorable outcome in patients treated with tamoxifen

Androgen receptor expression predicts beneficial tamoxifen response in oestrogen receptor-alpha-negative breast cancer

Background: Although the androgen receptor (AR) is frequently expressed in breast cancer, its relevance in the disease is not fully understood. In addition, the relevance of AR in determining tamoxifen treatment efficiency requires evaluation. Purpose: To investigate the tamoxifen predictive relevance of the AR protein expression in breast cancer. Methods Patients were randomised to tamoxifen 40 mg daily for 2 or 5 years or to no endocrine treatment. Mean follow-up was 15 years. Hazard ratios were calculated with recurrence-free survival as end point. Results: In patients with oestrogen receptor (ER)-negative tumours, expression of AR predicted decreased recurrence rate with tamoxifen (hazard ratio (HR) = 0.34; 95% confidence interval (CI) = 0.14-0.81; P = 0.015), whereas the opposite was seen in the AR- group (HR = 2.92; 95% CI = 1.16-7.31; P = 0.022). Interaction test was significant P &amp;lt; 0.001. Patients with triple-negative and AR+ tumours benefitted from tamoxifen treatment (HR = 0.12; 95% CI = 0.014-0.95 P = 0.044), whereas patients with AR- tumours had worse outcome when treated with tamoxifen (HR = 3.98; 95% CI = 1.32-12.03; P = 0.014). Interaction test was significant P = 0.003. Patients with ER+ tumours showed benefit from tamoxifen treatment regardless of AR expression. Conclusions: AR can predict tamoxifen treatment benefit in patients with ER- tumours and triple-negative breast cancer.Funding Agencies|Swedish research council [A0346701]; Swedish cancer foundation [13 0435]</p

C-X-C ligand 10 and C-X-C receptor 3 status can predict tamoxifen treatment response in breast cancer patients

To investigate the expression levels of CXCL10 and CXCR3 in tumors from breast cancer patients randomized to adjuvant tamoxifen treatment or no endocrine treatment, in order to further study the connection to prognosis and prediction of tamoxifen treatment outcome. Immunohistochemistry on tissue microarrays from 912 breast cancer patients randomized to tamoxifen or no endocrine treatment. CXCR3 status was found to be a prognostic tool in predicting distant recurrence, as well as reduced breast cancer-specific survival. In patients with estrogen receptor (ER)-positive tumors, tumors with strong CXCL10 levels had improved effect of tamoxifen treatment in terms of local recurrence-free survival [risk ratio (RR) 0.46 (95 % CI 0.25-0.85, P = 0.01)] compared with patients with tumors expressing weak CXCL10 expression. Further, patients with ER-positive tumors with strong CXCR3 expression had an improved effect of tamoxifen in terms of breast cancer-specific survival [RR 0.34 (95 % CI 0.19-0.62, P less than 0.001)] compared with the group with weak CXCR3 levels [RR 1.33 (95 % CI 0.38-4.79, P = 0.65)]. We show here for the first time that CXCL10 and CXCR3 expression are both predictors of favorable outcome in patients treated with tamoxifen

Androgen receptor expression predicts beneficial tamoxifen response in oestrogen receptor-alpha-negative breast cancer

Background: Although the androgen receptor (AR) is frequently expressed in breast cancer, its relevance in the disease is not fully understood. In addition, the relevance of AR in determining tamoxifen treatment efficiency requires evaluation. Purpose: To investigate the tamoxifen predictive relevance of the AR protein expression in breast cancer. Methods Patients were randomised to tamoxifen 40 mg daily for 2 or 5 years or to no endocrine treatment. Mean follow-up was 15 years. Hazard ratios were calculated with recurrence-free survival as end point. Results: In patients with oestrogen receptor (ER)-negative tumours, expression of AR predicted decreased recurrence rate with tamoxifen (hazard ratio (HR) = 0.34; 95% confidence interval (CI) = 0.14-0.81; P = 0.015), whereas the opposite was seen in the AR- group (HR = 2.92; 95% CI = 1.16-7.31; P = 0.022). Interaction test was significant P &amp;lt; 0.001. Patients with triple-negative and AR+ tumours benefitted from tamoxifen treatment (HR = 0.12; 95% CI = 0.014-0.95 P = 0.044), whereas patients with AR- tumours had worse outcome when treated with tamoxifen (HR = 3.98; 95% CI = 1.32-12.03; P = 0.014). Interaction test was significant P = 0.003. Patients with ER+ tumours showed benefit from tamoxifen treatment regardless of AR expression. Conclusions: AR can predict tamoxifen treatment benefit in patients with ER- tumours and triple-negative breast cancer.Funding Agencies|Swedish research council [A0346701]; Swedish cancer foundation [13 0435]</p