Estradiol measurement in translational studies of breast cancer

Alternative dosing regimen of exemestane in a randomized presurgical trial: the role of obesity in biomarker modulation

In a 3-arm presurgical trial, four-six weeks exemestane 25 mg three times/week (TIW) was non-inferior to 25 mg/day (QD) in suppressing circulating estradiol in postmenopausal women with ER-positive breast cancer. Since obesity may decrease exemestane efficacy, we analyzed changes in sex steroids, adipokines, Ki-67, and drug levels in relation to obesity. Postmenopausal women with early-stage ER-positive breast cancer were randomized to either exemestane 25 mg QD (n = 57), 25 mg TIW (n = 57), or 25 mg/week (QW, n = 62) for 4-6 weeks before breast surgery. Serum and tissue pre- and post-treatment biomarkers were stratified by body mass index (BMI)< or ≥30 kg/m2. Post-treatment median exemestane and 17-OH exemestane levels were 5-6 times higher in the QD arm compared to the TIW arm. For obese women, TIW maintained comparable reductions to QD in systemic estradiol levels, although the reduction in estrone was less with the TIW regimen. There was less suppression of SHBG with the TIW versus the QD dose schedule in obese women which should result in less systemic bioavailable estrogens. Metabolically, the effect of the TIW regimen was similar to the QD regimen for obese women in terms of leptin suppression and increase in the adiponectin-leptin ratio. Reduction in tissue Ki-67 was less for obese women on the TIW regimen than QD, although changes were similar for non-obese women. Our findings suggest that TIW exemestane should be explored further for primary cancer prevention in both normal weight and obese cohorts.

Potential therapeutic role for pigment epithelium-derived factor in post-menopausal breast cancer bone metastasis

OBJECTIVES

This review discusses key oestrogens associated with the circulating pre- and post-menopausal milieu and how they may impact intratumoral oestrogen levels and breast cancer (BC) metastasis. It also identifies critical steps in BC metastasis to bone from the viewpoint of pigment epithelium-derived factor (PEDF) function, and discusses the role of several associated pro-metastatic biomarkers in BC bone metastasis.

KEY FINDINGS

PEDF is regulated by oestrogen in a number of oestrogen-sensitive tissues. Changes in circulating oestrogen levels associated with menopause may enhance the growth of BC bone metastases, leading to the establishment of a pre-metastatic niche. The establishment of such a pre-metastatic niche is driven by several key mediators, with pro-osteoclastic and pro-metastatic function which are upregulated by BC cells. These mediators appear to be regulated by oestrogen, as well as differentially affected by menopausal status. PEDF interacts with several pro-metastatic, pro-osteoclastic biomarkers, including C-X-C motif chemokine receptor 4 (CXCR4) and nuclear factor kappa B (NFκB) in BC bone metastasis.

CONCLUSION

Mediators such as CXCR4 and MT1-MMP underpin the ability of PEDF to function as an antimetastatic in other cancers such as osteosarcoma, highlighting the possibility that this serpin could be used as a therapeutic against BC metastasis in future.

A New LC-MS/MS Method for Simultaneous and Quantitative Detection of Bisphenol-A and Steroids in Target Tissues: A Power Tool to Characterize the Interference of Bisphenol-A Exposure on Steroid Levels

Bisphenol A (BPA), an endocrine disruptor, may affect in situ steroidogenesis and alter steroids levels. The present work proposes a liquid chromatography tandem mass spectrometry method to simultaneously quantify BPA, 17β-Estradiol and testosterone in two target tissues: testis and visceral fat mass. Analytes were isolated and lipophilic impurities removed by two serial steps: liquid-liquid and solid phase extraction. All compounds were separated in a single gradient run by Kinetex F5 column and detected via multiple reaction monitoring using a triple quadrupole with a TurboIon electrospray source in both negative and positive modes. The method is selective and very sensitive. In the investigated concentration range, the linearity of the detector response is verified in both tissues. The use of specific SPE cartridges for affinity chromatography purification allows obtaining high percentages of process efficiency (68.0-83.3% for testicular tissue; 63.7-70.7% for visceral fat mass). Good repeatability and reproducibility was observed. The validated method can be efficiently applied for direct biological monitoring in testis and visceral fat mass from mice exposed to BPA. The quantification of compounds in a single assay could be achieved without a loss of sensitivity.

Simultaneous measurement of total estradiol and testosterone in human serum by isotope dilution liquid chromatography tandem mass spectrometry

Reliable measurement of total testosterone and estradiol is critical for their use as biomarkers of hormone-related disorders in patient care and translational research. We developed and validated a mass spectrometry method to simultaneously quantify these analytes in human serum without chemical derivatization. Serum is equilibrated with isotopic internal standards and treated with acidic buffer to release hormones from their binding proteins. Lipids are isolated and polar impurities are removed by two serial liquid-liquid extraction steps. Total testosterone and estradiol are measured using liquid chromatography tandem mass spectrometry (LC-MS/MS) in combination of positive and negative electrospray ionization modes. The method shows broad analytical measurement range for both testosterone 0.03-48.5 nM (0.75-1400 ng/dL) and estradiol 11.0-5138 pM (2.99-1400 pg/mL) and excellent agreement with certified reference materials (mean bias less than 2.1% to SRM 971, BCR 576, 577, and 578) and a high order reference method (mean bias 1.25% for testosterone and -0.84% for estradiol). The high accuracy of the method was monitored and certified by CDC Hormone Standardization (HoSt) Program for 2 years with mean bias -0.7% (95% CI -1.6% to 0.2%) for testosterone and 0.1% (95% CI -2.2% to 2.3%) for estradiol. The method precision over a 2-year period for quality control pools at low, medium, and high concentrations was 2.7-2.9% for testosterone and 3.3-5.3% for estradiol. With the consistently excellent accuracy and precision, this method is readily applicable for high-throughput clinical and epidemiological studies.

Falsely elevated serum oestradiol due to exemestane therapy

In this study, we present a case of falsely elevated oestradiol (E₂) concentration, determined by two immunoassays, in a breast cancer patient receiving exemestane therapy. The positive bias of immunochemical measurements was revealed using liquid chromatography tandem mass spectrometry which showed undetectable E₂ concentration. The discrepancy is expected to be a consequence of the structural resemblance of E₂ and exemestane sharing the same steroidal backbone. Inaccurate laboratory findings in therapy monitoring, as in this case, may lead to unnecessary changes of therapy.