Investigation of the cumulative body burden of estrogen-3,4-quinone in breast cancer patients and controls using albumin adducts as biomarkers

Profiling of Protein Adducts of Estrogen Quinones in 5-Year Survivors of Breast Cancer Without Recurrence

Aims

The aim of this study was to simultaneously analyze estrogen quinone-derived adducts, including 17β-estradiol-2,3-quinone (E₂-2,3-Q) and 17β-estradiol-3,4-quinone (E₂-3,4-Q), in human albumin (Alb) and hemoglobin (Hb) derived from breast cancer patients with five-year postoperative treatment without recurrence in Taiwan and to evaluate the treatment-related effects on the production of these adducts.

Settings and Design

Cohort

Methods and Material: Blood samples derived from breast cancer 5-year survivors without recurrence were collected. Albumin and hemoglobin adducts of E₂-3,4-Q and E₂-2,3-Q were analyzed to evaluate the degree of disposition of estrogen to quinones and to compare these adduct levels with those in patients before treatment.

Statistical Analysis

All data are expressed as mean ± standard deviation of three determinations. We used Student’s t-test to examine subgroups. Data were transformed to the natural logarithm and tested for normal distribution for parametric analyses. Linear correlations were investigated between individual adduct levels by simple regression. Statistical analysis was performed using the SPSS Statistics 20.0.

Results

Result confirmed that logged levels of E₂-2,3-Q-derived adducts correlated significantly with those of E₂-3,4-Q-derived adducts (correlation coefficient r=.336-.624). Mean levels of E₂-2,3-Q-4-S-Alb and E₂-3,4-Q-2-S-Alb in 5-year survivors were reduced by 60-70% when compared to those in the breast cancer patients with less than one year of diagnosis/preoperative treatment (P<.001).

Conclusions

Our findings add support to the theme that hormonal therapy including aromatase inhibitors and Tamoxifen may dramatically reduce burden of estrogen quinones. We hypothesize that combination of treatment-related effects and environmental factors may modulate estrogen homeostasis and diminish the production of estrogen quinones in breast cancer patients.

Quantification of the Endogenous Adduction Level on Hemoglobin and Correlation with Albumin Adduction via Proteomics: Multiple Exposure Markers of Catechol Estrogen

Catechol estrogens (CEs) are genotoxic metabolites whose detection is challenging due to their low concentrations and high variability in the blood. By intact protein and free CE measurement of the spiked hemolysate, endogenous CEs were revealed to mainly (>99%) exist as hemoglobin (Hb) adducts in red blood cells. In order to detect endogenous CE-Hb adducts, we developed a two-step method that involved protein precipitation and solid phase extraction to purify Hb from red blood cells, and the method was coupled with proteomics using liquid chromatography-tandem mass spectrometry. Using bottom-up proteomics and standard additions, we identified C93 and C112 of Hb-β as the main adduction sites of Hb, and this accounted for CE-induced oxidization of adducted peptides by sample preparation. The non-adducted, adducted, and oxidized tryptic peptides that covered the same Hb-β sequences were targeted by parallel reaction monitoring to determine the adduction level in red blood cells. A quantification limit (S/N < 8) below the endogenous CE-Hb adduction level with relative standard errors that ranged from 5 to 22% was achieved and applied to clinical samples. The human serum albumin (HSA) adduction levels from the same patient were also determined using a previously developed method (Anal. Chem. 2019, 91, 15922-15931). A positive correlation (R² = 0.673) between the CE-HSA and CE-Hb adduction level was obtained from all clinical samples, and both levels were significantly (p < 0.005) higher for patients with breast cancer compared to healthy controls. However, double indexes derived from the red blood cell and the serum, respectively, provide higher precision and confidence in predicting cancer risk than the single index. This study reported an efficient sample preparation for proteomics-based Hb adducts and revealed the potential of using multiple blood proteins for developing more reliable and specific markers based on protein adductomics.

Albumin and hemoglobin adducts of estrogen quinone as biomarkers for early detection of breast cancer

Cumulative estrogen concentration is an important determinant of the risk of developing breast cancer. Estrogen carcinogenesis is attributed to the combination of receptor-driven mitogenesis and DNA damage induced by quinonoid metabolites of estrogen. The present study was focused on developing an improved breast cancer prediction model using estrogen quinone-protein adduct concentrations. Blood samples from 152 breast cancer patients and 71 healthy women were collected, and albumin (Alb) and hemoglobin (Hb) adducts of estrogen-3,4-quinone and estrogen-2,3-quinone were extracted and evaluated as potential biomarkers of breast cancer. A multilayer perceptron (MLP) was used as the predictor model and the resultant prediction of breast cancer was more accurate than other existing detection methods. A MLP using the logarithm of the concentrations of the estrogen quinone-derived adducts (four input nodes, 10 hidden nodes, and one output node) was used to predict breast cancer risk with accuracy close to 100% and area under curve (AUC) close to one. The AUC value of one showed that both data sets were separable. We conclude that Alb and Hb adducts of estrogen quinones are promising biomarkers for the early detection of breast cancer.

Covalent adduction of endogenous and food-derived quinones to a protein: its biological significance

There are many chemically reactive compounds, including quinone, in living systems and also food. Even after the ingestion of food polyphenols, quinones derived from catechol moieties could form endogenously in the body. Dopaquinone, dopamine quinone, estrogen-derived quinones, tryptamine-4,5-dione, and ubiquinone are examples of an endogenous quinone. These indicate that quinone is ubiquitously formed or present in living systems and food. Quinones can induce a variety of hazardous effects and also could have beneficial physiological effects. This review focuses on the chemical reactivity of quinone toward a biomolecule and its biological action.

Genetic polymorphisms in APE1 Asp148Glu(rs3136820) as a modifier of the background levels of abasic sites in human leukocytes derived from breast cancer patients and controls

BACKGROUND

Apurinic/apyrimidinic (abasic/AP) sites are among the most common endogenous DNA lesions. AP sites, if not repaired, could result in genomic instability as well as chromosome aberrations. Information regarding the direct assay of the number of abasic sites in human leukocytes and its association with risk of breast cancer has not been reported.

METHODS

In this study, we investigated the association between certain risk factors for breast cancer and the background levels of AP sites in leukocytes derived from 148 Taiwanese women with breast cancer and 140 cancer-free controls. The risk factors studied include age, body mass index (BMI), and polymorphisms of apurinic/apyrimidinic endonuclease (APE1) [APE1 Asp148Glu(rs3136820)].

RESULTS

Mean levels of AP sites were estimated to be 23.3 and 50.3 per 10⁶ nucleotides in controls and breast cancer patients, respectively (~twofold, p < 0.001). In subjects with age <50 or BMI < 27 (kg/m²), the levels of AP sites in breast cancer patients were ~2-3-fold greater than those of controls (p < 0.05). Additionally, results from the AP site 3'-cleavage assay indicated that the AP sites detected in both controls and patients were likely to be oxidant-mediated 5'-cleaved AP sites (~61-64 %). The number of AP sites in breast cancer patients was ~twofold greater in subjects with Asp/Glu + Glu/Glugenotypes than those with Asp/Asp genotype (p < 0.001).

CONCLUSIONS

We confirmed that cumulative body burden of AP sites is a significant predictor of the risk of developing breast cancer and that genetic predisposition and environment factors may modulate the induction of oxidative DNA lesions in breast cancer patients.

Mechanisms of estrogen carcinogenesis: The role of E2/E1-quinone metabolites suggests new approaches to preventive intervention--A review

Studies in hamsters, mice and rats have demonstrated that estradiol (E2), its interconvertible metabolite estrone (E1) and their catechol metabolites, in particular 4-hydroxy E2/E1, are carcinogenic in the kidney, uterus and mammary gland. Observational studies and clinical trials consistently show that sustained exposure to E2/E1 is associated with the development of sporadic breast cancer. The weight of evidence supports the contribution of two complementary pathways in the initiation, promotion and progression of breast cancer. One pathway involves activation of nuclear and cytoplasmic signaling pathways through the binding of estrogen to nuclear and membrane-bound estrogen receptors leading to increased cell proliferation. The other pathway involves the oxidative metabolism of E2/E1 to catechols and then reactive quinones that can contribute to oxidative DNA damage and form specific, mutagenic depurinating adducts with adenine and guanine which then in turn can serve as biomarkers for the occurrence of these processes. Both pathways can serve as portals to preventive intervention. Antiestrogens are used clinically to block receptor-mediated signaling to block tumor growth. Various chemopreventive agents such as sulforaphane (SFN) and resveratrol have been shown in cell culture to block oxidative metabolism of E2/E1 and thus prevent DNA damage. Pretreatment of MCF-7 and MCF-10F cells with and inhibitor of catechol-O-methyltransferase (COMT) followed by treatment with E2 or 4-OH E2 caused increased oxidative DNA damage (8-oxo-dG) and depurinating DNA adducts showing the importance of E2-catechol O-methylation by COMT as a protective pathway. E2 treatment of MCF-10A cells with E2 or 4-OH E2 caused an increase in E2-adenine and guanine adducts. Treatment with sulforaphane increased

NAD(P)H

quinone oxidoreductase 1 (NQO1) and glutathione-S-transferase A1 (GSTA1) expression without affecting expression of catechol-O-methyltransferase (COMT) or cytochrome P450 1B1. Pretreatment with SFN decreased depurinating DNA adducts while increasing levels of 4-OCH3E1/2 and 4-OHE1/2-glutathione conjugates. Treatment of MCF-10F cells with E2 or 4-OH-E2 also caused increased depurinating DNA adducts and neoplastic transformation while pretreatment with resveratrol caused a reduction in adduct levels and neoplastic transformation. Increased levels of estrogen-quinone conjugates and DNA adducts have also been detected in urine of women at increased risk for and with breast cancer. These observations support the notion that targeting the estrogen/estrone metabolism pathway may be another way to reduce breast cancer risk.