Serum concentrations of DDE, PCBs, and other persistent organic pollutants and mammographic breast density in Triana, Alabama, a highly exposed population

INTRODUCTION

Although some persistent organic pollutants (POPs) are considered human carcinogens, results from studies evaluating exposures and breast cancer risk have been inconsistent, potentially related to varying ages at exposure. Additionally, few studies evaluated the association between POPs exposure and mammographic breast density (MBD), an intermediate biomarker of breast cancer risk. We carried out a cross-sectional study to investigate associations between serum POPs concentrations and MBD measured in 1998 in female residents of Triana, Alabama, in a predominately African American population with high POPs exposures, particularly to p,p'-DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane).

METHODS

We measured lipid-adjusted serum concentrations (ng/g lipid) of p,p'-DDT and its main metabolite p,p'-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene), polychlorinated biphenyls (PCBs), β-hexachlorocyclohexane (β-HCCH), heptachlor epoxide, oxychlordane, trans-nonachlor, mirex, and aldrin for each woman in our study (n = 210). We also measured two MBD metrics, percent MBD (%MBD) and area of MBD (aMBD). Using adjusted Spearman correlation coefficients (rs) we evaluated correlations between %MBD and aMBD with individual POPs in the overall population and by age group (19-40, 41-54, and 55-91 years) and also estimated adjusted mean measures of MBD with 95% confidence intervals across tertiles of analytes using generalized linear models (GLM). We calculated p-values for multiplicative interaction by age group using GLM. Additional analyses excluded women with current hormone replacement therapy (HRT) use and evaluated early-life exposure (prior to age 18) during the heaviest contamination period in Triana (1947-90).

RESULTS

Among all women, we found no correlation between p,p'-DDE and %MBD, but after age stratification and exclusion of HRT users, there was a suggestion of a difference by age group, with younger women having a weak positive correlation (rs = 0.12, p = 0.37) and older women having a weak negative correlation (rs = -0.12, p = 0.43); pinteraction = 0.06. In contrast, PCBs were weakly positively correlated with %MBD among all women, with the correlation magnitudes increasing after excluding current HRT users (rs-total PCBs = 0.17, p = 0.03). After age stratification and exclusion of HRT users, correlations for PCBs were higher among younger and middle-age women, with only a handful of these correlations being statistically significant. For β-HCCH, the strongest finding was a negative correlation among older women (rs = -0.26, p = 0.07). Correlations were positive predominantly in the younger age group for heptachlor epoxide (rs = 0.27, p = 0.04), oxychlordane (rs = 0.35, p = 0.006), and trans-nonachlor (rs = 0.37, p = 0.003), and largely null for the middle and older age groups; pinteraction range: 0.03-0.05. Similar patterns were found in GLM analyses using tertiles of exposure and aMBD as the metric for MBD. Women exposed during the heaviest chemical contamination period in Triana prior to age 18 had positive correlations between %MBD and PCBs, heptachlor epoxide, mirex, oxychlordane, and trans-nonachlor.

CONCLUSIONS

In this population, despite high exposures to p,p'-DDT and thus high serum concentrations of its main metabolite, p,p'-DDE, we did not find strong evidence of a positive association with MBD. In fact, there was some evidence of a negative association among older women for p,p'-DDE; a similar pattern was found for β-HCCH. However, younger women with higher serum levels of PCBs, heptachlor epoxide, oxychlordane, and trans-nonachlor, who were likely exposed in early life, had higher MBD. These findings should be replicated in larger studies.

Meeting report from the joint IARC-NCI international cancer seminar series: a focus on colorectal cancer

Despite significant progress in our understanding of the etiology, biology and genetics of colorectal cancer, as well as important clinical advances, it remains the third most frequently diagnosed cancer worldwide and is the second leading cause of cancer death. Based on demographic projections, the global burden of colorectal cancer would be expected to rise by 72% from 1.8 million new cases in 2018 to over 3 million in 2040 with substantial increases anticipated in low- and middle-income countries. In this meeting report, we summarize the content of a joint workshop led by the National Cancer Institute and the International Agency for Research on Cancer, which was held to summarize the important achievements that have been made in our understanding of colorectal cancer etiology, genetics, early detection and treatment and to identify key research questions that remain to be addressed.

Impact of molecular structure on the physicochemical properties of starches isolated from different field pea (Pisum sativum L.) cultivars grown in Saskatchewan, Canada

The objective of this study was to determine the molecular structure and properties of recently released cultivars of field peas [CDC Golden (CDCG), Abarth (ABAR), CDC Patrick (CDCP) and CDC Amarillo (CDCA)] grown at different locations in Saskatchewan, Canada. Starch yield (on whole seed basis), apparent amylose, total lipid and specific surface area were in the range 34-37%, 38.2-42.6%, 1.07-1.38% and 0.31-0.38m2/g, respectively. The proportion of short (DP 6-12) amylopectin chains, amylopectin branching density, molecular order, crystallinity, crystalline heterogeneity, gelatinization transition temperatures, pasting temperatures, peak viscosity, extent of acid hydrolysis, and resistant starch content were higher in CDCG and ABAR. However, amylopectin long chains (DP 13-26), average chain length and thermal stability were higher in CDCP and CDCA. The results of this study showed that differences in physicochemical properties among cultivars were mainly influenced by amylopectin chain length distribution, amylopectin branching density and co-crystallization of amylose with amylopectin.

Starch chain interactions within the amorphous and crystalline domains of pulse starches during heat-moisture treatment at different temperatures and their impact on physicochemical properties

Pulse (faba bean [FB], black bean [BB] and pinto bean [PB]) starches were heat-moisture treated (HMT) at 80, 100 and 120°C for 12h at a moisture content of ∼23%. Structural changes on HMT were monitored by microscopy, HPAEC-PAD, ATR-FTIR, WAXS, DSC and susceptibility towards acid and enzyme hydrolysis. Amylopectin chain length distribution remained unchanged in all starches on HMT. In all starches, HMT increased crystallinity and gelatinisation temperatures. The gelatinization enthalpy remained unchanged in some starches, whereas it decreased slightly in other starches on HMT. Slowly digestible starch content decreased at all temperatures of HMT, whereas resistant starch content increased at HMT80 and HMT100 (HMT80>HMT100), but decreased at HMT120. Birefringence, B-type crystallites and acid hydrolysis decreased on HMT. The extent of the above changes varied amongst starch sources and genotypes. HMT altered the X-ray pattern from A+B→A. The results of this study showed that structural reorganisation of starch chains during HMT temperature was influenced by starch chain flexibility, starch chain interactions and crystalline stability of the native granules.

Amperometric gas sensor response times

This work examines the relative importance of diffusion and the electrical time constant of the working electrode on the response time of amperometric gas sensors. The response curve of an electrochemical carbon monoxide sensor to a 200 ppm CO test gas was measured as a function of the added resistance that is in series with the working electrode to increase the time constant. It has been found that the response time increases with additional resistance. The experimental behavior was compared to the values predicted on the basis of Fick's second law of diffusion and to the values expected on the basis of the electrical properties of the sensor. The behavior of the sensor was explained using an equivalent electrical circuit, describing the time constants of the working electrode. Values obtained from this model were further compared to experimental values obtained from electrochemical impedance spectra. It has been found that the response time of the sensors depends on both the rate of diffusion and the electrical time constants of the working electrode.

In Asian-American Women, Westernization Influences Estrogen Metabolism, but Not Total Endogenous Estrogen Production

Background: Historically, breast cancer incidence rates were 4-7 times higher in the United States than in China and Japan. When Asian women migrate to the U.S., their risk rises over several generations and approaches that in U.S. Whites. Endogenous estrogen has been postulated to explain these international differences. Methods: In a population-based case-control study in Chinese, Japanese, and Filipino women living in San Francisco-Oakland, CA; Los Angeles, CA; or Oahu, HI, we documented a six-fold gradient in breast cancer risk with Westernization. Using 12-h, overnight urines from 263 premenopausal mid-luteal and 168 postmenopausal control subjects, we investigated associations of estrogens and estrogen metabolites (EM) with Westernization, particularly birthplace in the East or West. Fifteen EM were measured concurrently by liquid chromatography-tandem mass spectrometry with high accuracy, precision, and sensitivity. Log-transformed EM measures, adjusted for age and ethnicity, were compared by robust linear regression. Results: Total urinary EM (pmol/mg creatinine) was not associated with birthplace in premenopausal or postmenopausal women. When the three estrogen hydroxylation pathways were expressed as percent of total EM, the relative difference by birthplace, West compared to East, was 15% lower for 2-pathway EM (p=0.009), 7% lower for 4-pathway EM (p=0.37), and 10% higher for 16-pathway EM (p=0.008). Similar results were observed for individual EM in each pathway, premenopausal and postmenopausal women, and the three ethnicities. In both menopausal groups, 2-pathway EM concentration decreased steadily with increasing risk across six categories of Westernization. Conclusions: Our results do not indicate that total estrogen production explains the increased breast cancer risk in Western societies. However, estrogen metabolism patterns, especially reduced 2-hydroxylation, may contribute to the elevated risk; and underlying mechanisms merit further exploration.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3063.

Contributions of the kinase cross-reactivity profile of MK-0457 to clinical activity

7050

Background: MK-0457 was designed as a small-molecule inhibitor of the Aurora kinases, AUR A, B, and C (Ki,app = 0.66–18 nM). Kinase screens indicate high selectivity of MK-0457 over other Ser/Thr kinases, but nM potency against a small set of wild type and mutant Tyr kinases, including BCR-ABL, JAK-2, and FLT-3. Consistent with this biochemical profile, MK-0457 has clinical activity in patients with chronic myeloid leukemia (CML) and acute lymphocytic leukemia (ALL) with the T315I BCR-ABL mutation and in patients with JAK-2 positive myeloproliferative diseases (MPD). This study compared the enzyme inhibitory profile of MK0457 with kinase inhibition profiles in cell models to further associate biological and clinical activity. Methods: MK-0457 was tested against a panel of ∼200 kinases (at Km for ATP). Viability of BaF3 cells transfected with wild type or mutant BCR-ABL or FLT3 (D845Y and FLT3-ITD mutants) was measured in MTS assays (72 hrs). Cell cycle profiles were determined by FACS analyses. Cellular inhibition of kinase activities was measured by Western Blots using phospho-substrate specific antibodies. Results: In enzyme profiling, MK-0457 (200 nM) shows = 50% inhibition of ABL, T315I ABL, ABL2, FLT-3, FLT-3 D835Y, BMX, JAK2, YES, LYN, and LCK kinases. Western blot analyses indicate nM IC50s for inhibition of phosphorylation of AUR B, Histone H3 (AUR B substrate), FLT-3, BCR-ABL, and STAT5 (substrate of BCR-ABL and FLT-3 mutants). In addition to AUR kinase inhibition, the Tyr kinases are expected to be inhibited at clinical doses of 24–32 mg/m2/hr (achieving plasma exposures of >1 μM in patients). Depsite its multi-kinase profile, MK-0457 induces similar cytotoxicity (IC50 ∼300 nM) and shows an AUR B-like inhibitory phenotype of G2/M arrest, endoreduplication and apoptosis in BaF3 cells transfected with ABL or FLT-3 (mutant and wild type) kinases. Conclusions: MK-0457 is a potent Aurora kinase inhibitor with cross-reactivity against a small set of Tyr kinases. Although MK-0457 displays an AUR inhibition phenotype in cells, inhibition of these Tyr kinases may contribute to its observed clinical activity in T315I mutant CML and ALL and in JAK-2 positive MPD.

No significant financial relationships to disclose.