- Full (HTML) - Full (PDF) - Related EHP Articles - PubMed:Related Articles - PubMed:Citation - Cited in PMC - Purchase This Issue

Barry M. Markaverich,^1,2 Jan Crowley,³ Mary Rodriquez,¹ Kevin Shoulars,¹ and Trellis Thompson¹

¹Department of Molecular and Cellular Biology, and ²Center for Comparative Medicine, Baylor College of Medicine, Houston, Texas, USA; ³Department of Metabolism Mass Spectrometry Facility, Washington University School of Medicine, St. Louis, Missouri, USA

Abstract
Background: We characterized an endocrine disruptor from ground corncob bedding material that interferes with male and female sexual behavior and ovarian cyclicity in rats and stimulates estrogen receptor (ER) -positive and ER-negative breast cancer cell proliferation. The agents were identified as an isomeric mixture of tetrahydrofurandiols (THF-diols ; 9,12-oxy-10,13-dihydroxyoctadecanoic acid and 10,13-oxy-9,12-dihydroxyoctadecanoic acid) . Synthetic THF-diols inhibited rat male and female sexual behavior at oral concentrations of 0.5–1 ppm, and stimulated MCF-7 human breast cancer cell proliferation in vitro.

Objectives: Because THF-diols are derived from lipoxygenase and cyclooxygenase pathways, we suspected that these compounds may regulate cell proliferation by modulating specific enzymatic sites involved in linoleic acid metabolism including phospholipase A₂ (PLA2) , lipoxygenases (LOX-5 and LOX-12) , cyclooxygenases (COX-1 and COX-2) , and closely coupled enzymes including aromatase (AROM) .

Methods: MCF-7 human breast cancer cells were treated with inhibitors for PLA2 (quinacrine) , lipoxygenases (LOX-5 and LOX-12 ; baicalein, REV-5091, nordihydroguaiaretic acid) , cyclooxygenases (COX-1, COX-2, indomethacin) , and AROM (formestane) . The effects of these enzyme inhibitors on cell proliferation in response to THF-diols or estradiol (E₂) were assessed. THF-diol modulation of the expression (RNA and protein) of these enzymes was also evaluated by quantitative real-time PCR (QPCR) and Western blot analyses.

Results: The enzyme inhibition and gene expression (RNA and protein) studies identified PLA2, LOX-5, LOX-12, COX-2, and perhaps AROM as likely sites of THF-diol regulation in MCF-7 cells. COX-1 was not affected by THF-diol treatment.

Discussion: THF-diol stimulation of MCF-7 cell proliferation is mediated through effects on the expression of the PLA2, COX-2, LOX-5, and LOX-12 genesand/or their respective enzyme activities. The products of these enzymes, including prostaglandins, hydroxyeicosatetraenoic acids (HETEs) and hydroxyoctadecenoic acids (HODEs) , are well-established mitogens in normal and malignant cells. Therefore, it is likely that these compounds are involved in the mechanism of action of THF-diols in breast cancer cells. Although the formestane inhibition studies suggested that AROM activity might be modulated by THF-diols, this was not confirmed by the gene expression studies.

Key words: breast cancer cells, COX-2, LOX-5, LOX-12, and PLA2 gene expression, THF-diols. Environ Health Perspect 115:1727–1731 (2007) . doi:10.1289/ehp.10659 available via http://dx.doi.org/ [Online 30 August 2007]

Address correspondence to B.M. Markaverich, Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 USA. Telephone: (713) 798-6497. Fax: (713) 790-1275. E-mail: barrym@bcm.tmc.edu

This work was supported by grants from the National Institute of Environmental Health Sciences (ES09964) , the Office of Research on Women's Health, the National Cancer Institute (CA-35480) , and grant P41-RR-00954 from the National Council of Research Resources of the National Institutes of Health.

The authors declare they have no competing financial interests.

Received 12 July 2007 ; accepted 30 August 2007.