Differing transcriptional responses to pulsed or continuous estradiol exposure in human umbilical vein endothelial cells.

This study used human umbilical vein endothelial cells (HUVECs) that were treated with 17beta-estradiol for 5 days as 1h pulse or 24h continuous treatment at concentrations such that the 24h exposure (concentration x time) was identical in both conditions. Cell proliferation was studied and gene expression profiling was carried out using the Affymetrix GeneChip microarray analysis. Changes in morphology and apoptosis in HUVECs were examined with electron microscopy.

Absence of uterine tumours in CD-1 mice treated neonatally with subcutaneous tamoxifen or 4-hydroxyoestradiol.

The effects of subcutaneous dosing of neonatal CD-1 mice with tamoxifen on days 1-5 after birth at doses of 0, 5, 10, 25 or 50 microg/pup or with 4-hydroxyoestradiol at 2 microg/pup have been investigated. Animals were culled at 1.5, 3, 6, 12 and 18 months after dosing and changes in uterine and ovarian pathology examined.

Ishikawa cells exhibit differential gene expression profiles in response to oestradiol or 4-hydroxytamoxifen.

In this study, the oestrogen agonist/antagonist action of 4-hydroxytamoxifen (OHT; 1 x 10(-6) M) and 17beta-oestradiol (E(2); 1 x 10(-8) M) were assessed on the oestrogen receptor (ER)-positive epithelial cell line (Ishikawa) with respect to cell proliferation, and to gene and protein expression. qRT-PCR and western blotting confirmed that Ishikawa cells expressed both ER isoforms and that there was no change in transcript levels in response to either ligand. Gene expression profiles, using oligonucleotide arrays representing approxiamtely 19,000 human genes, showed that the expression of 716 and 534 genes were changed differentially by treatment with either OHT or E(2) respectively, at the 24-h time point, with modulation of 46 genes common to both ligands, whereas 335 (OHT) and 240 (E(2)) genes showed expression changes unique to ligand, with 13 common alterations at 48 h.

Tamoxifen forms DNA adducts in human colon after administration of a single [14C]-labeled therapeutic dose.

Tamoxifen is widely prescribed for the treatment of breast cancer and is also licensed in the United States for the prevention of this disease. However, tamoxifen therapy is associated with an increased occurrence of endometrial cancer in women, and there is also evidence that it may elevate the risk of colorectal cancer. The underlying mechanisms responsible for tamoxifen-induced carcinogenesis in women have not yet been elucidated, but much interest has focused on the role of DNA adduct formation.

Experimental adenomyosis.

Adenomyosis has been reported in a number of different animal species, whereas endometriosis appears limited to humans and non-human primates. This suggests a different aetiology of the two conditions. Adenomyosis develops spontaneously in certain strains of laboratory mice.

Applications of accelerator mass spectrometry for pharmacological and toxicological research.

The technique of accelerator mass spectrometry (AMS), known for radiocarbon dating of archeological specimens, has revolutionized high-sensitivity isotope detection in pharmacology and toxicology by allowing the direct determination of the amount of isotope in a sample rather than measuring its decay. It can quantify many isotopes, including 26Al, 14C, 41Ca, and 3H with detection down to attomole (10(-18)) amounts. Pharmacokinetic data in humans have been achieved with ultra-low levels of radiolabel.

Neonatal tamoxifen treatment of mice leads to adenomyosis but not uterine cancer.

Tamoxifen is contraindicated during pregnancy but many births have been reported in breast cancer patients taking this drug and numbers might be expected to increase with FDA approval of tamoxifen for risk reduction in women at high, risk of breast cancer. The neonatal mouse, exquisitely sensitive to xenobiotic estrogens, has been used to investigate the effects of short-term oral dosing with tamoxifen (1 mg/kg on days 2-5 after birth) on long-term changes in uterine pathology and gene expression. Increased adenomyosis incidence and severity was evident in the tamoxifen-treated mice with increasing age.

Techniques: the application of accelerator mass spectrometry to pharmacology and toxicology.

The exquisite sensitivity of accelerator mass spectrometry (AMS) is being used in biomedical applications to quantitate many isotopes, including 14C, 3H, 41Ca and 27Al, at attomole (10(-18)) concentrations. This enables compounds and metabolites to be measured in human urine and plasma after administration of low pharmacologically or toxicologically relevant doses of labelled chemicals and drugs. The detection of modified proteins or DNA in target organs after dosing with potential carcinogens has also been achieved in many studies.

Tamoxifen DNA damage detected in human endometrium using accelerator mass spectrometry.

This study was aimed to establish whether tamoxifen binds irreversibly to uterine DNA when given to women. Patients were given a single therapeutic dose of [(14)C]tamoxifen citrate orally (20 mg, 0.37 or 1.

Identification of human CYP forms involved in the activation of tamoxifen and irreversible binding to DNA.

This study investigates which CYP forms are responsible for the conversion of tamoxifen to its putative active metabolite alpha-hydroxytamoxifen and irreversible binding to DNA. We have used eight different baculovirus expressed recombinant human CYP forms and liquid chromatography-mass spectrometry to show that only CYP3A4 is responsible for the NADPH-dependent alpha-hydroxylation of tamoxifen. Surprisingly, this CYP did not catalyse the formation of 4-hydroxytamoxifen.