Association of tamoxifen use and ovarian function in patients with invasive or pre-invasive breast cancer.

The impact of long-term tamoxifen therapy on ovarian function is not known. Understanding these effects will help reproductive-aged patients who desire future pregnancy make more informed decisions regarding their treatment. This is a retrospective cohort study in patients identified through the UCSF Cancer Registry and SPORE database. We enrolled women with a history of ductal carcinoma in situ (DCIS) or early stage invasive breast cancer who were premenopausal at diagnosis and did not receive chemotherapy. Menstrual histories were obtained through electronic and paper surveys. We compared the age of menopause onset and menstrual pattern changes between women who received tamoxifen (TAM) and those who did not receive tamoxifen (control). Neither group received chemotherapy. 250 subjects were included in this study (125 TAM, 125 control). Mean age of menopause onset was 51.0 for both the groups and was not associated with duration of tamoxifen use or the age at tamoxifen initiation. Menstrual pattern changes, including amenorrhea, were more frequent in the TAM group than control group (any change: 48% TAM vs. 15 % control, p < 0.001; amenorrhea: 22% TAM vs. 3% control, p < 0.001). Older age was associated with an increased risk of developing amenorrhea within 6 months of starting tamoxifen (HR 1.32, p < 0.001). Menstrual pattern changes are common in premenopausal women taking tamoxifen. Tamoxifen use in the absence of chemotherapy is not associated with an earlier age onset of menopause in patients with DCIS or invasive breast cancer and is unlikely to significantly accelerate ovarian aging.

Identification of modulators of the nuclear receptor peroxisome proliferator-activated receptor α (PPARα) in a mouse liver gene expression compendium.

The nuclear receptor family member peroxisome proliferator-activated receptor α (PPARα) is activated by therapeutic hypolipidemic drugs and environmentally-relevant chemicals to regulate genes involved in lipid transport and catabolism. Chronic activation of PPARα in rodents increases liver cancer incidence, whereas suppression of PPARα activity leads to hepatocellular steatosis. Analytical approaches were developed to identify biosets (i.e., gene expression differences between two conditions) in a genomic database in which PPARα activity was altered. A gene expression signature of 131 PPARα-dependent genes was built using microarray profiles from the livers of wild-type and PPARα-null mice after exposure to three structurally diverse PPARα activators (WY-14,643, fenofibrate and perfluorohexane sulfonate). A fold-change rank-based test (Running Fisher's test (p-value ≤ 10(-4))) was used to evaluate the similarity between the PPARα signature and a test set of 48 and 31 biosets positive or negative, respectively for PPARα activation; the test resulted in a balanced accuracy of 98%. The signature was then used to identify factors that activate or suppress PPARα in an annotated mouse liver/primary hepatocyte gene expression compendium of ~1850 biosets. In addition to the expected activation of PPARα by fibrate drugs, di(2-ethylhexyl) phthalate, and perfluorinated compounds, PPARα was activated by benzofuran, galactosamine, and TCDD and suppressed by hepatotoxins acetaminophen, lipopolysaccharide, silicon dioxide nanoparticles, and trovafloxacin. Additional factors that activate (fasting, caloric restriction) or suppress (infections) PPARα were also identified. This study 1) developed methods useful for future screening of environmental chemicals, 2) identified chemicals that activate or suppress PPARα, and 3) identified factors including diets and infections that modulate PPARα activity and would be hypothesized to affect chemical-induced PPARα activity.