Human arylamine N-acetyltransferase 1 (NAT1) is a phase II xenobiotic-metabolizing enzyme (XME) involved in the biotransformation of many aromatic and heterocyclic amines. This XME plays key roles in both the detoxification and/or bioactivation of numerous drugs and carcinogens. NAT1 is polymorphic and displays a large tissue distribution. NAT1 activity have been extensively studied because of its potential role in the biotransformation of important carcinogens. Several recent studies suggest that NAT1 may have a role in breast cancer progression. Indeed, this XME has been shown to affect the growth and drug resistance of breast cancer cells and appears as a marker in human estrogen receptor positive breast cancer. In addition, it has been shown that this enzyme is inhibited in vivo by cancer drugs such as cisplatin or tamoxifen. Recent published data suggest that NAT1 could be of therapeutic interest for cancer. We provide here an overview on the putative involvement of NAT1 in cancer and its possible role as a drug target. less...

Fate maps are generated by marking and tracking cells in vivo to determine how progenitors contribute to specific structures and cell types in developing and adult tissue. An advance in this concept is Genetic Inducible Fate Mapping (GIFM), linking gene expression, cell fate, and cell behaviors in vivo, to create fate maps based on genetic lineage. GIFM exploits X-CreER lines where X is a gene or set of gene regulatory elements that confers spatial expression of a modified bacteriophage protein, Cre recombinase (CreER(T)). CreER(T) contains a modified estrogen receptor ligand binding domain which renders CreER(T) sequestered in the cytoplasm in the absence of the drug tamoxifen. The binding of tamoxifen releases CreER(T), which translocates to the nucleus and mediates recombination between DNA sequences flanked by loxP sites. In GIFM, recombination typically occurs between a loxP flanked Stop cassette preceding a reporter gene such as GFP. Mice are bred to contain either a region- or cell type-specific CreER and a conditional reporter allele. Untreated mice will not have marking because the Stop cassette in the reporter prevents further transcription of the reporter gene. We administer tamoxifen by oral gavage to timed-pregnant females, which provides temporal control of CreER(T) release and subsequent translocation to the nucleus removing the Stop cassette from the reporter. Following recombination, the reporter allele is constitutively and heritably expressed. This series of events marks cells such that their genetic history is indelibly recorded. The recombined reporter thus serves as a high fidelity genetic lineage tracer that, once on, is uncoupled from the gene expression initially used to drive CreER(T). We apply GIFM in mouse to study normal development and ascertain the contribution of genetic lineages to adult cell types and tissues. We also use GIFM to follow cells on mutant genetic backgrounds to better understand complex phenotypes that mimic salient features of human genetic disorders. This video article guides researchers through experimental methods to successfully apply GIFM. We demonstrate the method using our well characterized Wnt1-CreER(T);mGFP mice by administering tamoxifen at embryonic day (E)8.5 via oral gavage followed by dissection at E12.5 and analysis by epifluorescence stereomicroscopy. We also demonstrate how to micro-dissect fate mapped domains for explant preparation or FACS analysis and dissect adult fate-mapped brains for whole mount fluorescent imaging. Collectively, these procedures allow researchers to address critical questions in developmental biology and disease models. less...

Myc is activated in many tumours, yet, paradoxically, stimulates differentiation in mammalian epidermis. To test whether the epidermis responds differently to different levels of Myc, we treated K14MycER transgenic mice with a range of concentrations of the inducing agent, 4-hydroxy-tamoxifen (4OHT). Proliferation was stimulated at all levels of Myc activity; sebocyte differentiation was stimulated at low and intermediate levels; and interfollicular epidermal differentiation at intermediate and high levels. Mutational inactivation of the Myc p21 activated kinase 2 (PAK2) phosphorylation sites increased Myc activity and further enhanced epidermal differentiation. We conclude that Myc induced differentiation acts as a fail-safe device to prevent uncontrolled proliferation and neoplastic conversion of epidermal stem cells expressing high levels of Myc. less...

Objective: To compare the prognostic prediction between dichotomized and fractionated evaluations of hormone receptor expressions. Methods: Patients with stages I-III breast cancers, who received adjuvant tamoxifen, were enrolled. The expression of estrogen receptor (ER) and progesterone receptor (PR) was evaluated by immunohistochemistry (IHC). A fractionated score (F score), the percentage of positive-staining nuclei (0=none, 1=1%-10%, 2=11%-30%, 3=31%-50%, 4=51%-70%, and 5=71%-100%), was assigned to each case. The dichotomized scoring method defines an F score >1 as positive. The prognostic values of both scores were compared by multiple Cox's proportional hazard models of disease-free survival (DFS) and overall survival (OS). Results: Four hundred and sixteen patients with a median follow-up of 78.0 months were included. F scores for ER and PR correlated directly with DFS and OS. Although both the dichotomized and fractionated ER and PR scores were significantly associated with DFS and OS in univariate analyses, only fractionated ER and PR scores remained as independent prognostic factors of DFS and OS in the final multiple Cox's proportional hazard models. Conclusion: Fractionated IHC hormone receptor expression evaluation enhances the prognostic prediction compared with a dichotomized assessment. less...

Two in vitro systems were employed to delineate the estrogenic activity of daidzein (Da), alone or in combination with high or low concentrations of estrogen in two cell types possessing different estrogen-receptor (ER) isoforms, ERalpha and/or ERbeta: (1) vitellogenin capital PE, Cyrillic (VTG), the egg yolk precursor protein and the endpoint biomarker for estrogenicity, in chicken primary hepatocytes, and (2) CHO-K1 cells transiently co-transfected with ERalpha or ERbeta and estrogen-response elements (ERE) linked to a luciferase reporter gene. Da (100muM) alone induced VTG mRNA expression in chicken hepatocytes, albeit with much less potency compared to estradiol (E(2)). Da exhibited different effects in the presence of 1muM and 10muM E(2). At a concentration of 100muM, Da enhanced 1muM E(2)-induced VTG transcription by 2.4-fold, but significantly inhibited 10muM E(2)-induced VTG mRNA expression in a dose-dependent fashion from 1 to 100muM. Tamoxifen completely blocked the estrogenic effect of daidzein, alone or in combination with 1muM of E(2), but did not influence its anti-estrogenic effect on 10muM E(2)-induced VTG mRNA expression. Furthermore, neither E(2) nor daidzein, alone or in combination, affected ERalpha mRNA expression, yet all the treatments significantly up-regulated ERbeta mRNA expression in chicken hepatocytes. E(2) effectively triggered estrogen-response elements (ERE)-driven reporter gene transactivation in CHO-K1 cells expressing ERalpha or ERbeta and showed much greater potency with ERalpha than with ERbeta. In contrast, daidzein was 1000 times more powerful in stimulating ERbeta- over ERalpha-mediated transactivation. Daidzein, in concentrations ranging from 5nM to 50muM, did not affect ERbeta-mediated transactivation induced by 1nM E(2), but it significantly inhibited ERbeta-mediated transactivation induced by 10nM E(2) at 500nM. Despite the tremendous difference in sensitivity between the two in vitro systems, daidzein exhibited greater potency as an estrogen-antagonist for ERbeta-mediated activity. less...

Growing concern over possible adverse effects of endocrine-disrupting chemicals (EDCs) has driven the development of associated screening methods. The use of the vitellogenin (VTG) induction response in cultured teleost hepatocytes has been suggested as an in vitro screening assay for EDCs. However, current data do not sufficiently support this assay in the routine screening of chemicals. This study established and validated the use of primary cultured hepatocytes from zebrafish to screen chemicals for anti-estrogenic activities. Here we measured the transcript levels of selected hepatic estrogen-response genes, including vtg1, vtg2 and eralpha. Two model anti-estrogens, letrozole (LET), an aromatase inhibitor, and tamoxifen (TAM), a competitive estrogen receptor, were selected as representative chemicals. Additionally, comparisons between in vitro and in vivo assays were performed. As expected, there were concentration-dependent decreases for all three genes in the liver of female zebrafish exposed to LET in vivo for 72h. Similar responses were observed in males. As for in vitro testing, no discernable alterations in the gene transcripts were found in hepatocytes from males or females. In the case of TAM, exposure for 72h caused transcriptional reduction of hepatic estrogen-response genes in females in vivo and in vitro. In males, low concentrations of TAM resulted in increased expression of genes, while the expression decreased slightly at higher concentrations. Since these observations were in agreement with the pharmaceutical properties of two tested chemicals, the primary hepatocyte culture could be a promising tool for screening suspected EDCs. less...

Irradiation-induced brain injury, leading to cognitive impairment several months to years after whole brain irradiation (WBI) therapy, is a common health problem in patients with primary or metastatic brain tumor and greatly impairs quality of life for tumor survivors. Recently, it has been demonstrated that a rapid and sustained increase in activated microglia following WBI led to a chronic inflammatory response and a corresponding decrease in hippocampal neurogenesis. Tamoxifen, serving as a radiosensitizer and a useful agent in combination therapy of glioma, has been found to exert anti-inflammatory response both in cultured microglial cells and in a spinal cord injury model. In the present study, we investigated whether tamoxifen alleviated inflammatory damage seen in the irradiated microglia in vitro and in the irradiated brain. Irradiating BV-2 cells (a murine microglial cell line) with various radiation doses (2-10 Gy) led to the increase in IL-1beta and TNF-alpha expression determined by ELISA, and the conditioned culture medium of irradiated microglia with 10Gy radiation dose initiated astroglial activation and decreased the number of neuronal cells in vitro. Incubation BV-2 cells with tamoxifen (1 microM) for 45 min significantly inhibited the radiation-induced microglial inflammatory response. In the irradiated brain, WBI induced the breakdown of blood brain barrier permeability at day 1 post irradiation and tissue edema formation at day 3 post-radiation. Furthermore, WBI led to microglial activation and reactive astrogliosis in the cerebral cortex and neuronal apoptosis in the CA1 hippocampus at day 3 post-radiation. Tamoxifen administration (i.p, 5 mg/kg) immediately post-radiation reduced the irradiation-induced brain damage after WBI. Taken together, these data support that tamoxifen can decrease the irradiation-induced brain damage via attenuating the microglial inflammatory response. less...

Tamoxifen is a powerful drug used to treat breast cancer patients, and more than 500,000 women in the U. S. are being treated with this drug. In our study, tamoxifen is found to be photomutagenic in Salmonella typhimurium TA102 at concentrations as low as 0.08 muM and reaches maximum photomutagenicity at 0.4 muM under a light dose equivalent to 20 min sunlight. These concentrations are comparable to the plasma tamoxifen concentration of 0.4 to 3 muM for patients undergoing tamoxifen therapy. The toxicity seems to be the result of DNA damage and/or lipid peroxidation caused by light irradiation of tamoxifen. The DNA damage caused by irradiation of PhiX174 DNA in the presence of tamoxifen appears to be formation of DNA-tamoxifen covalent adducts, not single strand/double strand cleavages, and there is no oxygen involvement. This is confirmed by EPR experiments that carbon-centerd radicals are formed by light irradiation of tamoxifen and there is no singlet oxygen formation. Although superoxide radical is formed, it is not involved in DNA damage. less...

OBJECTIVE: The aim of this study is to investigate clinical implications of human leukocyte antigen-G (HLA-G) expression in breast cancer. METHODS: HLA-G expression in 235 primary breast cancer tissues was investigated using immunohistochemistry, and plasma soluble HLA-G (sHLA-G) was measured in 44 breast cancer patients using a specific HLA-G enzyme-linked immunosorbent assay (ELISA). Effects of estradiol/progesterone and their antagonists tamoxifen/RU486 on HLA-G expression in cultured breast cancer MCF-7 cells were determined by real-time polymerase chain reaction (PCR) and the ELISA. Alterations of HLA-G expression by the hormone treatments on subsequent allocytotoxic lymphocyte (allo-CTL) response were also examined. RESULTS: In the study, approximately 66% of neoplasm lesions were identified to have positive HLA-G expression. This expression was significantly correlated with tumor size, nodal status, and clinical disease stage (P = 0.0001, 0.012, and 0.0001, respectively). Patients with positive HLA-G expression had a lower survival rate than those with negative expression (P < 0.028). Plasma sHLA-G levels were significantly higher in breast cancer patients than in healthy controls (P < 0.001), with the area under the receiver-operating characteristic (ROC) curve being 0.95. HLA-G expression in breast cancer MCF-7 cells was enhanced by estradiol/progesterone but reduced by their antagonists. Cytotoxicity studies showed that allo-CTL response in MCF-7 cells was inhibited by prior treatment with estradiol/progesterone, but was amplified by their antagonists. The effects could be restored or further strengthened by the addition of anti-HLA-G antibodies. CONCLUSION: Our findings suggest that HLA-G may have potential clinical implications in diagnosis, prognosis, and immunotherapy of patients with breast cancer. less...

BACKGROUND:: Little information is available regarding the effects of new adjuvant treatment regimens on menstrual functioning in premenopausal women with early breast cancer. METHODS:: The authors conducted a retrospective review of data from premenopausal women who received treatment for early breast cancer to evaluate the rates of amenorrhea in follow-up. The women who were included received treatment with either doxorubicin and cyclophosphamide (AC) or combined AC and paclitaxel (T) (AC-T) given either every 3 weeks, or as a dose-dense (DD) regimen, or as AC followed by weekly T with trastuzumab or followed by trastuzumab (AC-T+trastuzumab). A multivariate logistic regression analysis was conducted to evaluate amenorrhea during follow-up. RESULTS:: Of 431 patients who were eligible for analysis, the average age at diagnosis was 13 years (range, 25-55 years), 61% of women received AC only, and 39% received AC-T. Of the 39% who received AC-T, 49% of women received DD therapy, 14% received AC-T+trastuzumab, and 71% of all patients received tamoxifen (TAM). The median follow-up was 33 months (range, 6-114 months). After adjusting for age, weight, gravidity, parity, age at menarche, smoking, alcohol use, TAM use, type and regimen of chemotherapy, and use of trastuzumab, the likelihood of remaining amenorrheic was not statistically different in patients who received AC-T versus AC (odds ratio [OR], 1.59; 95% confidence interval [CI], 0.8-3.2), DD treatment versus treatment every 3 weeks (OR, 0.56; 95% CI, 0.25-1.3), or AC-T + trastuzumab (OR, 0.6; 95% CI, 0.22-1.61). Amenorrhea was associated significantly with TAM use and age at diagnosis. CONCLUSIONS:: Recent advances in the adjuvant treatment of early breast cancer do not appear to have increased the risk of amenorrhea in premenopausal women. Cancer 2010. (c) 2010 American Cancer Society. less...