Tamoxifen has been a mainstay of adjuvant therapy for breast cancer for many years. We sought to determine if genetic variability in the tamoxifen metabolic pathway influenced overall survival in breast cancer patients treated with tamoxifen. We examined functional polymorphisms in CYP2D6, the P450 catalyzing the formation of active tamoxifen metabolites, and UGT2B15, a Phase II enzyme facilitating the elimination of active metabolite in a retrospective study of breast cancer patients. We also examined whether the combination of variant alleles in SULT1A1 and UGT2B15 had more of an impact on overall survival in tamoxifen-treated patients than when the genes were examined separately. We conducted a retrospective study using archived paraffin blocks for DNA extraction and data from pathology reports and hospital tumor registry data for information on clinical characteristics, treatment, and outcomes (162 patients receiving tamoxifen and 175 who did not). Genotypes for CYP2D6 and UGT2B15 were obtained and Cox proportional hazards modeling was performed. After adjusting for age, race, stage of disease at diagnosis, and hormone receptor status, we found no significant association between CYP2D6 genotype and overall survival in either group of breast cancer patients. Tamoxifen-treated patients with UGT2B15 high activity genotypes had increased risk of recurrence and poorer survival. When UGT2B15 and SULT1A1 'at-risk' alleles were combined, women with two variant alleles had significantly greater risk of recurrence and poorer survival than those with common alleles. These studies indicate that genetic variation in Phase II conjugating enzymes can influence the efficacy of tamoxifen therapy for breast cancer.

These data suggest that GREB 1 is critically involved in the estrogen induced growth of breast cancer cells and has the potential of being a clinical marker for response to endocrine therapy as well as a potential therapeutic target.

Long INterspersed Element-1 (LINE-1 or L1) retrotransposition continues to impact human genome evolution1,2. L1s can retrotranspose in the germline, during early development, and in select somatic cells3,4,5,6,7,8; however, the host response to L1 retrotransposition remains largely unexplored. Here, we show that reporter genes introduced into the genome of various human embryonic carcinoma-derived cell lines (ECs) by L1 retrotransposition are rapidly and efficiently silenced either during or immediately after their integration. Treating ECs with histone deacetylase inhibitors (IHDACs) rapidly reverses this silencing, and chromatin immunoprecipitation (ChIP) experiments revealed that reactivation of the reporter gene was correlated with changes in chromatin status at the L1 integration site. Under our assay conditions, rapid silencing also was observed when reporter genes were delivered into ECs by mouse L1s and a zebrafish LINE-2 element, but not when similar reporter genes were delivered into ECs by Moloney murine leukemia virus (MMLV) or human immunodeficiency virus (HIV), suggesting these integration events are silenced by distinct mechanisms. Finally, we demonstrate that subjecting ECs to culture conditions that promote differentiation attenuates the silencing of reporter genes delivered by L1 retrotransposition, but that differentiation, per se, is not sufficient to reactivate previously silenced reporter genes. Thus, our data suggest that ECs differ from many differentiated cells in their ability to silence reporter genes delivered by L1 retrotransposition.

Little et al., 1993Little et al., , 1999Staley et al., 1994), accompanied by up-regulation of dopamine uptake (Mash et al., 1997). Such functional alterations could be important, perhaps contributing to cocaine-induced binging, withdrawal symptoms, or craving. Beyond drug self-administration, dopamine neurons play a role in other rewarding phenomena, including sex (Everitt, 1990) and eating (Phillips et al., 1993), suggesting that regulatory alterations in DAT function could have interesting implications for understanding the dynamics of a number of motivational and appetitive processes. Recent experiments in cell culture have determined that phosphorylative treatments (Pristupa et al., 1998;Daniels et al., 1999;Melikian and Buckley, 1999) or exposure to the stimulant d-amphetamine (Saunders et al., 2000) dynamically regulate DAT function by changing DAT cellular localization, perhaps invoking mechanisms that might be related to those activated by cocaine.Understanding the mechanisms involved in DAT binding site changes is important because 1) binding site alterations are the primary alterations documented in postmortem brain from cocaine users; 2) DAT inhibitors/ligands are being developed extensively as both therapeutic and imaging agents for both the DAT as well as dopamine neurons; and 3) DAT regulation may provide broader insights into the pharmacological effects of drugs on transporter binding sites. In addition to our need to uncover cocaine's neurochemical effects that provoke symptoms associated with its dependence, it is possible that new therapeutic or imaging agents (many of which are often DAT uptake inhibitors) might themselves induce adaptations in DAT function, as well as alter cocaine's effect on dopamine uptake. Also, potentially, DAT inhibitor binding sites could be altered through some mechanism that is independent of changes in DAT concentration or function.

Scientists have long hypothesized the existence of tissue-specific (somatic) stem cells and have searched for their location in different organs. The theory that adrenocortical organ homeostasis is maintained by undifferentiated stem or progenitor cells can be traced back nearly a century. Similar to other organ systems, it is widely believed that these rare cells of the adrenal cortex remain relatively undifferentiated and quiescent until needed to replenish the organ, at which time they undergo proliferation and terminal differentiation. Historical studies examining cell cycle activation by label retention assays and regenerative potential by organ transplantation experiments suggested that the adrenocortical progenitors reside in the outer periphery of the adrenal gland. Over the past decade, the Hammer laboratory, building on this hypothesis and these observations, has endeavored to understand the mechanisms of adrenocortical development and organ maintenance. In this review, we summarize the current knowledge of adrenal organogenesis. We present evidence for the existence and location of adrenocortical stem/progenitor cells and their potential contribution to adrenocortical carcinomas. Data described herein come primarily from studies conducted in the Hammer laboratory with incorporation of important related studies from other investigators. Together, the work provides a framework for the emerging somatic stem cell field as it relates to the adrenal gland.

GREB1 is expressed in proliferating prostatic tissue and prostate cancer, is regulated by androgens, and suppression of GREB1 blocks androgen-induced growth suggesting GREB1 may be critically involved in prostate cancer proliferation.

Numerous genes required for adrenocortical steroidogenesis are activated by the nuclear hormone receptor steroidogenic factor 1 (SF-1) (NR5A1). Dax-1 (NR0B1), another nuclear hormone receptor, represses SF-1-dependent activation. Glucocorticoid products of the adrenal cortex provide negative feedback to the production of hypothalamic CRH and pituitary ACTH. We hypothesized that glucocorticoids stimulate an intraadrenal negative feedback loop via activation of Dax-1 expression. Reporter constructs show glucocorticoid-dependent synergy between SF-1 and glucocorticoid receptor (GR) in the activation of Dax-1, which is antagonized by ACTH signaling. We map the functional glucocorticoid response element between -718 and -704 bp, required for activation by GR and synergy with SF-1. Of three SF-1 response elements, only the -128-bp SF-1 response element is required for synergy with GR. Chromatin immunoprecipitation (ChIP) assays demonstrate that dexamethasone treatment increases GR and SF-1 binding to the endogenous murine Dax-1 promoter 10- and 3.5-fold over baseline. Serial ChIP assays reveal that that GR and SF-1 are part of the same complex on the Dax-1 promoter, whereas coimmunoprecipitation assay confirms the presence of a protein complex that contains both GR and SF-1. ACTH stimulation disrupts the formation of this complex by abrogating SF-1 binding to the Dax-1 promoter, while promoting SF-1 binding to the melanocortin-2 receptor (Mc2r) and steroidogenic acute regulatory protein (StAR) promoters. Finally, dexamethasone treatment increases endogenous Dax-1 expression and concordantly decreases StAR expression. ACTH signaling antagonizes the increase in Dax-1 yet strongly activates StAR transcription. These data indicate that GR provides feedback regulation of adrenocortical steroid production through synergistic activation of Dax-1 with SF-1, which is antagonized by ACTH activation of the adrenal cortex.

T he capacity of β cells to expand in response to insulin resistance is a critical factor in the development of type 2 diabetes. Proliferation of β cells is a major component for these adaptive responses in animal models. The extracellular signals responsible for β-cell expansion include growth factors, such as insulin, and nutrients, such as glucose and amino acids. AKT activation is one of the important components linking growth signals to the regulation of β-cell expansion. Downstream of AKT, tuberous sclerosis complex 1 and 2 (TSC1/2) and mechanistic target of rapamycin complex 1 (mTORC1) signaling have emerged as prime candidates in this process, because they integrate signals from growth factors and nutrients. Recent studies demonstrate the importance of mTORC1 signaling in β cells. This review will discuss recent advances in the understanding of how this pathway regulates β-cell mass and present data on the role of TSC1 in modulation of β-cell mass. Herein, we also demonstrate that deletion of Tsc1 in pancreatic β cells results in improved glucose tolerance, hyperinsulinemia and expansion of β-cell mass that persists with aging.