Golde, Todd E.

AbstractIntroductionWe hypothesized that common Alzheimer's disease (AD)‐associated variants within the triggering receptor expressed on myeloid (TREM) gene cluster influence disease through gene expression.MethodsExpression microarrays on temporal cortex and cerebellum from ∼400 neuropathologically diagnosed subjects and two independent RNAseq replication cohorts were used for expression quantitative trait locus analysis.ResultsA variant within a DNase hypersensitive site 5′ of TREM2, rs9357347‐C, associates with reduced AD risk and increased TREML1 and TREM2 levels (uncorrected P = 6.3 × 10−3 and 4.6 × 10−2, respectively). Meta‐analysis on expression quantitative trait locus results from three independent data sets (n = 1006) confirmed these associations (uncorrected P = 3.4 × 10−2 and 3.5 × 10−3, Bonferroni‐corrected P = 6.7 × 10−2 and 7.1 × 10−3, respectively).DiscussionOur findings point to rs9357347 as a functional regulatory variant that contributes to a protective effect observed at the TREM locus in the International Genomics of Alzheimer's Project genome‐wide association study meta‐analysis and suggest concomitant increase in TREML1 and TREM2 brain levels as a potential mechanism for protection from AD.

Abstract Notch genes encode membrane receptors that regulate cell fate decisions in metazoa. Notch receptors and ligands are expressed in developing lymphoid tissue and mature lymphocytes and the role of Notch signaling in early T and B cell development has been studied extensively. However, its contribution to mature T cell function is unknown. TCR-mediated T cell activation is a fundamental process of the adaptive immune system that has been studied for decades; however, the details of this process are incompletely understood. In this study, we present evidence that Notch is required for TCR-mediated activation of peripheral T cells. Inhibition of Notch activation dramatically decreases T cell proliferation in both CD4 and CD8 cells and blocks both NF-κB activity and IFN-γ production in peripheral T cells. Our data reveal a new, nondevelopmental function of Notch as a previously unknown key link in peripheral T cell activation and cytokine secretion.

Severe aplastic anemia (AA) is a bone marrow (BM) failure (BMF) disease frequently caused by aberrant immune destruction of blood progenitors. Although a Th1-mediated pathology is well described for AA, molecular mechanisms driving disease progression remain ill defined. The NOTCH signaling pathway mediates Th1 cell differentiation in the presence of polarizing cytokines, an action requiring enzymatic processing of NOTCH receptors by γ-secretase. Using a mouse model of AA, we demonstrate that expression of both intracellular NOTCH1IC and T-BET, a key transcription factor regulating Th1 cell differentiation, was increased in spleen and BM-infiltrating T cells during active disease. Conditionally deleting Notch1 or administering γ-secretase inhibitors (GSIs) in vivo attenuated disease and rescued mice from lethal BMF. In peripheral T cells from patients with untreated AA, NOTCH1IC was significantly elevated and bound to the TBX21 promoter, showing NOTCH1 directly regulates the gene encoding T-BET. Treating patient cells with GSIs in vitro lowered NOTCH1IC levels, decreased NOTCH1 detectable at the TBX21 promoter, and decreased T-BET expression, indicating that NOTCH1 signaling is responsive to GSIs during active disease. Collectively, these results identify NOTCH signaling as a primary driver of Th1-mediated pathogenesis in AA and may represent a novel target for therapeutic intervention.

Abstract Abstract #106 Breast cancer has been proposed as a stem cell-derived disorder based on studies identifying cancer stem cells (CSCs) in breast tumors and established cell lines. These self-renewing CSCs are thought to be responsible for breast cancer formation, progression and recurrence; therefore, a deeper understanding of the signaling pathways regulating CSC survival will benefit development of novel therapeutic strategies. Notch signaling, which is known to be dysregulated in breast cancer and has been implicated in mammary stem cell self-renewal, can be effectively blocked by gamma-secretase inhibitors (GSIs). While GSIs are currently in clinical trials for breast cancer, it is unclear how these compounds will affect CSCs or if CSCs from different breast cancer phenotypes (estrogen receptor-alpha (ER)-positive and negative) will be differentially affected. Here, we demonstrate stem-like cells derived from the T47D breast cancer cell line show elevated levels of Notch signaling, with an ER-negative subclone (T47D-C42) having higher intrinsic levels of Notch activity compared to an ER-positive subclone (T47D-A18). Blockade of Notch signaling with three structurally distinct GSIs reduced the number of stem-like cells, and completely abolished secondary mammosphere formation, which is a measure of stem cell self-renewal. Importantly, this effect was irreversible with MRK-003, but not with the two other GSIs. Moreover, our results suggest that the ER-negative cell line was more sensitive to the GSIs compared to the ER-positive line. This is consistent with our recent report that loss of estrogen signals results in Notch activation. These novel findings support a role for Notch signaling in CSC self-renewal and proliferation, and they suggest Notch inhibition may have clinical benefits in targeting CSCs. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 106.