Global analysis of estrogen receptor beta binding to breast cancer cell genome reveals an extensive interplay with estrogen receptor alpha for target gene regulation.

BACKGROUND: Estrogen receptors alpha (ERα) and beta (ERß) are transcription factors (TFs) that mediate estrogen signaling and define the hormone-responsive phenotype of breast cancer (BC). The two receptors can be found co-expressed and play specific, often opposite, roles, with ERß being able to modulate the effects of ERα on gene transcription and cell proliferation. ERß is frequently lost in BC, where its presence generally correlates with a better prognosis of the disease. The identification of the genomic targets of ERß in hormone-responsive BC cells is thus a critical step to elucidate the roles of this receptor in estrogen signaling and tumor cell biology. RESULTS: Expression of full-length ERß in hormone-responsive, ERα-positive MCF-7 cells resulted in a marked reduction in cell proliferation in response to estrogen and marked effects on the cell transcriptome. By ChIP-Seq we identified 9702 ERß and 6024 ERα binding sites in estrogen-stimulated cells, comprising sites occupied by either ERß, ERα or both ER subtypes. A search for TF binding matrices revealed that the majority of the binding sites identified comprise one or more Estrogen Response Element and the remaining show binding matrixes for other TFs known to mediate ER interaction with chromatin by tethering, including AP2, E2F and SP1. Of 921 genes differentially regulated by estrogen in ERß+ vs ERß- cells, 424 showed one or more ERß site within 10 kb. These putative primary ERß target genes control cell proliferation, death, differentiation, motility and adhesion, signal transduction and transcription, key cellular processes that might explain the biological and clinical phenotype of tumors expressing this ER subtype. ERß binding in close proximity of several miRNA genes and in the mitochondrial genome, suggests the possible involvement of this receptor in small non-coding RNA biogenesis and mitochondrial genome functions. CONCLUSIONS: Results indicate that the vast majority of the genomic targets of ERß can bind also ERα, suggesting that the overall action of ERß on the genome of hormone-responsive BC cells depends mainly on the relative concentration of both ERs in the cell.

Patients with acute coronary syndrome show oligoclonal T-cell recruitment within unstable plaque: evidence for a local, intracoronary immunologic mechanism.

BACKGROUND: Recent studies indicate that T-cell activation may play an important role in the pathophysiology of acute coronary syndromes (ACS). However, although those studies detected T-cell expansion in peripheral blood cells, demonstration of specific T-cell expansion within the plaque of patients with ACS is lacking. The present study aims to address whether a specific, immune-driven T-lymphocyte recruitment occurs within the unstable plaque of patients with ACS. METHODS AND RESULTS: We simultaneously examined the T-cell repertoire using CDR3 size analysis both in coronary plaques (obtained by directional atherectomy) and in peripheral blood of patients with either ACS (n=11) or chronic stable angina (n=10). Unstable plaques showed a 10-fold increase in T-cell content by quantitative PCR. Using spectratyping analysis, we found several specific T-cell clonotype expansions only in unstable plaque from each patient with ACS, indicating a specific, antigen-driven recruitment of T cells within unstable lesions. CONCLUSIONS: For the first time, T-cell repertoire was investigated directly into coronary plaques; using this approach, we demonstrate that coronary plaque instability in the setting of ACS is associated with immune-driven T-cell recruitment, specifically within the plaque.