Project description:The FOXA1 pioneer factor is an essential mediator of steroid receptor function in multiple hormone dependent cancers, including breast and prostate cancers, enabling nuclear receptors such as ER and AR to activate lineage specific growth programs. . Analyzing data from loss-of-function screens, we identified a subset of NSCLC tumor lines where proliferation is FOXA1-dependent. Using rapid immunoprecipitation and mass spectrometry of endogenous protein (RIME) we identified chromatin-localized interaction between FOXA1 and glucocorticoid receptor (GR) in these tumor cells. Knockdown of GR inhibited proliferation of FOXA1-dependent, but not FOXA1-independent NSCLC cells. Here, we utilized ChIP-sequencing to identify a permissive set of genes potentially regulated by FOXA1 and GR to understand potential mechanisms underlying FOXA1-GR dependence in NSCLC.
Project description:The estrogen receptor (ER), glucocorticoid receptor (GR), and forkhead box protein 1 (FoxA1) are significant factors in breast cancer progression. FoxA1 is well-established as a pioneer factor for steroid receptor recruitment to chromatin. Here we show that ER and GR have the ability to alter the genomic response of FoxA1 to specific binding sites within the genome. These findings alter the classical understood mechanism of FoxA1 establishing a dynamic transcription factor that can be regulated by hormones.
Project description:Exogenous glucocorticoids are widely used in the clinic for the treatment of inflammatory disorders and auto-immune diseases. Unfortunately, their use is hampered by many side effects and therapy resistance. Efforts to find more selective glucocorticoid receptor (GR) agonists and modulators (called SEGRAMs), able to separate anti-inflammatory effects via gene suppression from metabolic effects via gene activation, have been unsuccessful so far. In this study, we characterized a set of functionally diverse GR ligands in A549 cells, first using a panel of luciferase-based reporter gene assays evaluating GR-driven gene activation and gene suppression. We expanded this minimal assay set with novel luciferase-based read-outs monitoring GR protein levels, GR dimerization and GR Serine 211 (Ser211) phosphorylation status and compared their outcomes with compound effects on the mRNA levels of known GR target genes in A549 cells and primary hepatocytes. We found that luciferase reporters evaluating GR-driven gene activation and gene repression were not always reliable predictors for effects on endogenous target genes. Remarkably, our novel assay monitoring GR Ser211 phosphorylation levels proved to be the most reliable predictor for compound effects on almost all tested endogenous GR targets, both driven by gene activation and repression. The integration of this novel assay in existing screening platforms may therefore increase chances to find novel GR ligands with an improved therapeutic benefit.
Project description:We report the dual role of FoxA1 in androgen receptor recruitment to the chromatin of androgen responsive prostate cancer cell line LNCaP-1F5 using ChIP-sequencing. Depletion of FoxA1 reprograms both androgen and glucocorticoid receptor recruitment and subsequent gene expression. The ChIP-seq has been performed using AR, FoxA1, GR, H3K4me2 antibodies. We have also mapped the DNaseI-hypersensitive sites (DHS) using deep sequencing. Examination of AR, FoxA1, GR, H3K4me2 binding sites and DHS sites in parental and FoxA1 depleted LNCaP-1F5 cells.
Project description:Treatment of prostate cancer relies predominantly on the inhibition of androgen receptor (AR) signaling. Despite the initial effectiveness of the AR-targeted therapies, the cancer often develops resistance to the AR blockade. One mechanism of the resistance is glucocorticoid receptor (GR)-mediated replacement of AR. Nevertheless, the mechanistic ways and means how the GR-mediated antiandrogen resistance occurs has remained elusive. Here, we have discovered several crucial features of GR action in prostate cancer cells through genome-wide techniques. We detected that the replacement of AR by GR in antiandrogen-exposed prostate cancer cells occurs almost exclusively at pre-accessible chromatin sites displaying FOXA1 occupancy. Counterintuitively to the classical pioneer factor model, silencing of FOXA1 potentiated the chromatin binding and transcriptional activity of GR. This was attributed to FOXA1-mediated repression of the NR3C1 (gene encoding GR) expression via the corepressor TLE3. In comparison to FOXA1, inhibition of coregulator activity efficiently restricted GR-mediated gene regulation and cell proliferation. Overall, we identified chromatin pre-accessibility and FOXA1-mediated repression as important regulators of GR action in prostate cancer, pointing out new avenues to oppose steroid receptor-mediated drug resistance.
Project description:Treatment of prostate cancer relies predominantly on the inhibition of androgen receptor (AR) signaling. Despite the initial effectiveness of the AR-targeted therapies, the cancer often develops resistance to the AR blockade. One mechanism of the resistance is glucocorticoid receptor (GR)-mediated replacement of AR. Nevertheless, the mechanistic ways and means how the GR-mediated antiandrogen resistance occurs has remained elusive. Here, we have discovered several crucial features of GR action in prostate cancer cells through genome-wide techniques. We detected that the replacement of AR by GR in antiandrogen-exposed prostate cancer cells occurs almost exclusively at pre-accessible chromatin sites displaying FOXA1 occupancy. Counterintuitively to the classical pioneer factor model, silencing of FOXA1 potentiated the chromatin binding and transcriptional activity of GR. This was attributed to FOXA1-mediated repression of the NR3C1 (gene encoding GR) expression via the corepressor TLE3. In comparison to FOXA1, inhibition of coregulator activity efficiently restricted GR-mediated gene regulation and cell proliferation. Overall, we identified chromatin pre-accessibility and FOXA1-mediated repression as important regulators of GR action in prostate cancer, pointing out new avenues to oppose steroid receptor-mediated drug resistance.
Project description:Treatment of prostate cancer relies predominantly on the inhibition of androgen receptor (AR) signaling. Despite the initial effectiveness of the AR-targeted therapies, the cancer often develops resistance to the AR blockade. One mechanism of the resistance is glucocorticoid receptor (GR)-mediated replacement of AR. Nevertheless, the mechanistic ways and means how the GR-mediated antiandrogen resistance occurs has remained elusive. Here, we have discovered several crucial features of GR action in prostate cancer cells through genome-wide techniques. We detected that the replacement of AR by GR in antiandrogen-exposed prostate cancer cells occurs almost exclusively at pre-accessible chromatin sites displaying FOXA1 occupancy. Counterintuitively to the classical pioneer factor model, silencing of FOXA1 potentiated the chromatin binding and transcriptional activity of GR. This was attributed to FOXA1-mediated repression of the NR3C1 (gene encoding GR) expression via the corepressor TLE3. In comparison to FOXA1, inhibition of coregulator activity efficiently restricted GR-mediated gene regulation and cell proliferation. Overall, we identified chromatin pre-accessibility and FOXA1-mediated repression as important regulators of GR action in prostate cancer, pointing out new avenues to oppose steroid receptor-mediated drug resistance.
Project description:The Glucocorticoid Receptor (GR) is both one of the most widely used clinical drug targets and a very potent metabolic regulator. GR belongs to the nuclear hormone receptor family of ligand-gated transcription factors that govern mammalian physiology. Upon ligand binding, GR enters the nucleus to regulate gene expression both positively and negatively. It is known to bind to consensus DNA sequences termed glucocorticoid response elements (GREs), but the mechanisms determining transcriptional activation versus repression remain an unresolved molecular paradox. Prevailing models suggest that tethering of GR to AP-1 or NF-κB via protein-protein interactions, rather than direct DNA binding, specifies negative regulation. However, here we show that the repression of inflammatory genes as well as all other glucocorticoid responses, require direct DNA binding of GR. Generating GR point mutant mice that retain the ability to tether via protein-protein interactions while unable to recognize DNA sequences, we demonstrate that response element recognition via the Zinc finger is absolutely required for both transcriptional activation and repression. We have used ChIP-Seq and RNA-Seq in inflammatory and metabolic cells and tissues together with proteomics to reveal that DNA binding of GR is necessary for the assembly of a functional SWI/SNF coregulator complex. Generally, the desired anti-inflammatory actions of GR are attributed to the silencing of inflammatory genes, while its adverse effects are believed to result from the transcriptional upregulation of metabolic targets. Our findings not only challenge classical models and dogmas of GR mediated gene regulation, but will provide an important basis for the development of novel immunosuppressants with reduced side effect profiles.
Project description:Differentiation status of tumors is correlated with metastatic potential and malignancy. FOXA1 (forkhead box A1) is a transcription factor known to regulate differentiation in certain tissues. Here, we investigate FOXA1 function in human colorectal cancer (CRC). We found that FOXA1 is robustly expressed in the normal human colon but significantly downregulated in colon adenocarcinoma (COAD). Applying FOXA1 ChIP-seq and RNA-seq upon FOXA1 knockdown in well-differentiated colon-like cells, and FOXA1 overexpression in poorly differentiated CRC cells, we identified novel protein-coding and lncRNA genes regulated by FOXA1. Among the numerous novel FOXA1 targets we identified, we focused on CEACAM5, a tumor marker and facilitator of cell adhesion. We show that FOXA1 binds to a distal enhancer downstream of CEACAM5 and strongly activates its expression. Consistent with these data, we show that FOXA1 inhibits anoikis in CRC cells. Collectively, our results uncover novel protein-coding and non-coding targets of FOXA1 and suggest a vital role of FOXA1 in enhancing CEACAM5 expression and anoikis resistance in CRC cells.