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The transcription factor FOXM1 coordinates the expression of cell cycle-related genes and plays a pivotal role in tumorigenesis and cancer progression

ABSTRACT: The transcription factor FOXM1 coordinates the expression of cell cycle-related genes and plays a pivotal role in tumorigenesis and cancer progression. We have previously shown that FOXM1 acts downstream of 14-3-3ζ signaling, which correlates with a more aggressive tumor phenotype. However, the role that FOXM1 might play in engendering the resistance to endocrine treatments in estrogen receptor-positive (ER+) patients when tumor FOXM1 is high, has not been clearly defined. To understand the role of FOXM1 in endocrine resistance and cancer aggressiveness, we analyzed FOXM1 protein expression by IHC in 501 ER-positive breast cancers; this revealed high FOXM1 expression in 20% of the tumors and a significantly reduced survival in these patients (p=0.003, log rank Mantel-Cox). We also mapped genome-wide FOXM1 binding events by chromatin immunoprecipitation, followed by high-throughput sequencing (ChIP-seq), in hormone-sensitive and resistant breast cancer cells after tamoxifen treatment. FOXM1 binding sites were enriched at the transcription start site of genes involved in cell cycle progression, maintenance of stem cell properties, and invasion and metastasis, all of which are correlated with the worst prognosis in ERα-positive patients treated with tamoxifen. Binding profiles were also integrated with gene expression data from cells before and after FOXM1 knockdown to highlight specific FOXM1 transcriptional networks. By modulating the levels of FOXM1 and newly discovered FOXM1-regulated genes [in breast cancer cells], we demonstrate that increased expression of FOXM1 was associated with an expansion of the cancer stem-like cell population and with increased cell invasiveness and resistance to endocrine treatments. Use of a selective FOXM1 inhibitor proved very effective in restoring endocrine therapy sensitivity and decreasing breast cancer aggressiveness. Collectively, our findings uncover novel roles for FOXM1 and FOXM1-regulated genes in promoting cancer stem-like cell properties and therapy resistance, and highlight the relevance of FOXM1 as a therapeutic target to be considered for reducing invasiveness and enhancing breast cancer response to endocrine treatments.

ORGANISM(S): Homo sapiens

PROVIDER: GSE55204 | GEO | 2014/08/07

SECONDARY ACCESSION(S): PRJNA238893

REPOSITORIES: GEO

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Project description:The transcription factor FOXM1 coordinates the expression of cell cycle-related genes and plays a pivotal role in tumorigenesis and cancer progression. We have previously shown that FOXM1 acts downstream of 14-3-3ζ signaling, which correlates with a more aggressive tumor phenotype. However, the role that FOXM1 might play in engendering the resistance to endocrine treatments in estrogen receptor-positive (ER+) patients when tumor FOXM1 is high, has not been clearly defined. To understand the role of FOXM1 in endocrine resistance and cancer aggressiveness, we analyzed FOXM1 protein expression by IHC in 501 ER-positive breast cancers; this revealed high FOXM1 expression in 20% of the tumors and a significantly reduced survival in these patients (p=0.003, log rank Mantel-Cox). We also mapped genome-wide FOXM1 binding events by chromatin immunoprecipitation, followed by high-throughput sequencing (ChIP-seq), in hormone-sensitive and resistant breast cancer cells after tamoxifen treatment. FOXM1 binding sites were enriched at the transcription start site of genes involved in cell cycle progression, maintenance of stem cell properties, and invasion and metastasis, all of which are correlated with the worst prognosis in ERα-positive patients treated with tamoxifen. Binding profiles were also integrated with gene expression data from cells before and after FOXM1 knockdown to highlight specific FOXM1 transcriptional networks. By modulating the levels of FOXM1 and newly discovered FOXM1-regulated genes [in breast cancer cells], we demonstrate that increased expression of FOXM1 was associated with an expansion of the cancer stem-like cell population and with increased cell invasiveness and resistance to endocrine treatments. Use of a selective FOXM1 inhibitor proved very effective in restoring endocrine therapy sensitivity and decreasing breast cancer aggressiveness. Collectively, our findings uncover novel roles for FOXM1 and FOXM1-regulated genes in promoting cancer stem-like cell properties and therapy resistance, and highlight the relevance of FOXM1 as a therapeutic target to be considered for reducing invasiveness and enhancing breast cancer response to endocrine treatments. MCF-7 human breast adenocarcinoma cells were tranfected with control, and FOXM1 siRNA for 72 hours and treated with 0.1% EtOH (Vehicle) or 1 uM TOT for 24 hours, and cDNA microarray analyses were carried out using Affymetrix [HG-U133A_2] Affymetrix Human Genome U133A 2.0 Array.

Project description:MCM3 is one of several genes whose expression profile is markedly altered in tamoxifen-resistant breast cancer cell lines. We observed that increased MCM3 expression is associated with tamoxifen resistance. Knockdown of MCM3 resulted in increased susceptibility of tamoxifen-resistant breast cancer cell lines. Moreover, MCM3 expression is significantly associated with clinical outcome of endocrine treated receptor positive breast cancer. To understand the effect of MCM3 on the mechanism of endocrine resistance, we performed gene expression array on tamoxifen-resistant breast cancer cell lines. Here we show that MCM3 knockdown affects the expression of hundreds of genes. Resistance to endocrine therapy in estrogen receptor-positive (ER+) breast cancer is a major clinical problem with poorly understood mechanisms. There is an unmet need for prognostic and predictive biomarkers to allow appropriate therapeutic targeting. We evaluated the mechanism by which minichromosome maintenance protein 3 (MCM3) influences endocrine resistance and its predictive/prognostic potential in ER+ breast cancer. We discovered that ER+ breast cancer cells survive tamoxifen and letrozole treatments through upregulation of minichromosome maintenance proteins (MCMs), including MCM3, which are key molecules in cell cycle and DNA replication. Lowering MCM3 expression in endocrine-resistant cells restored drug sensitivity and altered phosphorylation of cell cycle regulators, including p53(Ser315,33), CHK1(Ser317) and cdc25b(Ser323), suggesting that the interaction of MCM3 with cell cycle proteins is an important mechanism of overcoming replicative stress and anti-proliferative effects of endocrine treatments. Evaluation of MCM3 levels in primary tumors from four independent cohorts of breast cancer patients receiving adjuvant tamoxifen mono-therapy or no adjuvant treatment, including the Stockholm tamoxifen (STO-3) trial, showed MCM3 to be an independent prognostic adding information beyond Ki67. In addition, MCM3 was shown to be a predictive marker of response to endocrine treatment. Our study reveals a coordinated signaling network centered around MCM3 that limits response to endocrine therapy in ER+ breast cancer and identifies MCM3 as a clinically useful prognostic and predictive biomarker that allows personalized treatment of ER+ breast cancer patients.

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The transcription factor FOXM1 coordinates the expression of cell cycle-related genes and plays a pivotal role in tumorigenesis and cancer progression

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