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: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.

Project description:Here we report the generation of 84 mouse ES cell lines with doxycycline-controllable transcription factors (TFs) which, together with the previous 53 lines, cover 7 - 10% of all TFs encoded in the mouse genome. Global gene expression profiles of all 137 lines after the induction of TFs for 48 hrs can associate each TF with the direction of ES cell differentiation, regulatory pathways, and mouse phonotypes. These cell lines and microarray data provide the building blocks for a variety of future biomedical research applications as a community resource. This set of data does not use Universal Mouse Reference on Cy5 channel. ES cells (passage 25) were cultured in the standard LIF+ medium with Dox+ on a gelatin-coated dish through the experiments. Cells from each cell line were split into 6 wells and the media was changed 24 hr after cell plating: 3 wells with Dox+ medium, and 3 wells with Dox- medium to induce transgenic TFs. Dox was removed via washing 3 times with PBS at 3 hours intervals. Total RNA was isolated by TRIzol (Invitrogen) after 48 hr, and two replications were used for real time qPCR (see primers in Supplementary Table S2) and for microarray hybridization. RNA samples were labeled with total RNA by Low RNA Input Fluorescent Linear Amplification Kit (Agilent). For most TFs, we hybridized Cy3-CTP labeled sample from Dox- medium together with Cy5-CTP labeled sample from Dox+ medium. But for 7 TFs we labeled samples from Dox- and Dox+ with Cy3, and hybridized them independently with Cy5-labeled reference target, which is a mixture of Stratagene Universal Mouse Reference RNA and MC1 cells RNA (this method requires a double number of arrays). Analysis showed that both methods produce results of comparable quality. The arrays are for 2 channel agilent 44K. We used treated two channels are two separate arrays, and normalized them with an quantile method described in the data processing sections. So we used one supplemental file for two samples (Cy3 and Cy5, or ch1 and ch2). Supplementary 'processed data' file linked below.

Dataset Information

Gene expression profile of FOXM1 with Doxorubicin in MDA-MB-231 breast cancer cells

Publications

FOXM1 mediates Dox resistance in breast cancer by enhancing DNA repair.

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