Down-regulation of Forkhead Box M1 Transcription Factor Leads to the Inhibition of Invasion and Angiogenesis of Pancreatic Cancer Cells

Overexpression of FOXM1 predicts poor prognosis and promotes cancer cell proliferation, migration and invasion in epithelial ovarian cancer

BACKGROUND

The Forkhead box M1 (FOXM1), an important regulator of cell differentiation and proliferation, is overexpressed in a number of aggressive human carcinomas. The purpose of this study was to examine the expression levels of FOXM1 in epithelial ovarian cancer (EOC), to identify the relationship between FOXM1 expression and patient survival, and to investigate the role of FOXM1 in human ovarian cancer development.

METHODS

Immunohistochemical analysis for FOXM1 was performed in a total of 158 ovarian tissue specimens, all with linked clinical outcome data. Kaplan-Meier method and Cox proportional hazards analysis were used to relate FOXM1 expression to clinicopathological variables and to progression-free survival (PFS) and overall survival (OS). In vitro studies were performed to determine the function of FOXM1 in cell proliferation, migration and invasion in EOC cells using pcDNA3.1-FOXM1 and FOXM1 shRNA.

RESULTS

Elevated FOXM1 levels were associated with lymph node metastasis (P = 0.009), but not with age, FIGO stage, histological grade and histological type. Patients with high expression of FOXM1 had poorer PFS (P = 0.0001) and OS (P < 0.0001) than patients with low expression of FOXM1. Furthermore, multivariate analyses indicated that FOXM1 positivity was an independent prognostic factor for PFS (P = 0.046) and OS (P = 0.022), respectively. Overexpression of FOXM1 increased expression and activity of matrix metalloproteinase-2 (MMP-2), MMP-9 and vascular endothelial growth factor-A (VEGF-A), and cancer cell proliferation, migration and invasion of HO-8910 cells, whereas knockdown of FOXM1 reduced expression and activity of MMP-2, MMP-9 and VEGF-A, and cancer cell proliferation, migration and invasion of HO-8910 PM cells.

CONCLUSIONS

Our results suggest that FOXM1 expression is likely to play important roles in EOC development and progression. FOXM1 expression is a potential prognostic factor for PFS and OS, and it could be a novel treatment target in EOC patients.

Overexpression of FOXM1 is associated with EMT and is a predictor of poor prognosis in non-small cell lung cancer

Forkhead box M1 (FOXM1), a member of the Fox family of transcriptional factors, is considered to be an independent predictor of poor survival in many solid cancers. However, the underlying mechanism is not yet clear. The aim of the present study was to investigate the clinical significance of the correlation between FOXM1 and epithelial-mesenchymal transition (EMT) in non-small cell lung carcinoma and the possible mechanism responsible for FOXM1-induced EMT and metastasis. In the present study, expression levels of FOXM1 and EMT indicator proteins were determined by tissue microarray (TMA) and immunohistochemical staining, western blotting and reverse transcription-PCR (RT-PCR). Other cellular and molecular approaches including gene transfection, small interfering RNA (siRNA), and migration and invasion assays were utilized. Our results demonstrated that FOXM1 overexpression was statistically significantly associated with a higher TNM stage (p=0.036), lymph node metastasis (p=0.009) and a positive smoking history of the patients (p=0.044). Additionally, high expression of FOXM1 correlated with loss of E-cadherin expression (p<0.001) and anomalous immunopositivity of Vimentin (p=0.002). Moreover, patient survival analysis demonstrated that high expression of FOXM1 (p=0.043) and the presence of lymph node metastasis (p=0.042) were independent prognostic factors for non-small cell lung cancer (NSCLC). Furthermore, various in vitro experiments indicated that overexpression or knockdown of FOXM1 expression altered EMT through activation or inhibition of the AKT/p70S6K signaling pathway. Collectively, the results suggest that FOXM1 may be used as a prognostic indicator for patients with NSCLC and promotes metastasis by inducing EMT of lung cancer cells through activation of the AKT/p70S6K pathway. Therefore, we suggest that FOXM1 may be a potential target for lung cancer therapy.

Functional O-GlcNAc modifications: implications in molecular regulation and pathophysiology

O-linked β-N-acetylglucosamine (O-GlcNAc) is a regulatory post-translational modification of intracellular proteins. The dynamic and inducible cycling of the modification is governed by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) in response to UDP-GlcNAc levels in the hexosamine biosynthetic pathway (HBP). Due to its reliance on glucose flux and substrate availability, a major focus in the field has been on how O-GlcNAc contributes to metabolic disease. For years this post-translational modification has been known to modify thousands of proteins implicated in various disorders, but direct functional connections have until recently remained elusive. New research is beginning to reveal the specific mechanisms through which O-GlcNAc influences cell dynamics and disease pathology including clear examples of O-GlcNAc modification at a specific site on a given protein altering its biological functions. The following review intends to focus primarily on studies in the last half decade linking O-GlcNAc modification of proteins with chromatin-directed gene regulation, developmental processes, and several metabolically related disorders including Alzheimer's, heart disease and cancer. These studies illustrate the emerging importance of this post-translational modification in biological processes and multiple pathophysiologies.

Casticin induces breast cancer cell apoptosis by inhibiting the expression of forkhead box protein M1

Casticin is an active ingredient derived from Fructus Viticis, a traditional Chinese medicine. This study aimed to investigate the role of forkhead box O3 (FOXO3a) in breast cancer cells and examine the regulatory mechanisms of FOXO3a in response to casticin treatment of the cells by ELISA, flow cytometry, small interfering RNA (siRNA) transfection and western blot analysis. Casticin treatment induced apoptosis and reduced the expression of the transcription factor forkhead box protein M1 (FOXM1). In addition, FOXM1 repression induced by casticin treatment was associated with the activation of FOXO3a via increased dephosphorylation. Notably, silencing FOXO3a expression by siRNA-mediated gene knockdown attenuated casticin-mediated apoptosis. Collectively, these findings suggest that FOXO3a is a critical mediator of the inhibitory effects of casticin on apoptosis in breast cancer cells.

FOXM1c promotes pancreatic cancer epithelial-to-mesenchymal transition and metastasis via upregulation of expression of the urokinase plasminogen activator system

PURPOSE

The transcription factor Forkhead box M1 (FOXM1) plays important roles in the formation of several human tumors, including pancreatic cancer. However, the molecular mechanisms by which FOXM1 promotes pancreatic tumor epithelial-to-mesenchymal transition (EMT) and metastasis are unknown.

EXPERIMENTAL DESIGN

The effect of altered expression of FOXM1 and urokinase-type plasminogen activator receptor (uPAR) on EMT and metastasis was examined using animal models of pancreatic cancer. Also, the underlying mechanisms of altered pancreatic cancer invasion and metastasis were analyzed using in vitro molecular biology assays. Finally, the clinical relevance of dysregulated FOXM1/uPAR signaling was investigated using pancreatic tumor and normal pancreatic tissue specimens.

RESULTS

Pancreatic tumor specimens and cell lines predominantly overexpressed the FOXM1 isoform FOXM1c. FOXM1c overexpression promoted EMT in and migration, invasion, and metastasis of pancreatic cancer cells, whereas downregulation of FOXM1 expression inhibited these processes. The level of FOXM1 expression correlated directly with that of uPAR expression in pancreatic cancer cell lines and tumor specimens. Moreover, FOXM1c overexpression upregulated uPAR expression in pancreatic cancer cells, whereas inhibition of FOXM1 expression suppressed uPAR expression. Furthermore, transfection of FOXM1c into pancreatic cancer cells directly activated the uPAR promoter, whereas inhibition of FOXM1 expression by FOXM1 siRNA suppressed its activation in these cells. Finally, we identified an FOXM1-binding site in the uPAR promoter and demonstrated that FOXM1 protein bound directly to it. Deletion mutation of this site significantly attenuated uPAR promoter activity.

CONCLUSIONS

Our findings demonstrated that FOXM1c contributes to pancreatic cancer development and progression by enhancing uPAR gene transcription, and thus, tumor EMT and metastasis.

FOXM1 and its oncogenic signaling in pancreatic cancer pathogenesis

Pancreatic cancer is a devastating disease with an overall 5-year survival rate less than 5%. Multiple signaling pathways are implicated in the pathogenesis of pancreatic cancer, such as Wnt/β-catenin, Notch, Hedgehog, hypoxia-inducible factor, signal transducer and activator of transcription, specificity proteins/Krüppel-like factors, and Forkhead box (FOX). Recently, increasing evidence has demonstrated that the transcription factor FOXM1 plays important roles in the initiation, progression, and metastasis of a variety of human tumors, including pancreatic cancer. In this review, we focus on the current understanding of the molecular pathogenesis of pancreatic cancer with a special focus on the function and regulation of FOXM1 and rationale for FOXM1 as a novel molecular target for pancreatic cancer prevention and treatment.

Targeting miRNAs for pancreatic cancer therapy

Pancreatic cancer (PC) is the fourth leading cause of cancer-related deaths in the United States and has a median 5-year survival rate less than 5%. Although surgery offers the best chance for a cure for pancreatic cancer, less than 20% of patients are eligible for potentially curative resection, because in most cases, the cancer has already spread locally or to distant organs at diagnosis, precluding resection. MicroRNAs (miRNAs) are small noncoding, endogenous, single-stranded RNAs that are pivotal regulators of posttranscriptional gene expression. Extensive studies of miRNAs over the past several years have revealed that the expression of miRNAs is frequently deregulated in pancreatic cancer patients and that this deregulation contributes to the pathogenesis and aggressiveness of the disease. Currently, investigators are studying the use of miRNAs as diagnostic and/or prognostic biomarkers and therapeutic tools for pancreatic cancer. Rapid discovery of many miRNA targets and their relevant pathways has contributed to the development of miRNA-based therapeutics. In particular, the transcription factor Forkhead box M1 (FOXM1) is overexpressed in the majority of cancer patients, including those with pancreatic cancer. This overexpression is implicated to have a role in tumorigenesis, progression, and metastasis. This important role of FOXM1 affirms its usefulness in therapeutic interventions for pancreatic cancer. In this review, we summarize the current knowledge and concepts concerning the involvement of miRNAs and FOXM1 in pancreatic cancer development and describe the roles of the miRNA-FOXM1 signaling pathway in pancreatic cancer initiation and progression. Additionally, we describe some of the technical challenges in the use of the miRNA-FOXM1 signaling pathway in pancreatic cancer treatment.

Genistein exhibits anti-cancer effects via down-regulating FoxM1 in H446 small-cell lung cancer cells

Genistein, a major isoflavone constituent in soybeans, has been reported to exhibit multiple anti-tumor effects, such as inducing cell cycle arrest, triggering apoptosis, and inactivating critical signaling pathways in a few human cancer cells. Here, we investigated the anti-tumor effects of genistein on the small-cell lung cancer (SCLC) cell line H446 and the underlying molecular mechanisms. H446 cells were treated with various concentrations of genistein, and experiments including CCK-8 assay, colony formation assay, flow cytometry analysis, wound healing assay, real-time polymerase chain reaction (PCR), western blot analysis, and plasmid transfection were used to investigate the influence of genistein on cell proliferation, migration ability, apoptosis, cell cycle progression, as well as the mRNA and protein alterations of FoxM1 pathway molecules. We found that genistein significantly inhibited the proliferation and migration ability of H446 cell, accompanied by apoptosis and G2/M phase cell cycle arrest. In addition, genistein enhanced the anti-proliferative effect of cisplatin on H446 cells. Importantly, genistein led to attenuation of the FoxM1 protein and down-regulated a series of FoxM1 target genes regulating cell cycle and apoptosis including Cdc25B, cyclin B1, and survivin. In addition, up-regulation of FoxM1 by cDNA transfection prior to genistein treatment could reduce genistein-induced H446 proliferation inhibition. Thus, for the first time, we demonstrated that genistein exerted multiple anti-tumor effects in H446 SCLC cell line at least partly mediated by the down-regulation of FoxM1. FoxM1 has the potential as a novel therapeutic agent in SCLC and is worthy of further study.

Downregulation of p21 in myelodysplastic syndrome is associated with p73 promoter hypermethylation and indicates poor prognosis

OBJECTIVES

p21 Can both promote and inhibit tumorigenic processes. We explored the role of p21 in myelodysplastic syndrome (MDS).

METHODS

In this study, we analyzed p21 expression and p73 methylation in 88 patients with de novo MDS.

RESULTS

We found decreased expression of the p21 gene in higher-risk MDS compared with lower-risk groups or healthy controls (P < .05). Patients with p73 methylation had lower p21 than those in the unmethylated group (P < .001). Moreover, there was a significantly positive correlation between p73 and p21 expression in MDS (r = 0.436, P < .001). In vitro assays further confirm the role of p73 methylation in p21 expression. Compared with patients with normal expression levels of p21, patients with lower p21 expression levels experienced much higher rates of transformation to acute myeloid leukemia and lower overall survival both in univariate as well as multivariate analyses.

CONCLUSIONS

Our results suggest p21 expression may serve as a new biomarker to predict clinical outcome in patients with MDS.

The transcription factor FOXM1 (Forkhead box M1): proliferation-specific expression, transcription factor function, target genes, mouse models, and normal biological roles

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor, which stimulates cell proliferation and exhibits a proliferation-specific expression pattern. Accordingly, both the expression and the transcriptional activity of FOXM1 are increased by proliferation signals, but decreased by antiproliferation signals, including the positive and negative regulation by protooncoproteins or tumor suppressors, respectively. FOXM1 stimulates cell cycle progression by promoting the entry into S-phase and M-phase. Moreover, FOXM1 is required for proper execution of mitosis. Accordingly, FOXM1 regulates the expression of genes, whose products control G1/S-transition, S-phase progression, G2/M-transition, and M-phase progression. Additionally, FOXM1 target genes encode proteins with functions in the execution of DNA replication and mitosis. FOXM1 is a transcriptional activator with a forkhead domain as DNA binding domain and with a very strong acidic transactivation domain. However, wild-type FOXM1 is (almost) inactive because the transactivation domain is repressed by three inhibitory domains. Inactive FOXM1 can be converted into a very potent transactivator by activating signals, which release the transactivation domain from its inhibition by the inhibitory domains. FOXM1 is essential for embryonic development and the foxm1 knockout is embryonically lethal. In adults, FOXM1 is important for tissue repair after injury. FOXM1 prevents premature senescence and interferes with contact inhibition. FOXM1 plays a role for maintenance of stem cell pluripotency and for self-renewal capacity of stem cells. The functions of FOXM1 in prevention of polyploidy and aneuploidy and in homologous recombination repair of DNA-double-strand breaks suggest an importance of FOXM1 for the maintenance of genomic stability and chromosomal integrity.

Identification of cell cycle-regulated genes periodically expressed in U2OS cells and their regulation by FOXM1 and E2F transcription factors

Characterization of the cell cycle–regulated transcripts in U2OS cells yielded 1871 unique genes. FOXM1 targets were identified via ChIP-seq, and novel targets in G2/M and S phases were verified using a real-time luciferase assay. ChIP-seq data were used to map cell cycle transcriptional regulators of cell cycle–regulated gene expression in U2OS cells.

We identify the cell cycle–regulated mRNA transcripts genome-wide in the osteosarcoma-derived U2OS cell line. This results in 2140 transcripts mapping to 1871 unique cell cycle–regulated genes that show periodic oscillations across multiple synchronous cell cycles. We identify genomic loci bound by the G2/M transcription factor FOXM1 by chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) and associate these with cell cycle–regulated genes. FOXM1 is bound to cell cycle–regulated genes with peak expression in both S phase and G2/M phases. We show that ChIP-seq genomic loci are responsive to FOXM1 using a real-time luciferase assay in live cells, showing that FOXM1 strongly activates promoters of G2/M phase genes and weakly activates those induced in S phase. Analysis of ChIP-seq data from a panel of cell cycle transcription factors (E2F1, E2F4, E2F6, and GABPA) from the Encyclopedia of DNA Elements and ChIP-seq data for the DREAM complex finds that a set of core cell cycle genes regulated in both U2OS and HeLa cells are bound by multiple cell cycle transcription factors. These data identify the cell cycle–regulated genes in a second cancer-derived cell line and provide a comprehensive picture of the transcriptional regulatory systems controlling periodic gene expression in the human cell division cycle.

Signaling of miRNAs-FOXM1 in cancer and potential targeted therapy

The transcription factor Forkhead box protein M1 (FOXM1) is overexpressed in the majority of cancer patients. This overexpression is implicated to play a role in the pathogenesis, progression, and metastasis of cancer. This important role of FOXM1 demonstrates its significance to cancer therapy. MicroRNAs (miRNAs) are small noncoding, endogenous, single-stranded RNAs that are pivotal posttranscriptional gene expression regulators. MiRNAs aberrantly expressed in cancer cells have important roles in tumorigenesis and progression. Currently, miRNAs are being studied as diagnostic and prognostic biomarkers and therapeutic tools for cancer. The rapid discovery of many target miRNAs and their relevant pathways has contributed to the development of miRNA-based therapeutics for cancer. In this review, we summarize the latest and most significant findings on FOXM1 and miRNA involvement in cancer development and describe the role/roles of miRNA/FOXM1 signaling pathways in cancer initiation and progression. Targeting FOXM1 via regulation of miRNA expression may have a role in cancer treatment, although the miRNA delivery method remains the key challenge to the establishment of this novel therapy.

The DREAM complex: master coordinator of cell cycle-dependent gene expression

The dimerization partner, RB-like, E2F and multi-vulval class B (DREAM) complex provides a previously unsuspected unifying role in the cell cycle by directly linking p130, p107, E2F, BMYB and forkhead box protein M1. DREAM mediates gene repression during the G0 phase and coordinates periodic gene expression with peaks during the G1/S and G2/M phases. Perturbations in DREAM complex regulation shift the balance from quiescence towards proliferation and contribute to the increased mitotic gene expression levels that are frequently observed in cancers with a poor prognosis.

Overexpressed transcription factor FOXM1 is a potential diagnostic and adverse prognostic factor in postoperational gastric cancer patients

PURPOSE

In the present study, we intend to detect the expression of Forkhead box transcription (FOXM1) in gastric cancer tissues and cell lines, and analyze the correlation between FOXM1 expression and clinic-pathological features as well as their association with clinic outcomes in patients with resectable gastric cancers.

METHODS

We examined the expression of FOXM1 in 103 cancer tissues from patients who underwent gastrectomy during Jan 2007 to Nov 2007 and 68 randomly selected para-cancer tissues by immunohistochemistry. The expression of FOXM1 protein in the benign and malignant human gastric cell lines was simultaneously detected using Western blot analysis. Data on clinic-pathological features and relevant prognostic factors in these patients were then analyzed.

RESULTS

FOXM1 expression was absolutely higher in gastric cancer than para-cancer tissues (P < 0.001) and normal gastric epithelium cell lines (P = 0.022). No significant association was found between FOXM1 expression and any clinic-pathological parameters (P > 0.1). FOXM1 amplification was showed to be independently associated with prognosis in gastric cancer patients (P = 0.001), and its affection is more significant in patients with tumor size larger than 5 cm (P = 0.004), pT3-4 (P = 0.003) or pIII-IV (P = 0.001) as a result of stage-stratified analysis.

CONCLUSIONS

Overexpressed FOXM1 is a potential diagnostic and poor prognostic biomarker in postoperational gastric cancer patients.

The dual inhibitory effect of thiostrepton on FoxM1 and EWS/FLI1 provides a novel therapeutic option for Ewing's sarcoma

The poor prognosis of Ewing’s sarcoma (EWS), together with its high lethal recurrence rate and the side-effects of current treatments, call for novel targeted therapies with greater curative effectiveness and substantially reduced side-effects. The oncogenic chimeric protein EWS/FLI1 is the key malignancy driver in most EWSs, regulating numerous target genes, many of which influence cell cycle progression. It has often been argued that targeting proteins regulated directly or indirectly by EWS/FLI1 may provide improved therapeutic options for EWS. In this context, our study examined FoxM1, a key cell cycle regulating transcription factor, reported to be expressed in EWS and influenced by EWS/FLI1. Thiostrepton, a naturally occurring small molecule, has been shown to selectively inhibit FoxM1 expression in cancer cells. We demonstrate that in EWS, in addition to inhibiting FoxM1 expression, thiostrepton downregulates the expression of EWS/FLI1, both at the mRNA and protein levels, leading to cell cycle arrest and, ultimately, to apoptotic cell death. We also show that thiostrepton treatment reduces the tumorigenicity of EWS cells, significantly delaying the growth of nude mouse xenograft tumors. Results from this study demonstrate a novel action of thiostrepton as inhibitor of the expression of the EWS/FLI1 oncoprotein in vitro and in vivo, and that it shows greater efficacy against EWS than against other tumor types, as it is active on EWS cells and tumors at concentrations lower than those reported to have effective inhibitory activity on tumor cells derived from other cancers. Owing to the dual action of this small molecule, our findings suggest that thiostrepton may be particularly effective as a novel agent for the treatment of EWS patients.

FOXM1 promotes the epithelial to mesenchymal transition by stimulating the transcription of Slug in human breast cancer

The Forkhead Box M1 (FOXM1) transcription factor is involved in tumorigenesis and tumor progression in multiple human carcinomas. In this study, we found that FOXM1 promoted the epithelial to mesenchymal transition (EMT) in human breast cancer. We observed a strong correlation between the expression levels of FOXM1 and the mesenchymal phenotype. Knockdown of FOXM1 inhibited the mesenchymal phenotype, whereas stable overexpression of FOXM1 induced EMT in breast cancer cells. FOXM1 was found to endogenously bind to and stimulate the promoter of Slug that is crucial for EMT progression. The knockdown of Slug abolished the EMT-inducing function of FOXM1. The stable overexpression of FOXM1 promoted metastasis of breast cancer cells in vivo. This study confirmed that FOXM1 promoted EMT in breast cancer cells by stimulating the transcription of EMT-related genes such as Slug.

The DREAM complex: master coordinator of cell cycle-dependent gene expression

The dimerization partner, RB-like, E2F and multi-vulval class B (DREAM) complex provides a previously unsuspected unifying role in the cell cycle by directly linking p130, p107, E2F, BMYB and forkhead box protein M1. DREAM mediates gene repression during the G0 phase and coordinates periodic gene expression with peaks during the G1/S and G2/M phases. Perturbations in DREAM complex regulation shift the balance from quiescence towards proliferation and contribute to the increased mitotic gene expression levels that are frequently observed in cancers with a poor prognosis.

Forkhead box proteins: tuning forks for transcriptional harmony

Forkhead box (FOX) proteins are multifaceted transcription factors that are responsible for fine-tuning the spatial and temporal expression of a broad range of genes both during development and in adult tissues. This function is engrained in their ability to integrate a multitude of cellular and environmental signals and to act with remarkable fidelity. Several key members of the FOXA, FOXC, FOXM, FOXO and FOXP subfamilies are strongly implicated in cancer, driving initiation, maintenance, progression and drug resistance. The functional complexities of FOX proteins are coming to light and have established these transcription factors as possible therapeutic targets and putative biomarkers for specific cancers.

Adenovirus-mediated RNA interference targeting FOXM1 transcription factor suppresses cell proliferation and tumor growth of nasopharyngeal carcinoma

BACKGROUND

The Forkhead Box M1 (FOXM1) transcription factor, which regulates the expression of genes essential for cell proliferation and transformation, is implicated in tumorigenesis and tumor progression. FOXM1 has attracted much attention as a potential target for the prevention and/or therapeutic intervention in human carcinomas.

METHODS

The levels of FOXM1 expression in clinical tissue specimens and cell lines of human malignant nasopharyngeal carcinoma (NPC) were measured. Knockdown of FOXM1 expression was performed by small interfering RNA in NPC cells. An adenovirus vector (named AdFOXM1shRNA) was constructed to express a short hairpin RNA specific to FOXM1. The efficacy of AdFOXM1shRNA for tumor gene therapy in NPC cells and an in vivo NPC grafting model was assessed.

RESULTS

A strong expression of FOXM1 was observed in clinical tissue specimens and cell lines of human NPC. Knockdown of FOXM1 expression by FOXM1 specific small interfering RNA diminished the NPC cell proliferation. The infection of AdFOXM1shRNA in NPC cells resulted in the knockdown of FOXM1 mRNA and protein levels, correlated with the reduction of proliferation and anchorage-independent growth of the cancer cells. The growth of NPC tumors was significantly suppressed when inoculated mice were injected with AdFOXM1shRNA in the tumor.

CONCLUSIONS

Together, our results suggest that FOXM1 is a potential therapeutic target for NPC and AdFOXM1shRNA may be an additional gene therapeutic intervention to be evaluated in future treatment strategies for patients with NPC.

FOXL1, a novel candidate tumor suppressor, inhibits tumor aggressiveness and predicts outcome in human pancreatic cancer

The forkhead box L1 (FOXL1) transcription factor regulates epithelial proliferation and development of gastrointestinal tract and has been implicated in gastrointestinal tumorigenesis in mouse models. However, the role of FOXL1 in pancreatic cancer development and progression remains to be elucidated. Here, we report that higher expression of FOXL1 is significantly associated with better clinical outcome in human pancreatic ductal adenocarcinoma (PDAC). A lower FOXL1 expression is correlated with metastasis and advanced pathologic stage of pancreatic cancer. Mechanistic analyses showed that overexpression of FOXL1 induces apoptosis and inhibits proliferation and invasion in pancreatic cancer cells, whereas silencing of FOXL1 by siRNA inhibits apoptosis and enhances tumor cell growth and invasion. Furthermore, FOXL1 overexpression significantly suppressed the growth of tumor xenografts in nude mice. FOXL1 promoted apoptosis partly through the induction of TNF-related apoptosis-inducing ligand (TRAIL) in pancreatic cancer cells. In addition, FOXL1 suppressed the transcription of zinc finger E-box-binding homeobox 1 (ZEB1), an activator of epithelial-mesenchymal transition, and the negative regulation of ZEB1 contributed to the inhibitory effect of FOXL1 on tumor cell invasion. Taken together, our findings suggest that FOXL1 expression is a candidate predictor of clinical outcome in patients with resected PDAC and it plays an inhibitory role in pancreatic tumor progression.

Foxm1 expression in prostate epithelial cells is essential for prostate carcinogenesis

The treatment of advanced prostate cancer (PCa) remains a challenge. Identification of new molecular mechanisms that regulate PCa initiation and progression would provide targets for the development of new cancer treatments. The Foxm1 transcription factor is highly up-regulated in tumor cells, inflammatory cells, and cells of tumor microenvironment. However, its functions in different cell populations of PCa lesions are unknown. To determine the role of Foxm1 in tumor cells during PCa development, we generated two novel transgenic mouse models, one exhibiting Foxm1 gain-of-function and one exhibiting Foxm1 loss-of-function under control of the prostate epithelial-specific Probasin promoter. In the transgenic adenocarcinoma mouse prostate (TRAMP) model of PCa that uses SV40 large T antigen to induce PCa, loss of Foxm1 decreased tumor growth and metastasis. Decreased prostate tumorigenesis was associated with a decrease in tumor cell proliferation and the down-regulation of genes critical for cell proliferation and tumor metastasis, including Cdc25b, Cyclin B1, Plk-1, Lox, and Versican. In addition, tumor-associated angiogenesis was decreased, coinciding with reduced Vegf-A expression. The mRNA and protein levels of 11β-Hsd2, an enzyme playing an important role in tumor cell proliferation, were down-regulated in Foxm1-deficient PCa tumors in vivo and in Foxm1-depleted TRAMP C2 cells in vitro. Foxm1 bound to, and increased transcriptional activity of, the mouse 11β-Hsd2 promoter through the -892/-879 region, indicating that 11β-Hsd2 was a direct transcriptional target of Foxm1. Without TRAMP, overexpression of Foxm1 either alone or in combination with inhibition of a p19(ARF) tumor suppressor caused a robust epithelial hyperplasia, but was insufficient to induce progression from hyperplasia to PCa. Foxm1 expression in prostate epithelial cells is critical for prostate carcinogenesis, suggesting that inhibition of Foxm1 is a promising therapeutic approach for prostate cancer chemotherapy.

Involvement of FoxM1 in non-small cell lung cancer recurrence

BACKGROUND

Predictive biomarkers for lung cancer recurrence after curative tumor resection remain unclear. This study set out to assess the role of FoxM1 in the recurrence of non-small cell lung cancer.

METHODS

Immunohistochemistry for FoxM1 expression was performed on paraffin-embedded tumor tissues from 165 NSCLC patients. Association of FoxM1 expression with clinicopathological parameters and disease free survival were evaluated.

RESULTS

Our results indicated FoxM1 expression to be significantly associated with poorer tissue differentiation (P =0.03), higher TNM stage (P <0.01), lymph node metastasis (P <0.01), advanced tumor stage (P <0.01), and poorer disease free survival (P <0.01). Multivariable analysis showed that FoxM1 expression increased the hazard of recurrence (hazard ratio= 1.96, 95% CI, 1.04-3.17, P <0.05), indicating that FoxM1 is an independent and significant predictor of lung cancer recurrence.

CONCLUSION

Therefore, FoxM1 is an independent risk factor for recurrence of NSCLC. Elevated FoxM1 expression could be used as an indicator of poor disease free survival.

ACP5, a direct transcriptional target of FoxM1, promotes tumor metastasis and indicates poor prognosis in hepatocellular carcinoma

Tartrate-resistant acid phosphatase 5 (ACP5), which is essential for bone resorption and osteoclast differentiation, promotes cell motility through the modulation of focal adhesion kinase phosphorylation. However, whether ACP5 contributes to the metastasis and progression of hepatocellular carcinoma (HCC) remains unknown. In this paper, a complementary DNA microarray, serial deletion, site-directed mutagenesis and a chromatin immunoprecipitation assays confirmed that ACP5 is a direct transcriptional target of Forkhead box M1 (FoxM1). ACP5 expression was markedly higher in HCC tissues compared with adjacent noncancerous tissues. ACP5 overexpression was correlated with microvascular invasion, poor differentiation and higher tumor-node-metastasis stage. HCC patients with positive ACP5 expression had poorer prognoses than those with negative ACP5 expression. A multivariate analysis revealed that ACP5 expression was an independent and significant risk factor for disease recurrence and reduced-patient survival following curative resection. Transwell assays and an orthotopic metastatic model showed that the upregulation of ACP5 promoted HCC invasion and lung metastasis, whereas ACP5 knockdown inhibited these processes. The knockdown of ACP5 significantly attenuated FoxM1-enhanced invasion and lung metastasis. Immunohistochemistry revealed that ACP5 expression was positively correlated with FoxM1 expression in human HCC tissues, and their coexpression was associated with poor prognoses. In summary, ACP5 is a direct transcriptional and functional target of FoxM1. This novel FoxM1/ACP5 signaling pathway promotes HCC metastasis and may be a candidate biomarker for prognosis and a target for new therapies.

Dysregulated expression of FOXM1 isoforms drives progression of pancreatic cancer

The transcription factor Forkhead box M1 (FOXM1) plays important roles in oncogenesis. However, the expression statuses of FOXM1 isoforms and their impact on and molecular basis in oncogenesis are unknown. We sought to determine the identities of FOXM1 isoforms in and the impact of their expression on pancreatic cancer development and progression using human tissues, cell lines, and animal models. Overexpression of FOXM1 mRNA and protein was pronounced in human pancreatic tumors and cancer cell lines. We identified five FOXM1 isoforms present in pancreatic cancer: FOXM1a, FOXM1b, and FOXM1c along with two isoforms tentatively designated as FOXM1b1 and FOXM1b2 because they were closely related to FOXM1b. Interestingly, FOXM1c was predominantly expressed in pancreatic tumors and cancer cell lines, whereas FOXM1a expression was generally undetectable in them. Functional analysis revealed that FOXM1b, FOXM1b1, FOXM1b2, and FOXM1c, but not FOXM1a, promoted pancreatic tumor growth and metastasis. Consistently, FOXM1b, FOXM1b1, FOXM1b2, and FOXM1c activated transcription of their typical downstream genes. Also, Sp1 mechanistically activated the FOXM1 promoter, whereas Krüppel-like factor 4 (KLF4) repressed its activity. Finally, we identified an Sp1- and KLF4-binding site in the FOXM1 promoter and showed that both Sp1 and KLF4 protein bound directly to it. Deletion mutation of this binding site significantly attenuated the transcriptional regulation of the FOXM1 promoter positively by Sp1 and negatively by KLF4. We showed that overexpression of specific FOXM1 isoforms critically regulates pancreatic cancer development and progression by enhancing tumor cell invasion and metastasis. Our findings strongly suggest that targeting specific FOXM1 isoforms effectively attenuates pancreatic cancer development and progression.

Diallyl trisulfide inhibits proliferation, invasion and angiogenesis of osteosarcoma cells by switching on suppressor microRNAs and inactivating of Notch-1 signaling

Notch signaling pathway plays critical roles in human cancers, including osteosarcoma, suggesting that the discovery of specific agents targeting Notch would be extremely valuable for osteosarcoma. Our previous studies have shown that diallyl trisulfide (DATS) inhibits proliferation of osteosarcoma cells by triggering cell cycle arrest and apoptosis in vitro. However, the underlying mechanism is still unclear. In this study, we found that DATS suppressed cell survival, wound-healing capacity, invasion and angiogenesis in osteosarcoma cells. These effects were associated with decreased expression of Notch-1 and its downstream genes, such as vascular endothelial growth factor and matrix metalloproteinases, as well as increased expression of a panel of tumor-suppressive microRNAs (miRNAs), including miR-34a, miR-143, miR-145 and miR-200b/c that are typically lost in osteosarcoma. We also found that reexpression of miR-34a and miR-200b by transfection led to reduced expression of Notch-1, resulting in the inhibition of osteosarcoma cell proliferation, invasion and angiogenesis. These results clearly suggest that DATS inhibited osteosarcoma growth and aggressiveness via a novel mechanism targeting a Notch-miRNA regulatory circuit. Our data provide the first evidence that the downregulation of Notch-1 and reexpression of miRNAs by DATS may be an effective approach for the treatment of osteosarcoma.

Down-regulation of MTA1 protein leads to the inhibition of migration, invasion, and angiogenesis of non-small-cell lung cancer cell line

Metastasis-associated protein 1 (MTA1) high expression has been detected in a wide variety of human aggressive tumors and plays important roles in the malignant biological behaviors such as invasion, metastasis, and angiogenesis. However, the specific roles and mechanisms of MTA1 protein in regulating the malignant behaviors of non-small-cell lung cancer (NSCLC) cells still remain unclear. To elucidate the detailed functions of MTA1 protein, we down-regulated the MTA1 protein expression in NSCLC cell line by RNA interference (RNAi) in vitro, and found that down-regulation of MTA1 protein significantly inhibited the migration and invasion potentials of 95D cells. Further research revealed that down-regulation of MTA1 protein significantly decreased the activity of matrix metalloproteinase-9, which could be the mechanism responsible for the inhibition of 95D cells migration and invasion. In addition, the tube formation assay demonstrated that the number of complete tubes induced by the conditioned medium of MTA1-siRNA 95D cells was significantly smaller than that of 95D cells. These findings demonstrate that MTA1 protein plays important roles in regulating the migration, invasion, and angiogenesis potentials of 95D cells, suggesting that MTA1 protein down-regulation by RNAi might be a novel therapeutic approach to inhibit the progression of NSCLC.

Phosphoglycerate dehydrogenase induces glioma cells proliferation and invasion by stabilizing forkhead box M1

Phosphoglycerate dehydrogenase (PHGDH) is the first enzyme branching from glycolysis in the three-step serine biosynthetic pathway. Recent evidence has shown that PHGDH is amplified in human breast cancer and melanoma and plays a key role in cancer metabolism. However, PHGDH expression in glioma and a potential non-metabolic role in tumorigenesis have not been reported. We analyzed PHGDH levels in specimens from glioma patients and found that PHGDH, although negative in normal brain tissues, was highly expressed in astrocytic tumors and increasingly expressed in more aggressive cancer types. Inhibition of PHGDH expression in glioma cells downregulated the expression of VEGF, MMP-2, CHK2 and cyclin D1 and reduced glioma cell proliferation, invasion and tumorigenicity in vitro and in vivo. Interestingly, we found that the oncogenic transcription factor FOXM1 was also downregulated in PHDGH-silenced glioma cells. Using LC/LC MS analysis, we identified PHGDH as a novel binding partner of FOXM1. PHGDH interacted with and stabilized FOXM1 at the protein level, promoting the proliferation, invasion and tumorigenicity of glioma cells. Our data identified PHGDH as a potential prognostic marker of glial brain tumors and identified a non-metabolic role for PHGDH in glioma tumorigenesis, providing a novel angle of targeting the PHGDH-FOXM1 axis in future brain tumor therapy.

Genome-wide mapping of FOXM1 binding reveals co-binding with estrogen receptor alpha in breast cancer cells

BACKGROUND

The forkhead transcription factor FOXM1 is a key regulator of the cell cycle. It is frequently over-expressed in cancer and is emerging as an important therapeutic target. In breast cancer FOXM1 expression is linked with estrogen receptor (ERα) activity and resistance to endocrine therapies, with high levels correlated with poor prognosis. However, the precise role of FOXM1 in ER positive breast cancer is not yet fully understood.

RESULTS

The study utilizes chromatin immunoprecipitation followed by high-throughput sequencing to map FOXM1 binding in both ERα-positive and -negative breast cancer cell lines. The comparison between binding site distributions in the two cell lines uncovered a previously undescribed relationship between binding of FOXM1 and ERα. Further molecular analyses demonstrated that these two factors can bind simultaneously at genomic sites and furthermore that FOXM1 regulates the transcriptional activity of ERα via interaction with the coactivator CARM1. Inhibition of FOXM1 activity using the natural product thiostrepton revealed down-regulation of a set of FOXM1-regulated genes that are correlated with patient outcome in clinical breast cancer samples.

CONCLUSIONS

These findings reveal a novel role for FOXM1 in ERα transcriptional activity in breast cancer and uncover a FOXM1-regulated gene signature associated with ER-positive breast cancer patient prognosis.

3, 3'-Diindolylmethane enhances the effectiveness of herceptin against HER-2/neu-expressing breast cancer cells

Herceptin failure is a major clinical problem in breast cancer. A subset of breast cancer patients with high HER-2/neu levels eventually experience metastatic disease progression when treated with Herceptin as a single agent. Mechanistic details of development of this aggressive disease are not clear. Therefore, there is a dire need to better understand the mechanisms by which drug resistance develops and to design new combined treatments that benefit patients with aggressive breast cancer and have minimal toxicity. We hypothesized that 3, 3′-diindolylmethane (DIM), a non-toxic agent can be combined with Herceptin to treat breast cancers with high levels of HER-2/neu. Here, we evaluated the effects of Herceptin alone and in combination with DIM on cell viability, apoptosis and clonogenic assays in SKBR3 (HER-2/neu-expressing) and MDA-MB-468 (HER-2/neu negative) breast cancer cells. We found that DIM could enhance the effectiveness of Herceptin by significantly reducing cell viability, which was associated with apoptosis-induction and significant inhibition of colony formation, compared with single agent treatment. These results were consistent with the down-regulation of Akt and NF-kB p65. Mechanistic investigations revealed a significant upregulation of miR-200 and reduction of FoxM1 expression in DIM and Herceptin-treated breast cancer cells. We, therefore, transfected cells with pre-miR-200 or silenced FoxM1 in these cells for understanding the molecular mechanism involved. These results provide experimental evidence, for the first time, that DIM plus Herceptin therapy could be translated to the clinic as a therapeutic modality to improve treatment outcome of patients with breast cancer, particularly for the patients whose tumors express high levels of HER-2/neu.

Inhibition of FOXM1 transcription factor suppresses cell proliferation and tumor growth of breast cancer

The forkhead box M1 (FOXM1) transcription factor regulates the expression of genes essential for cell proliferation and transformation and is implicated in tumorigenesis and tumor progression. FOXM1 has been considered as a potential target for the prevention and/or therapeutic intervention in human carcinomas. In this study, we observed a strong expression of FOXM1 in clinical tissue specimens and cell lines of human breast cancer and a correlation between FOXM1 levels and the proliferation ability in the tested MCF-7, MDA-MB-231 and ZR-75-30 cells. By using an adenovirus vector (named AdFOXM1shRNA) that expresses a short hairpin RNA (shRNA) to downregulate FOXM1 expression specifically, we found that the knockdown of FOXM1 expression diminished the proliferation and anchorage-independent growth of the breast cancer cells. The FOXM1 silencing in ZR-75-30 cells dramatically prevented the tumorigenicity of the AdFOXM1shRNA-treated cells in vitro and in vivo. Furthermore, the efficacy of AdFOXM1shRNA for tumor gene therapy was assessed with the breast cancer xenograft mouse model and the tumor growth was significantly suppressed when inoculated mice were injected with AdFOXM1shRNA in the tumors. Together, our results suggest that FOXM1 is a potential therapeutic target for breast cancer and AdFOXM1shRNA may be an additional gene therapeutic intervention for breast cancer treatment.

FOXM1 (Forkhead box M1) in tumorigenesis: overexpression in human cancer, implication in tumorigenesis, oncogenic functions, tumor-suppressive properties, and target of anticancer therapy

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor and is also intimately involved in tumorigenesis. FOXM1 stimulates cell proliferation and cell cycle progression by promoting the entry into S-phase and M-phase. Additionally, FOXM1 is required for proper execution of mitosis. In accordance with its role in stimulation of cell proliferation, FOXM1 exhibits a proliferation-specific expression pattern and its expression is regulated by proliferation and anti-proliferation signals as well as by proto-oncoproteins and tumor suppressors. Since these factors are often mutated, overexpressed, or lost in human cancer, the normal control of the foxm1 expression by them provides the basis for deregulated FOXM1 expression in tumors. Accordingly, FOXM1 is overexpressed in many types of human cancer. FOXM1 is intimately involved in tumorigenesis, because it contributes to oncogenic transformation and participates in tumor initiation, growth, and progression, including positive effects on angiogenesis, migration, invasion, epithelial-mesenchymal transition, metastasis, recruitment of tumor-associated macrophages, tumor-associated lung inflammation, self-renewal capacity of cancer cells, prevention of premature cellular senescence, and chemotherapeutic drug resistance. However, in the context of urethane-induced lung tumorigenesis, FOXM1 has an unexpected tumor suppressor role in endothelial cells because it limits pulmonary inflammation and canonical Wnt signaling in epithelial lung cells, thereby restricting carcinogenesis. Accordingly, FOXM1 plays a role in homologous recombination repair of DNA double-strand breaks and maintenance of genomic stability, that is, prevention of polyploidy and aneuploidy. The implication of FOXM1 in tumorigenesis makes it an attractive target for anticancer therapy, and several antitumor drugs have been reported to decrease FOXM1 expression.

Increased expression of forkhead box M1 protein is associated with poor prognosis in clear cell renal cell carcinoma

Forkhead box protein M1 (FoxM1) is crucial in the regulation of various biological processes, including cell proliferation, organogenesis, and angiogenesis. Overexpression of FoxM1 is associated with carcinogenesis. In this study, immunohistochemistry was carried out to examine FoxM1 expression in clear cell renal cell carcinoma (ccRCC), and these data were examined for correlation with clinicopathological parameters and prognosis. FoxM1 protein had high expression in 37 of 87 cases of ccRCC (42.5 %), which was significantly higher than in normal tissues, and FoxM1 overexpression was significantly associated with tumor stage (P = 0.005) and recurrence (P = 0.027). The Kaplan-Meier survival analysis demonstrated that FoxM1 expression was significantly associated with shorter recurrence-free survival and overall survival (P = 0.007 and P = 0.008, respectively). Multivariate analysis further demonstrated that FoxM1 was an independent prognostic factor for patients with ccRCC. So FoxM1 might be a potential molecular marker to predict the prognosis of patients with ccRCC.

Negative regulation of transcription factor FoxM1 by p53 enhances oxaliplatin-induced senescence in hepatocellular carcinoma

Previous studies have demonstrated the involvement of transcriptional factor forkhead box M1 (FoxM1) in cellular senescence of hepatocellular carcinoma (HCC). In the present study, we revealed that oxaliplatin could induce senescence in HCC cells, since advanced HCC patients with lower expression of FoxM1 were more sensitive to oxaliplatin therapy. Our data indicated that due to the repression by p53, FoxM1 played a critical role in oxaliplatin-induced senescence via regulating cycle-related proteins p21, p27, cyclins B1 and D1. Furthermore, inhibition of FoxM1, combined with oxaliplatin treatment, could significantly promote the senescence of HCC cells. Taken together, our findings suggest that FoxM1 may represent a promising therapeutic target for the medication of the chemosensitivity to oxaliplatin in HCC patients.

FOXM1 expression correlates with tumor invasion and a poor prognosis of colorectal cancer

FOXM1, a member of the Forkhead Box (Fox) family of transcription factors, plays a critical role in tumor development and metastasis. The aim of this study was to elucidate its role in colorectal cancer (CRC), particularly prognosis and metastasis. Semi-quantitative RT-PCR and Western blot assays were used to measure the expression levels of FOXM1 mRNA and protein in 15 CRC and adjacent normal mucosa tissues. Immunohistochemical assay was performed to detect FOXM1 protein expression in 112 CRC tissues and further determine its clinicopathological and prognostic significance. RNA interference (RNAi) was used to knockdown endogenous FOXM1 expression in CRC cell lines and to analyze the effects of FOXM1 knockdown on migration and invasion of CRC cells. The relative expression levels of FOXM1 mRNA and protein were significantly higher in CRC tissues than in adjacent normal mucosa tissues (P<0.01). In addition, the immunostaining of FOXM1 protein was stronger in CRC tissues than in adjacent normal mucosa tissues. By statistical analysis, we showed that high FOXM1 expression was closely correlated with the presence of lymph node metastasis, incidence of liver metastasis, and advanced TNM stage. Moreover, the cumulative 5-year survival rate of CRC patients with high FOXM1 expression was lower than that of those with low FOXM1 expression (P=0.0047). Multivariate analysis showed that the status of FOXM1 expression was an independent prognostic factor for CRC patients (P=0.025). Furthermore, RNAi-mediated FOXM1 knockdown could significantly inhibit growth, migration and invasion of CRC cells. Our results showed that FOXM1 over-expression is a molecular marker predicting increased invasive/metastatic potential of CRC and a poorer prognosis.

Forkhead box M1 is regulated by heat shock factor 1 and promotes glioma cells survival under heat shock stress

The forkhead box M1 (FoxM1) is a key transcription factor regulating multiple aspects of cell biology. Prior studies have shown that FoxM1 is overexpressed in a variety of human tumors, including brain tumor, and plays a critical role in cancer development and progression. In this study we found that FoxM1 was up-regulated by heat shock factor 1 (HSF1) under heat shock stress condition in multiple cell lines. Knockdown of HSF1 with HSF1 siRNA or inhibition of HSF1 with a HSF1 inhibitor abrogated heat shock-induced expression of FoxM1. Genetic deletion of HSF1 in mouse embryo fibroblast cells also abolished heat shock stress-induced FoxM1 expression. Moreover, we showed that HSF1 directly bound to FoxM1 promoter and increased FoxM1 promoter activity. Furthermore, we demonstrated that FoxM1 was required for the G(2)-M phase progression through regulating Cdc2, Cdc20, and Cdc25B under a mild heat shock stress but enhanced cell survival under lethal heat shock stress condition. Finally, in human glioblastoma specimens, FoxM1 overexpression correlated with elevated HSF1 expression. Our results indicate that FoxM1 is regulated by HSF1 and is critical for HSF1-mediated heat shock response. We demonstrated a novel mechanism of stress resistance controlled by HSF1 and a new HSF-FoxM1 connection that mediates cellular thermotolerance.

Establishment and characterization of a highly tumourigenic and cancer stem cell enriched pancreatic cancer cell line as a well defined model system

Standard cancer cell lines do not model the intratumoural heterogeneity situation sufficiently. Clonal selection leads to a homogeneous population of cells by genetic drift. Heterogeneity of tumour cells, however, is particularly critical for therapeutically relevant studies, since it is a prerequisite for acquiring drug resistance and reoccurrence of tumours. Here, we report the isolation of a highly tumourigenic primary pancreatic cancer cell line, called JoPaca-1 and its detailed characterization at multiple levels. Implantation of as few as 100 JoPaca-1 cells into immunodeficient mice gave rise to tumours that were histologically very similar to the primary tumour. The high heterogeneity of JoPaca-1 was reflected by diverse cell morphology and a substantial number of chromosomal aberrations. Comparative whole-genome sequencing of JoPaca-1 and BxPC-3 revealed mutations in genes frequently altered in pancreatic cancer. Exceptionally high expression of cancer stem cell markers and a high clonogenic potential in vitro and in vivo was observed. All of these attributes make this cell line an extremely valuable model to study the biology of and pharmaceutical effects on pancreatic cancer.

Forkhead box M1 (FoxM1) gene is a new STAT3 transcriptional factor target and is essential for proliferation, survival and DNA repair of K562 cell line

The forkhead box (Fox) M1 gene belongs to a superfamily of evolutionarily conserved transcriptional regulators that are involved in a wide range of biological processes, and its deregulation has been implicated in cancer survival, proliferation and chemotherapy resistance. However, the role of FoxM1, the signaling involved in its activation and its role in leukemia are poorly known. Here, we demonstrate by gene promoter analysis, Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays that FoxM1 is a new target of the STAT3 transcriptional activator. Additionally, FoxM1 is transcriptionally dependent on STAT3 signaling activation. Furthermore, we verified that FoxM1 is crucial for K562 cell proliferation, cell cycle checkpoints and viability and could be related to chemotherapeutic resistance. By microarray analysis, we determined the signaling pathways related to FoxM1 expression and its role in DNA repair using K562 cells. Our results revealed new signaling involved in FoxM1 expression and its role in leukemic cells that elucidate cellular mechanisms associated with the development of leukemia and disease progression.

Targeting FOXM1 in cancer

Oncogenic transcription factor FOXM1 is overexpressed in the majority of human cancers. In addition, FOXM1 has been implicated in cell migration, invasion, angiogenesis and metastasis. The important role of FOXM1 in cancer affirms its significance for therapeutic intervention. Current data suggest that targeting FOXM1 in mono- or combination therapy may have promising therapeutic benefits for the treatment of cancer. However, challenges with the delivery of anti-FOXM1 siRNA to tumors and the absence of small molecules, which specifically inhibit FOXM1, are delaying the development of FOXM1 inhibitors as feasible anticancer drugs. In this review, we describe and summarize the efforts that have been made to target FOXM1 in cancer and the consequences of FOXM1 suppression in human cancer cells.

Overexpression of forkhead box M1 transcription factor (FOXM1) is a potential prognostic marker and enhances chemoresistance for docetaxel in gastric cancer

BACKGROUND

Mammalian forkhead box transcription factor 1 (FoxM1) has been overexpressed and correlated with pathogenesis in a variety of human malignancies. We investigated the expression status and clinical significance of its overexpression in gastric adenocarcinoma. Furthermore, we demonstrated correlations between FoxM1 overexpression and drug resistance to chemotherapeutic agents in gastric cancer cells and gastric cancer patients treated with chemotherapy.

METHODS

Fifty-three (69%) of 77 tumors were diagnosed as positive for FoxM1 by immunohistochemistry. Multivariate analysis identified FoxM1 expression as a significant independent prognostic predictor for overall and disease-free survival in gastric cancer patients (hazard ratio 3.9 and 3.5, respectively). Furthermore, we investigated associations between FoxM1 overexpression and clinical response of chemotherapy for patients with advanced gastric cancer.

RESULTS

Our clinical results showed that FoxM1 overexpression was significantly associated with resistance in chemotherapy of docetaxel in addition to 5-fluorouracil (5-FU) plus S-1 plus cisplatin (CDDP) and was not significant in chemotherapy of 5-FU plus CDDP for patients with advanced gastric cancer. In vitro experiments showed that Mkn7 transfected FoxM1 siRNA significantly reduced chemoresistance to docetaxel over that with parental cell lines and Mkn45 transfected with FoxM1 significantly enhanced chemoresistance to docetaxel over that with parental cell lines.

CONCLUSIONS

Our study showed that FoxM1 was an independent prognostic factor in gastric cancer. Furthermore, we showed that FoxM1 was a critical molecule for chemoresistance to a microtubule-stabilizing anticancer agent, docetaxel. Taken together, those results suggest that inhibition of overexpressed FoxM1 will be a promising therapeutic strategy for advanced gastric cancer.

FOXM1 is a molecular determinant of the mitogenic and invasive phenotype of anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is a very aggressive thyroid cancer. forkhead box protein M1 (FOXM1) is a member of the forkhead box family of transcription factors involved in control of cell proliferation, chromosomal stability, angiogenesis, and invasion. Here, we show that FOXM1 is significantly increased in ATCs compared with normal thyroid, well-differentiated thyroid carcinomas (papillary and/or follicular), and poorly differentiated thyroid carcinomas (P=0.000002). Upregulation of FOXM1 levels in ATC cells was mechanistically linked to loss-of-function of p53 and to the hyperactivation of the phosphatidylinositol-3-kinase/AKT/FOXO3a pathway. Knockdown of FOXM1 by RNA interference inhibited cell proliferation by arresting cells in G2/M and reduced cell invasion and motility. This phenotype was associated with decreased expression of FOXM1 target genes, like cyclin B1 (CCNB1), polo-like kinase 1 (PLK1), Aurora B (AURKB), S-phase kinase-associated protein 2 (SKP2), and plasminogen activator, urokinase: uPA (PLAU). Pharmacological inhibition of FOXM1 in an orthotopic mouse model of ATC reduced tumor burden and metastasization. All together, these findings suggest that FOXM1 represents an important player in thyroid cancer progression to the anaplastic phenotype and a potential therapeutic target for this fatal cancer.

Overexpression of FoxM1 is associated with tumor progression in patients with clear cell renal cell carcinoma

Background

Fork head box M1 (FoxM1) is a proliferation-associated transcription factor essential for cell cycle progression. Numerous studies have documented that FoxM1 has multiple functions in tumorigenesis and its elevated levels are frequently associated with cancer progression. The present study was conducted to investigate the expression of FoxM1 and its prognostic significance in clear cell renal cell carcinoma (ccRCC). Meanwhile, the function of FoxM1 in human ccRCC was further investigated in cell culture models.

Methods

Real-time quantitative PCR, western blot and immunohistochemistry were used to explore FoxM1 expression in ccRCC cell lines and primary ccRCC clinical specimens. FoxM1 expression was knocked down by small interfering RNA (siRNA) in Caki-1 and 786-O cells; proliferation, colony formation, cell cycle, migration, invasion, and angiogenesis were assayed.

Results

FoxM1 expression was up-regulated in the majority of the ccRCC clinical tissue specimens at both mRNA and protein levels. Clinic pathological analysis showed that FoxM1 expression was significantly correlated with primary tumor stage (P <0.001), lymph node metastasis (P = 0.01), distant metastasis (P = 0.01), TNM stage (P < 0.001) and histological grade (P = 0.003). The Kaplan–Meier survival curves revealed that high FoxM1 expression was associated with poor prognosis in ccRCC patients (P < 0.001). FoxM1 expression was an independent prognostic marker of overall ccRCC patient survival in a multivariate analysis (P = 0.008). Experimentally, we found that down-regulation of FoxM1 inhibited cell proliferation and induced cell cycle arrest with reduced expression of cyclin B1, cyclin D1, and Cdk2, and increased expression of p21 and p27. Also, down-regulation of FoxM1 reduced expression and activity of matrix metalloproteinase-2 (MMP-2), MMP-9 and vascular endothelial growth factor (VEGF), resulting in the inhibition of migration, invasion, and angiogenesis.

Conclusions

These results suggest that FoxM1 expression is likely to play important roles in ccRCC development and progression, and that FoxM1 is a prognostic biomarker and a promising therapeutic target for ccRCC.

miR-134 inhibits epithelial to mesenchymal transition by targeting FOXM1 in non-small cell lung cancer cells

Recent studies have implied that miRNAs act as crucial modulators for epithelial-to-mesenchymal transition (EMT). We found that miR-134 expression correlated with invasive potential and EMT phenotype of NSCLC cells. Functional assays demonstrated that miR-134 inhibited EMT in NSCLC cells. In addition, we showed that Forkhead Box M1 (FOXM1) is a direct target of miR-134. Knockdown of FOXM1 reversed EMT resembling that of miR-134 overexpression. We further found that FOXM1 was involved in TGF-β1-induced EMT in A549 cells. These findings suggest that miR-134 acts as a novel EMT suppressor in NSCLC cells.