FoxM1: at the crossroads of ageing and cancer

The EGF receptor ligand amphiregulin controls cell division via FoxM1

Epidermal growth factor receptor (EGFR) is central to epithelial cell physiology, and deregulated EGFR signaling has an important role in a variety of human carcinomas. Here we show that silencing of the EGF-related factor amphiregulin (AREG) markedly inhibits the expansion of human keratinocytes through mitotic failure and accumulation of cells with ⩾ 4n DNA content. RNA-sequencing-based transcriptome analysis revealed that tetracycline-mediated AREG silencing significantly altered the expression of 2331 genes, 623 of which were not normalized by treatment with EGF. Interestingly, genes irreversibly upregulated by suppression of AREG overlapped with genes involved in keratinocyte differentiation. Moreover, a significant proportion of the irreversibly downregulated genes featured upstream binding sites recognized by forkhead box protein M1 (FoxM1), a key transcription factor in the control of mitosis that is widely dysregulated in cancer. The downregulation of FoxM1 and its target genes preceded mitotic arrest. Constitutive expression of FoxM1 in AREG knockdown cells normalized cell proliferation, reduced the number of cells with ⩾ 4n DNA content and rescued expression of FoxM1 target genes. These results demonstrate that AREG controls G2/M progression and cytokinesis in keratinocytes via activation of a FoxM1-dependent transcriptional program, suggesting new avenues for treatment of epithelial cancer.

FOXM1 is a therapeutic target for high-risk multiple myeloma

The transcription factor forkhead box M1 (FOXM1) is a validated oncoprotein in solid cancers, but its role in malignant plasma cell tumors such as multiple myeloma (MM) is unknown. We analyzed publicly available MM data sets and found that overexpression of FOXM1 prognosticates inferior outcome in a subset (~15%) of newly diagnosed cases, particularly patients with high-risk disease based on global gene expression changes. Follow-up studies using human myeloma cell lines (HMCLs) as the principal experimental model system demonstrated that enforced expression of FOXM1 increased growth, survival and clonogenicity of myeloma cells, whereas knockdown of FOXM1 abolished these features. In agreement with that, constitutive upregulation of FOXM1 promoted HMCL xenografts in laboratory mice, whereas inducible knockdown of FOXM1 led to growth inhibition. Expression of cyclin-dependent kinase 6 (CDK6) and NIMA-related kinase 2 (NEK2) was coregulated with FOXM1 in both HMCLs and myeloma patient samples, suggesting interaction of these three genes in a genetic network that may lend itself to targeting with small-drug inhibitors for new approaches to myeloma therapy and prevention. These results establish FOXM1 as high-risk myeloma gene and provide support for the design and testing of FOXM1-targeted therapies specifically for the FOXM1(High) subset of myeloma.

FOXO factors and breast cancer: outfoxing endocrine resistance

The majority of metastatic breast cancers cannot be cured and present a major public health problem worldwide. Approximately 70% of breast cancers express the estrogen receptor, and endocrine-based therapies have significantly improved patient outcomes. However, the development of endocrine resistance is extremely common. Understanding the molecular pathways that regulate the hormone sensitivity of breast cancer cells is important to improving the efficacy of endocrine therapy. It is becoming clearer that the PI3K-AKT-forkhead box O (FOXO) signaling axis is a key player in the hormone-independent growth of many breast cancers. Constitutive PI3K-AKT pathway activation, a driver of breast cancer growth, causes down-regulation of FOXO tumor suppressor functions. This review will summarize what is currently known about the role of FOXOs in endocrine-resistance mechanisms. It will also suggest potential therapeutic strategies for the restoration of normal FOXO transcriptional activity.

The Role of Forkhead Box Protein M1 in Breast Cancer Progression and Resistance to Therapy

The Forkhead box M1 (FOXM1) is a transcription factor that has been implicated in normal cell growth and proliferation through control of cell cycle transition and mitotic spindle. It is implicated in carcinogenesis of various malignancies where it is activated by either amplification, increased stability, enhanced transcription, dysfunction of regulatory pathways, or activation of PI3K/AKT, epidermal growth factor receptor, Raf/MEK/MAPK, and Hedgehog pathways. This review describes the role of FOXM1 in breast cancer. This includes how FOXM1 impacts on different subtypes of breast cancer, that is, luminal/estrogen receptor positive (ER+), expressing human epidermal growth factor receptor 2 (HER2), basal-like breast cancer (BBC), and triple negative breast cancer (TNBC). The review also describes different tested preclinical therapeutic strategies targeting FOXM1. Developing clinically applicable therapies that specifically inhibit FOXM1 activity is a logical next step in biomarker-driven approaches against breast cancer but will not be without its challenges due to the unique properties of this transcription factor.

Integrated genomic characterization of IDH1-mutant glioma malignant progression

Gliomas represent approximately 30% of all central nervous system tumors and 80% of malignant brain tumors. To understand the molecular mechanisms underlying the malignant progression of low-grade gliomas with mutations in IDH1 (encoding isocitrate dehydrogenase 1), we studied paired tumor samples from 41 patients, comparing higher-grade, progressed samples to their lower-grade counterparts. Integrated genomic analyses, including whole-exome sequencing and copy number, gene expression and DNA methylation profiling, demonstrated nonlinear clonal expansion of the original tumors and identified oncogenic pathways driving progression. These include activation of the MYC and RTK-RAS-PI3K pathways and upregulation of the FOXM1- and E2F2-mediated cell cycle transitions, as well as epigenetic silencing of developmental transcription factor genes bound by Polycomb repressive complex 2 in human embryonic stem cells. Our results not only provide mechanistic insight into the genetic and epigenetic mechanisms driving glioma progression but also identify inhibition of the bromodomain and extraterminal (BET) family as a potential therapeutic approach.

Senescence-Derived Extracellular Molecules as Modulators of Oral Cancer Development: A Mini-Review

Oral cancers are predominantly oral squamous cell carcinomas (OSCCs) derived from keratinocytes, and there is now very detailed knowledge of the genetics and molecular biology of the epithelial tumourigenic component of these cancers, including the identification of cancer stem or tumour-initiating cells. Several key genetic alterations have been identified including the near ubiquitous loss of the CDKN2A/p16INK4A and p53 pathways and telomerase activation, together with frequent inactivation of the NOTCH1 canonical pathway either by somatic genetic alterations or by the presence of human papilloma virus. There is also evidence that OSCCs arise from a ‘field' of altered cells and that malignant conversion takes place pre-dominantly at the microscopic level. However, in the last decade, it has been realised that tumour development and progression are influenced by the cells of the microenvironment with cross-talk between the epithelial (tumour) and mesenchymal components. OSCCs, especially those that have bypassed cellular senescence, produce an array of proteins and metabolites that induce cellular senescence in the normal surrounding cells; indeed, senescence is a common property of cancer-associated fibroblasts (CAFs). Cellular senescence is defined as an irreversible cell cycle arrest and is associated with the release of molecules known as the senescence-associated secretory phenotype that can selectively promote the growth of pre-neoplastic keratinocytes (osteopontin) and cancer invasion (transforming growth factor β, matrix metalloproteinases, interleukin 6 and lactate). In addition, both old and new work has shown that keratinocytes harbouring NOTCH loss-of-function mutations that lead to defective keratinocyte differentiation and loss of squamous epithelial barrier function may act as a tumour-promoting stimulus for initiated cells harbouring RAS pathway mutations by activating a wound response in the tumour mesenchyme. Thus, not all keratinocytes in the tumour tissue may be tumourigenic and may instead act as promoters of tumour growth and progression analogous to the much-studied CAFs which co-evolve with the genetically altered tumourigenic cells. This new data is discussed in relation to attempts to develop novel non-invasive diagnostics and therapeutics for oral cancer.

FOXM1 and polo-like kinase 1 are co-ordinately overexpressed in patients with gastric adenocarcinomas

BACKGROUND

Gastric cancers present late in life with advanced disease and carry a poor prognosis. Polo-like Kinase 1 (PLK1) is a mitotic kinase with regulatory functions during G2/M and mitosis in the cell cycle. In mammalian cells, there is an intricate co-regulatory relationship between PLK1 and the forkhead transcription factor FOXM1. It has been demonstrated that individually either PLK1 or FOXM1 expression predicts poorer survival. However, the co-expression of both of these markers in gastric adenocarcinomas has not been reported previously.

METHODS

We aimed to assess the expression of PLK1 and FOXM1 in Gastric adenocarcinomas in a Western Population, to examine whether there is a relationship of PLK1 to FOXM1 in cancer samples. We assess both the protein and mRNA expression in this patient population by Tissue Microarray immunohistochemistry and RT-PCR.

RESULTS

Immunohistochemistry was performed on biopsy samples from 79 patients with gastric cancer. Paired normal controls were available in 47 patients. FOXM1 expression was significantly associated with gastric adenocarcinoma (p = 0.001). PLK1 and FOXM1 co-expression was demonstrated in 6/8 (75 %) tumours when analysed by RT-PCR. FOXM1 is overexpressed in a large proportion of gastric carcinomas at the protein level and FOXM1 and PLK1 are concomitantly overexpressed at the mRNA level in this cancer type.

CONCLUSIONS

This study has demonstrated that FOXM1 and its target gene PLK1 are coordinately overexpressed in a proportion of gastric adenocarcinomas. This suggests that chemotherapeutic treatments that target this pathway may be of clinical utility.

A Novel Function of Molecular Chaperone HSP70: SUPPRESSION OF ONCOGENIC FOXM1 AFTER PROTEOTOXIC STRESS

The oncogenic transcription factor FOXM1 is overexpressed in the majority of human cancers, and it is a potential target for anticancer therapy. We identified proteasome inhibitors as the first type of drugs that target FOXM1 in cancer cells. Here we found that HSP90 inhibitor PF-4942847 and heat shock also suppress FOXM1. The common effector, which was induced after treatment with proteasome and HSP90 inhibitors or heat shock, was the molecular chaperone HSP70. We show that HSP70 binds to FOXM1 following proteotoxic stress and that HSP70 inhibits FOXM1 DNA-binding ability. Inhibition of FOXM1 transcriptional autoregulation by HSP70 leads to the suppression of FOXM1 protein expression. In addition, HSP70 suppression elevates FOXM1 expression, and simultaneous inhibition of FOXM1 and HSP70 increases the sensitivity of human cancer cells to anticancer drug-induced apoptosis. Overall, we determined the unique and novel mechanism of FOXM1 suppression by proteasome inhibitors.

FOXM1 expression in rhabdomyosarcoma: a novel prognostic factor and therapeutic target

The transcription factor Forkhead box M1 (FOXM1) is known to play critical roles in the development and progression of various types of cancer, but the clinical significance of FOXM1 expression in rhabdomyosarcoma (RMS) is unknown. This study aimed to determine the role of FOXM1 in RMS. We investigated the expression levels of FOXM1 and vascular endothelial growth factor (VEGF) and angiogenesis in a large series of RMS clinical cases using immunohistochemistry (n = 92), and we performed clinicopathologic and prognostic analyses. In vitro studies were conducted to examine the effect of FOXM1 knock-down on VEGF expression, cell proliferation, migration, and invasion in embryonal RMS (ERMS) and alveolar RMS (ARMS) cell lines, using small interference RNA (siRNA). High FOXM1 expression was significantly increased in the cases of ARMS, which has an adverse prognosis compared to ERMS (p = 0.0310). The ERMS patients with high FOXM1 expression (n = 25) had a significantly shorter survival than those with low FOXM1 expression (n = 24; p = 0.0310). FOXM1 expression was statistically correlated with VEGF expression in ERMS at the protein level as shown by immunohistochemistry and at the mRNA level by RT-PCR. The in vitro study demonstrated that VEGF mRNA levels were decreased in the FOXM1 siRNA-transfected ERMS and ARMS cells. FOXM1 knock-down resulted in a significant decrease of cell proliferation and migration in all four RMS cell lines and invasion in three of the four cell lines. Our results indicate that FOXM1 overexpression may be a prognostic factor of RMS and that FOXM1 may be a promising therapeutic target for the inhibition of RMS progression.

FoxM1 Promotes Stemness and Radio-Resistance of Glioblastoma by Regulating the Master Stem Cell Regulator Sox2

Glioblastoma (GBM) is the most aggressive and most lethal brain tumor. As current standard therapy consisting of surgery and chemo-irradiation provides limited benefit for GBM patients, novel therapeutic options are urgently required. Forkhead box M1 (FoxM1) transcription factor is an oncogenic regulator that promotes the proliferation, survival, and treatment resistance of various human cancers. The roles of FoxM1 in GBM remain incompletely understood, due in part to pleotropic nature of the FoxM1 pathway. Here, we show the roles of FoxM1 in GBM stem cell maintenance and radioresistance. ShRNA-mediated FoxM1 inhibition significantly impeded clonogenic growth and survival of patient-derived primary GBM cells with marked downregulation of Sox2, a master regulator of stem cell phenotype. Ectopic expression of Sox2 partially rescued FoxM1 inhibition-mediated effects. Conversely, FoxM1 overexpression upregulated Sox2 expression and promoted clonogenic growth of GBM cells. These data, with a direct binding of FoxM1 in the Sox2 promoter region in GBM cells, suggest that FoxM1 regulates stemness of primary GBM cells via Sox2. We also found significant increases in FoxM1 and Sox2 expression in GBM cells after irradiation both in vitro and in vivo orthotopic tumor models. Notably, genetic or a small-molecule FoxM1 inhibitor-mediated FoxM1 targeting significantly sensitized GBM cells to irradiation, accompanying with Sox2 downregulation. Finally, FoxM1 inhibition combined with irradiation in a patient GBM-derived orthotopic model significantly impeded tumor growth and prolonged the survival of tumor bearing mice. Taken together, these results indicate that the FoxM1-Sox2 signaling axis promotes clonogenic growth and radiation resistance of GBM, and suggest that FoxM1 targeting combined with irradiation is a potentially effective therapeutic approach for GBM.

FoxM1 Directs STAT3 Expression Essential for Human Endometrial Stromal Decidualization

Human endometrium decidualization, which involves endometrial stromal proliferation and differentiation, is a prerequisite for embryo implantation, thus successful pregnancy. The Forkhead Box M1 (FoxM1), previously known as HNF-3, HFH-11, MPP2, Win, and Trident, is a transcriptional factor that plays crucial roles in cell proliferation and cell cycle progression. However, the molecular mechanism of FoxM1 during human endometrial decidualization remains unexplored. In this study, we first found FoxM1 is dynamically expressed in human endometrium during menstrual cycle. Employing a human endometrial stromal cell (HESC) line, we then demonstrated that FoxM1 inhibition downregulates cyclin B1 expression, delaying G2/M phase transition during HESC proliferation. Additionally, loss of FoxM1 expression blocks the differentiation of HESCs in response to estrogen, progesterone, and dbcAMP. Applying chromatin immunoprecipitation (ChIP) technique and luciferase assay, we further approved that FoxM1 can transcriptionally active signal transducer and activator of transcription 3 (STAT3), ensuring normal HESC differentiation. Besides enriching our knowledge on molecular basis underlying stromal decidualization, these findings help to shed light on the potential molecular causes for the endometrial disorders in humans.

Siomycin A Induces Apoptosis in Human Lung Adenocarcinoma A549 Cells by Suppressing the Expression of FoxM1

Forkhead box M1 (FoxM1), a transcription factor of the Forkhead family, is demonstrated to be critical for proliferation, apoptosis, migration and invasion of lung cancer. In this study, we extensively investigated the anticancer effect of siomycin A, which was identified as an inhibitor of FoxM1 transcriptional activity, on human lung adenocarcinoma A549 cells. Our study indicated that treatment with siomycin A resulted in the suppression of FoxM1 expression, which consequently contributed to its effect of cell growth inhibition and cell apoptosis induction in A549 cells. Then the molecular mechanism of siomycin A's apoptotic action on A549 cells was further investigated. The results revealed that siomycin A induced apoptosis by influencing the downstream events of FoxM1, including inhibiting the expression of Bcl-2 and Mcl-1, as well as leading to caspase-3 cleavage. Taken together, our findings may be useful for understanding the mechanism of action of siomycin A on lung cancer cells and provide new insights into the possible application of such a compound in lung cancer therapy in the future.

Targeting of mutant p53-induced FoxM1 with thiostrepton induces cytotoxicity and enhances carboplatin sensitivity in cancer cells

FoxM1 is an oncogenic Forkhead transcription factor that is overexpressed in ovarian cancer. However, the mechanisms by which FoxM1 is deregulated in ovarian cancer and the extent to which FoxM1 can be targeted in ovarian cancer have not been reported previously. In this study, we showed that MDM2 inhibitor Nutlin-3 upregulated p53 protein and downregulated FoxM1 expression in several cancer cell lines with wild type TP53 but not in cell lines with mutant TP53. FoxM1 downregulation was partially blocked by cycloheximide or actinomycin D, and pulse-chase studies indicate Nutlin-3 enhances FoxM1 mRNA decay. Knockdown of p53 using shRNAs abrogated the FoxM1 downregulation by Nutlin-3, indicating a p53-dependent mechanism. FoxM1 inhibitor, thiostrepton, induces apoptosis in cancer cell lines and enhances sensitivity to cisplatin in these cells. Thiostrepton downregulates FoxM1 expression in several cancer cell lines and enhances sensitivity to carboplatin in vivo. Finally, FoxM1 expression is elevated in nearly all (48/49) ovarian tumors, indicating that thiostrepton target gene is highly expressed in ovarian cancer. In summary, the present study provides novel evidence that both amorphic and neomorphic mutations in TP53 contribute to FoxM1 overexpression and that FoxM1 may be targeted for therapeutic benefits in cancers.

Elevated expression of FoxM1 promotes the tumor cell proliferation in hepatocellular carcinoma

The Forkhead box M1 (FoxM1) transcription factor plays crucial roles in multiple biological processes, including cell proliferation, differentiation, migration, and transformation. Recent studies have reported that aberrant expression of FoxM1 was found in a variety of human cancers. However, the expression pattern of FoxM1 and its clinical significance in human hepatocellular carcinoma (HCC) have not been well characterized to date. In this study, the expression of FoxM1 was evaluated in 46 pairs of human HCC, the adjacent non-tumorous liver tissues, and 12 pairs of normal liver tissues by immumohistochemistry. FoxM1 expression was upregulated in the HCC (76.09 %) compared with non-tumorous liver tissues (39.13 %) and normal liver tissues (8.33 %) (P < 0.05). FoxM1 expression was significantly associated with tumor stage, tumor size, tumor number, integrality of tumor encapsulation, tumor thrombus, and AFP level (P < 0.05). Functionally, enforced expression of FoxM1 in HCC cell line (HHCC) remarkably enhanced cell proliferation in vitro and in vivo. Further analysis of cell cycle-related molecules showed that FoxM1 overexpression increased expressions of cyclin B1 and cyclin D1 but reduced expressions of p27(Kip1) and p21(Cip1). Our findings suggest that FoxM1 overexpression promotes HCC cell proliferation by cell cycle regulation, which is a potential target for hepatocellular carcinoma therapy.

FoxM1 transactivates PTTG1 and promotes colorectal cancer cell migration and invasion

Background

Metastasis is the major cause of cancer-related death. Forkhead Box M1 (FoxM1) is a master regulator of tumor metastasis. This study aims to identify new FoxM1 targets in regulating tumor metastasis using bioinformatics tools as well as biological experiments.

Methods

Illumina microarray was used to profile WT and PTTG1 knockout HCT116 cells. R2 Genomics Analysis was used to identify PTTG1 as a potential FoxM1 targeted gene. Luciferase reporter array, EMSA and Chromatin Immunoprecipitation (ChIP) were used to determine the binding of FoxM1 to PTTG1 promoter. Boyden chamber assay was used to evaluate the effects of FoxM1-PTTG1 on cell migration and invasion. Splenic-injection induced liver metastasis model was used to evaluate the effects of FoxM1-PTTG1 on liver metastasis of colorectal cancer.

Results

Analyses of multiple microarray datasets derived from human colorectal cancer indicated that correlation levels of FoxM1 and pituitary tumor transforming gene (PTTG1) are highly concordant (R = 0.68 ~ 0.89, p = 2.1E-226 ~ 9.6E-86). FoxM1 over-expression increased and knock-down decreased PTTG1 expression. Luciferase reporter assay identified that the −600 to −300 bp region of PTTG1 promoter is important for FoxM1 to enhance PTTG1 promoter activity. EMSA and ChIP assays confirmed that FoxM1 directly binds to PTTG1 promoter at the −391 to −385 bp region in colorectal cancer cells. Boyden chamber assay indicated that both FoxM1 and PTTG1 regulate migration and invasion of HCT116 and SW620 colorectal cancer cells. Further in vivo assays indicated that PTTG1 knock out decreased the liver metastasis of FoxM1 over-expressing HCT116 cells. Microarray analyses identified 662 genes (FDR < 0.05) differentially expressed between WT and PTTG1^−/− HCT116 cells. Among them, dickkopf homolog 1 (DKK1), a known WNT pathway inhibitor, was suppressed by PTTG1 and FoxM1.

Conclusions

PTTG1 is a FoxM1 targeted gene. FoxM1 binds to PTTG1 promoter to enhance PTTG1 transcription, and FoxM1-PTTG1 pathway promotes colorectal cancer migration and invasion.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0126-9) contains supplementary material, which is available to authorized users.

Prognostic Value of FOXM1 in Patients with Malignant Solid Tumor: A Meta-Analysis and System Review

Forkhead box M1 (FOXM1), a member of the Fox transcription factors family, was closely related with cell cycle. FOXM1 played an important role in MST and prompted a poor prognosis for MST patients. However, there were also some studies revealing no significant association between the FOXM1 expression and prognosis of patients. Therefore, we conducted meta-analysis to investigate whether the expression of FOXM1 was associated with MST prognosis. We collected 36 relevant studies through PubMed database and obtained research data of 4946 patients. Stata 12.0 was used to express the results as hazard ratio (HR) for time-to-event outcomes with 95% confidence intervals (95% CI). It was shown that overexpression of FOXM1 was relevant to worse survival of MST patients (HR = 1.99, 95% CI = 1.79–2.21, P < 0.001; I² = 26.4%, P_h = 0.076). Subgroup analysis suggested that overexpression of FOXM1 in breast cancer (BC), gastric cancer (GC), hepatocellular carcinoma (HCC), pancreatic ductal adenocarcinoma (PDA), and non-small-cell lung cancer (NSCLC) all predicted a worse survival (P < 0.05), in addition to ovarian cancer (OC) (P = 0.084). In conclusion, our research indicated that overexpression of FOXM1 was to the disadvantage of the prognosis for majority of MST and therefore can be used as an evaluation index of prognosis.

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.

Beyond cytokinesis: the emerging roles of CEP55 in tumorigenesis

CEP55 was initially identified as a pivotal component of abscission, the final stage of cytokinesis, serving to regulate the physical separation of two daughter cells. Over the past 10 years, several studies have illuminated additional roles for CEP55 including regulating the PI3K/AKT pathway and midbody fate. Concurrently, CEP55 has been studied in the context of cancers including those of the breast, lung, colon and liver. CEP55 overexpression has been found to significantly correlate with tumor stage, aggressiveness, metastasis and poor prognosis across multiple tumor types and therefore has been included as part of several prognostic 'gene signatures' for cancer. Here by discussing in depth the functions of CEP55 across different effector pathways, and also its roles as a biomarker and driver of tumorigenesis, we assemble an exhaustive review, thus commemorating a decade of research on CEP55.

Quinoline-based clioquinol and nitroxoline exhibit anticancer activity inducing FoxM1 inhibition in cholangiocarcinoma cells

Purpose

Fork head box M1 (FoxM1) is an oncogenic transcription factor frequently elevated in numerous cancers, including cholangiocarcinoma (CCA). A growing body of evidence documents its diverse functions contributing to tumorigenesis and cancer progression. As such, discovery of agents that can target FoxM1 would be valuable for the treatment of CCA. The quinoline-based compounds, namely clioquinol (CQ) and nitroxoline (NQ), represent a new class of anticancer drug. However, their efficacy and underlying mechanisms have not been elucidated in CCA. In this study, anticancer activities and inhibitory effects of CQ and NQ on FoxM1 signaling were explored using CCA cells.

Methods

The effects of CQ and NQ on cell viability and proliferation were evaluated using the colorimetric 3-(4,5-dimethylthiazol-2yl)-5-(3-carboxymethoxyphenyl)-(4-sulfophenyl)-2H-tetrazolium (MTS assay). Colony formation and cell migration affected by CQ and NQ were investigated using a clonogenic and a wound healing assay, respectively. To demonstrate the agents’ effects on FoxM1 signaling, expression levels of the target genes were quantitatively determined using real-time polymerase chain reaction.

Results

CQ and NQ significantly inhibited cell survival of HuCCT1 and Huh28 in a dose- and a time-dependent fashion. Further investigations using the rapidly proliferating HuCCT1 cells revealed significant suppression of cell proliferation and colony formation induced by low doses of the compounds. Treatment of CQ and NQ repressed expression of cyclin D1 but enhanced expression of p21. Most importantly, upon CQ and NQ treatment, expression of oncogenic FoxM1 was markedly decreased concomitant with downregulation of various FoxM1’s downstream targets including cdc25b, CENP-B, and survivin. In addition, the compounds distinctly impaired HuCCT1 migration as well as inhibited expression of matrix metalloproteinase (MMP)-2 and MMP-9.

Conclusion

Collectively, this study reports for the first time the anticancer effects of CQ and NQ against CCA cells, and highlights new insights into the mechanism of actions of the quinoline-based compounds to disrupt FoxM1 signaling.

Deregulation of the FOXM1 target gene network and its coregulatory partners in oesophageal adenocarcinoma

Background

Survival rates for oesophageal adenocarcinoma (OAC) remain disappointingly poor and current conventional treatment modalities have minimal impact on long-term survival. This is partly due to a lack of understanding of the molecular changes that occur in this disease. Previous studies have indicated that the transcription factor FOXM1 is commonly upregulated in this cancer type but the impact of this overexpression on gene expression in the context of OAC is largely unknown. FOXM1 does not function alone but works alongside the antagonistically-functioning co-regulatory MMB and DREAM complexes.

Methods

To establish how FOXM1 affects gene expression in OAC we have identified the FOXM1 target gene network in OAC-derived cells using ChIP-seq and determined the expression of both its coregulatory partners and members of this target gene network in OAC by digital transcript counting using the Nanostring gene expression assay.

Results

We find co-upregulation of FOXM1 with its target gene network in OAC. Furthermore, we find changes in the expression of its coregulatory partners, including co-upregulation of LIN9 and, surprisingly, reduced expression of LIN54. Mechanistically, we identify LIN9 as the direct binding partner for FOXM1 in the MMB complex. In the context of OAC, both coregulator (eg LIN54) and target gene (eg UHRF1) expression levels are predictive of disease stage.

Conclusions

Together our data demonstrate that there are global changes to the FOXM1 regulatory network in OAC and the expression of components of this network help predict cancer prognosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0339-8) contains supplementary material, which is available to authorized users.

Polo-like kinase 1-mediated phosphorylation of Forkhead box protein M1b antagonizes its SUMOylation and facilitates its mitotic function

Transcription factor Forkhead box protein M1b (FoxM1b) plays an important role during mitotic entry and progression. Our previous studies identified polo-like kinase 1 (PLK1) as a major regulator of FoxM1b. During G2/M transition, PLK1 directly interacts with and phosphorylates FoxM1b, resulting in full activation of the transactivation capacity of FoxM1b. Such a vital regulatory mechanism is essential for timely mitotic entry and progression. However, the molecular mechanism by which PLK1-mediated phosphorylation enhances the transcriptional activity of FoxM1b remains to be determined. We demonstrate that FoxM1b can be SUMOylated in vitro and in vivo, preferentially by SUMO-1. SUMOylation of FoxM1b was found to occur at multiple sites, leading to suppression of FoxM1b transcriptional activity. Such a posttranslational modification of FoxM1b was antagonized by PLK1-mediated phosphorylation. By immunofluorescence staining and subcellular fractionation, we demonstrate that SUMO conjugation promotes cytosolic translocation of FoxM1b. Moreover, SUMO modification of FoxM1b facilitates the ubiquitin-mediated proteasomal degradation of FoxM1b. PLK1-mediated phosphorylation of FoxM1b abrogates the inhibitory effect on FoxM1b by SUMO modification, thereby promoting its nuclear translocation and preventing its proteolytic degradation in the cytoplasm. Such an antagonistic regulatory mechanism is essential for the mitotic function of FoxM1b, ensuring timely mitotic entry and progression. Taken together, our studies have revealed a working mechanism by which PLK1 positively regulates the activity and level of FoxM1b, which would greatly facilitate therapeutic interventions that focus on targeting the PLK1-mediated and/or FoxM1-mediated signaling network.

Sorafenib inhibits proliferation and invasion of human hepatocellular carcinoma cells via up-regulation of p53 and suppressing FoxM1

AIM

Forkhead box M1 (FoxM1) is a transcription factor that plays important roles in the pathogenesis and progression of human cancers, including hepatocellular carcinoma (HCC). The aim of this study was to examine the involvement of FoxM1 in the anti-cancer action of sorafenib, a multikinase inhibitor, in human HCC cells.

METHODS

HCC cell lines HepG2 and HuH-7 were tested. Cell viability was examined using MTT assay and cell invasion was determined with Transwell migration assay. The relevant mRNA expression was determined with RT-PCR, and the proteins were detected using Western blotting and immunofluorescence assays. RNA interference was used to modify the expression of p53 and FoxM1. HuH-7 cell line xenograft mice were used for in vivo study, which were treated with sorafenib (40 mg/kg, po) daily for 3 weeks.

RESULTS

Sorafenib (2-20 μmol/L) inhibited the proliferation of the cells in dose- and time-dependent manners with an IC50 value of nearly 6 μmol/L at 48 h. Sorafenib (6 μmol/L) markedly suppressed the cell invasion. Furthermore, sorafenib (2-6 μmol/L) dose-dependently decreased the expression of FoxM1, MMP-2, and Ki-67, and up-regulated that of p53 in the cells. Silencing p53 abolished the decrease of FoxM1 and increase of p53 in sorafenib-treated cells. Silencing FoxM1 significantly reduced the expression of MMP-2 and Ki-67, and enhanced the anti-proliferation action of sorafenib in the cells, whereas overexpression of FoxM1 increased the expression of MMP-2 and Ki-67, and abrogated the anti-proliferation action of sorafenib. In the xenograft mice, sorafenib administration decreased the tumor growth by 40%, and markedly increased the expression of p53, and decreased the expression of FoxM1, MMP-2, and Ki-67 in tumor tissues.

CONCLUSION

Sorafenib inhibits HCC proliferation and invasion by inhibiting MMP-2 and Ki-67 expression due to up-regulation of P53 and suppressing FoxM1.

Bile acid signaling and liver regeneration

The liver is able to regenerate itself in response to partial hepatectomy or liver injury. This is accomplished by a complex network of different cell types and signals both inside and outside the liver. Bile acids (BAs) are recently identified as liver-specific metabolic signals and promote liver regeneration by activating their receptors: Farnesoid X Receptor (FXR) and G-protein-coupled BA receptor 1 (GPBAR1, or TGR5). FXR is a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors. FXR promotes liver regeneration after 70% partial hepatectomy (PHx) or liver injury. Moreover, activation of FXR is able to alleviate age-related liver regeneration defects. Both liver- and intestine-FXR are activated by BAs after liver resection or injury and promote liver regeneration through distinct mechanism. TGR5 is a membrane-bound BA receptor and it is also activated during liver regeneration. TGR5 regulates BA hydrophobicity and stimulates BA excretion in urine during liver regeneration. BA signaling thus represents a novel metabolic pathway during liver regeneration. This article is part of a Special Issue entitled: Nuclear receptors in animal development.

FoxM1 overexpression promotes epithelial-mesenchymal transition and metastasis of hepatocellular carcinoma

AIM: To investigate the expression of forkhead box protein M1 (FoxM1) in the process of epithelial mesenchymal transition in hepatocellular carcinoma (HCC) and its role in metastasis.

METHODS: FoxM1 and E-cadherin expression in HCC tissue microarray specimens was evaluated by immunohistochemical staining, and statistical methods were applied to analyze the correlation between FoxM1 and epithelial-mesenchymal transition (EMT). Kaplan-Meier analysis of the correlation between the FoxM1 expression level and recurrence or overall survival of HCC patients was performed. The expression of FoxM1, E-cadherin and snail homologue 1 (SNAI1) in HCC cell lines was evaluated by real-time reverse transcription-polymerase chain reaction and Western blot. Hepatocyte growth factor (HGF) was used to induce EMT and stimulate cell migration in HCC cells. The expression of FoxM1 and SNAI1 was regulated by transfection with plasmids pcDNA3.1 and siRNAs in vitro. The occurrence of EMT was evaluated by Transwell assay, morphologic analysis and detection of the expression of EMT markers (E-cadherin and vimentin). Luciferase and chromatin immunoprecipitation assays were used to evaluate whether SNAI1 is a direct transcriptional target of FoxM1.

RESULTS: FoxM1 expression was increased significantly in HCC compared with para-carcinoma (10.7 ± 0.9 vs 8.2 ± 0.7, P < 0.05) and normal hepatic (10.7 ± 0.9 vs 2.7 ± 0.4, P < 0.05) tissues. Overexpression of FoxM1 was correlated with HCC tumor size, tumor number, macrovascular invasion and higher TNM stage, but was negatively correlated with E-cadherin expression in microarray specimens and in cell lines. FoxM1 overexpression was correlated significantly with HCC metastasis and EMT. In vitro, we found that FoxM1 plays a key role in HGF-induced EMT, and overexpression of FoxM1 could suppress E-cadherin expression and induce EMT changes, which were associated with increased HCC cell invasiveness. Next, we confirmed that FOXM1 directly binds to and activates the SNAI1 promoter, and we identified SNAI1 as a direct transcriptional target of FOXM1. Moreover, inhibiting the expression of SNAI1 significantly inhibited FoxM1-mediated EMT.

CONCLUSION: FoxM1 overexpression promotes EMT and metastasis of HCC, and SNAI1 plays a critical role in FoxM1-mediated EMT.

Targeting FoxM1 by thiostrepton inhibits growth and induces apoptosis of laryngeal squamous cell carcinoma

PURPOSE

We have previously reported that forkhead box M1 (FoxM1) transcription factor was overexpressed in laryngeal squamous cell carcinoma (LSCC) and was associated with development of LSCC. However, there are limited studies regarding the functional significance of FoxM1 and FoxM1 inhibitor thiostrepton in LSCC. Therefore, the aim of this study was to examine both in vitro and in vivo activity of FoxM1 inhibitor thiostrepton against LSCC cell line and nude mice.

METHODS

Cell viability was studied by CCK-8 assay. Cell growth was evaluated by CFSE staining and cell cycle analysis. Apoptosis was measured by flow cytometry. The mRNA and protein expression were detected by quantitative real-time RT-PCR, Western blot and immunohistochemical staining. Xenograft model of tumor formation was used to investigate how thiostrepton influences tumorigenesis in vivo.

RESULTS

Overexpression of FoxM1 in LSCC cells was down-regulated by thiostrepton in a dose-dependent manner. Thiostrepton caused dose- and time-dependent suppression of cell viability of LSCC. Moreover, thiostrepton induced cell cycle arrest at S phase at early time and inhibited DNA synthesis in LSCC cells in a dose- and time-dependent manner by down-regulation of cyclin D1 and cyclin E1. Thiostrepton also induced dose- and time-dependent apoptosis of LSCC cells by down-regulation of Bcl-2, up-regulation of Bax and p53, and inducing release of cytochrome c accompanied by activation of cleaved caspase-9, cleaved caspase-3 and cleaved PARP. In addition, z-VAD-fmk, a universal inhibitor of caspases, prevented activation of cleavage caspase-3 and abrogates cell death induced by thiostrepton treatment. Furthermore, FADD and cleaved caspase-8 were activated, and expression of cIAP1, XIAP and survivin were inhibited by thiostrepton. Finally, treatment of LSCC cell line xenografts with thiostrepton resulted in tumorigenesis inhibition of tumors in nude mice by reducing proliferation and inducing apoptosis of LSCC cells.

CONCLUSIONS

Collectively, our finding suggest that targeting FoxM1 by thiostrepton inhibit growth and induce apoptosis of LSCC through mitochondrial- and caspase-dependent intrinsic pathway and Fas-dependent extrinsic pathway as well as IAP family. Thiostrepton may represent a novel lead compound for targeted therapy of LSCC.

Suppression of the FOXM1 transcriptional programme via novel small molecule inhibition

The transcription factor FOXM1 binds to sequence-specific motifs on DNA (C/TAAACA) through its DNA binding domain (DBD), and activates proliferation- and differentiation-associated genes. Aberrant overexpression of FOXM1 is a key feature in oncogenesis and progression of many human cancers. Here — from a high-throughput screen applied to a library of 54,211 small molecules — we identify novel small molecule inhibitors of FOXM1 that block DNA binding. One of the identified compounds: FDI-6 (NCGC00099374) is characterized in depth and is shown to bind directly to FOXM1 protein, to displace FOXM1 from genomic targets in MCF-7 breast cancer cells, and induce concomitant transcriptional down-regulation. Global transcript profiling of MCF-7 cells by RNA-seq shows that FDI-6 specifically down regulates FOXM1-activated genes with FOXM1 occupancy confirmed by ChIP-seq. This small molecule mediated effect is selective for FOXM1-controlled genes with no effect on genes regulated by homologous forkhead family factors.

Overexpression of FOXM1 is associated with metastases of nasopharyngeal carcinoma

BACKGROUND

The forkhead box M1 (FOXM1) transcription factor plays an important role in the metastases of many cancers. Down-regulation of FOXM1 by its inhibitor, thiostrepton, can inhibit the metastatic potential of some cancers; however, there are few studies regarding the functional significance of FOXM1 and thiostrepton in the metastases of nasopharyngeal carcinoma (NPC) and the underlying mechanism.

METHODS

Expression of FOXM1 in NPC, normal nasopharyngeal tissues, a NPC cell line (C666-1), and a nasopharyngeal epithelial cell line (NP69) was investigated by immunohistochemical staining, qRT-PCR, and Western blot. The correlation between FOXM1 expression and the clinical characteristics of patients was analyzed. Moreover, the effects of thiostrepton on expression of FOXM1 in C666-1 and NP69 cells, and the invasion and migration ability of C666-1 cells were examined. The expressions of MMP-2, MMP-9, fascin-1, ezrin, and paxillin were determined after treatment with thiostrepton.

RESULTS

FOXM1 was overexpressed in NPC and C666-1 cells compared with normal nasopharyngeal tissues and NP69 cells. Overexpression of FOXM1 was associated with lymph node metastasis and advanced tumor stage. Moreover, thiostrepton inhibited expression of FOXM1 in C666-1 cells in a dose-dependent manner, but had a minimal effect on NP69 cells. Thiostrepton inhibited the migration and invasion ability of C666-1 cells by down-regulating the expression of MMP-2, MMP-9, fascin-1, and paxillin.

CONCLUSIONS

Overexpression of FOXM1 is associated with metastases of NPC patients. Thiostrepton inhibits the metastatic ability of NPC cells by down-regulating the expression of FOXM1, MMP-2, MMP-9, fascin-1, and paxillin.

Small molecule inhibition of FOXM1: How to bring a novel compound into genomic context

Deregulation of transcription factor (TF) networks is emerging as a major pathogenic event in many human cancers (Darnell, 2002 [1]; Libermann and Zerbini, 2006 [2]; Laoukili et al., 2007 [3]). Small molecule intervention is an attractive avenue to understand TF regulatory mechanisms in healthy and disease state, as well as for exploiting these targets therapeutically (Koehler et al., 2003 [4]; Berg, 2008 [5]; Koehler, 2010 [6]). However, because of their physico-chemical properties, TF targeting has been proven to be difficult (Verdine and Walensky, 2007 [7]). The TF FOXM1 is an important mitotic player (Wonsey and Follettie, 2005 [8]; Laoukili et al., 2005 [9]; McDonald, 2005 [10]) also implicated in cancer progression (Laoukili et al., 2007 [3]; Teh, 2011 [11]; Koo, 2012 [12]) and drug resistance development (Kwok et al., 2010 [13]; Carr et al., [14]). Therefore, its inhibition is an attractive goal for cancer therapy. Here, we describe a computational biology approach, by giving detailed insights into methodologies and technical results, which was used to analyze the transcriptional RNA-Seq data presented in our previous work (Gormally et al., 2014 [20]). Our Bioinformatics analysis shed light on the cellular effect of a novel FOXM1 inhibitor (FDI-6) newly identified through a biophysical screen. The data for this report is available at the public GEO repository (accession number http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE58626).

Forkhead box M1 regulates quiescence-associated radioresistance of human head and neck squamous carcinoma cells

Cellular quiescence is a reversible growth arrest in which cells retain their ability to enter into and exit from the proliferative cycle. This study investigates the hypothesis that cell growth-state specific oxidative stress response regulates radiosensitivity of cancer cells. Results showed that quiescent (low proliferative index; >75% G1 phase and lower RNA content) Cal27 and FaDu human head and neck squamous cell carcinoma (HNSCC) are radioresistant compared to proliferating cells. Quiescent cells exhibited a three to tenfold increase in mRNA levels of Mn-superoxide dismutase (MnSOD), dual oxidase 2 (DUOX2) and dual-specificity phosphatase 1 (DUSP1), while mRNA levels of catalase (CAT), peroxiredoxin 3 (PRDX3) and C-C motif ligand 5 (CCL5) were approximately two to threefold lower compared to proliferating cells. mRNA levels of forkhead box M1 (FOXM1) showed the largest decrease in quiescent cells at approximately 18-fold. Surprisingly, radiation treatment resulted in a distinct gene expression pattern that is specific to proliferating and quiescent cells. Specifically, FOXM1 expression increased two to threefold in irradiated quiescent cells, while the same treatment had no net effect on FOXM1 mRNA expression in proliferating cells. RNA interference and pharmacological-based downregulation of FOXM1 abrogated radioresistance of quiescent cells. Furthermore, radioresistance of quiescent cells was associated with an increase in glucose consumption and expression of glucose-6-phosphate dehydrogenase (G6PD). Knockdown of FOXM1 resulted in a significant decrease in G6PD expression, and pharmacological-inhibition of G6PD sensitized quiescent cells to radiation. Taken together, these results suggest that targeting FOXM1 may overcome radioresistance of quiescent HNSCC.

Down-regulation of FoxM1 inhibits viability and invasion of gallbladder carcinoma cells, partially dependent on inducement of cellular senescence

AIM: To investigate the effect of knockdown of Forkhead box M1 (FoxM1) on the proliferation and invasion capacities of human gallbladder carcinoma (GBC)-SD cells.

METHODS: Four FoxM1 shRNAs were transfected into GBC-SD cells with Lipofectamine 2000 to select the appropriate shRNA for down-regulation of FoxM1. A recombinant lentivirus for shFoxM1 (Lv-shFoxM1), which expresses FoxM1-specific shRNA, and a negative control carrying green fluorescent protein, which expresses a scrambled RNA, were constructed. After transfection with the recombinant adenovirus and screened with puromycin, RT-PCR and Western blot were utilized to evaluate the inhibition efficiency. Cell viability was evaluated by MTT assay, and cell migration and invasion were assessed using the Transwell system. Cells were suspended in serum-free medium and seeded into Transwell inserts either uncoated (for migration assay) or coated (for invasion assay) with growth factor-reduced Matrigel. To verify the involvement of FoxM1 in the senescence of tumor cells, staining of senescence β-galactosidase (SA β-gal), the widely used biomarker of cellular senescence, was also performed.

RESULTS: After successful transfection of four FoxM1 small interfering RNAs (shRNAs) with Lipofectamine 2000, the shF1822 was selected as the most appropriate shRNA according to its obvious inhibitory effect. The recombinant adenovirus was then constructed with the shF1822 and successfully transfected into the GBC-SD cells, resulting in the significant inhibition of FoxM1 expression at both the mRNA and protein levels, compared with the negative control (P < 0.05). After transfection, down-regulation of FoxM1 significantly inhibited cell viability according to the MTT assay (P < 0.05). In addition, Transwell migration and invasion assays also suggested the suppression of invasion ability of the transfected cells. SA β-gal staining showed that down-regulation of FoxM1 could induce more senescent GBC cells (P < 0.05), suggesting the possible involvement of the senescence process of the FoxM1-deficient cells in GBC.

CONCLUSION: FoxM1 is functionally involved in viability of GBC cells, partially dependent on the inducement of cellular senescence, and is a potential target for GBC therapy.

Suppression of the Oncogenic Transcription Factor FOXM1 by Proteasome Inhibitors

The oncogenic transcription factor FOXM1 is one of the key regulators of tumorigenesis. We found that FOXM1 upregulates its own transcription and its protein stability depends on its interaction with the chaperone nucleophosmin. We also determined that FOXM1 is negatively regulated by the tumor suppressor p53. We identified the thiazole antibiotics Siomycin A and thiostrepton as inhibitors of transcriptional activity and FOXM1 expression via proteasome inhibition. In addition, we found that all tested proteasome inhibitors target FOXM1. We showed synergy between thiostrepton and bortezomib in different human cancer cell lines and in vivo. We generated isogenic human cancer cell lines of different origin with wild-type p53 or p53 knockdown and we demonstrated that proteasome inhibitors induce p53-independent apoptosis in these cells. Using RNA-interference or proteasome inhibitors to inhibit FOXM1 we found that suppression of FOXM1 sensitized human cancer cells to apoptosis induced by DNA-damaging agents or oxidative stress. We encapsulated thiostrepton into micelle-nanoparticles and after injection we detected accumulation of nanoparticles in tumors and in the livers of treated mice. This treatment led to inhibition of human xenograft tumor growth in nude mice. Our data indicate that targeting FOXM1 increases apoptosis and inhibits tumor growth.

SUMOylation of FOXM1B alters its transcriptional activity on regulation of MiR-200 family and JNK1 in MCF7 human breast cancer cells

Transcription factor Forkhead Box Protein M1 (FOXM1) is a well-known master regulator in controlling cell-cycle pathways essential for DNA replication and mitosis, as well as cell proliferation. Among the three major isoforms of FOXM1, FOXM1B is highly associated with tumor growth and metastasis. The activities of FOXM1B are modulated by post-translational modifications (PTMs), such as phosphorylation, but whether it is modified by small ubiquitin-related modifier (SUMO) remains unknown. The aim of the current study was to determine whether FOXM1B is post-translationally modified by SUMO proteins and also to identify SUMOylation of FOXM1B on its target gene transcription activity. Here we report that FOXM1B is clearly defined as a SUMO target protein at the cellular levels. Moreover, a SUMOylation protease, SENP2, significantly decreased SUMOylation of FOXM1B. Notably, FOXM1B is selectively SUMOylated at lysine residue 463. While SUMOylation of FOXM1B is required for full repression of its target genes MiR-200b/c and p21, SUMOylation of FOXM1B is essential for full activation of JNK1 gene. Overall, we provide evidence that FOXM1B is post-translationally modified by SUMO and SUMOylation of FOXM1B plays a functional role in regulation of its target gene activities.

Antigen-specific culture of memory-like CD8 T cells for adoptive immunotherapy

Cytotoxic T cells typically are expanded ex vivo in culture with IL2 for adoptive immunotherapy. This culture period leads to a differentiated phenotype and acquisition of effector function, as well as a loss of in vivo proliferative capability and antitumor efficacy. Here, we report antigen-specific and polyclonal expansion of cytotoxic T cells in a cocktail of cytokines and small molecules that leads to a memory-like phenotype in mouse and human cells even during extended culture, leading to enhanced in vivo expansion and tumor control in mice.

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.

FOXM1 modulates cisplatin sensitivity by regulating EXO1 in ovarian cancer

Cisplatin is commonly used in ovarian cancer chemotherapy, however, chemoresistance to cisplatin remains a great clinical challenge. Oncogenic transcriptional factor FOXM1 has been reported to be overexpressed in ovarian cancer. In this study, we aimed to investigate the potential role of FOXM1 in ovarian cancers with chemoresistance to cisplatin. Our results indicate that FOXM1 is upregulated in chemoresistant ovarian cancer samples, and defends ovarian cancer cells against cytotoxicity of cisplatin. FOXM1 facilitates DNA repair through regulating direct transcriptional target EXO1 to protect ovarian cancer cells from cisplatin-mediated apoptosis. Attenuating FOXM1 and EXO1 expression by small interfering RNA, augments the chemotherapy efficacy against ovarian cancer. Our findings indicate that targeting FOXM1 and its target gene EXO1 could improve cisplatin effect in ovarian cancer, confirming their role in modulating cisplatin sensitivity.

Glucose deprivation induces G2/M transition-arrest and cell death in N-GlcNAc2-modified protein-producing renal carcinoma cells

Some cancer cells can survive under glucose deprivation within the microenvironment of a tumor. Recently, we reported that N-linked (β-N-acetylglucosamine)2 [N-GlcNAc2]-modified proteins induce G2/M arrest and cell death under glucose deprivation. Here, we investigated whether such a response to glucose deprivation contributes to the survival of renal cell carcinomas, which are sensitive to nutritional stress. Specifically, we analyzed seven renal carcinoma cell lines. Four of these cell lines produced N-GlcNAc2-modified proteins and led G2/M-phase arrest under glucose deprivation, leading to cell death. The remaining three cell lines did not produce N-GlcNAc2-modified proteins and undergo G1/S-phase arrest under glucose deprivation, leading to survival. The four dead cell lines displayed significant up-regulation in the UDP-GlcNAc biosynthesis pathway as well as increased phosphorylation of p53, which was not observed in the surviving three cell lines. In addition, the four dead cell lines showed prolonged up-regulated expression of ATF3, which is related to unfolded protein response (UPR), while the surviving three cell lines showed only transient up-regulation of ATF3. In this study, we demonstrated that the renal carcinoma cells which accumulate N-GlcNAc2-modified proteins under glucose deprivation do not survive with abnormaly prolonged UPR pathway. By contrast, renal carcinoma cells that do not accumulate N-GlcNAc2-modified proteins under these conditions survive. Morover, we demonstrated that buformin, a UPR inhibitor, efficiently reduced cell survival under conditions of glucose deprivation for both sensitive and resistant phenotypes. Further studies to clarify these findings will lead to the development of novel chemotherapeutic treatments for renal cancer.

A novel function for Foxm1 in interkinetic nuclear migration in the developing telencephalon and anxiety-related behavior

Interkinetic nuclear migration (INM) is a key feature of cortical neurogenesis. INM functions to maximize the output of the neuroepithelium, and more importantly, balance the self-renewal and differentiation of the progenitors. Although INM has been reported to be highly correlated with the cell cycle, little is known about the effects of cell cycle regulators on INM. In this study, by crossing Foxm1(fl/fl) mice with Emx1-Cre line, we report that a conditional disruption of forkhead transcription factor M1 (Foxm1) in dorsal telencephalon results in abnormal cell cycle progression, leading to impaired INM through the downregulation of Cyclin b1 and Cdc25b. The impairment of INM disturbs the synchronization of apical progenitors (APs) and promotes the transition from APs to basal progenitors (BPs) in a cell-autonomous fashion. Moreover, ablation of Foxm1 causes anxiety-related behaviors in adulthood. Thus, this study provides evidence of linkages among the cell cycle regulator Foxm1, INM, and adult behavior.

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.

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.

Gene-gene interaction network analysis of ovarian cancer using TCGA data

BACKGROUND

The Cancer Genome Atlas (TCGA) Data portal provides a platform for researchers to search, download, and analysis data generated by TCGA. The objective of this study was to explore the molecular mechanism of ovarian cancer pathogenesis.

METHODS

Microarray data of ovarian cancer were downloaded from TCGA database, and Limma package in R language was used to identify the differentially expressed genes (DEGs) between ovarian cancer and normal samples, followed by the function and pathway annotations of the DEGs. Next, NetBox software was used to for the gene-gene interaction (GGI) network construction and the corresponding modules identification, and functions of genes in the modules were screened using DAVID.

RESULTS

Our studies identified 332 DEGs, including 146 up-regulated genes which mainly involved in the cell cycle related functions and cell cycle pathway, and 186 down-regulated genes which were enriched in extracellular region par function, and Ether lipid metabolism pathway. GGI network was constructed by 127 DEGs and their significantly interacted 209 genes (LINKERs). In the top 10 nodes ranked by degrees in the network, 5 were LINKERs. Totally, 7 functional modules in the network were selected, and they were enriched in different functions and pathways, such as mitosis process, DNA replication and DNA double-strand synthesis, lipid synthesis processes and metabolic pathways. AR, BRCA1, TFDP1, FOXM1, CDK2, and DBF4 were identified as the transcript factors of the 7 modules.

CONCLUSION

our data provides a comprehensive bioinformatics analysis of genes, functions, and pathways which may be involved in the pathogenesis of ovarian cancer.

Identification of candidate B-lymphoma genes by cross-species gene expression profiling

Comparative genome-wide expression profiling of malignant tumor counterparts across the human-mouse species barrier has a successful track record as a gene discovery tool in liver, breast, lung, prostate and other cancers, but has been largely neglected in studies on neoplasms of mature B-lymphocytes such as diffuse large B cell lymphoma (DLBCL) and Burkitt lymphoma (BL). We used global gene expression profiles of DLBCL-like tumors that arose spontaneously in Myc-transgenic C57BL/6 mice as a phylogenetically conserved filter for analyzing the human DLBCL transcriptome. The human and mouse lymphomas were found to have 60 concordantly deregulated genes in common, including 8 genes that Cox hazard regression analysis associated with overall survival in a published landmark dataset of DLBCL. Genetic network analysis of the 60 genes followed by biological validation studies indicate FOXM1 as a candidate DLBCL and BL gene, supporting a number of studies contending that FOXM1 is a therapeutic target in mature B cell tumors. Our findings demonstrate the value of the “mouse filter” for genomic studies of human B-lineage neoplasms for which a vast knowledge base already exists.

The expression of Nek7, FoxM1, and Plk1 in gallbladder cancer and their relationships to clinicopathologic features and survival

PURPOSE

Gallbladder carcinoma (GC) is generally considered as a relatively rare malignancy with poor prognosis. In order to guide clinicians in selecting suitable treatment for GC patients, reliable markers predictive of poor clinical outcome are desirable. This study analyzed the expression of Polo-like kinase 1 (Plk1), Nima related kinases 7 (Nek7) and Forkhead box M1 (FoxM1) in GC tissues and their relationship to clinicopathologic features and survival.

METHODS

We immunohistochemically investigated the 76 specimens of gallbladder carcinoma, pericarcinoma and normal tissues using Nek7, FoxM1 and Plk1 antibodies and analyzed the overall survival time of these 76 patients.

RESULTS

There were significant correlations between the high level expression of Nek7, FoxM1 and Plk1 and the tumor differentiation, Nevin staging and metastasis. The high level expression of Nek7, FoxM1 and Plk1 was significantly associated with shorter overall survival time in univariate analysis (log-rank test), also identified as an independent prognostic factor in multivariate analysis.

CONCLUSION

Nek7, FoxM1 and Plk1 were significantly associated with certain clinicopathologic indices in GC. Evaluation of Nek7, FoxM1 and Plk1 expression may be an important factor in identifying a group of poor GC prognosis.

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.

Fkh1 and Fkh2 associate with Sir2 to control CLB2 transcription under normal and oxidative stress conditions

The Forkhead (Fkh) box family of transcription factors is evolutionary conserved from yeast to higher eukaryotes and its members are involved in many physiological processes including metabolism, DNA repair, cell cycle, stress resistance, apoptosis, and aging. In budding yeast, four Fkh transcription factors were identified, namely Fkh1, Fkh2, Fhl1, and Hcm1, which are implicated in chromatin silencing, cell cycle regulation, and stress response. These factors impinge transcriptional regulation during cell cycle progression, and histone deacetylases (HDACs) play an essential role in this process, e.g., the nuclear localization of Hcm1 depends on Sir2 activity, whereas Sin3/Rpd3 silence cell cycle specific gene transcription in G2/M phase. However, a direct involvement of Sir2 in Fkh1/Fkh2-dependent regulation of target genes is at present unknown. Here, we show that Fkh1 and Fkh2 associate with Sir2 in G1 and M phase, and that Fkh1/Fkh2-mediated activation of reporter genes is antagonized by Sir2. We further report that Sir2 overexpression strongly affects cell growth in an Fkh1/Fkh2-dependent manner. In addition, Sir2 regulates the expression of the mitotic cyclin Clb2 through Fkh1/Fkh2-mediated binding to the CLB2 promoter in G1 and M phase. We finally demonstrate that Sir2 is also enriched at the CLB2 promoter under stress conditions, and that the nuclear localization of Sir2 is dependent on Fkh1 and Fkh2. Taken together, our results show a functional interplay between Fkh1/Fkh2 and Sir2 suggesting a novel mechanism of cell cycle repression. Thus, in budding yeast, not only the regulation of G2/M gene expression but also the protective response against stress could be directly coordinated by Fkh1 and Fkh2.

MELK-dependent FOXM1 phosphorylation is essential for proliferation of glioma stem cells

Glioblastoma multiforme (GBM) is a life-threatening brain tumor. Accumulating evidence suggests that eradication of glioma stem-like cells (GSCs) in GBM is essential to achieve cure. The transcription factor FOXM1 has recently gained attention as a master regulator of mitotic progression of cancer cells in various organs. Here, we demonstrate that FOXM1 forms a protein complex with the mitotic kinase MELK in GSCs, leading to phosphorylation and activation of FOXM1 in a MELK kinase-dependent manner. This MELK-dependent activation of FOXM1 results in a subsequent increase in mitotic regulatory genes in GSCs. MELK-driven FOXM1 activation is regulated by the binding and subsequent trans-phosphorylation of FOXM1 by another kinase PLK1. Using mouse neural progenitor cells (NPCs), we found that transgenic expression of FOXM1 enhances, while siRNA-mediated gene silencing diminishes neurosphere formation, suggesting that FOXM1 is required for NPC growth. During tumorigenesis, FOXM1 expression sequentially increases as cells progress from NPCs, to pretumorigenic progenitors and GSCs. The antibiotic Siomycin A disrupts MELK-mediated FOXM1 signaling with a greater sensitivity in GSC compared to neural stem cell. Treatment with the first-line chemotherapy agent for GBM, Temozolomide, paradoxically enriches for both FOXM1 (+) and MELK (+) cells in GBM cells, and addition of Siomycin A to Temozolomide treatment in mice harboring GSC-derived intracranial tumors enhances the effects of the latter. Collectively, our data indicate that FOXM1 signaling through its direct interaction with MELK regulates key mitotic genes in GSCs in a PLK1-dependent manner and thus, this protein complex is a potential therapeutic target for GBM.

Role and regulation of the forkhead transcription factors FOXO3a and FOXM1 in carcinogenesis and drug resistance

The FOXO3a and FOXM1 forkhead transcription factors are key players in cancer initiation, progression, and drug resistance. Recent research shows that FOXM1 is a direct transcriptional target of FOXO3a, a vital downstream effector of the PI3K-AKT-FOXO signaling cascade. In addition, FOXM1 and FOXO3a also antagonize each other's activity by competitively binding to the same target genes, which are involved in chemotherapeutic drug sensitivity and resistance. Understanding the role and regulation of the FOXO-FOXM1 axis will provide insight into chemotherapeutic drug action and resistance in patients, and help to identify novel therapeutic approaches as well as diagnostic and predictive biomarkers.

Mitochondrial-targeted nitroxides disrupt mitochondrial architecture and inhibit expression of peroxiredoxin 3 and FOXM1 in malignant mesothelioma cells

Malignant mesothelioma (MM) is an intractable tumor of the peritoneal and pleural cavities primarily linked to exposure to asbestos. Recently, we described an interplay between mitochondrial-derived oxidants and expression of FOXM1, a redox-responsive transcription factor that has emerged as a promising therapeutic target in solid malignancies. Here we have investigated the effects of nitroxides targeted to mitochondria via triphenylphosphonium (TPP) moieties on mitochondrial oxidant production, expression of FOXM1 and peroxiredoxin 3 (PRX3), and cell viability in MM cells in culture. Both Mito-carboxy-proxyl (MCP) and Mito-TEMPOL (MT) caused dose-dependent increases in mitochondrial oxidant production that was accompanied by inhibition of expression of FOXM1 and PRX3 and loss of cell viability. At equivalent concentrations TPP, CP, and TEMPOL had no effect on these endpoints. Live cell ratiometric imaging with a redox-responsive green fluorescent protein targeted to mitochondria (mito-roGFP) showed that MCP and MT, but not CP, TEMPOL, or TPP, rapidly induced mitochondrial fragmentation and swelling, morphological transitions that were associated with diminished ATP levels and increased production of mitochondrial oxidants. Mdivi-1, an inhibitor of mitochondrial fission, did not rescue mitochondria from fragmentation by MCP. Immunofluorescence microscopy experiments indicate a fraction of FOXM1 coexists in the cytoplasm with mitochondrial PRX3. Our results indicate that MCP and MT inhibit FOXM1 expression and MM tumor cell viability via perturbations in redox homeostasis caused by marked disruption of mitochondrial architecture, and suggest that both compounds, either alone or in combination with thiostrepton or other agents, may provide credible therapeutic options for the management of MM.

Combination of oxidative stress and FOXM1 inhibitors induces apoptosis in cancer cells and inhibits xenograft tumor growth

Tumor cells accumulate high level of reactive oxygen species (ROS) because they are metabolically more active than normal cells. Elevated ROS levels increase tumorigenecity but also render cancer cells more vulnerable to oxidative stress than normal cells. The oncogenic transcription factor Forkhead Box M1 (FOXM1), which is overexpressed in a wide range of human cancers, was reported to protect cancer cells from the adverse effects of oxidative stress by up regulating the expression of scavenger enzymes. We therefore hypothesized that the combination of FOXM1 ablation and ROS inducers could selectively eradicate cancer cells. We show that RNA interference-mediated knockdown of FOXM1 further elevates intracellular ROS levels and increases sensitivity of cancer cells to ROS-mediated cell death after treatment with ROS inducers. We also demonstrate that the combination of ROS inducers with FOXM1/proteasome inhibitors induces robust apoptosis in different human cancer cells. In addition, we show evidence that FOXM1/proteasome inhibitor bortezomib in combination with the ROS inducer β-phenylethyl isothiocyanate efficiently inhibits the growth of breast tumor xenografts in nude mice. We conclude that the combination of ROS inducers and FOXM1 inhibitors could be used as a therapeutic strategy to selectively eliminate cancer cells.