Sustained hepatic expression of FoxM1B in transgenic mice has minimal effects on hepatocellular carcinoma development but increases cell proliferation rates in preneoplastic and early neoplastic lesions

Novel benzothiazole/benzothiazole thiazolidine-2,4-dione derivatives as potential FOXM1 inhibitors: In silico, synthesis, and in vitro studies

The oncogenic transcription factor FOXM1 overexpressed in breast and other solid cancers, is a key driver of tumor growth and progression through complex interactions, making it an attractive molecular target for the development of targeted therapies. Despite the availability of small-molecule inhibitors, their limited specificity, potency, and efficacy hinder clinical translation. To identify effective FOXM1 inhibitors, we synthesized novel benzothiazole derivatives (KC10-KC13) and benzothiazole hybrids with thiazolidine-2,4-dione (KC21-KC36). These compounds were evaluated for FOXM1 inhibition. Molecular docking and molecular dynamics simulation analysis revealed their binding patterns and affinities for the FOXM1-DNA binding domain. The interactions with key amino acids such as Asn283, His287, and Arg286, crucial for FOXM1 inhibition, have been determined with the synthesized compounds. Additionally, the molecular modeling study indicated that KC12, KC21, and KC30 aligned structurally and interacted similarly to the reference compound FDI-6. In vitro studies with the MDA-MB-231 breast cancer cell line demonstrated that KC12, KC21, and KC30 significantly inhibited FOXM1, showing greater potency than FDI-6, with IC50 values of 6.13, 10.77, and 12.86 µM, respectively, versus 20.79 µM for FDI-6. Our findings suggest that KC12, KC21, and KC30 exhibit strong activity as FOXM1 inhibitors and may be suitable for in vivo animal studies.

Liver Regeneration: Changes in Oxidative Stress, Immune System, Cytokines, and Epigenetic Modifications Associated with Aging

The regenerative capacity of the liver decreases with increase in age. In recent years, studies in mice have found that the regenerative capacity of the liver is associated with changes in the immune system of the liver, cytokines in the body, aging-related epigenetic modifications in the cell, and intracellular signaling pathways. In the immune system of the aging liver, monocytes and macrophages play an important role in tissue repair. During tissue repair, monocytes and macrophages undergo a series of functional and phenotypic changes to initiate and maintain tissue repair. Studies have discovered that knocking out macrophages in the liver during the repair phase results in significant impairment of liver regeneration. Furthermore, as the body ages, the secretion and function of cytokines undergo a series of changes. For example, the levels of interleukin-6, transforming growth factor-alpha, hepatocyte growth factor, and vascular endothelial growth factor undergo changes that alter hepatocyte regulation, thereby affecting its proliferation. In addition, body aging is accompanied by cellular aging, which leads to changes in gene expression and epigenetic modifications. Additionally, this in turn causes alterations in cell function, morphology, and division and affects the regenerative capacity of the liver. As the body ages, the activity of associated functional proteins, such as CCAAT-enhancer-binding proteins, p53, and switch/sucrose nonfermentable complex, changes in the liver, leading to alterations in several signaling pathways, such as the Hippo, PI3K-Akt, mTOR, and STAT3 pathways. Therefore, in recent years, research on aging and liver regeneration has primarily focused on the immune system, signaling pathways, epigenetic changes of senescent cells, and cytokine secretion in the liver. Hence, this review details the roles of these influencing factors in liver regeneration and impact of aging-related factors.

FOXM1: A Multifunctional Oncoprotein and Emerging Therapeutic Target in Ovarian Cancer

Forkhead box M1 (FOXM1) is a member of the conserved forkhead box (FOX) transcription factor family. Over the last two decades, FOXM1 has emerged as a multifunctional oncoprotein and a robust biomarker of poor prognosis in many human malignancies. In this review article, we address the current knowledge regarding the mechanisms of regulation and oncogenic functions of FOXM1, particularly in the context of ovarian cancer. FOXM1 and its associated oncogenic transcriptional signature are enriched in >85% of ovarian cancer cases and FOXM1 expression and activity can be enhanced by a plethora of genomic, transcriptional, post-transcriptional, and post-translational mechanisms. As a master transcriptional regulator, FOXM1 promotes critical oncogenic phenotypes in ovarian cancer, including: (1) cell proliferation, (2) invasion and metastasis, (3) chemotherapy resistance, (4) cancer stem cell (CSC) properties, (5) genomic instability, and (6) altered cellular metabolism. We additionally discuss the evidence for FOXM1 as a cancer biomarker, describe the rationale for FOXM1 as a cancer therapeutic target, and provide an overview of therapeutic strategies used to target FOXM1 for cancer treatment.

LncRNA HOXA11-AS Aggravates Keloid Progression by the Regulation of HOXA11-AS-miR-205-5p-FOXM1 Pathway

BACKGROUND

Keloid is troublesome for patients' skin appearance and mental health, although it is a benign tumor. Long noncoding RNA (lncRNA) troubling keloid is frequently reported. The purpose of this study was to investigate the role of lncRNA homeobox (HOX) A11 antisense (HOXA11-AS) and related action mechanisms during the development of keloid.

METHODS

The expression of HOXA11-AS, miR-205-5p, and forkhead box M1 (FOXM1) was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation or apoptosis was assessed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium (MTT) assay or flow cytometry assay. Cell migration and invasion were monitored by transwell assay. The protein levels of extracellular matrix (ECM) proteins (collagen I and collagen III), fibronectin, glucose transporter 1 (GLUT1), lactate dehydrogenase A (LDHA), and FOXM1 were quantified by Western blot. Glycolysis processes were investigated by the glycolysis stress test, glucose consumption, and lactate production. The relationship between miR-205-5p and HOXA11-AS or FOXM1 was predicted by the online tool MIRcode or starBase v2.0 and verified by dual-luciferase reporter assay or RNA immunoprecipitation (RIP).

RESULTS

HOXA11-AS and FOXM1 were significantly upregulated in keloid tissues and keloid fibroblasts, while miR-205-5p was downregulated. HOXA11-AS knockdown or miR-205-5p enrichment inhibited proliferation, migration, invasion, ECM accumulation, and glycolysis but accelerated apoptosis of keloid fibroblasts. MiR-205-5p was targeted by HOXA11-AS, and its inhibition overturned the effects of HOXA11-AS knockdown. Moreover, FOXM1 was a target of miR-205-5p, and HOXA11-AS regulated the expression of FOXM1 by adsorbing miR-205-5p. FOXM1 overexpression abolished the role of miR-205-5p enrichment.

CONCLUSIONS

The HOXA11-AS-miR-205-5p-FOXM1 pathway may be an active mode in which HOXA11-AS participates in the progression of keloid.

Replication stress and FOXM1 drive radiation induced genomic instability and cell transformation

In contrast to the vast majority of research that has focused on the immediate effects of ionizing radiation, this work concentrates on the molecular mechanism driving delayed effects that emerge in the progeny of the exposed cells. We employed functional protein arrays to identify molecular changes induced in a human bronchial epithelial cell line (HBEC3-KT) and osteosarcoma cell line (U2OS) and evaluated their impact on outcomes associated with radiation induced genomic instability (RIGI) at day 5 and 7 post-exposure to a 2Gy X-ray dose, which revealed replication stress in the context of increased FOXM1b expression. Irradiated cells had reduced DNA replication rate detected by the DNA fiber assay and increased DNA resection detected by RPA foci and phosphorylation. Irradiated cells increased utilization of homologous recombination-dependent repair detected by a gene conversion assay and DNA damage at mitosis reflected by RPA positive chromosomal bridges, micronuclei formation and 53BP1 positive bodies in G1, all known outcomes of replication stress. Interference with the function of FOXM1, a transcription factor widely expressed in cancer, employing an aptamer, decreased radiation-induced micronuclei formation and cell transformation while plasmid-driven overexpression of FOXM1b was sufficient to induce replication stress, micronuclei formation and cell transformation.

High FOXK1 expression correlates with poor outcomes in hepatocellular carcinoma and regulates stemness of hepatocellular carcinoma cells

AIMS

Forkhead box (FOX) proteins constitute a huge family of transcriptional regulators, which are involved in a wide range of cancers. FOXK1 is a little studied member of FOXK subfamily. This study aimed to investigate the potential prognostic value of FOXK1 in human hepatocellular carcinoma (HCC) and explore potential underlying mechanisms.

MAIN METHODS

We performed bioinformatic analyses to evaluate the prognostic value of FOXK1 expression in human HCC and to reveal the underlying mechanism by which FOXK1 regulates HCC. RT-PCR, FACS analysis and sphere formation assay were carried out to investigate the role of FOXK1 in regulating liver cancer stem cells.

KEY FINDINGS

Our results demonstrated that FOXK1 was overexpressed in human HCC and positively correlated with cancer progression. DNA hypomethylation and gene copy number variation contributed to the overexpression of FOXK1. Importantly, high FOXK1 expression was associated with both low overall survival probability (OS) and low relapse free survival probability (RFS) of HCC patients. Intriguingly, we found that high FOXK1 expression was correlated with activation of stem cell-regulating pathways in human HCC. Knockdown of FOXK1 resulted in downregulation of the cancer stem cell marker EpCAM and ALDH1 and decreased sphere-forming ability of hepatocellular carcinoma cells.

SIGNIFICANCE

Overall, our study identified FOXK1 as a new biomarker for prognosis of HCC patients and revealed its role in regulating stemness of hepatocellular carcinoma cells.

The roles of FOX proteins in virus-associated cancers

Forkhead box (FOX) proteins play a crucial role in regulating the expression of genes involved in multiple biological processes, such as metabolism, development, differentiation, proliferation, apoptosis, migration, invasion, and longevity. Deregulation of FOX proteins is commonly associated with cancer initiation, progression, and chemotherapeutic drug resistance in many human tumors. FOX proteins deregulate through genetic events and the perturbation of posttranslational modification. The purpose of the present review is to describe the deregulation of FOX proteins by oncoviruses. Oncoviruses utilize various mechanisms to deregulate FOX proteins, including alterations in posttranslational modifications, cellular localization independently of posttranslational modifications, virus-encoded miRNAs, activation or suppression of a series of cell signaling pathways. This deregulation can affect proliferation, metastasis, chemotherapy resistance, and immunosuppression in virus-induced cancers and help to chronic viral infection, development of gluconeogenic responses, and inflammation. Since the PI3K/Akt/mTOR signaling pathway is the upstream FOXO, suppressing it can cause FOXO function to return, and this can be one of the reasons for patients to recover from the infection of the viruses used to treat these inhibitors. Hence, FOX proteins could serve as prognosis markers and target therapy specifically in cancers caused by oncoviruses.

Untying the knot of transcription factor druggability: Molecular modeling study of FOXM1 inhibitors

The FOXM1 protein is a relevant transcription factor involved in cancer cell proliferation. The direct or indirect inhibition of this protein's transcriptional activity by small molecule drugs correlates well with a potentially significant anti-cancer profile, making this macro molecule a promising drug target. There are a few drug molecules reported to interact with (and inhibit) the FOXM1 DNA binding domain (FOXM1-BD), causing downregulation of protein expression and cancer cell proliferation inhibition. Among these drug molecules are the proteasome inhibitor thiostrepton, the former antidiabetic drug troglitazone, and the new FDI-6 molecule. Despite their structural differences, these drugs exert a similar inhibitory profile, and this observation prompted us to study a possible similar mechanism of action. Using a series of molecular dynamics simulations and docking protocols, we identified essential binding interactions exerted by all three classes of drugs, among which, a π-sulfur interaction (between a His287 and a sulfur-containing heterocycle) was the most important. In this report, we describe the preliminary evidence suggesting the presence of a drug-binding pocket within FOXM1 DNA binding domain, in which inhibitors fit to dissociate the protein-DNA complex. This finding suggests a common mechanism of action and a basic framework to design new FOXM1 inhibitors.

Effects of Wnt-1 blockade in DEN-induced hepatocellular adenomas of mice

Recent evidence has suggested that downregulation of the Wnt/β-catenin signaling pathway may contribute to the development and growth of HCC. Consequently, elements of this pathway have begun to emerge as potential targets for improving outcomes of anti-HCC. Thus, the present study sought to examine the effects of Wnt-1 blockade using the classical diethylnitrosamine (DEN)-induced chemical carcinogenesis mouse model of HCC. The depletion of Wnt-1 using neutralizing antisera was done for ten consecutive days at the age of 9 months and mice were examined for the following 20 days. At that time, DEN-treated mice had multiple variably-sized hepatic cell adenomas. Anti-Wnt-1 was particularly potent in suppressing the expression of critical elements of the Wnt/β-catenin signaling pathway, such as β-catenin and Frizzled-1 receptor, however, not Dickkopf-related protein 1. This effect co-existed with the suppression of Cyclin D1, FOXM1, NF-κΒ and c-Jun commensurate with proliferation and apoptosis blockade in hepatocellular adenomas, and reduced Bcl-2 and c-Met in the serum of mice. Nonetheless, tumor size and multiplicity were found to be unaffected, suggesting that apoptosis may be equally important to proliferation in the context of counteracting DEN induced hepatocellular adenomas of mice.

The Emerging Roles of Forkhead Box (FOX) Proteins in Osteosarcoma

Osteosarcoma is the most common bone cancer primarily occurring in children and young adults. Over the past few years, the deregulation of a superfamily transcription factors, known as forkhead box (FOX) proteins, has been demonstrated to contribute to the pathogenesis of osteosarcoma. Molecular mechanism studies have demonstrated that FOX family proteins participate in a variety of signaling pathways and that their expression can be regulated by multiple factors. The dysfunction of FOX genes can alter osteosarcoma cell differentiation, metastasis and progression. In this review, we summarized the evidence that FOX genes play direct or indirect roles in the development and progression of osteosarcoma, and evaluated the emerging role of FOX proteins as targets for therapeutic intervention.

DNA Methylation Mediated Down-Regulation of miR-370 Regulates Cell Growth through Activation of the Wnt/β-Catenin Signaling Pathway in Human Osteosarcoma Cells

MicroRNA-370 (miR-370) has been observed to act as a tumor suppressor through the targeting of different proteins in a variety of tumors. Our previous study indicated that miR-370 was able to target forkhead box protein M1 (FOXM1) to inhibit cell growth and metastasis in human osteosarcoma cells. In this study, we reported that FOXM1 interacted with β-catenin in vitro and in vivo. Similar to FOXM1, critical components of the Wnt signaling pathway, including β-catenin, c-Myc, and Cyclin D1, were also highly expressed in different human osteosarcoma cells lines. Pharmacological inhibition of FOXM1 or β-catenin but not of c-Myc was associated with the increased expression of miR-370. Ectopic expression of miR-370 inhibited the downstream signaling of β-catenin. Moreover, osteosarcoma cells treated with 5-AZA-2'-deoxycytidine (AZA), a DNA methylation inhibitor, exhibited increased levels of miR-370 and decreased levels of β-catenin downstream targets, which resulted in inhibition of cell proliferation and colony formation ability. In conclusion, our results supported a model in which the DNA methylation-mediated down-regulation of miR-370 reduced its inhibitory effect on FOXM1, thereby promoting FOXM1-β-catenin interaction and activating the Wnt/β-Catenin signaling pathway in human osteosarcoma cells.

Roles of FoxM1 in cell regulation and breast cancer targeting therapy

Forkhead box M1 (FoxM1) is an oncogenic transcription factor involved in a wide variety of cellular processes, such as cell cycle progression, proliferation, differentiation, migration, metabolism and DNA damage response. It is overexpressed in many human cancers, especially in breast cancers. Posttranslational modifications are known to play an important role in regulating the expression and transcriptional activity of FoxM1. In this review, we characterize the posttranslational modifications of FoxM1, summarize modifications of FoxM1 by different kinases, explore the relationship between the different sites of modifications and comprehensively describe how posttranslational modifications to regulate the function of FoxM1 by changing protein stability, nucleus localization and transcriptional activity. Additionally, we systematically summarize the roles of FoxM1 in breast cancer occurrence, therapy and drug resistance. The purpose of this paper tries to give a better understanding of the regulatory mechanisms of FoxM1 in cell regulation and highlights potential of a new method for breast cancer therapy by targeting FoxM1.

Fox transcription factors: from development to disease

Forkhead box (Fox) transcription factors are evolutionarily conserved in organisms ranging from yeast to humans. They regulate diverse biological processes both during development and throughout adult life. Mutations in many Fox genes are associated with human disease and, as such, various animal models have been generated to study the function of these transcription factors in mechanistic detail. In many cases, the absence of even a single Fox transcription factor is lethal. In this Primer, we provide an overview of the Fox family, highlighting several key Fox transcription factor families that are important for mammalian development.

Insights into a Critical Role of the FOXO3a-FOXM1 Axis in DNA Damage Response and Genotoxic Drug Resistance

FOXO3a and FOXM1 are two forkhead transcription factors with antagonistic roles in cancer and DNA damage response. FOXO3a functions like a typical tumour suppressor, whereas FOXM1 is a potent oncogene aberrantly overexpressed in genotoxic resistant cancers. FOXO3a not only represses FOXM1 expression but also its transcriptional output. Recent research has provided novel insights into a central role for FOXO3a and FOXM1 in DNA damage response. The FOXO3a-FOXM1 axis plays a pivotal role in DNA damage repair and the accompanied cellular response through regulating the expression of genes essential for DNA damage sensing, mediating, signalling and repair as well as for senescence, cell cycle and cell death control. In this manner, the FOXO3a-FOXM1 axis also holds the key to cell fate decision in response to genotoxic therapeutic agents and controls the equilibrium between DNA repair and cell termination by cell death or senescence. As a consequence, inhibition of FOXM1 or reactivation of FOXO3a in cancer cells could enhance the efficacy of DNA damaging cancer therapies by decreasing the rate of DNA repair and cell survival while increasing senescence and cell death. Conceptually, targeting FOXO3a and FOXM1 may represent a promising molecular therapeutic option for improving the efficacy and selectivity of DNA damage agents, particularly in genotoxic agent resistant cancer. In addition, FOXO3a, FOXM1 and their downstream transcriptional targets may also be reliable diagnostic biomarkers for predicting outcome, for selecting therapeutic options, and for monitoring treatments in DNA-damaging agent therapy.

Increased FOXM1 expression can stimulate DNA repair in normal hepatocytes in vivo but also increases nuclear foci associated with senescence

OBJECTIVES

FOXM1 is a transcription factor that has been shown to promote cell proliferation in many tissues during early development and high cell turnover tissues in adults. In a number of tumour cell lines, enrichment of FOXM1 has been shown to reduce the DNA damage response (DDR) and induction of senescence by a range of DNA-damaging agents, suggesting a role for the protein in DNA repair. Endogenous FOXM1 is expressed at detectable levels in hepatocytes of mice up to 2 weeks of age, but not in older mice. The aim of this investigation has been to better understand the role of the protein in DDR in normal cells in vivo.

MATERIALS AND METHODS

Mice with artificially prolonged elevated FOXM1 expression in hepatocytes, were exposed to alkylating diethylnitrosamine.

RESULTS

FOXM1-enriched mice had dampened DDR after treatment with this alkylating agent, which was consistent with observed increase in expression of genes involved in DNA repair. Paradoxically, mice with FOXM1 expression, within weeks after exposure to the DNA-damaging agent, had increased levels of potentially senescent hepatocytes with large nuclear foci, containing 53BP1. Similarly, spontaneous accumulation of these cells seen with normal ageing in mice was increased with FOXM1 enrichment.

CONCLUSION

Despite its known abilities to promote proliferation and DNA repair, and to reduce ROS, enrichment of FOXM1, as with other oncoproteins, may cause increased persistent DNA lesions and/or senescence in normal murine hepatocytes.

FOXM1: an emerging master regulator of DNA damage response and genotoxic agent resistance

FOXM1 is a transcription factor required for a wide spectrum of essential biological functions, including DNA damage repair, cell proliferation, cell cycle progression, cell renewal, cell differentiation and tissue homeostasis. Recent evidence suggests that FOXM1 also has a role in many aspects of the DNA damage response. Accordingly, FOXM1 drives the transcription of genes for DNA damage sensors, mediators, signal transducers and effectors. As a result of these functions, it plays an integral part in maintaining the integrity of the genome and so is key to the propagation of accurate genetic information to the next generation. Preserving the genetic code is a vital means of suppressing cancer and other genetic diseases. Conversely, FOXM1 is also a potent oncogenic factor that is essential for cancer initiation, progression and drug resistance. An enhanced FOXM1 DNA damage repair gene expression network can confer resistance to genotoxic agents. Developing a thorough understanding of the regulation and function of FOXM1 in DNA damage response will improve the diagnosis and treatment of diseases including cancer, neurodegenerative conditions and immunodeficiency disorders. It will also benefit cancer patients with acquired genotoxic agent resistance.

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FOXM1 is a potent oncogenic factor essential for cancer initiation, progression and drug resistance.

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FOXM1 also drives the transcription of genes for DNA damage sensors, mediators, signal transducers and effectors.

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It plays an integral part in maintaining the integrity of the genome.

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An enhanced FOXM1 DNA damage repair gene expression network can confer resistance to genotoxic agents.

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.

Non-viral FoxM1 gene delivery to hepatocytes enhances liver repopulation

Hepatocyte transplantation as a substitute strategy of orthotopic liver transplantation is being studied for treating end-stage liver diseases. Several technical hurdles must be overcome in order to achieve the therapeutic liver repopulation, such as the problem of insufficient expansion of the transplanted hepatocytes in recipient livers. In this study, we analyzed the application of FoxM1, a cell-cycle regulator, to enhance the proliferation capacity of hepatocytes. The non-viral sleeping beauty (SB) transposon vector carrying FoxM1 gene was constructed for delivering FoxM1 into the hepatocytes. The proliferation capacities of hepatocytes with FoxM1 expression were examined both in vivo and in vitro. Results indicated that the hepatocytes with FoxM1 expression had a higher proliferation rate than wild-type (WT) hepatocytes in vitro. In comparison with WT hepatocytes, the hepatocytes with FoxM1 expression had an enhanced level of liver repopulation in the recipient livers at both sub-acute injury (fumaryl acetoacetate hydrolase (Fah)^–/– mice model) and acute injury (2/3 partial hepatectomy mice model). Importantly, there was no increased risk of tumorigenicity with FoxM1 expression in recipients even after serial transplantation. In conclusion, expression of FoxM1 in hepatocytes enhanced the capacity of liver repopulation without inducing tumorigenesis. FoxM1 gene delivered by non-viral SB vector into hepatocytes may be a viable approach to promote therapeutic repopulation after hepatocyte transplantation.

FOXM1 promotes the warburg effect and pancreatic cancer progression via transactivation of LDHA expression

PURPOSE

The transcription factor Forkhead box protein M1 (FOXM1) plays critical roles in cancer development and progression. However, the regulatory role and underlying mechanisms of FOXM1 in cancer metabolism are unknown. In this study, we characterized the regulation of aerobic glycolysis by FOXM1 and its impact on pancreatic cancer metabolism.

EXPERIMENTAL DESIGN

The effect of altered expression of FOXM1 on expression of glycolytic enzymes and tumor development and progression was examined using animal models of pancreatic cancer. Also, the underlying mechanisms of altered pancreatic cancer glycolysis were analyzed using in vitro molecular biology. The clinical relevance of aberrant metabolism caused by dysregulated FOXM1 signaling was determined using pancreatic tumor and normal pancreatic tissue specimens.

RESULTS

We found that FOXM1 did not markedly change the expression of most glycolytic enzymes except for phosphoglycerate kinase 1 (PGK-1) and lactate dehydrogenase A (LDHA). FOXM1 and LDHA were overexpressed concomitantly in pancreatic tumors and cancer cell lines. Increased expression of FOXM1 upregulated the expression of LDHA at both the mRNA and protein level and elevated LDH activity, lactate production, and glucose utilization, whereas reduced expression of FOXM1 did the opposite. Further studies demonstrated that FOXM1 bound directly to the LDHA promoter region and regulated the expression of the LDHA gene at the transcriptional level. Also, elevated FOXM1-LDHA signaling increased the pancreatic cancer cell growth and metastasis.

CONCLUSIONS

Dysregulated expression and activation of FOXM1 play important roles in aerobic glycolysis and tumorigenesis in patients with pancreatic cancer via transcriptional regulation of LDHA expression.

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.

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.

FOXM1: From cancer initiation to progression and treatment

The Forkhead box protein M1 (FOXM1) transcription factor is a regulator of myriad biological processes, including cell proliferation, cell cycle progression, cell differentiation, DNA damage repair, tissue homeostasis, angiogenesis and apoptosis. Elevated FOXM1 expression is found in cancers of the liver, prostate, brain, breast, lung, colon, pancreas, skin, cervix, ovary, mouth, blood and nervous system, suggesting it has an integral role in tumorigenesis. Recent research findings also place FOXM1 at the centre of cancer progression and drug sensitivity. In this review the involvement of FOXM1 in various aspects of cancer, in particular its role and regulation within the context of cancer initiation, progression, and cancer drug response, will be summarised and discussed.

Multiple faces of FoxM1 transcription factor: lessons from transgenic mouse models

FoxM1 transcription factor (previously called HFH-11B, Trident, FoxM1b, Win, and MPP2) is expressed in actively dividing cells and critical for cell cycle progression. FoxM1 expression is induced in a variety of tissues during embryogenesis, and Foxm1 (-/-) mice exhibit embryonic lethal phenotype due to multiple abnormalities in the liver, heart, lung and blood vessels. FoxM1 levels are dramatically decreased in adult tissues, but FoxM1 expression is re-activated during organ injury and numerous cancers. In this review, we discussed the role of FoxM1 in different cell lineages using recent data from transgenic mouse models with conditional "gain-of-function" and "loss-of-function" of FoxM1, as well as tissue samples from human patients. In addition, we provided experimental data showing additional sites of FoxM1 expression in the mouse embryo. Novel cell-autonomous roles of FoxM1 in embryonic development, organ injury and cancer formation in vivo were analyzed. Potential application of these findings for the diagnosis and treatment of human diseases were discussed.

Deregulation of FoxM1b leads to tumour metastasis

The forkhead box M1b (FoxM1b) transcription factor is over-expressed in human cancers, and its expression often correlates with poor prognosis. Previously, using conditional knockout strains, we showed that FoxM1b is essential for hepatocellular carcinoma (HCC) development. However, over-expression of FoxM1b had only marginal effects on HCC progression. Here we investigated the effect of FoxM1b expression in the absence of its inhibitor Arf. We show that transgenic expression of FoxM1b in an Arf-null background drives hepatic fibrosis and metastasis of HCC. We identify novel mechanisms of FoxM1b that are involved in epithelial–mesenchymal transition, cell motility, invasion and a pre-metastatic niche formation. FoxM1b activates the Akt-Snail1 pathway and stimulates expression of Stathmin, lysyl oxidase, lysyl oxidase like-2 and several other genes involved in metastasis. Furthermore, we show that an Arf-derived peptide, which inhibits FoxM1b, impedes metastasis of the FoxM1b-expressing HCC cells. The observations indicate that FoxM1b is a potent activator of tumour metastasis and that the Arf-mediated inhibition of FoxM1b is a critical mechanism for suppression of tumour metastasis.

Upregulation of FOXM1 induces genomic instability in human epidermal keratinocytes

Background

The human cell cycle transcription factor FOXM1 is known to play a key role in regulating timely mitotic progression and accurate chromosomal segregation during cell division. Deregulation of FOXM1 has been linked to a majority of human cancers. We previously showed that FOXM1 was upregulated in basal cell carcinoma and recently reported that upregulation of FOXM1 precedes malignancy in a number of solid human cancer types including oral, oesophagus, lung, breast, kidney, bladder and uterus. This indicates that upregulation of FOXM1 may be an early molecular signal required for aberrant cell cycle and cancer initiation.

Results

The present study investigated the putative early mechanism of UVB and FOXM1 in skin cancer initiation. We have demonstrated that UVB dose-dependently increased FOXM1 protein levels through protein stabilisation and accumulation rather than de novo mRNA expression in human epidermal keratinocytes. FOXM1 upregulation in primary human keratinocytes triggered pro-apoptotic/DNA-damage checkpoint response genes such as p21, p38 MAPK, p53 and PARP, however, without causing significant cell cycle arrest or cell death. Using a high-resolution Affymetrix genome-wide single nucleotide polymorphism (SNP) mapping technique, we provided the evidence that FOXM1 upregulation in epidermal keratinocytes is sufficient to induce genomic instability, in the form of loss of heterozygosity (LOH) and copy number variations (CNV). FOXM1-induced genomic instability was significantly enhanced and accumulated with increasing cell passage and this instability was increased even further upon exposure to UVB resulting in whole chromosomal gain (7p21.3-7q36.3) and segmental LOH (6q25.1-6q25.3).

Conclusion

We hypothesise that prolonged and repeated UVB exposure selects for skin cells bearing stable FOXM1 protein causes aberrant cell cycle checkpoint thereby allowing ectopic cell cycle entry and subsequent genomic instability. The aberrant upregulation of FOXM1 serves as a 'first hit' where cells acquire genomic instability which in turn predisposes cells to a 'second hit' whereby DNA-damage checkpoint response (eg. p53 or p16) is abolished to allow damaged cells to proliferate and accumulate genetic aberrations/mutations required for cancer initiation.

The Fox genes in the liver: from organogenesis to functional integration

Formation and function of the liver are highly controlled, essential processes. Multiple signaling pathways and transcriptional regulatory networks cooperate in this complex system. The evolutionarily conserved FOX, for Forkhead bOX, class of transcriptional regulators is critical to many aspects of liver development and function. The FOX proteins are small, mostly monomeric DNA binding factors containing the so-called winged helix DNA binding motif that distinguishes them from other classes of transcription factors. We discuss the biochemical and genetic roles of Foxa, Foxl1, Foxm1, and Foxo, as these have been shown to regulate many processes throughout the life of the organ, controlling both formation and function of the liver.

Phenotype-assisted transcriptome analysis identifies FOXM1 downstream from Ras-MKK3-p38 to regulate in vitro cellular invasion

The Ras oncogene is known to activate three major MAPK pathways, ERK, JNK, p38 and exert distinct cellular phenotypes, that is, apoptosis and invasion through the Ras-MKK3-p38-signaling cascade. We attempted to identify the molecular targets of this pathway that selectively govern the invasive phenotype. Stable transfection of NIH3T3 fibroblasts with MKK3(act) cDNA construct revealed similar p38-dependent in vitro characteristics observed in Ha-Ras(EJ)-transformed NIH3T3 cells, including enhanced invasiveness and anchorage-independent growth correlating with p38 phosphorylation status. To identify the consensus downstream targets of the Ras-MKK3-p38 cascade involved in invasion, in vitro invasion assays were used to isolate highly invasive cells from both, MKK3 and Ha-Ras(EJ) transgenic cell lines. Subsequently a genome-wide transcriptome analysis was employed to investigate differentially regulated genes in invasive Ha-Ras(EJ)- and MKK3(act)-transfected NIH3T3 fibroblasts. Using this phenotype-assisted approach combined with system level protein-interaction network analysis, we identified FOXM1, PLK1 and CDK1 to be differentially regulated in invasive Ha-Ras(EJ)-NIH3T3 and MKK3(act)-NIH3T3 cells. Finally, a FOXM1 RNA-knockdown approach revealed its requirement for both invasion and anchorage-independent growth of Ha-Ras(EJ)- and MKK3(act)-NIH3T3 cells. Together, we identified FOXM1 as a key downstream target of Ras and MKK3-induced cellular in vitro invasion and anchorage-independent growth signaling.

Aging and liver regeneration

The loss of regenerative capacity is the most dramatic age-associated alteration in the liver. Although this phenomenon was reported over 50 years ago, the molecular basis for the loss of regenerative capacity of aged livers has not been fully elucidated. Aging causes alterations of several signal-transduction pathways and changes in the expression of CCAAT/enhancer-binding protein (C/EBP) and chromatin-remodeling proteins. Consequently, aging livers accumulate a multi-protein C/EBPalpha-Brm-HDAC1 complex that occupies and silences E2F-dependent promoters, reducing the regenerative capacity of livers in older mice. Recent studies have provided evidence for the crucial role of epigenetic silencing in the age-dependent inhibition of liver proliferation. This review focuses on mechanisms of age-dependent inhibition of liver proliferation and approaches for correcting liver regeneration in the elderly.

FoxM1c counteracts oxidative stress-induced senescence and stimulates Bmi-1 expression

The Forkhead box transcription factor FoxM1 is expressed in proliferating cells. When it was depleted in mice and cell lines, cell cycle defects and chromosomal instability resulted. Premature senescence was observed in embryonic fibroblasts derived from FoxM1 knock-out mice, but the underlying cause has remained unclear. To investigate whether FoxM1 can protect cells against stress-induced premature senescence, we established NIH3T3 lines with doxycycline-inducible overexpression of FoxM1c. Treatment of these lines with sublethal doses (20 and 100 microm) of H(2)O(2) induced senescence with senescence-associated beta-galactosidase expression and elevated levels of p53 and p21. Induction of FoxM1c expression markedly suppressed senescence and expression of p53 and p21. Consistent with down-regulation of the p19(Arf)-p53 pathway, p19(Arf) levels decreased while expression of the Polycomb group protein Bmi-1 was induced. That Bmi-1 is a downstream target of FoxM1c was further supported by the dose-dependent induction of Bmi-1 by FoxM1c at both the protein and mRNA levels, and FoxM1 and Bmi-1 reached maximal levels in cells at the G(2)/M phase. Depletion of FoxM1 by RNA interference decreased Bmi-1 expression. Using Bmi-1 promoter reporters with wild-type and mutated c-Myc binding sites and short hairpin RNAs targeting c-Myc, we further demonstrated that FoxM1c activated Bmi-1 expression via c-Myc, which was recently reported to be regulated by FoxM1c. Our results reveal a functional link between FoxM1c, c-Myc, and Bmi-1, which are major regulators of tumorigenesis. This link has important implications for the regulation of cell proliferation and senescence by FoxM1 and Bmi-1.

RNA from brush oral cytology to measure squamous cell carcinoma gene expression

BACKGROUND

RNA expression analysis of oral keratinocytes can be used to detect early stages of disease such as oral cancer or to monitor on-going treatment responses of the same or other oral diseases. A limitation is the inability to obtain high quality RNA from oral tissue without using biopsies. While oral cytology cell samples can be obtained from patients in a minimally invasive manner they have not been validated for quantitative analysis of RNA expression.

METHODS

As a starting point in the analysis of tumor markers in oral squamous cell carcinoma (OSCC), we examined RNA in brush cytology samples from hamsters treated with dibenzo[a,l]pyrene to induce oral carcinoma. Three separate samples from each animal were assessed for expression of candidate marker genes and control genes measured with real-time RT-PCR.

RESULTS

Brush oral cytology samples from normal mucosa were shown to consist almost exclusively of epithelial cells. Remarkably, ss-2 microglobulin and cytochrome p450, 1B1 (CYP1B1) RNA showed potential utility as markers of OSCC in samples obtained in this rapid and non-surgical manner.

CONCLUSION

Brush oral cytology may prove useful as a source of RNA for gene expression analysis during the progression of diseases of the oral epithelium such as OSCC.

FOXM1, a typical proliferation-associated transcription factor

FOXM1 is a typical proliferation-associated transcription factor: it stimulates proliferation by promoting S-phase entry as well as M-phase entry and is involved in proper execution of mitosis. Accordingly, FOXM1 regulates genes that control G1/S-transition, S-phase progression, G2/M-transition and M-phase progression. Consistently, its expression and its activity are antagonistically regulated by many important proliferation and anti-proliferation signals. Furthermore, FOXM1 is implicated in tumorigenesis and contributes to both tumor initiation and progression. In addition to its function as a conventional transcription factor, FOXM1 transactivates the human c-myc P1 and P2 promoters directly via their TATA-boxes by a new transactivation mechanism, which it also employs for transactivation of the human c-fos, hsp70 and histone H2B/a promoters. This review summarizes the current knowledge on FOXM1, in particular its two different transactivation mechanisms, the regulation of its transcriptional activity by proliferation versus anti-proliferation signals and its function in normal cell cycle progression and tumorigenesis.

FoxM1 regulates growth factor-induced expression of kinase-interacting stathmin (KIS) to promote cell cycle progression

The Forkhead box M1 (FoxM1) transcription factor is essential for cell cycle progression and mitosis. FoxM1 regulates expression of Skp2 and Cks1, subunits of the SCF ubiquitin ligase complex, which ubiquitinates p27(Kip1) and targets it for degradation. Kinase-interacting stathmin (KIS) is a growth factor-dependent nuclear kinase that regulates cell cycle progression by phosphorylating p27(Kip1) to promote its nuclear export. Here we present an additional mechanism of FoxM1-mediated regulation of p27(Kip1) and provide evidence that FoxM1 regulates growth factor-induced expression of KIS. In cells harboring FoxM1 deletion or expressing FoxM1-short interfering RNA, the expression of KIS is impaired, leading to an accumulation of p27(Kip1) in the nucleus. Furthermore, we show that KIS is a direct transcriptional target of FoxM1. Thus FoxM1 promotes cell cycle progression by down-regulating p27(Kip1) through multiple mechanisms.

Transplanted hepatocytes over-expressing FoxM1B efficiently repopulate chronically injured mouse liver independent of donor age

Orthotopic liver transplantation is limited by the shortage of liver donors, leading to elderly patients being enrolled as donors with increasing frequency. Alternative strategies such as cell therapy are therefore needed. Because transplanted hepatocytes do not proliferate into a recipient liver, repopulation strategies have been developed. We have previously published a proof of concept that hepatocytes harboring a survival selective advantage can efficiently repopulate a mouse liver. We develop here an alternative approach by conferring a selective proliferative advantage on transplanted hepatocytes over resident ones. FoxM1B is a transcription factor that, when over-expressed into hepatocytes, accelerates the cell cycle and maintains the hepatocyte in vivo proliferative capacity of aged livers. We now demonstrate that transplanted hepatocytes over-expressing FoxM1B repopulate the liver of mice subjected to continuous injury far more efficiently than control hepatocytes. We show that old hepatocytes that over-express FoxM1B retain their cell division capacity and repopulate liver as well as young ones, in contrast with old non-modified hepatocytes, which lose their proliferative capacity. In conclusion, our results point to the potential use of FoxM1B expression in hepatocyte-based therapy protocols in diseases where host hepatocytes are chronically injured, especially if donor hepatocytes come from old livers.

FoxM1: at the crossroads of ageing and cancer

Forkhead transcription factors are intimately involved in the regulation of organismal development, cell differentiation and proliferation. Here we review the current knowledge of the role played by FoxM1 in these various processes. This particular member of the Forkhead family is broadly expressed in actively dividing cells and is crucial for cell cycle-dependent gene expression in the G2 phase of the cell cycle. FoxM1 plays a crucial role in insuring the fidelity of the cell division process, as inhibition of FoxM1 activity results in serious aberrancies during mitosis, such as frequent chromosome missegregation, defects in cytokinesis and overt aneuploidy. FoxM1 expression also appears to be tightly correlated with the proliferative rate of a cell. For example, FoxM1 is one of the most significantly down-regulated genes in prematurely aged human fibroblasts (Progeria syndrome), while elevated expression of FoxM1 is seen in most human carcinomas. These observations suggest that interference with FoxM1 activity may contribute to the increase in mitotic errors seen in human diseases such as cancer and early onset of ageing diseases. In this review, several aspects of FoxM1 function will be discussed, as well as their implication in tumorigenesis.

Despite its strong transactivation domain, transcription factor FOXM1c is kept almost inactive by two different inhibitory domains

FOXM1c (MPP2) is an activating transcription factor with several nuclear localization signals, a forkhead domain for DNA binding, and a very strong acidic transactivation domain. Despite its very strong transactivation domain, FOXM1c is kept almost inactive by two different independent inhibitory domains, the N-terminus and the central domain. The N-terminus as a specific negative-regulatory domain directly binds to and thus inhibits the transactivation domain completely. However, it lacks any transrepression potential. In contrast, the central domain functions as a strong RB-independent transrepression domain and as an RB-recruiting negative-regulatory domain. The N-terminus alone is sufficient to eliminate transactivation, while the central domain alone represses the transactivation domain only partially. This hierarchy of the two inhibitory domains offers the possibility to activate the almost inactive wild type in two steps in vitro: deletion of the N-terminus results in a strong transactivator, while additional deletion of the central domain in a very strong transactivator. We suggest that the very high potential of the transactivation domain has to be tightly controlled by these two inhibitory domains because FOXM1 stimulates proliferation by promoting G1/S transition, as well as G2/M transition, and because deregulation of such potent activators of proliferation can result in tumorigenesis.

New and unexpected: forkhead meets ARF

Recent genetic studies demonstrate that mice deficient in the forkhead box m1b (Foxm1b) transcription factor are highly resistant to developing hepatocellular carcinoma, which is among the most lethal cancers worldwide. In addition, the Foxm1b transcription factor was identified as a novel inhibitory target of the p19ARF tumor suppressor during early stages of liver tumorigenesis, but p19ARF expression is extinguished in hepatic tumors that develop at later stages. Structure-function studies demonstrate that amino acids 26-46 of the p19ARF protein are sufficient to bind Foxm1b and reduce Foxm1b transcriptional activity by targeting it to the nucleolus. A peptide containing amino acids 24-46 of p19ARF, which was modified to enhance cellular uptake, is an effective inhibitor of Foxm1b transcriptional activity and prevents Foxm1b stimulation of anchorage-independent growth of cells on soft agar. Thus, the p19ARF peptide is an effective inhibitor of Foxm1b and represents a potential therapy for hepatocellular carcinoma.

Foxm1b transcription factor is essential for development of hepatocellular carcinomas and is negatively regulated by the p19ARF tumor suppressor

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide. Here, we provide evidence that the Forkhead Box (Fox) m1b (Foxm1b or Foxm1) transcription factor is essential for the development of HCC. Conditionally deleted Foxm1b mouse hepatocytes fail to proliferate and are highly resistant to developing HCC in response to a Diethylnitrosamine (DEN)/Phenobarbital (PB) liver tumor-induction protocol. The mechanism of resistance to HCC development is associated with nuclear accumulation of the cell cycle inhibitor p27(Kip1) protein and reduced expression of the Cdk1-activator Cdc25B phosphatase. We showed that the Foxm1b transcription factor is a novel inhibitory target of the p19(ARF) tumor suppressor. Furthermore, we demonstrated that conditional overexpression of Foxm1b protein in osteosarcoma U2OS cells greatly enhances anchorage-independent growth of cell colonies on soft agar. A p19(ARF) 26-44 peptide containing nine D-Arg to enhance cellular uptake of the peptide was sufficient to significantly reduce both Foxm1b transcriptional activity and Foxm1b-induced growth of U2OS cell colonies on soft agar. These results suggest that this (D-Arg)(9)-p19(ARF) 26-44 peptide is a potential therapeutic inhibitor of Foxm1b function during cellular transformation. Our studies demonstrate that the Foxm1b transcription factor is required for proliferative expansion during tumor progression and constitutes a potential new target for therapy of human HCC tumors.