The FOXM1 transcriptional factor promotes the proliferation of leukemia cells through modulation of cell cycle progression in acute myeloid leukemia

Regulation of HOX gene expression in AML

As key developmental regulators, HOX cluster genes have varied and context-specific roles in normal and malignant hematopoiesis. A complex interaction of transcription factors, epigenetic regulators, long non-coding RNAs and chromatin structural changes orchestrate HOX expression in leukemia cells. In this review we summarize molecular mechanisms underlying HOX regulation in clinical subsets of AML, with a focus on NPM1 mutated (NPM1mut) AML comprising a third of all AML patients. While the leukemia initiating function of the NPM1 mutation is clearly dependent on HOX activity, the favorable treatment responses in these patients with upregulation of HOX cluster genes is a poorly understood paradoxical observation. Recent data confirm FOXM1 as a suppressor of HOX activity and a well-known binding partner of NPM suggesting that FOXM1 inactivation may mediate the effect of cytoplasmic NPM on HOX upregulation. Conversely the residual nuclear fraction of mutant NPM has also been recently shown to have chromatin modifying effects permissive to HOX expression. Recent identification of the menin-MLL interaction as a critical vulnerability of HOX-dependent AML has fueled the development of menin inhibitors that are clinically active in NPM1 and MLL rearranged AML despite inconsistent suppression of the HOX locus. Insights into context-specific regulation of HOX in AML may provide a solid foundation for targeting this common vulnerability across several major AML subtypes.

FOXM1: a new therapeutic target of extramammary Paget disease

Extramammary Paget disease (EMPD) is a rare skin cancer that primarily affects older individuals predominantly in areas with apocrine sweat glands. Although most early EMPD lesions are indolent, patients with metastatic EMPD have a poor prognosis due to the lack of effective systemic treatment. In this study, we investigated the role of forkhead box M1 (FOXM1), a potent transcription factor, in EMPD and assessed the potential of FOXM1 as a therapeutic target. Immunohistochemistry of 112 primary and 17 metastatic EMPD samples revealed that FOXM1 expression increased with tumor progression. Patients in whom FOXM1 was expressed in more than 10% of tumor cells had significantly shorter disease-specific survival than the other patients (p = 0.0397). In in vitro studies using our newly established EMPD cell line, KS-EMPD-1, we found high expression of FOXM1. Knockdown of FOXM1 impaired tumor cell viability, migration, and invasion. Inhibition of FOXM1 using thiostrepton also reduced tumor cell viability in a dose-dependent manner. These findings suggest that FOXM1 is a promising therapeutic target for patients with EMPD.

Peptide-based PROTAC degrader of FOXM1 suppresses cancer and decreases GLUT1 and PD-L1 expression

Background

Peptide proteolysis-targeting chimeras (p-PROTACs) with advantages of high specificity and low toxicity have emerged as a powerful technology of targeted protein degradation for biomedical applications. FOXM1, a proliferation-associated transcription factor, is overexpressed in a variety of human tumors as a key driver of tumorigenesis and cancer progression, and is a potential anticancer therapeutic target. However, FOXM1-targeting p-PROTACs has not been researched.

Methods

Here, we first analyzed the expression of FOXM1, GLUT1 and PD-L1 in liver cancer through database and clinical samples of patients. FOXM1-targeting peptides, selected by screening phage display library, are verified its targeting effect by immunofluorescence and CCK-8 test. The novel p-PROTAC degrader of FOXM1 is chemically synthesis, named FOXM1-PROTAC, by linking a FOXM1-binding antagonistic peptide, with the E3 ubiquitin ligase recruitment ligand Pomalidomide and with the cell membrane penetrating peptide TAT. Its degradation effect on FOXM1 was detected by Western blotting, qPCR, and we verified its effect on the behavior of cancer cells by flow cytometry, scratch assay, and Transwell in vitro. The tumor xenografted mice model was used for evaluating FOXM1-PROTAC therapeutic response in vivo. Finally, we detected the expression of GLUT1 and PD-L1 after FOXM1-PROTAC degraded FOXM1 by using Western Blotting and hippocampal detectors and dual immunofluorescence.

Results

We found that the novel FOXM1-PROTAC efficiently entered cells and induced degradation of FOXM1 protein, which strongly inhibits viability as well as migration and invasion in various cancer cell lines, and suppressed tumor growth in HepG2 and MDA-MB-231 cells xenograft mouse models, without detected toxicity in normal tissues. Meanwhile, FOXM1-PROTAC decreased the cancer cells glucose metabolism via downregulating the protein expression levels of glucose transporter GLUT1 and the immune checkpoint PD-L1, which suggests involvement of FOXM1 in cancer cell metabolism and immune regulation.

Conclusions

Our results indicate that biologically targeted degradation of FOXM1 is an attractive therapeutic strategy, and antagonist peptide-containing FOXM1-PROTACs as both degrader and inhibitor of FOXM1 could be developed as a safe and promising drug for FOXM1-overexpressed cancer therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02483-2.

DRP1 contributes to head and neck cancer progression and induces glycolysis through modulated FOXM1/MMP12 axis

Abnormal DRP1 expression has been identified in a variety of human cancers. However, the prognostic potential and mechanistic role of DRP1 in head and neck cancer (HNC) are currently poorly understood. Here, we demonstrated a significant upregulation of DRP1 in HNC tissues, and that DRP1 expression correlates with poor survival of HNC patients. Diminished DRP1 expression suppressed tumor growth and metastasis in both in vitro and in vivo models. DRP1 expression was positively correlated with FOXM1 and MMP12 expression in HNC patient samples, suggesting pathological relevance in the context of HNC development. Moreover, DRP1 depletion affected aerobic glycolysis through the downregulation of glycolytic genes, and overexpression of MMP12 in DRP1‐depleted cells could help restore glucose consumption and lactate production. Using ChIP‐qPCR, we showed that DRP1 modulates FOXM1 expression, which can enhance MMP12 transcription by binding to its promoter. We also showed that miR‐575 could target 3’UTR of DRP1 mRNA and suppress DRP1 expression. Collectively, our study provides mechanistic insights into the role of DRP1 in HNC and highlights the potential of targeting the miR‐575/DRP1/FOXM1/MMP12 axis as a novel therapy for the prevention of HNC progression.

USP21 regulates Hippo signaling to promote radioresistance by deubiquitinating FOXM1 in cervical cancer

The ectopic expression of ubiquitin-specific peptidase 21 (USP21) is common in different types of cancer. However, its relationship with radio-sensitivity in cervical cancer (CC) remains unclear. In this study, we aimed to uncover the effect of USP21 on CC radio-resistance and its underlying mechanism. Our results showed that the expression of USP21 was markedly increased in CC tissues of radio-resistant patients and CC cells treated with radiation. Besides, knockdown of USP21 restrained the survival fractions, and facilitated apoptosis of CC cells in the absence or presence of radiation. Additionally, USP21 in combination with FOXM1 regulated the stability and ubiquitination of FOXM1. However, FOXM1 reversed the effects of USP21 knockdown on the radio-resistance of CC cells. Furthermore, FOXM1 knockdown activated the Hippo pathway by inhibiting the nuclear translocation of Yes-associated protein 1 (YAP1), and FOXM1 knockdown attenuated the radio-resistance of CC cells via inhibiting the Hippo-YAP1 pathway. USP21 activated the Hippo pathway by mediating FOXM1. Knockdown of USP21 enhanced the radio-sensitivity of CC cells in vivo. In summary, USP21 contributed to the radio-resistance of CC cells via FOXM1/Hippo signaling, and may serve as a promising target for radio-sensitizers in the radiotherapy of CC.

Blast cells surviving acute myeloid leukemia induction therapy are in cycle with a signature of FOXM1 activity

BACKGROUND

Disease relapse remains common following treatment of acute myeloid leukemia (AML) and is due to chemoresistance of leukemia cells with disease repopulating potential. To date, attempts to define the characteristics of in vivo resistant blasts have focused on comparisons between leukemic cells at presentation and relapse. However, further treatment responses are often seen following relapse, suggesting that most blasts remain chemosensitive. We sought to characterise in vivo chemoresistant blasts by studying the transcriptional and genetic features of blasts from before and shortly after induction chemotherapy using paired samples from six patients with primary refractory AML.

METHODS

Leukemic blasts were isolated by fluorescence-activated cell sorting. Fluorescence in situ hybridization (FISH), targeted genetic sequencing and detailed immunophenotypic analysis were used to confirm that sorted cells were leukemic. Sorted blasts were subjected to RNA sequencing. Lentiviral vectors expressing short hairpin RNAs were used to assess the effect of FOXM1 knockdown on colony forming capacity, proliferative capacity and apoptosis in cell lines, primary AML cells and CD34+ cells from healthy donors.

RESULTS

Molecular genetic analysis revealed early clonal selection occurring after induction chemotherapy. Immunophenotypic characterisation found leukemia-associated immunophenotypes in all cases that persisted following treatment. Despite the genetic heterogeneity of the leukemias studied, transcriptional analysis found concerted changes in gene expression in resistant blasts. Remarkably, the gene expression signature suggested that post-chemotherapy blasts were more proliferative than those at presentation. Resistant blasts also appeared less differentiated and expressed leukemia stem cell (LSC) maintenance genes. However, the proportion of immunophenotypically defined LSCs appeared to decrease following treatment, with implications for the targeting of these cells on the basis of cell surface antigen expression. The refractory gene signature was highly enriched with targets of the transcription factor FOXM1. shRNA knockdown experiments demonstrated that the viability of primary AML cells, but not normal CD34+ cells, depended on FOXM1 expression.

CONCLUSIONS

We found that chemorefractory blasts from leukemias with varied genetic backgrounds expressed a common transcriptional program. In contrast to the notion that LSC quiescence confers resistance to chemotherapy we find that refractory blasts are both actively proliferating and enriched with LSC maintenance genes. Using primary patient material from a relevant clinical context we also provide further support for the role of FOXM1 in chemotherapy resistance, proliferation and stem cell function in AML.

Thiostrepton inhibits growth and induces apoptosis by targeting FoxM1/SKP2/MTH1 axis in B-precursor acute lymphoblastic leukemia cells

Forkhead box M1 (FoxM1) is a transcription factor that plays an important role in the etiology of many cancers, however, its role has not been elucidated in B-precursor acute lymphoblastic leukemia (B-pre-ALL). In the current study, we showed that the downregulation of FoxM1 by its inhibitor thiostrepton inhibited cell viability and induced caspase-dependent apoptosis in a panel of B-pre-ALL cell lines. Thiostrepton led downregulation of FoxM1 accompanied by decreased expression of Aurora kinase A, B, matrix metalloproteinases, and oncogene SKP2 as well as MTH1. Downregulation of the FoxM1/SKP2/MTH1 axis led to increase in the Bax/Bcl2 ratio and suppression of antiapoptotic proteins. Thiostrepton-mediated apoptosis was prevented by N-acetyl cysteine, a scavenger of reactive oxygen species. Co-treatment of B-pre-ALL with subtoxic doses of thiostrepton and bortezomib potentiated the proapoptotic action. Altogether, our results suggest that targeting FoxM1expression could be an attractive strategy for the treatment of B-pre-ALL.

Acyl-CoA synthetase-4 mediates radioresistance of breast cancer cells by regulating FOXM1

The development of radioresistance during radiotherapy is a major cause of tumor recurrence and metastasis. To provide new insights of the mechanisms underlying radioresistance, we established radioresistant cell lines derived from two different subtypes of breast cancer cells, HER2-positive SK-BR-3 and ER-positive MCF-7 breast cancer cells, by exposing cells to 48 ~ 70 Gy of radiation delivered at 4-5 Gy twice weekly over 9 ~ 10 months. The established radioresistant SK-BR-3 (SR) and MCF-7 (MR) cells were resistant not only to a single dose of radiation (2 Gy or 4 Gy) but also to fractionated radiation delivered at 2 Gy/day for 5 days. Furthermore, these cells exhibited tumor-initiating potential in vivo and high CD24-/CD44 + ratio. To identify novel therapeutic molecular targets, we analyzed differentially expressed genes in both radioresistant cell lines and found that the expression of ACSL4 was significantly elevated in both cell lines. Targeting ACSL4 improved response to irradiation and inhibited migration activities. Furthermore, inhibition of ACLS4 using ASCL4 siRNA or triacsin C suppressed FOXM1 expression, whereas inhibition of FOXM1 using thiostrepton did not affect ACSL4 expression. Targeting the ACSL4-FOXM1 signaling axis by inhibiting ASCL4 or FOXM1 overcame the radioresistance by suppressing DNA damage responses and inducing apoptosis. This is the first study to report that ACSL4 plays a crucial role in mediating the radioresistance of breast cancer by regulating FOXM1. We propose the ACSL4-FOXM1 signaling axis be considered a novel therapeutic target in radioresistant breast cancer and suggest treatment strategies targeting this signaling axis might overcome breast cancer radioresistance.

Cell cycle arrest-mediated cell death by morin in MDA-MB-231 triple-negative breast cancer cells

BACKGROUND

Morin, a flavonoid extracted from Moraceace family and exhibits several pharmacological activities including anti-cancer activity. Although the anticancer activity of morin in breast cancer was estimated in some investigations, the pharmaceutical mechanism has not been fully elucidated. Therefore, we investigated to unveil the detail signaling pathway in morin-treated in MDA-MB-231 triple-negative breast cancer cells.

METHODS

The cytotoxicity of morin in MDA-MB-231 cells was confirmed by sulforhodamine B (SRB) assay and colony formation assay. Flow cytometry was performed to examine the cell cycle and cell death patterns and the protein expression and phosphorylation were detected by western blotting.

RESULTS

Our results showed that morin inhibited MDA-MB-231 cells proliferation in time and concentration-dependent manner. Morphological changes were observed when treated with various concentration of morin in MDA-MB-231 cells. In regard to protein expression, morin induced the phosphorylation of ERK and p-H2A.X and decreased the level of DNA repair markers, RAD51 and survivin. In addition, flow cytometry showed S and G2/M arrest by morin that was associated with the decrease in the protein expression of cyclin A2 and cyclin B1 and upregulation of p21. Interestingly, annexin V/PI staining result clearly showed that morin induced cell death without apoptosis. Furthermore, attenuated FoxM1 by morin was co-related with cell cycle regulators including p21, cyclin A2 and cyclin B1.

CONCLUSION

Taken together, our study indicates that morin-induced cell death of MDA-MB-231 is caused by sustained cell cycle arrest via the induction of p21 expression by activation of ERK and repression of FOXM1 signaling pathways.

Liposomal Thiostrepton Formulation and Its Effect on Breast Cancer Growth Inhibition

Forkhead box M1 (FOXM1) is known to play a role in breast cancer progression. FOXM1 inhibition becomes one of the strategies in developing the novel cancer therapy. Recently, thiostrepton has been recognized as a potent FOXM1 inhibitor. To improve its potential, we aimed to develop a nanodelivery system for thiostrepton. Here, liposome-encapsulated thiostrepton (TSLP) was developed. Physiochemical properties were characterized by TEM and dynamic light scattering technique. The biological activities were also evaluated, by cellular internalization, MTT assay, spheroid formation assay and RT-PCR. The result showed that the range sizes of TSLP were 152 ± 2 nm, polydispersity index (PdI) of 0.23 ± 0.02 and zeta potential of -20.2 ± 0.1 mV. As expected, TSLP showed a higher potential in reducing FOXM1 levels in MCF-7 cells than free thiostrepton. Additionally, TSLP significantly improved the efficiently and specificity of thiostrepton in reducing cell viability of MCF-7, but not of the fibroblast (HDFn) cells. Interestingly, TSLP had an ability to induce MCF-7 cell death in both 2D monolayer and 3D spheroid culture. In conclusions, TSLP could possibly be one of the potential developments using nano-delivery system to improve abilities and specificity of thiostrepton in breast cancer cell inhibition and death inducing, with decreasing non-specific toxicity.

FOXM1 modulates docetaxel resistance in prostate cancer by regulating KIF20A

Background

Docetaxel resistance affects prognosis in advanced prostate cancer (PCa). The precise mechanisms remain unclear. Transcription factor Forkhead box M1 (FOXM1), which participates in cell proliferation and cell cycle progression, has been reported to affect the sensitivity of chemotherapy. This study explores the role of FOXM1 in PCa docetaxel resistance and its association with kinesin family member 20 A (KIF20A), which is known to promote therapeutic resistance in some cancers.

Methods

We monitored cell growth using MTT and colony formation assays, and cell apoptosis and cell cycle progression using flow cytometry. Wound-healing and transwell assays were used to detect cell invasion and migration. mRNA and protein expression were analyzed using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blotting. We monitored FOXM1 binding to the KIF20A promoter using a ChIP assay. Tumorigenicity in nude mice was used to assess in vivo tumorigenicity.

Results

FOXM1 knockdown induced cell apoptosis and G2/M cell cycle arrest, suppressing cell migration and invasion in docetaxel-resistant PCa cell lines (DU145-DR and VCaP-DR). Exogenous FOXM1 overexpression was found in their parental cells. Specific FOXM1 inhibitor thiostrepton significantly weakened docetaxel resistance in vitro and in vivo. We also found that FOXM1 and KIF20A exhibited consistent and highly correlated overexpression in PCa cells and tissues. FOXM1 also regulated KIF20A expression at the transcriptional level by acting directly on a Forkhead response element (FHRE) in its promoter. KIF20A overexpression could partially reverse the effect on cell proliferation, cell cycle proteins (cyclinA2, cyclinD1 and cyclinE1) and apoptosis protein (bcl-2 and PARP) of FOXM1 depletion.

Conclusions

Our findings indicate that highly expressed FOXM1 may help promote docetaxel resistance by inducing KIF20A expression, providing insight into novel chemotherapeutic strategies for combatting PCa docetaxel resistance.

Transcriptional landscape of cholangiocarcinoma revealed by weighted gene coexpression network analysis

Cholangiocarcinoma (CCA) is a type of cancer with limited treatment options and a poor prognosis. Although some important genes and pathways associated with CCA have been identified, the relationship between coexpression and phenotype in CCA at the systems level remains unclear. In this study, the relationships underlying the molecular and clinical characteristics of CCA were investigated by employing weighted gene coexpression network analysis (WGCNA). The gene expression profiles and clinical features of 36 patients with CCA were analyzed to identify differentially expressed genes (DEGs). Subsequently, the coexpression of DEGs was determined by using the WGCNA method to investigate the correlations between pairs of genes. Network modules that were significantly correlated with clinical traits were identified. In total, 1478 mRNAs were found to be aberrantly expressed in CCA. Seven coexpression modules that significantly correlated with clinical characteristics were identified and assigned representative colors. Among the 7 modules, the green and blue modules were significantly related to tumor differentiation. Seventy-eight hub genes that were correlated with tumor differentiation were found in the green and blue modules. Survival analysis showed that 17 hub genes were prognostic biomarkers for CCA patients. In addition, we found five new targets (ISM1, SULT1B1, KIFC1, AURKB and CCNB1) that have not been studied in the context of CCA and verified their differential expression in CCA through experiments. Our results not only promote our understanding of the relationship between the transcriptome and clinical data in CCA but will also guide the development of targeted molecular therapy for CCA.

Rosmarinic Acid Methyl Ester Regulates Ovarian Cancer Cell Migration and Reverses Cisplatin Resistance by Inhibiting the Expression of Forkhead Box M1

Rosmarinic acid methyl ester (RAME), a derivative of rosmarinic acid (RA), is reported to have several therapeutic effects, including anti-tumor effects against cervical cancer. However, its anti-tumor effects in ovarian cancer is unclear. In this study, we studied the molecular pathways associated with the anti-tumor effects of RAME in ovarian cancer. To identify the effects of RAME in ovarian cancer, RNA sequencing was performed in RAME-treated ovarian cancer cells; we found that RAME treatment downregulated the genes closely involved with the target genes of the transcription factor Forkhead box M1 (FOXM1). It was reported that FOXM1 is overexpressed in a variety of cancer cells and is associated with cell proliferation and tumorigenesis. Therefore, we hypothesized that FOXM1 is a key target of RAME; this could result in its anti-tumor effects. Treatment of ovarian cancer cells with RAME-inhibited cell migration and invasion, as shown by wound healing and transwell migration assays. To examine whether RAME represses the action of FOXM1, we performed quantitative RT-PCR and ChIP-qPCR. Treatment of ovarian cancer cells with RAME decreased the mRNA expression of FOXM1 target genes and the binding of FOXM1 to its target genes. Moreover, FOXM1 expression was increased in cisplatin-resistant ovarian cancer cells, and combination treatment with RAME and cisplatin sensitized the cisplatin-resistant ovarian cancer cells, which was likely due to FOXM1 inhibition. Our research suggests that RAME is a promising option in treating ovarian cancer patients, as it revealed a novel molecular pathway underlying its anti-tumor effects.

SP1-independent inhibition of FOXM1 by modified thiazolidinediones

This research article describes an approach to modify the thiazolidinedione scaffold to produce test drugs capable of binding to, and inhibit, the in vitro transcriptional activity of the oncogenic protein FOXM1. This approach allowed us to obtain FOXM1 inhibitors that bind directly to the FOXM1-DNA binding domain without targeting the expression levels of Sp1, an upstream transcription factor protein known to activate the expression of FOXM1. Briefly, we modified the chemical structure of the thiazolidinedione scaffold present in anti-diabetic medications such as pioglitazone, rosiglitazone and the former anti-diabetic drug troglitazone, because these drugs have been reported to exert inhibition of FOXM1 but hit other targets as well. After the chemical synthesis of 11 derivatives possessing a modified thiazolidinedione moiety, we screened all test compounds using in vitro protocols to measure their ability to (a) dissociate a FOXM1-DNA complex (EMSA assay); (b) decrease the expression of FOXM1 in triple negative-breast cancer cells (WB assay); (c) downregulate the expression of FOXM1 downstream targets (luciferase reporter assays and qPCR); and inhibit the formation of colonies of MDA-MB-231 cancer cells (colony formation assay). We also identified a potential binding mode associated with these compounds in which compound TFI-10, one of the most active molecules, exerts binding interactions with Arg289, Trp308, and His287. Unlike the parent drug, troglitazone, compound TFI-10 does not target the in vitro expression of Sp1, suggesting that it is possible to design FOXM1 inhibitors with a better selectivity profile.

A non-viral nano-delivery system targeting epigenetic methyltransferase EZH2 for precise acute myeloid leukemia therapy

Acute myeloid leukemia (AML), which is common in the elderly population, accounts for poor long-term survival with a high possibility of relapse. The associated lack of currently developed therapeutics is directing the search for new therapeutic targets relating to AML. EZH2 (Enhancer of Zeste Homolog 2) is a histone methyltransferase member of the polycomb-group (PcG) family, and its significant overexpression in AML means it has emerged as a potential epigenetic target. Here, we propose the human serum albumin (HSA) nanoparticle based delivery of small interfering RNA (siRNA), which can target EZH2-expressing genes in AML. EZH2 specific siRNA loaded in a polyethyleneimine (PEI) conjugated HSA nanocarrier can overcome the systemic instability of siRNA and precisely target the AML cell population for increased EZH2 gene silencing. A stable nanosized complex (HSANPs-PEI@EZH2siRNA), achieved via the electrostatic interaction of PEI and EZH2 siRNA, shows increased systemic stability and hemocompatibility, and enhanced EZH2 gene silencing activity in vitro, compared to conventional transfection reagents. HSANPs-PEI@EZH2siRNA-treated AML cells showed downregulated EZH2, which is associated with a reduced level of Bmi-1 protein, and H3K27me3 and H2AK119ub modification. The ubiquitin-mediated proteasomal degradation pathway plays a critical role in the downregulation of associated proteins following HSANPs-PEI@EZH2siRNA exposure to AML cells. c-Myb is the AML-responsive transcription factor that directly binds on the EZH2 promoter and was downregulated in HSANPs-PEI@EZH2siRNA-treated AML cells. The systemic exposure to HSANPs-PEI@EZH2siRNA of AML engrafted immunodeficient nude mice displayed efficient EZH2 gene silencing and a reduced AML cell population in peripheral blood and bone marrow. The present study demonstrates a non-viral siRNA delivery system for epigenetic targeting based superior anti-leukemic therapy.

Quercetin Promotes Cell Cycle Arrest and Apoptosis and Attenuates the Proliferation of Human Chronic Myeloid Leukemia Cell Line-K562 Through Interaction with HSPs (70 and 90), MAT2A and FOXM1

BACKGROUND

Chronic Myeloid Leukaemia (CML) starts in certain blood-forming cells of the bone marrow when cells acquire Philadelphia chromosome. Nowadays, scientists attempt to find novel and safe therapeutic agents and approaches for CML therapy using Tyrosine Kinase Inhibitors (TKIs), CML conventional treatment agents, has some restrictions and also adverse effects. Recently, it has been proposed that phytochemicals, such as flavonoids due to their low side effects and notable safety have the potential to be used for CML therapy.

MATERIALS AND METHODS

K-562 cells were exposed with three concentrations of the querectin (10, 40 and 80µM) for 12, 24 and 48 hours. After that, these cells apoptosis rate was estimated using Annexin-V/PI staining and flowcytometry analysis, and their proliferation rate was evaluated using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT). Finally, the expression of the 70 and 90 kilodalton heat shock proteins (HSP70 and 90), methionine adenosyltransferase 2A (MAT2A), Forkhead box protein M1 (FOXM1), caspase-3 and -8, Bcl-X(L) and Bax involved in leukemic cells survival and proliferation was assessed using Real-Time PCR within 12, 24 and 48 hours after exposure with quercetin 40 and 80µM.

RESULTS

Considering consequences, querecetin induced apoptosis in K-562 cells, and also abrogated these cells proliferation. On the other hand, RT-PCR results showed a reduction in some of the candidate genes expression, especially HSP70, Bcl-X(L) and FOXM1, when cells were treated with quercetin 40 and 80µM. Also, Bax, caspase-3 and caspase-8 expression was significantly improved in K-562 cells upon quercetin exposure.

CONCLUSION

We concluded that CML therapy by querecetin due to its anti-proliferative and anti-survival potentials could lead to the promising therapeutic outcome through targeting major survival and proliferation involved genes expression.

FOXM1 regulates leukemia stem cell quiescence and survival in MLL-rearranged AML

FOXM1, a known transcription factor, promotes cell proliferation in a variety of cancer cells. Here we show that Foxm1 is required for survival, quiescence and self-renewal of MLL-AF9 (MA9)-transformed leukemia stem cells (LSCs) in vivo. Mechanistically, Foxm1 upregulation activates the Wnt/β-catenin signaling pathways by directly binding to β-catenin and stabilizing β-catenin protein through inhibiting its degradation, thereby preserving LSC quiescence, and promoting LSC self-renewal in MLL-rearranged AML. More importantly, inhibition of FOXM1 markedly suppresses leukemogenic potential and induces apoptosis of primary LSCs from MLL-rearranged AML patients in vitro and in vivo in xenograft mice. Thus, our study shows a critical role and mechanisms of Foxm1 in MA9-LSCs, and indicates that FOXM1 is a potential therapeutic target for selectively eliminating LSCs in MLL-rearranged AML.

The Clinical and Experimental Research on the Treatment of Endometriosis with Thiostrepton

BACKGROUND/OBJECTIVE

Forkhead Box M1 (FOXM1) is frequently activated in tumors. We studied the expression and the possible mechanism of FOXM1 and evaluated the effects of thiostrepton in an endometriotic rat model.

METHODS AND MATERIAL

This was a randomized study in a rat model of endometriosis. Fifty female Wistar rats were surgically induced with endometriosis. After 4 weeks of observation, twenty and thirty rats were randomly allocated to an ovariectomized (OVX) group and a treatment group, respectively. The OVX group was ovariectomized and randomly divided into an OVX-estrogen group and a control (OVX -oil) group. All rats were allowed a resting period of 3 days prior to any operation. The rats in the estrogen group were given estradiol (20 µg/kg, 0.1 ml /d), while the control group was treated with an equivalent amount of sesame oil. Every group was injected with subcutaneous injection for 7 days. The treatment group was randomly divided into three groups to receive the following: TST at 150 mg/kg, ip.; TST at 250 mg/kg, ip.; or sterile normal saline, ip. The groups received these dosages every 2 days for 2 weeks. Lesion growth, histological examination, and protein expression were subsequently analyzed using caliper measurement, histology, immunostaining, and Western blot after each rat received an injection in its own group.

RESULTS

Our results showed that FOXM1 is enriched in nucleus of an ectopic endometrium when compared with a eutopic uterus. Furthermore, we found that an ERK/FOXM1/matrix metalloproteinase-9 (MMP9) signaling pathway might result in the establishment and development of endometriosis. Finally, a thiostrepton concentration dependently reduced the expression of FOXM1, MMP9 and Bcl-2 in endometriotic lesions of the treated rats. Statistical significance was accepted for a value of P < 0.05.

CONCLUSION

We postulate that thiostrepton could inhibit the endometriotic lesions, at least in part, by decreasing the FOXM1 expression and exerting a pro-apoptotic effect. We reported for the first time that FOXM1 expresses in experimental endometriosis rat and thiostrepton may also be suitable for the administration of endometriosis by inhibiting the growth of endometriotic implants. More studies are needed to further evaluate thiostrepton's effect.

Silencing transcription factor FOXM1 represses proliferation, migration, and invasion while inducing apoptosis of liver cancer stem cells by regulating the expression of ALDH2

OBJECTIVE

This study is performed to explore the role of transcription factor FOXM1 in promoting the self-renewal and proliferation of liver cancer stem cells (LCSCs) by regulating the expression of acetaldehyde dehydrogenase-2 (ALDH2).

METHODS

CD133⁺ CD24⁺ LCSCs were sorted and identified. A series of experiments were carried out to determine the proliferation, colony formation rate, migration, invasion, and apoptosis of LCSCs after interfering with FOXM1. Proliferation-, epithelial-mesenchymal transition (EMT)-, apoptosis-, and stemness-related factors were then detected by western blot analysis. Tumor xenograft in nude mice was used to figure out the role of FOXM1 in tumorigenesis in vivo by regulating ALDH2 expression. Luciferase activity assay was conducted to determine whether FOXM1 could target ALDH2 promoter region and thereby affecting ALDH2 expression.

RESULTS

The sorted CD133⁺ CD24⁺ Huh-7 cells had the characteristic of stem cells. FOXM1 was highly expressed in CD133⁺ CD24⁺ Huh-7 cells. Silencing FOXM1 inhibited the proliferation and colony formation of LCSCs and decreased the expression of proliferating cell nuclear antigen and Ki-67 protein; inhibited the migration, invasion, and EMT of LCSCs while promoting the apoptosis of LCSCs, as well as promoted the expression of Bax and cleaved-caspase-3, and inhibited the expression of Bcl-2. Silencing FOXM1 inhibited the expression of Nanog, Oct4, and Sox2 in LCSCs by decreasing the expression of ALDH2. in vivo experiment, silencing FOXM1 suppressed tumorigenesis of LCSCs by decreasing the expression of ALDH2.

CONCLUSION

Our study provides evidence that silencing FOXM1 inhibits stemness of LCSCs by decreasing the expression of ALDH2, and represses the proliferation, migration, invasion, and tumorigenesis while inducing the apoptosis of LCSCs.

Analysis of the Mechanisms of Action of Naphthoquinone-Based Anti-Acute Myeloid Leukemia Chemotherapeutics

Acute myeloid leukemia (AML) is a neoplastic disorder resulting from clonal proliferation of poorly differentiated immature myeloid cells. Distinct genetic and epigenetic aberrations are key features of AML that account for its variable response to standard therapy. Irrespective of their oncogenic mutations, AML cells produce elevated levels of reactive oxygen species (ROS). They also alter expression and activity of antioxidant enzymes to promote cell proliferation and survival. Subsequently, selective targeting of redox homeostasis in a molecularly heterogeneous disease, such as AML, has been an appealing approach in the development of novel anti-leukemic chemotherapeutics. Naphthoquinones are able to undergo redox cycling and generate ROS in cancer cells, which have made them excellent candidates for testing against AML cells. In addition to inducing oxidative imbalance in AML cells, depending on their structure, naphthoquinones negatively affect other cellular apparatus causing neoplastic cell death. Here we provide an overview of the anti-AML activities of naphthoquinone derivatives, as well as analysis of their mechanism of action, including induction of reduction-oxidation imbalance, alteration in mitochondrial transmembrane potential, Bcl-2 modulation, initiation of DNA damage, and modulation of MAPK and STAT3 activity, alterations in the unfolded protein response and translocation of FOX-related transcription factors to the nucleus.

Molecular mechanism of Forkhead box M1 inhibition by thiostrepton in breast cancer cells

Breast cancer is the most common type of malignancies in women worldwide, and genotoxic chemotherapeutic drugs are effective by causing DNA damage in cancer cells. However, >90% of patients with metastatic cancer are resistant to chemotherapy. The Forkhead box M1 (FOXM1) transcription factor plays a pivotal role in the resistance of breast cancer cells to chemotherapy by promoting DNA damage repair following genotoxic drug treatment. The aim of the present study was to investigate the inhibition of the FOXM1 protein by thiostrepton, a natural antibiotic produced by the Streptomyces species. Experimental studies were designed to examine the effectiveness of thiostrepton in downregulating FOXM1 mRNA expression and activity, leading to senescence and apoptosis of breast cancer cells. The cytotoxicity of thiostrepton in breast cancer was determined using cell viability assay. Additionally, thiostrepton treatment decreased the mRNA expression of cyclin B1 (CCNB1), a downstream target of FOXM1. The present results indicated that thiostrepton inhibited FOXM1 mRNA expression and its effect on CCNB1. Molecular dynamic simulations were performed to study the interactions between FOXM1-DNA and thiostrepton after molecular docking. The results revealed that the possible mechanism underlying the inhibitory effect of thiostrepton on FOXM1 function was by forming a tight complex with the DNA and FOXM1 via its binding domain. Collectively, these results indicated that thiostrepton is a specific and direct inhibitor of the FOXM1 protein in breast cancer. The findings of the present study may lead to the development of novel therapeutic strategies for breast cancer and help overcome resistance to conventional chemotherapeutic drugs.

The Role of Forkhead Box Proteins in Acute Myeloid Leukemia

Forkhead box (FOX) proteins are a group of transcriptional factors implicated in different cellular functions such as differentiation, proliferation and senescence. A growing number of studies have focused on the relationship between FOX proteins and cancers, particularly hematological neoplasms such as acute myeloid leukemia (AML). FOX proteins are widely involved in AML biology, including leukemogenesis, relapse and drug sensitivity. Here we explore the role of FOX transcription factors in the major AML entities, according to "The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia", and in the context of the most recurrent gene mutations identified in this heterogeneous disease. Moreover, we report the new evidences about the role of FOX proteins in drug sensitivity, mechanisms of chemoresistance, and possible targeting for personalized therapies.

FOXM1 is a novel predictor of recurrence in patients with oral squamous cell carcinoma associated with an increase in epithelial‑mesenchymal transition

Although forkhead box protein M1 (FOXM1) is markedly upregulated in human premalignant and oral squamous cell carcinoma (OSCC) tissues and cultured cells, the association of FOXM1 expression with OSCC prognosis is not well understood. The present study investigated the possible association of FOXM1 expression in patients with OSCC with their clinicopathological characteristics and clinical outcomes. The expression of FOXM1 protein in OSCC tissues from 119 patients was evaluated by immunohistochemistry, and the results demonstrated that FOXM1 overexpression in patients with OSCC was associated with tumour recurrence and poor prognosis. To study the in vitro effects of FOXM1, its expression was decreased by small interfering RNA (siRNA) in OSCC cell lines, and FOXM1 knockdown decreased the proliferative, migratory and invasive capacities of cells. FOXM1 inhibition by siRNA gave rise to reduced expression of vimentin and increased expression of E‑cadherin. The present study reported FOXM1 as a novel predictor of tumour recurrence in patients with OSCC and its potential involvement in epithelial‑mesenchymal transition in OSCC cells.

DEPDC1, negatively regulated by miR-26b, facilitates cell proliferation via the up-regulation of FOXM1 expression in TNBC

Triple negative breast cancer (TNBC), characterized by lack of estrogen receptors, progesterone hormone receptors, and HER2 overexpression, is a more aggressive high grade tumor and not sensitive to current targeted drugs. The clinical prognosis of TNBC is poorer than other types of breast cancer, and there is no effective therapy strategy until now. Thus, it is necessary to determine important factors involved in regulating the progression of TNBC. In this study, we found DEPDC1 was up-regulated in the tissues of TNBC compared with their paired peritumoral tissues. DEPDC1 over-expression facilitated cell proliferation and tumor growth through increasing the expression of FOXM1 in TNBC cells. Conversely, knockdown of DEPDC1 had the opposite effects. Moreover, miR-26b, acting as a tumor suppressor in TNBC, directly repressed the expression of DEPDC1 and mitigated its promotive effects on cell growth and colony formation. These results indicate that DEPDC1, negatively regulated by miR-26b, promotes cell proliferation and tumor growth via up-regulating FOXM1 expression, implying an important underlying mechanism of regulating the progression of TNBC.

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.

FoxM1 is associated with metastasis in colorectal cancer through induction of the epithelial-mesenchymal transition

The aim of the present study was to investigate the role of forkhead box M1 (FoxM1) in epithelial-mesenchymal transition (EMT) and metastasis in colorectal cancer (CRC). Immunohistochemical assays were performed to detect FoxM1 and epithelial (E-) cadherin protein expression in 92 CRC, 61 colonic adenoma and 32 wild-type colonic tissue samples. Quantitative polymerase chain reaction (qPCR) assays were performed to determine the expression levels of FoxM1 and E-cadherin mRNAs in 30 CRC and adjacent normal mucosal tissues. RNA interference was used to knock down endogenous FoxM1 expression in CRC cell lines, and the migratory and invasive capacity of the CRC cells was analyzed. The expression of FoxM1, E-cadherin and neuronal (N-) cadherin in the CRC cell lines was evaluated using qPCR and Western blot analysis. The relative expression levels of FoxM1 mRNA and protein were significantly increased in the CRC tissues compared with those in the colonic adenoma and wild-type mucosal tissue samples (P<0.01). In contrast, the relative expression levels of E-cadherin mRNA and protein were significantly decreased in the CRC tissues compared with in the colonic adenoma and normal mucosal tissues (P<0.01). FoxM1 overexpression and decreased E-cadherin expression were significantly associated with poor colonic tissue differentiation, lymph node metastasis and an advanced tumor-node-metastasis stage. Additionally, the increased expression of FoxM1 was associated with a decrease in E-cadherin expression (P<0.01). Furthermore, RNA interference-mediated FoxM1 knockdown significantly inhibited the proliferation, migration and invasion of CRC cells. Downregulation of FoxM1 expression significantly increased E-cadherin expression and decreased N-cadherin expression. The results of the present study suggest that FoxM1 overexpression in tumor tissues is significantly associated with metastasis in CRC through the induction of EMT.

FoxM1 overexpression promotes cell proliferation and migration and inhibits apoptosis in hypopharyngeal squamous cell carcinoma resulting in poor clinical prognosis

Forkhead box M1 (FoxM1), a member of the Fox family of transcriptional factors, is involved in the development of various human malignancies. However, the expression level of FoxM1 and its functional role in hypopharyngeal squamous cell carcinoma (HSCC) remained unclear to date. The aim of the present study was to investigate the FoxM1 expression in 63 HSCC and 20 adjacent normal tissues, as well as to evaluate its association with the clinicopathological parameters and its diagnostic value in HSCC. To further explore the biological function of FoxM1 in vitro, siRNAs were used to knockdown the expression of FoxM1 in the HSCC cell line Fadu. The results revealed that FoxM1 protein was highly expressed in HSCC tissues and that its high expression was closely associated with HSCC tumor differentiation (P=0.004), tumor size (P=0.002), clinical stage (P=0.001), lymph node metastasis (P=0.002), treatment (P=0.045) and expression of the proliferation marker Ki-67 (P<0.001). Additionally, the elevated expression of FoxM1 in HSCC patients consistently predicted a poor survival time. Knockdown of FoxM1 expression blocked Fadu cell proliferation and promoted apoptosis, and also led to the down-regulation of cyclin A1 expression. Furthermore, decreased expression of FoxM1 markedly impeded cell migration and reversed the epithelial-mesenchymal transition phenotype, as indicated by decreased expression of vimentin and increased expression of E-cadherin in Fadu cells. These results indicate that FoxM1 may act as an oncogene and serve as a therapeutic target against malignant progression in HSCC.

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.

miR-671-5p inhibits epithelial-to-mesenchymal transition by downregulating FOXM1 expression in breast cancer

MicroRNA (miRNA) dysfunction is associated with a variety of human diseases, including cancer. Our previous study showed that miR-671-5p was deregulated throughout breast cancer progression. Here, we report for the first time that miR-671-5p is a tumor-suppressor miRNA in breast tumorigenesis. We found that expression of miR-671-5p was decreased significantly in invasive ductal carcinoma (IDC) compared to normal in microdissected formalin-fixed, paraffin-embedded (FFPE) tissues. Forkhead Box M1 (FOXM1), an oncogenic transcription factor, was predicted as one of the direct targets of miR-671-5p, which was subsequently confirmed by luciferase assays. Forced expression of miR-671-5p in breast cancer cell lines downregulated FOXM1 expression, and attenuated the proliferation and invasion in breast cancer cell lines. Notably, overexpression of miR-671-5p resulted in a shift from epithelial-to-mesenchymal transition (EMT) to mesenchymal-to-epithelial transition (MET) phenotypes in MDA-MB-231 breast cancer cells and induced S-phase arrest. Moreover, miR-671-5p sensitized breast cancer cells to cisplatin, 5-fluorouracil (5-FU) and epirubicin exposure. Host cell reactivation (HCR) assays showed that miR-671-5p reduces DNA repair capability in post-drug exposed breast cancer cells. cDNA microarray data revealed that differentially expressed genes when miR-671-5p was transfected are associated with cell proliferation, invasion, cell cycle, and EMT. These data indicate that miR-671-5p functions as a tumor suppressor miRNA in breast cancer by directly targeting FOXM1. Hence, miR-671-5p may serve as a novel therapeutic target for breast cancer management.

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.

Prognostic significance of FOXM1 expression and antitumor effect of FOXM1 inhibition in synovial sarcomas

Background

Synovial sarcoma (SS) is a soft tissue sarcoma of unknown histogenesis. Most metastatic or unresectable cases are incurable. Novel antitumor agents and precise prognostication are needed for SS patients. The protein forkhead box M1 (FOXM1), which belongs to the FOX family of transcription factors, is considered to be an independent predictor of poor survival in many cancers and sarcomas, but the prognostic implications and oncogenic roles of FOXM1 in SS are poorly understood. Here we examined the correlation between FOXM1 expression and clinicopathologic and prognostic factors, and we investigated the efficacy of FOXM1 target therapy in SS cases.

Methods

Immunohistochemical study of 106 tumor specimens was conducted to evaluate their immunohistochemical expression of FOXM1. An in vitro study examined the antitumor effect of the FOXM1 inhibitor thiostrepton and small interference RNA (siRNA) on two SS cell lines. We also assessed the efficacy of the combined use of doxorubicin (DOX) and thiostrepton.

Results

Univariate and multivariate analyses revealed that FOXM1 expression was associated with poor prognosis in SS. The cDNA microarray analysis using clinical samples revealed that the expression of cell cycle-associated genes was correlated with FOXM1 expression. FOXM1 inhibition by thiostrepton showed significant antitumor activity on the SS cell lines in vitro. FOXM1 interruption by siRNA increased the chemosensitivity for DOX in both SS cell lines.

Conclusion

FOXM1 expression is a novel biomarker, and its inhibition is a potential treatment option for SS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2542-4) contains supplementary material, which is available to authorized users.

Prognostic significance of FoxM1 expression in non-small cell lung cancer

BACKGROUND

Various studies examined the relationship between FoxM1 overexpression with the clinical outcome in patients with non-small cell lung cancer (NSCLC), but yielded conflicting results.

METHODS

Electronic databases updated to Jan 01, 2015 were searched to find relevant studies. A meta-analysis was conducted with eligible studies which quantitatively evaluated the relationship between FoxM1 overexpression and survival of patients with NSCLC Survival data were aggregated and quantitatively analyzed.

RESULTS

We performed a meta-analysis of seven studies (n=860 patients) that evaluated the correlation between FoxM1 overexpression and survival in patients with NSCLC. Combined hazard ratios suggested that FoxM1 overexpression was associated with poor prognosis of overall survival (OS) (HR =1.73, 95% CI: 1.32-2.14) in patients with NSCLC.

CONCLUSIONS

FoxM1 overexpression indicates a poor prognosis for patients with NSCLC.

Prognostic Significance of Forkhead Box M1 (FOXM1) Expression and Antitumor Effect of FOXM1 Inhibition in Angiosarcoma

Background: The prognosis of angiosarcoma is poor and a novel treatment option for the disease is desired. The aim of this study was to investigate the prognostic significance of Forkhead box M1 (FOXM1), a transcription factor that regulates cell-cycle progression and various crucial processes in tumor progression, and its potential as a new therapeutic target.

Methods: We investigated 125 angiosarcoma clinical samples (94 primary lesions and 31 metastatic lesions in 94 patients) and a human angiosarcoma cell line (HAMON) using immunohistochemical staining and molecular biological approaches. FOXM1 expression in angiosarcoma samples was also compared with that in Kaposi's sarcomas (n = 13), epithelioid hemangioendotheliomas (n = 13) and benign hemangiomas (n = 10).

Results: Patients with FOXM1-overexpressing angiosarcoma had significantly shorter survival (both for disease-specific survival [DSS] and event-free survival [EFS]) than other patients (5-year DSS, 23.5% vs. 47.1%, P = 0.013; and 5-year EFS, 5.5% vs. 28.7%, P = 0.004). FOXM1 overexpression was also an independent prognostic factor for both DSS and EFS in Cox multivariate analyses (hazard ratio [HR] 2.84, 95% confidence interval [CI] 1.10-5.81, P = 0.039; and HR 4.16, 95%CI 2.03-8.67, P = 0.0001, respectively). FOXM1 inhibition using both small interfering RNA and a specific inhibitor (thiostrepton) suppressed cell proliferation of the angiosarcoma cell line. Furthermore, FOXM1 inhibition improved the chemosensitivity to docetaxel in vitro.

Conclusions: FOXM1 inhibition may be a potential therapeutic option for angiosarcoma.

F-box protein FBXL2 inhibits gastric cancer proliferation by ubiquitin-mediated degradation of forkhead box M1

F-box/LRR-repeat protein 2 (FBXL2), a component of Skp-Cullin-F box (SCF) ubiquitin E3 ligase, has been shown to inhibit tumorigenesis by targeting and ubiquitinating several oncoproteins. However, its role in gastric cancer remains poorly understood. Here, by tandem mass spectrometry, we show that FBXL2 interacts with forkhead box M1 (FoxM1) transcription factor. As a result, FBXL2 promotes ubiquitination and degradation of FoxM1 in gastric cancer cells. Furthermore, overexpression of FBXL2 inhibits, while its deficiency promotes cell proliferation and invasion. Expression levels of cell-cycle regulators (Cdc25B and p27), which are down-stream target effectors of FoxM1, are also regulated by FBXL2. Therefore, our results uncover a previous unknown network involving FBXL2 and FoxM1 in the regulation of gastric cancer growth.

Expression of Forkhead box M1 in soft tissue leiomyosarcoma: Clinicopathologic and in vitro study using a newly established cell line

Leiomyosarcoma (LMS) of soft tissue is a sarcoma with smooth‐muscle differentiation, and conventional chemotherapy does not improve its outcome. The application of novel antitumor agents and precise prognostication has been demanded. The expression of the protein Forkhead box M1 (FOXM1), a member of the FOX family, is considered an independent predictor of poor survival in many cancers and sarcomas. However, the expression status of FOXM1 in LMS is poorly understood. The purposes of this study were to examine the correlation between the expression of FOXM1 and clinicopathologic or prognostic factors and to clarify the efficacy of FOXM1 target therapy in LMS. We evaluated the immunohistochemical expressions of FOXM1 using 123 LMS tumor specimens. Univariate and multivariate survival analyses revealed that FOXM1 expression was associated with poor prognosis in LMS. An in vitro study was then carried out to examine the antitumor effect of a FOXM1 inhibitor (thiostrepton) and siRNA on a novel LMS cell line, TC616. We also assessed the efficacy of the combined use of doxorubicin and thiostrepton. Thiostrepton showed dose‐dependent antitumor activity and TC616 cells treated with the combination of thiostrepton and doxorubicin showed lower proliferation compared to those treated with either drug individually. FOXM1 interruption by siRNA decreased cell proliferation and increased chemosensitivity. In conclusion, FOXM1 has potential to be a therapeutic target for LMS.

Prognostic significance of forkhead box M1 (FoxM1) expression and antitumour effect of FoxM1 inhibition in melanoma

AIMS

Forkhead box M1 (FoxM1) is a transcription factor that regulates cell-cycle progression and tumour progression, but limited information is available regarding its clinical significance in melanoma. The aim of this study was to investigate the potency of FoxM1 as a therapeutic target in melanoma.

METHODS AND RESULTS

We investigated 60 melanoma clinical samples and a melanoma WM266-4 cell line using immunohistochemical staining and molecular biological approaches. Patients with a FoxM1-overexpressing melanoma had significantly shorter survival [both for melanoma-specific survival (MSS) and disease-free survival (DFS)] than the other patients (P < 0.001, respectively). The FoxM1 overexpression was also an adverse prognostic factor for both MSS and DFS on the Cox multivariate analyses [hazard ratio (HR): 3.96, 95% confidence interval (CI): 1.12-14.27, P = 0.032; HR: 3.21, 95% CI: 1.08-9.67, P = 0.037, respectively). FoxM1 inhibition using siRNA and an inhibitor (thiostrepton) each suppressed the cell proliferation of the melanoma cell line. Furthermore, FoxM1 inhibition improved chemosensitivity to dacarbazine, whereas it reduced cell migration and invasion. These results suggest that FoxM1 plays important roles in tumour progression and the chemoresistance of melanoma.

CONCLUSION

We have shown the prognostic impact of FoxM1 on melanoma patients. FoxM1 inhibition may be a potential therapeutic option for advanced melanoma.

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.

Preclinical efficacy of maternal embryonic leucine-zipper kinase (MELK) inhibition in acute myeloid leukemia

Maternal embryonic leucine-zipper kinase (MELK), which was reported to be frequently up-regulated in various types of solid cancer, plays critical roles in formation and maintenance of cancer stem cells. However, little is known about the relevance of this kinase in hematologic malignancies. Here we report characterization of possible roles of MELK in acute myeloid leukemia (AML). MELK is expressed in AML cell lines and AML blasts with higher levels in less differentiated cells. MELK is frequently upregulated in AML with complex karyotypes and is associated with worse clinical outcome. MELK knockdown resulted in growth inhibition and apoptosis of leukemic cells. Hence, we investigated the potent anti-leukemia activity of OTS167, a small molecule MELK kinase inhibitor, in AML, and found that the compound induced cell differentiation and apoptosis as well as decreased migration of AML cells. MELK expression was positively correlated with the expression of FOXM1 as well as its downstream target genes. Furthermore, MELK inhibition resulted in downregulation of FOXM1 activity and the expression of its downstream targets. Taken together, and given that OTS167 is undergoing a phase I clinical trial in solid cancer, our study warrants clinical evaluation of this compound as a novel targeted therapy for AML patients.

FOXM1 targets XIAP and Survivin to modulate breast cancer survival and chemoresistance

Drug resistance is a major hurdle for successful treatment of breast cancer, the leading cause of deaths in women throughout the world. The FOXM1 transcription factor is a potent oncogene that transcriptionally regulates a wide range of target genes involved in DNA repair, metastasis, cell invasion, and migration. However, little is known about the role of FOXM1 in cell survival and the gene targets involved. Here, we show that FOXM1-overexpressing breast cancer cells display an apoptosis-resistant phenotype, which associates with the upregulation of expression of XIAP and Survivin antiapoptotic genes. Conversely, FOXM1 knockdown results in XIAP and Survivin downregulation as well as decreased binding of FOXM1 to the promoter regions of XIAP and Survivin. Consistently, FOXM1, XIAP, and Survivin expression levels were higher in taxane and anthracycline-resistant cell lines when compared to their sensitive counterparts and could not be downregulated in response to drug treatment. In agreement with our in vitro findings, we found that FOXM1 expression is significantly associated with Survivin and XIAP expression in samples from patients with IIIa stage breast invasive ductal carcinoma. Importantly, patients co-expressing FOXM1, Survivin, and nuclear XIAP had significantly worst overall survival, further confirming the physiological relevance of the regulation of Survivin and XIAP by FOXM1. Together, these findings suggest that the overexpression of FOXM1, XIAP, and Survivin contributes to the development of drug-resistance and is associated with poor clinical outcome in breast cancer patients.

FOXM1 is overexpressed in B-acute lymphoblastic leukemia (B-ALL) and its inhibition sensitizes B-ALL cells to chemotherapeutic drugs

The Forkhead box protein M1 (FOXM1) is a transcription factor that plays a central role in the regulation of cell cycle, proliferation, DNA repair, and apoptosis. FOXM1 is overexpressed in many human tumors and its upregulation has been linked to high proliferation rates and poor prognosis. We therefore studied the role of FOXM1 in B-lymphoblastic leukemia (B-ALL) in order to understand whether FOXM1 could be a key target for leukemia therapy. RT-PCR and western blot analysis were carried out in a small cohort of pediatric B-ALL patients to evaluate FOXM1 levels. To assess its biological relevance, its expression was down-modulated by transient RNA interference in B-ALL cell lines (REH and NALM-6). Our results show that FOXM1 expression is higher in both B-ALL patients and cell lines when compared to PBMC or normal B-cells (CD19+) from healthy donors. Furthermore, blocking FOXM1 activity in two B-ALL cell lines, by either knockdown or treatment with the FOXM1 inhibitor thiostrepton, causes significant decrease in their cell proliferation. This decrease in cell proliferation was coupled with both an induction of the G2/M cell cycle arrest and with a reduction in the S phase population. Finally, we noted how thiostrepton synergises with chemotherapeutic agents commonly used in B-ALL therapy, thus increasing their efficiency. Therefore our results suggest that FOXM1 is highly expressed in both patients and B-ALL cell lines, and that targeting FOXM1 could be an attractive strategy for leukemia therapy and for overcoming drug resistance.

Inhibition of Forkhead box protein M1 by thiostrepton increases chemosensitivity to doxorubicin in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive type of blood malignancy, deriving from T-cell progenitors in the thymus, and comprises 10-15% of pediatric and 25% of adult primary ALL cases. Despite advances, 20% of pediatric and the majority of adult patients with T-ALL succumb to mortality from resistant or relapsed disease, and the survival rate for patients with resistant or relapsed T-ALL remains poor. Alterations in the expression of Forkhead box protein M1 (FoxM1) have been detected in several types of cancer, and the inhibition of FoxM1 has been investigated as therapeutic strategy in cancer. The present study investigated the effects of the inhibition of FoxM1 by thiostrepton in human T-ALL Jurkat cells. The cells were treated with different concentrations of thiostrepton, either alone or in combination with doxorubicin. Cell viability was measured using CCK-8 assays and the cell cycle distribution, apoptosis and cell-associated mean fluorescence intensity of intracellular doxorubicin were assessed using flow cytometric analysis. The mRNA and protein expression levels were detected by reverse transcription-quantitative polymerase chain reaction and western blot analyses. The inhibition of FoxM1 by thiostrepton significantly decreased the proliferation of the Jurkat cells proliferation in a time- and dose-dependent manner. Cell arrest at the G2/M phase, and apoptosis was significantly increased in the thiostrepton-treated Jurkat cells. Thiostrepton reduced the half maximal inhibitory concentration of doxorubicin in the Jurkat cells, and significantly enhanced the cytotoxicity of doxorubicin within the Jurkat cells by enhancing doxorubicin-induced apoptosis and increasing the accumulation of intracellular doxorubicin. Furthermore, the inhibition of FoxM1 by thiostrepton enhanced doxorubicin-induced apoptosis, possibly through a caspase-3-dependent pathway, and increased the accumulation of intracellular doxorubicin, possibly through downregulating the expression of glutathione S-transferase pi. Collectively, the results of the present study suggested that targeting FoxM1 with thiostrepton resulted in potent antileukemia activity and chemosensitizing effects in human T-ALL Jurkat cells.

Identification of FOXM1 as a therapeutic target in B-cell lineage acute lymphoblastic leukaemia

Despite recent advances in the cure rate of acute lymphoblastic leukaemia (ALL), the prognosis for patients with relapsed ALL remains poor. Here we identify FOXM1 as a candidate responsible for an aggressive clinical course. We show that FOXM1 levels peak at the pre-B-cell receptor checkpoint but are dispensable for normal B-cell development. Compared with normal B-cell populations, FOXM1 levels are 2- to 60-fold higher in ALL cells and are predictive of poor outcome in ALL patients. FOXM1 is negatively regulated by FOXO3A, supports cell survival, drug resistance, colony formation and proliferation in vitro, and promotes leukemogenesis in vivo. Two complementary approaches of pharmacological FOXM1 inhibition-(i) FOXM1 transcriptional inactivation using the thiazole antibiotic thiostrepton and (ii) an FOXM1 inhibiting ARF-derived peptide-recapitulate the findings of genetic FOXM1 deletion. Taken together, our data identify FOXM1 as a novel therapeutic target, and demonstrate feasibility of FOXM1 inhibition in ALL.

Breast tissue-based microRNA panel highlights microRNA-23a and selected target genes as putative biomarkers for breast cancer

We explored the differential expression of breast tissue-based panel of microRNAs (miRNAs) and their potential application as prognostic markers of breast cancer (BC). This study was divided into the following phases: (1) A panel of 6 BC characteristic miRNAs, which were retrieved based on the microarray signature profiling (released by miRWalk), was explored using SYBR Green-based polymerase chain reaction (PCR) array in 16 cancerous and 16 noncancerous breast tissue; (2) pathway enrichment analysis of the key miRNA target genes; (3) marker choice and validation by real-time PCR in a larger set of 76 patients with BC, 36 benign breast conditions, and 36 healthy volunteers; (4) validation of miRNA (miR)-23a target genes (forkhead box m [FOXM1] and histidine-rich glycoprotein [HRG]) by conventional reverse transcriptase (RT)-PCR; and (5) the prognostic significance of the investigated parameters in the BC validation group was explored. In PCR array-based miRNA expression analysis, 4 miRNAs were found to be altered more than twice (miR-96, miR-29c, miR-221, and miR-23a). Bioinformatic analysis of the target genes revealed enrichment for special biological process categories, that is, cell cycle, angiogenesis, apoptosis, cell proliferation, and cell adhesion. miR-23a, HRG messenger RNA, and FOX messenger RNA were positive in BC by 82.9%, 72.4%, and 71.1%, respectively. The overall concordance rates between miR-23a with HRG and FOXM1 tissue RNAs were 91% and 79%, respectively. The median follow-up period was 49 months. mi-23a and HRG RNA were significant independent prognostic markers in relapse-free survival. miR-23a may have an oncogenic function and enhance BC progression by directly activating FOXM1 and HRG at RNA level.

Targeting FoxM1 transcription factor in T-cell acute lymphoblastic leukemia cell line

The Forkhead box protein M1 (FoxM1) is an important transcription factor having significant roles in various cellular events. FoxM1 overexpression has been reported to be related with many types of cancer. However, it is not known whether it contributes to oncogenesis of acute lymphoblastic leukemia. Siomycin A, a thiazol antibiotic, is known to inhibit FoxM1 transcriptional activity. In this study, we aimed to determine gene expression levels of FoxM1 in Jurkat cells (T-cell acute lymphoblastic leukemia cell line) and therapeutic potential of targeting FoxM1 by siomycin A alone and in combination with dexamethasone which improves the survival of children with T-cell acute lymphoblastic leukemia (ALL). We also examined the molecular mechanisms of siomycin A and dexamethasone-induced cell death in Jurkat cells. We demonstrated that FoxM1 mRNA is highly expressed in Jurkat cells. Dexamethasone and siomycin A caused a significant reduction in gene expression levels of FoxM1 in Jurkat cells. Targeting FoxM1 by siomycin A and dexamethasone caused a significant decrease in T-ALL cell line proliferation through induction of G1 cell cycle arrest. All these findings suggest a possible role of FoxM1 in T-cell ALL pathogenesis and represent FoxM1 as an attractive target for T-cell ALL therapy.