The FOXM1 Inhibitor RCM-1 Decreases Carcinogenesis and Nuclear β-Catenin

The bone marrow of mouse-rat chimeras contains progenitors of multiple pulmonary cell lineages

Radiation-induced lung injury (RILI) is a common complication of anti-cancer treatments for thoracic and hematologic malignancies. Bone marrow (BM) transplantation restores hematopoietic cell lineages in cancer patients. However, it is ineffective in improving lung repair after RILI due to the paucity of respiratory progenitors in BM transplants. In the present study, we used blastocyst injection to create mouse-rat chimeras, these are artificial animals in which BM is enriched with mouse-derived progenitor cells. FACS-sorted mouse BM cells from mouse-rat chimeras were transplanted into lethally irradiated syngeneic mice, and the contribution of donor cells to the lung tissue was examined using immunostaining and flow cytometry. Donor BM cells provided long-term contributions to all lung-resident hematopoietic cells which includes alveolar macrophages and dendritic cells. Surprisingly, donor BM cells also contributed up to 8% in pulmonary endothelial cells and stromal cells after RILI. To identify respiratory progenitors in donor BM, we performed single-cell RNA sequencing (scRNAseq). Compared to normal mouse BM, increased numbers of hematopoietic progenitors were found in the BM of mouse-rat chimeras. We also identified unique populations of hemangioblast-like progenitor cells expressing Hes1, Dntt and Ebf1, along with mesenchymal stromal cells expressing Cpox, Blvrb and Ermap that were absent or ultra-rare in the normal mouse BM. In summary, by using rats as "bioreactors", we created a unique mouse BM cell transplant that contributes to multiple respiratory cell types after RILI. Interspecies chimeras have promise for future generations of BM transplants enriched in respiratory progenitor cells.

DLK1/DIO3 locus upregulation by a β-catenin-dependent enhancer drives cell proliferation and liver tumorigenesis

The CTNNB1 gene, encoding β-catenin, is frequently mutated in hepatocellular carcinoma (HCC, ∼30%) and in hepatoblastoma (HB, >80%), in which DLK1/DIO3 locus induction is correlated with CTNNB1 mutations. Here, we aim to decipher how sustained β-catenin activation regulates DLK1/DIO3 locus expression and the role this locus plays in HB and HCC development in mouse models deleted for Apc (ApcΔhep) or Ctnnb1-exon 3 (β-cateninΔExon3) and in human CTNNB1-mutated hepatic cancer cells. We identified an enhancer site bound by TCF-4/β-catenin complexes in an open conformation upon sustained β-catenin activation (DLK1-Wnt responsive element [WRE]) and increasing DLK1/DIO3 locus transcription in β-catenin-mutated human HB and mouse models. DLK1-WRE editing by CRISPR-Cas9 approach impaired DLK1/DIO3 locus expression and slowed tumor growth in subcutaneous CTNNB1-mutated tumor cell grafts, ApcΔhep HB and β-cateninΔExon3 HCC. Tumor growth inhibition resulted either from increased FADD expression and subsequent caspase-3 cleavage in the first case or from decreased expression of cell cycle actors regulated by FoxM1 in the others. Therefore, the DLK1/DIO3 locus is an essential determinant of FoxM1-dependent cell proliferation during β-catenin-driven liver tumorigenesis. Targeting the DLK1-WRE enhancer to silence the DLK1/DIO3 locus might thus represent an interesting therapeutic strategy to restrict tumor growth in primary liver cancers with CTNNB1 mutations.

The Promise of Combination Therapies with FOXM1 Inhibitors for Cancer Treatment

Forkhead box M1 (FOXM1) is a transcription factor in the forkhead (FOX) family, which is required for cellular proliferation in normal and neoplastic cells. FOXM1 is highly expressed in many different cancers, and its expression is associated with a higher tumor stage and worse patient-related outcomes. Abnormally high expression of FOXM1 in cancers compared to normal tissue makes FOXM1 an attractive target for pharmacological inhibition. FOXM1-inhibiting agents and specific FOXM1-targeted small-molecule inhibitors have been developed in the lab and some of them have shown promising efficacy and safety profiles in mouse models. While the future goal is to translate FOXM1 inhibitors to clinical trials, potential synergistic drug combinations can maximize anti-tumor efficacy while minimizing off-target side effects. Hence, we discuss the rationale and efficacy of all previously studied drug combinations with FOXM1 inhibitors for cancer therapies.

Small-molecule inhibitors targeting FOXM1: Current challenges and future perspectives in cancer treatments

Forkhead box (FOX) protein M1 (FOXM1) is a critical proliferation-associated transcription factor (TF) that is aberrantly overexpressed in the majority of human cancers and has also been implicated in poor prognosis. A comprehensive understanding of various aspects of this molecule has revealed its role in, cell proliferation, cell migration, invasion, angiogenesis and metastasis. The FOXM1 as a TF directly or indirectly regulates the expression of several target genes whose dysregulation is associated with almost all hallmarks of cancer. Moreover, FOXM1 expression is associated with chemoresistance to different anti-cancer drugs. Several studies have confirmed that suppression of FOXM1 enhanced the drug sensitivity of various types of cancer cells. Current data suggest that small molecule inhibitors targeting FOXM1 in combination with anticancer drugs may represent a novel therapeutic strategy for chemo-resistant cancers. In this review, we discuss the clinical utility of FOXM1, further, we summarize and discuss small-molecule inhibitors targeting FOXM1 and categorize them according to their mechanisms of targeting FOXM1. Despite great progress, small-molecule inhibitors targeting FOXM1 face many challenges, and we present here all small-molecule FOXM1 inhibitors in different stages of development. We discuss the current challenges and provide insights on the future application of FOXM1 inhibition to the clinic.

Ultra-high dose-rate proton FLASH improves tumor control

BACKGROUND AND PURPOSE

Proton radiotherapy (PRT) offers potential benefits over other radiation modalities, including photon and electron radiotherapy. Increasing the rate at which proton radiation is delivered may provide a therapeutic advantage. Here, we compared the efficacy of conventional proton therapy (CONVpr) to ultrahigh dose-rate proton therapy, FLASHpr, in a mouse model of non-small cell lung cancers (NSCLC).

MATERIALS AND METHODS

Mice bearing orthotopic lung tumors received thoracic radiation therapy using CONVpr (<0.05 Gy/s) and FLASHpr (>60 Gy/s) dose rates.

RESULTS

Compared to CONVpr, FLASHpr was more effective in reducing tumor burden and decreasing tumor cell proliferation. Furthermore, FLASHpr was more efficient in increasing the infiltration of cytotoxic CD8+ T-lymphocytes inside the tumor while simultaneously reducing the percentage of immunosuppressive regulatory T-cells (Tregs) among T-lymphocytes. Also, compared to CONVpr, FLASHpr was more effective in decreasing pro-tumorigenic M2-like macrophages in lung tumors, while increasing infiltration of anti-tumor M1-like macrophages. Finally, FLASHpr treatment reduced expression of checkpoint inhibitors in lung tumors, indicating reduced immune tolerance.

CONCLUSIONS

Our results suggest that FLASH dose-rate proton delivery modulates the immune system to improve tumor control and might thus be a promising new alternative to conventional dose rates for NSCLC treatment.

Development of an interfering peptide M1-20 with potent anti-cancer effects by targeting FOXM1

Disrupting protein-protein interactions (PPIs) has emerged as a promising strategy for cancer drug development. Interfering peptides disrupting PPIs can be rationally designed based on the structures of natural sequences mediating these interactions. Transcription factor FOXM1 overexpresses in multiple cancers and is considered an effective target for cancer therapeutic drug development. Using a rational design approach, we have generated a peptide library from the FOXM1 C-terminal sequence and screened FOXM1-binding peptides. Combining FOXM1 binding and cell inhibitory results, we have obtained a FOXM1-targeting interfering peptide M1-20 that is optimized from the natural parent peptide to the D-retro-inverso peptide. With improved stability characteristics, M1-20 inhibits proliferation and migration, and induces apoptosis of cancer cells. Mechanistically, M1-20 inhibits FOXM1 transcriptional activities by disrupting its interaction between the MuvB complex and the transcriptional co-activator CBP. These are consistent with the results that M1-20 suppresses cancer progression and metastasis without noticeable toxic and side effects in wild-type mice. These findings reveal that M1-20 has the potential to be developed as an anti-cancer drug candidate targeting FOXM1.

RNF112-mediated FOXM1 ubiquitination suppresses the proliferation and invasion of gastric cancer

Forkhead box M1 (FOXM1) plays a critical role in development physiologically and tumorigenesis pathologically. However, insufficient efforts have been dedicated to exploring the regulation, in particular the degradation of FOXM1. Here, the ON-TARGETplus siRNA library targeting E3 ligases was used to screen potential candidates to repress FOXM1. Of note, mechanism study revealed that RNF112 directly ubiquitinates FOXM1 in gastric cancer, resulting in a decreased FOXM1 transcriptional network and suppressing the proliferation and invasion of gastric cancer. Interestingly, the well-established small-molecule compound RCM-1 significantly enhanced the interaction between RNF112 and FOXM1, which further promoted FOXM1 ubiquitination and subsequently exerted promising anticancer effects in vitro and in vivo. Altogether, we demonstrate that RNF112 suppresses gastric cancer progression by ubiquitinating FOXM1 and highlight the RNF112/FOXM1 axis serves as both prognosis biomarker and therapeutic target in gastric cancer.

Whole exome and transcriptome analysis revealed the activation of ERK and Akt signaling pathway in canine histiocytic sarcoma

Histiocytic sarcoma (HS) is an incurable aggressive tumor, and no consensus has been made on the treatment due to its rare occurrence. Since dogs spontaneously develop the disease and several cell lines are available, they have been advocated as translational animal models. In the present study, therefore, we explored gene mutations and aberrant molecular pathways in canine HS by next generation sequencing to identify molecular targets for treatment. Whole exome sequencing and RNA-sequencing revealed gene mutations related to receptor tyrosine kinase pathways and activation of ERK1/2, PI3K-AKT, and STAT3 pathways. Analysis by quantitative PCR and immunohistochemistry revealed that fibroblast growth factor receptor 1 (FGFR1) is over-expressed. Moreover, activation of ERK and Akt signaling were confirmed in all HS cell lines, and FGFR1 inhibitors showed dose-dependent growth inhibitory effects in two of the twelve canine HS cell lines. The findings obtained in the present study indicated that ERK and Akt signaling were activated in canine HS and drugs targeting FGFR1 might be effective in part of the cases. The present study provides translational evidence that leads to establishment of novel therapeutic strategies targeting ERK and Akt signaling in HS patients.

Lung endothelial cells regulate pulmonary fibrosis through FOXF1/R-Ras signaling

Pulmonary fibrosis results from dysregulated lung repair and involves multiple cell types. The role of endothelial cells (EC) in lung fibrosis is poorly understood. Using single cell RNA-sequencing we identified endothelial transcription factors involved in lung fibrogenesis, including FOXF1, SMAD6, ETV6 and LEF1. Focusing on FOXF1, we found that FOXF1 is decreased in EC within human idiopathic pulmonary fibrosis (IPF) and mouse bleomycin-injured lungs. Endothelial-specific Foxf1 inhibition in mice increased collagen depositions, promoted lung inflammation, and impaired R-Ras signaling. In vitro, FOXF1-deficient EC increased proliferation, invasion and activation of human lung fibroblasts, and stimulated macrophage migration by secreting IL-6, TNFα, CCL2 and CXCL1. FOXF1 inhibited TNFα and CCL2 through direct transcriptional activation of Rras gene promoter. Transgenic overexpression or endothelial-specific nanoparticle delivery of Foxf1 cDNA decreased pulmonary fibrosis in bleomycin-injured mice. Nanoparticle delivery of FOXF1 cDNA can be considered for future therapies in IPF.

FOXM1: A small fox that makes more tracks for cancer progression and metastasis

Transcription factors (TFs) are indispensable for the modulation of various signaling pathways associated with normal cell homeostasis and disease conditions. Among cancer-related TFs, FOXM1 is a critical molecule that regulates multiple aspects of cancer cells, including growth, metastasis, recurrence, and stem cell features. FOXM1 also impacts the outcomes of targeted therapies, chemotherapies, and immune checkpoint inhibitors (ICIs) in various cancer types. Recent advances in cancer research strengthen the cancer-specific role of FOXM1, providing a rationale to target FOXM1 for developing targeted therapies. This review compiles the recent studies describing the pivotal role of FOXM1 in promoting metastasis of various cancer types. It also implicates the contribution of FOXM1 in the modulation of chemotherapeutic resistance, antitumor immune response/immunotherapies, and the potential of small molecule inhibitors of FOXM1.

Improving anti-tumor efficacy of low-dose Vincristine in rhabdomyosarcoma via the combination therapy with FOXM1 inhibitor RCM1

Rhabdomyosarcoma (RMS) is a highly metastatic soft-tissue sarcoma that often develops resistance to current therapies, including vincristine. Since the existing treatments have not significantly improved survival, there is a critical need for new therapeutic approaches for RMS patients. FOXM1, a known oncogene, is highly expressed in RMS, and is associated with the worst prognosis in RMS patients. In the present study, we found that the combination treatment with specific FOXM1 inhibitor RCM1 and low doses of vincristine is more effective in increasing apoptosis and decreasing RMS cell proliferation in vitro compared to single drugs alone. Since RCM1 is highly hydrophobic, we developed innovative nanoparticle delivery system containing poly-beta-amino-esters and folic acid (NP^FA), which efficiently delivers RCM1 to mouse RMS tumors in vivo. The combination of low doses of vincristine together with intravenous administration of NP^FA nanoparticles containing RCM1 effectively reduced RMS tumor volumes, increased tumor cell death and decreased tumor cell proliferation in RMS tumors compared to RCM1 or vincristine alone. The combination therapy was non-toxic as demonstrated by liver metabolic panels using peripheral blood serum. Using RNA-seq of dissected RMS tumors, we identified Chac1 as a uniquely downregulated gene after the combination treatment. Knockdown of Chac1 in RMS cells in vitro recapitulated the effects of the combination therapy. Altogether, combination treatment with low doses of vincristine and nanoparticle delivery of FOXM1 inhibitor RCM1 in a pre-clinical model of RMS has superior anti-tumor effects and decreases CHAC1 while reducing vincristine toxicity.

AKT1 phosphorylates RBM17 to promote Sox2 transcription by modulating alternative splicing of FOXM1 to enhance cancer stem cell properties in colorectal cancer cells

Colorectal cancer (CRC) is one of the leading causes of cancer-related death worldwide. The existence of cancer stem cells (CSC) causes tumor relapses, metastasis, and resistance to conventional therapy. Alternative splicing has been shown to affect physiological and pathological processes. Accumulating evidence has confirmed that targeting alternative splicing could be an effective strategy to treat CRC. Currently, the role of alternative splicing in the regulation of CSC properties in CRC has not been elucidated. Here, we show that RBM17 displays oncogenic roles in CRC cells. RBM17 enhances cell proliferation and reduces chemotherapeutic-induced apoptosis in CRC cells. Besides, RBM17 increases CD133 positive and ALDEFLUOR positive populations and promotes sphere formation in CRC cells. In mechanism studies, we found that FOXM1 is critical for RBM17 enhanced CSC properties. Moreover, FOXM1 alternative splicing is essential for RBM17 enhanced CSC properties in CRC cells. Additionally, RBM17 enhances CSC characteristics by controlling FOXM1 expression to promote Sox2 expression. Furthermore, AKT1 works as an upstream kinase to control RBM17-mediated FOXM1 alternative splicing and enhancement of CSC properties in CRC cells. Our study reveals that AKT1-RBM17-FOXM1-Sox2 axis could be a potential target for modulating alternative splicing to reduce CSC properties in CRC cells.

Structure-based virtual screening identified novel FOXM1 inhibitors as the lead compounds for ovarian cancer

Ovarian cancer (OC) is a gynecological tumor with possibly the worst prognosis, its 5-year survival rate being only 47.4%. The first line of therapy prescribed is chemotherapy consisting of platinum and paclitaxel. The primary reason for treatment failure is drug resistance. FOXM1 protein has been found to be closely associated with drug resistance, and inhibition of FOXM1 expression sensitizes cisplatin-resistant ovarian cancer cells. Combining existing first-line chemotherapy drugs with FOXM1 prolongs the overall survival of patients, therefore, FOXM1 is considered a potential therapeutic target in ovarian cancer. Previous research conducted by our team revealed a highly credible conformation of FOXM1 which enables binding by small molecules. Based on this conformation, the current study conducted virtual screening to determine a new structural skeleton for FOXM1 inhibitors which would enhance their medicinal properties. DZY-4 showed the highest affinity towards FOXM1, and its inhibitory effect on proliferation and migration of ovarian cancer at the cellular level was better than or equal to that of cisplatin, while its efficacy was equivalent to that of cisplatin in a nude mouse model. In this study, the anti-tumor effect of DZY-4 is reported for the first time. DZY-4 shows potential as a drug that can be used for ovarian cancer treatment, as well as a drug lead for future research.

Identification of new small molecules as dual FoxM1 and Hsp70 inhibitors using computational methods

Background and purpose

FoxM1 and Hsp70 proteins are highly expressed in many cancers. Thus, their inhibition serves as Bonafede targets in cancer treatment.

Experimental approach

FDI-6, an inhibitor of FoxM1, was selected as a template, and based on its structure, a new library from the ZINC database was obtained. Virtual screening was then performed using the created pharmacophore model. The second virtual screening phase was conducted with molecular docking to get the best inhibitor for both FoxM1 and Hsp70 active sites. In silico, ADMET properties were also calculated. Finally, molecular dynamics simulation was performed on the best ligand, ZINC1152745, for both Hsp70 and FoxM1 proteins during 100 ns.

Findings / Results

The results of this study indicated that ZINC1152745 was stable in the active site of both proteins, Hsp70 and FoxM1. The final scaffold identified by the presented computational approach could offer a hit compound for designing promising anticancer agents targeting both FoxM1 and Hsp70.

Conclusion and implications

Molecular dynamics simulations were performed on ZINC1152745 targeting FoxM1 and Hsp70 active sites. The results of several hydrogen bonds, the radius of gyration, RMSF, RMSD, and free energy during the simulations showed good stability of ZINC1152745 with FoxM1 and Hsp70.

FOXM1 Inhibition Enhances the Therapeutic Outcome of Lung Cancer Immunotherapy by Modulating PD-L1 Expression and Cell Proliferation

Programmed death-ligand 1 (PD-L1) is a major target to cancer immunotherapy, and anti-PD-L1 and anti-PD-1 antibody-mediated immunotherapy are being increasingly used. However, immune checkpoint inhibitors (ICIs) are ineffective in treating large tumors and cause various immune-related adverse events in nontarget organs, including life-threatening cardiotoxicity. Therefore, the development of new therapeutic strategies to overcome these limitations is crucial. The focus of this study is the forkhead box protein M1 (FOXM1), which is identified as a potential therapeutic target for cancer immunotherapy and is associated with the modulation of PD-L1 expression. Selective small interfering RNA knockdown of FOXM1 or treatment with thiostrepton (TST) significantly reduces PD-L1 expression in non-small-cell lung cancer (NSCLC) cells and inhibits proliferation. Chromatin immunoprecipitation-PCR reveals that FOXM1 selectively upregulates PD-L1 expression by binding directly to the PD-L1 promoter. In vivo animal studies have shown that TST treatment significantly downregulates PD-L1 expression in human NSCLC tumors, while greatly reducing tumor size without side effects on normal tissues. Combined treatment with TST and anti-4-1BB antibody in the LLC-1 syngeneic tumor model induces synergistic therapeutic outcomes against immune resistant lung tumors as well as 2.72-folds higher CD3⁺ T cells in tumor tissues compared to that in the anti-4-1BB antibody treatment group.

Down-regulated m6A reader FTO destabilizes PHF1 that triggers enhanced stemness capacity and tumor progression in lung adenocarcinoma

Aberrant epigenetic drivers or suppressors contribute to LUAD progression and drug resistance, including KRAS, PTEN, Keap1. Human Plant Homeodomain (PHD) finger protein 1 (PHF1) coordinates with H3K36me3 to increase nucleosomal DNA accessibility. Previous studies revealed that PHF1 is markedly upregulated in various tumors and enhances cell proliferation, migration and tumorigenesis. However, its roles in LUAD are still unknown. We aimed to depict the biological roles of PHF1 and identify useful targets for clinical treatment of LUAD. Based on the bioinformatic analysis, we found that PHF1 was down-regulated in LUAD samples and low PHF1 expressions correlated with unfavorable clinical characteristics. Patients with low PHF1 had poorer survival outcomes relative to those with high PHF1. Targeting PHF1 potentiated cell growth, migration and in vivo proliferation. Mechanistically, FTO mediated the stabilization of PHF1 mRNA by demethylating m6A, which particularly prevented YTHDF2 from degrading PHF1 transcripts. Of note, FTO also expressed lowly in LUAD that predicts poor prognosis of patients. FTO inhibition promoted LUAD progression, and PHF1 overexpression could reverse the effect. Lastly, down-regulated FTO/PHF1 axis could mainly elevate FOXM1 expression to potentiate the self-renewal capacity. Targeting FOXM1 was effective to suppress PHF1^low/− LUAD growth. Collectively, our findings revealed that FTO positively regulates PHF1 expression and determined the tumor-suppressive role of FTO/PHF1 axis, thereby highlighting insights into its epigenetic remodeling mechanisms in LUAD progression and treatment.

FOXM1 regulates glycolysis and energy production in multiple myeloma

The transcription factor, forkhead box M1 (FOXM1), has been implicated in the natural history and outcome of newly diagnosed high-risk myeloma (HRMM) and relapsed/refractory myeloma (RRMM), but the mechanism with which FOXM1 promotes the growth of neoplastic plasma cells is poorly understood. Here we show that FOXM1 is a positive regulator of myeloma metabolism that greatly impacts the bioenergetic pathways of glycolysis and oxidative phosphorylation (OxPhos). Using FOXM1-deficient myeloma cells as principal experimental model system, we find that FOXM1 increases glucose uptake, lactate output, and oxygen consumption in myeloma. We demonstrate that the novel 1,1-diarylethylene small-compound FOXM1 inhibitor, NB73, suppresses myeloma in cell culture and human-in-mouse xenografts using a mechanism that includes enhanced proteasomal FOXM1 degradation. Consistent with the FOXM1-stabilizing chaperone function of heat shock protein 90 (HSP90), the HSP90 inhibitor, geldanamycin, collaborates with NB73 in slowing down myeloma. These findings define FOXM1 as a key driver of myeloma metabolism and underscore the feasibility of targeting FOXM1 for new approaches to myeloma therapy and prevention.

Endothelial progenitor cells stimulate neonatal lung angiogenesis through FOXF1-mediated activation of BMP9/ACVRL1 signaling

Pulmonary endothelial progenitor cells (EPCs) are critical for neonatal lung angiogenesis and represent a subset of general capillary cells (gCAPs). Molecular mechanisms through which EPCs stimulate lung angiogenesis are unknown. Herein, we used single-cell RNA sequencing to identify the BMP9/ACVRL1/SMAD1 pathway signature in pulmonary EPCs. BMP9 receptor, ACVRL1, and its downstream target genes were inhibited in EPCs from Foxf1WT/S52F mutant mice, a model of alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV). Expression of ACVRL1 and its targets were reduced in lungs of ACDMPV subjects. Inhibition of FOXF1 transcription factor reduced BMP9/ACVRL1 signaling and decreased angiogenesis in vitro. FOXF1 synergized with ETS transcription factor FLI1 to activate ACVRL1 promoter. Nanoparticle-mediated silencing of ACVRL1 in newborn mice decreased neonatal lung angiogenesis and alveolarization. Treatment with BMP9 restored lung angiogenesis and alveolarization in ACVRL1-deficient and Foxf1WT/S52F mice. Altogether, EPCs promote neonatal lung angiogenesis and alveolarization through FOXF1-mediated activation of BMP9/ACVRL1 signaling.

Targeting of the FOXM1 Oncoprotein by E3 Ligase-Assisted Degradation

The transcription factor FOXM1 that regulates multiple proliferation-related genes through selective protein-DNA and protein-protein interactions is now considered an attractive oncotarget. There are several small-molecule inhibitors that indirectly suppress the expression of FOXM1 or block its DNA binding domain (FOXM1-DBD). However, insufficient specificity or/and efficacy are two potential drawbacks. Here, we employed in silico modeling of FOXM1-DBD with inhibitors to enable the design of an effective CRBN-recruiting molecule that induced significant FOXM1 protein degradation and exerted promising in vivo antitumor activity against TNBC xenograft models. This study is the first of its kind showcasing the use of an approach described in the literature as protein-targeting chimeras to degrade the elusive FOXM1, providing an alternative strategy to counter the pathological effects resulting from the increased transcriptional activity of FOXM1 observed in cancer cells.

USP28 facilitates pancreatic cancer progression through activation of Wnt/β-catenin pathway via stabilising FOXM1

Ubiquitination is an important post-translational modification that can be reversed by a family of enzymes called deubiquitinating enzymes (DUBs). Ubiquitin-specific protease 28 (USP28), a member of the DUBs family, functions as a potential tumour promoter in various cancers. However, the biological function and clinical significance of USP28 in pancreatic cancer (PC) are still unclear. Here, we showed that PC tumours had higher USP28 expression compared with that of normal pancreatic tissues, and high USP28 level was significantly correlated with malignant phenotype and shorter survival in patients with PC. Overexpression of USP28 accelerated PC cell growth, whereas USP28 knockdown impaired PC cell growth both in vitro and in vivo. Further, we found that USP28 promoted PC cell growth by facilitating cell cycle progression and inhibiting apoptosis. Mechanistically, USP28 deubiquitinated and stabilised FOXM1, a critical mediator of Wnt/β-catenin signalling. USP28-mediated stabilisation of FOXM1 significantly promoted nucleus β-catenin trans-activation, which in turn led to the activation of the Wnt/β-catenin pathway. Finally, restoration of FOXM1 expression abolished the anti-tumour effects of USP28-silencing. Thus, USP28 contributes to PC pathogenesis through enhancing the FOXM1-mediated Wnt/β-catenin signalling, and could be a potential diagnostic and therapeutic target for PC cases.

Wnt/β-catenin signaling in cancers and targeted therapies

Wnt/β-catenin signaling has been broadly implicated in human cancers and experimental cancer models of animals. Aberrant activation of Wnt/β-catenin signaling is tightly linked with the increment of prevalence, advancement of malignant progression, development of poor prognostics, and even ascendence of the cancer-associated mortality. Early experimental investigations have proposed the theoretical potential that efficient repression of this signaling might provide promising therapeutic choices in managing various types of cancers. Up to date, many therapies targeting Wnt/β-catenin signaling in cancers have been developed, which is assumed to endow clinicians with new opportunities of developing more satisfactory and precise remedies for cancer patients with aberrant Wnt/β-catenin signaling. However, current facts indicate that the clinical translations of Wnt/β-catenin signaling-dependent targeted therapies have faced un-neglectable crises and challenges. Therefore, in this study, we systematically reviewed the most updated knowledge of Wnt/β-catenin signaling in cancers and relatively targeted therapies to generate a clearer and more accurate awareness of both the developmental stage and underlying limitations of Wnt/β-catenin-targeted therapies in cancers. Insights of this study will help readers better understand the roles of Wnt/β-catenin signaling in cancers and provide insights to acknowledge the current opportunities and challenges of targeting this signaling in cancers.

FOXM1-AKT Positive Regulation Loop Provides Venetoclax Resistance in AML

Forkhead box protein M1 (FOXM1) is a crucial regulator of cancer development and chemoresistance. It is often overexpressed in acute myeloid leukemia (AML) and is associated with poor survival and reduced efficacy of cytarabine therapy. Molecular mechanisms underlying high FOXM1 expression levels in malignant cells are still unclear. Here we demonstrate that AKT and FOXM1 constitute a positive autoregulatory loop in AML cells that sustains high activity of both pro-oncogenic regulators. Inactivation of either AKT or FOXM1 signaling results in disruption of whole loop, coordinated suppression of FOXM1 or AKT, respectively, and similar transcriptomic changes. AML cells with inhibited AKT activity or stable FOXM1 knockdown display increase in HOXA genes expression and BCL2L1 suppression that are associated with prominent sensitization to treatment with Bcl-2 inhibitor venetoclax. Taken together, our data indicate that AKT and FOXM1 in AML cells should not be evaluated as single independent regulators but as two parts of a common FOXM1-AKT positive feedback circuit. We also report for the first time that FOXM1 inactivation can overcome AML venetoclax resistance. Thus, targeting FOXM1-AKT loop may open new possibilities in overcoming AML drug resistance and improving outcomes for AML patients.

Therapeutic Potential of Endothelial Progenitor Cells in Pulmonary Diseases

Compromised alveolar development and pulmonary vascular remodeling are hallmarks of pediatric lung diseases such as bronchopulmonary dysplasia (BPD) and alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV). Although advances in surfactant therapy, corticosteroids, and anti-inflammatory drugs have improved clinical management of preterm infants, still those who suffer with severe vascular complications lack viable treatment options. Paucity of the alveolar capillary network in ACDMPV causes respiratory distress and leads to mortality in a vast majority of ACDMPV infants. The discovery of endothelial progenitor cells (EPCs) in 1997 brought forth the paradigm of postnatal vasculogenesis and hope for promoting vascularization in fragile patient populations, such as those with BPD and ACDMPV. The identification of diverse EPC populations, both hematopoietic and nonhematopoietic in origin, provided a need to identify progenitor cell selective markers which are linked to progenitor properties needed to develop cell-based therapies. Focusing to the future potential of EPCs for regenerative medicine, this review will discuss various aspects of EPC biology, beginning with the identification of hematopoietic, nonhematopoietic, and tissue-resident EPC populations. We will review knowledge related to cell surface markers, signature gene expression, key transcriptional regulators, and will explore the translational potential of EPCs for cell-based therapy for BPD and ACDMPV. The ability to produce pulmonary EPCs from patient-derived induced pluripotent stem cells (iPSCs) in vitro, holds promise for restoring vascular growth and function in the lungs of patients with pediatric pulmonary disorders.

Regulation of Wnt Signaling by FOX Transcription Factors in Cancer

Simple Summary

Cancer is caused by a breakdown of cell-to-cell communication, which results in the unrestricted expansion of cells within a tissue. In many cases, tumor growth is maintained by the continuous activation of cell signaling programs that normally drive embryonic development and wound repair. In this review article, I discuss how one of the largest human protein families, namely FOX proteins, controls the activity of the Wnt pathway, a major regulatory signaling cascade in developing organisms and adult stem cells. Evidence suggests that there is considerable crosstalk between FOX proteins and the Wnt pathway, which contributes to cancer initiation and progression. A better understanding of FOX biology may therefore lead to the development of new targeted treatments for many types of cancer.

Abstract

Aberrant activation of the oncogenic Wnt signaling pathway is a hallmark of numerous types of cancer. However, in many cases, it is unclear how a chronically high Wnt signaling tone is maintained in the absence of activating pathway mutations. Forkhead box (FOX) family transcription factors are key regulators of embryonic development and tissue homeostasis, and there is mounting evidence that they act in part by fine-tuning the Wnt signaling output in a tissue-specific and context-dependent manner. Here, I review the diverse ways in which FOX transcription factors interact with the Wnt pathway, and how the ectopic reactivation of FOX proteins may affect Wnt signaling activity in various types of cancer. Many FOX transcription factors are partially functionally redundant and exhibit a highly restricted expression pattern, especially in adults. Thus, precision targeting of individual FOX proteins may lead to safe treatment options for Wnt-dependent cancers.

Blastocyst complementation reveals that NKX2-1 establishes the proximal-peripheral boundary of the airway epithelium

BACKGROUND

Distinct boundaries between the proximal conducting airways and more peripheral-bronchial regions of the lung are established early in foregut embryogenesis, demarcated in part by the distribution of SOX family and NKX2-1 transcription factors along the cephalo-caudal axis of the lung. We used blastocyst complementation to identify the role of NKX2-1 in the formation of the proximal-peripheral boundary of the airways in mouse chimeric embryos.

RESULTS

While Nkx2-1-/- mouse embryos form primordial tracheal cysts, peripheral pulmonary structures are entirely lacking in Nkx2-1-/- mice. Complementation of Nkx2-1-/- embryos with NKX2-1-sufficient embryonic stem cells (ESCs) enabled the formation of all tissue components of the peripheral lung but did not enhance ESC colonization of the most proximal regions of the airways. In chimeric mice, a precise boundary was formed between NKX2-1-deficient basal cells co-expressing SOX2 and SOX9 in large airways and ESC-derived NKX2-1+ SOX9+ epithelial cells of smaller airways. NKX2-1-sufficient ESCs were able to selectively complement peripheral, rather than most proximal regions of the airways. ESC complementation did not prevent ectopic expression of SOX9 but restored β-catenin signaling in Nkx2-1-/- basal cells of large airways.

CONCLUSIONS

NKX2-1 and β-catenin function in an epithelial cell-autonomous manner to establish the proximal-peripheral boundary along developing airways.

Nanoparticle Delivery Systems with Cell-Specific Targeting for Pulmonary Diseases

Respiratory disorders are among the most important medical problems threatening human life. The conventional therapeutics for respiratory disorders are hindered by insufficient drug concentrations at pathological lesions, lack of cell-specific targeting, and various biobarriers in the conducting airways and alveoli. To address these critical issues, various nanoparticle delivery systems have been developed to serve as carriers of specific drugs, DNA expression vectors, and RNAs. The unique properties of nanoparticles, including controlled size and distribution, surface functional groups, high payload capacity, and drug release triggering capabilities, are tailored to specific requirements in drug/gene delivery to overcome major delivery barriers in pulmonary diseases. To avoid off-target effects and improve therapeutic efficacy, nanoparticles with high cell-targeting specificity are essential for successful nanoparticle therapies. Furthermore, low toxicity and high degradability of the nanoparticles are among the most important requirements in the nanoparticle designs. In this review, we provide the most up-to-date research and clinical outcomes in nanoparticle therapies for pulmonary diseases. We also address the current critical issues in key areas of pulmonary cell targeting, biosafety and compatibility, and molecular mechanisms for selective cellular uptake.

FOXM1 and Cancer: Faulty Cellular Signaling Derails Homeostasis

Forkhead box transcription factor, FOXM1 is implicated in several cellular processes such as proliferation, cell cycle progression, cell differentiation, DNA damage repair, tissue homeostasis, angiogenesis, apoptosis, and redox signaling. In addition to being a boon for the normal functioning of a cell, FOXM1 turns out to be a bane by manifesting in several disease scenarios including cancer. It has been given an oncogenic status based on several evidences indicating its role in tumor development and progression. FOXM1 is highly expressed in several cancers and has also been implicated in poor prognosis. A comprehensive understanding of various aspects of this molecule has revealed its role in angiogenesis, invasion, migration, self- renewal and drug resistance. In this review, we attempt to understand various mechanisms underlying FOXM1 gene and protein regulation in cancer including the different signaling pathways, post-transcriptional and post-translational modifications. Identifying crucial molecules associated with these processes can aid in the development of potential pharmacological approaches to curb FOXM1 mediated tumorigenesis.

FOXM1 nuclear transcription factor translocates into mitochondria and inhibits oxidative phosphorylation

Forkhead box M1 (FOXM1), a nuclear transcription factor that activates cell cycle regulatory genes, is highly expressed in a majority of human cancers. The function of FOXM1 independent of nuclear transcription is unknown. In the present study, we found the FOXM1 protein inside the mitochondria. Using site-directed mutagenesis, we generated FOXM1 mutant proteins that localized to distinct cellular compartments, uncoupling the nuclear and mitochondrial functions of FOXM1. Directing FOXM1 into the mitochondria decreased mitochondrial mass, membrane potential, respiration, and electron transport chain (ETC) activity. In mitochondria, the FOXM1 directly bound to and increased the pentatricopeptide repeat domain 1 (PTCD1) protein, a mitochondrial leucine-specific tRNA binding protein that inhibits leucine-rich ETC complexes. Mitochondrial FOXM1 did not change cellular proliferation. Thus, FOXM1 translocates into mitochondria and inhibits mitochondrial respiration by increasing PTCD1. We identify a new paradigm that FOXM1 regulates mitochondrial homeostasis in a process independent of nuclear transcription.

Circ-MMP2 (circ-0039411) induced by FOXM1 promotes the proliferation and migration of lung adenocarcinoma cells in vitro and in vivo

Numerous reports have stated the significance of cellular events such as proliferation, migration and EMT (epithelial-mesenchymal transition) for cancer development, but the related molecular mechanism remains elusive. FOXM1 (forkhead box transcription M1) is a nuclear co-activator participating in lung adenocarcinoma (LUAD). Thus, this study tried to explain the function of FOXM1 and its downstream molecular mechanism in LUAD. We uncovered FOXM1 upregulation in LUAD and demonstrated that FOXM1 facilitated β-catenin nuclear translocation to activate the transcription of downstream genes. Moreover, we discovered that FOXM1 transcriptionally activated circ0039411 which derived from matrix metallopeptidase 2 (MMP2) (also named as circ-MMP2), while MMP2 is a known downstream target of β-catenin. As for functional investigation, knockdown of circ-0039411 suppressed the proliferation, migration and EMT in LUAD cells and also hindered in vivo growth and metastasis of LUAD tumor. Mechanistically, circ-0039411 enhanced the stability of FOXM1 mRNA by recruiting IGF2BP3 (insulin like growth factor 2 mRNA binding protein 3), thus forming a positive feedback loop. In conclusion, this study revealed that FOXM1-induced circ-MMP2 (circ-0039411) contributes to malignant behaviors of LUAD cells via relying on FOXM1, potentially infusing inspirations for the search of new molecular targets for LUAD treatment.

FOXM1: a potential therapeutic target in human solid cancers

Introduction: FOXM1 is one of the most frequently overexpressed proteins in human solid cancers. Here, we discuss novel direct targets of FOXM1 as well as new pathways involving FOXM1, through which this protein exerts its oncogenic activity.Areas covered: We give a detailed review of FOXM1 transcriptional targets involved in 16 different types of human cancer as published in the literature in the last 5 years. We also discuss a novel positive feedback loop between FOXM1 and AKT - both well-established master regulators of cancer.Expert opinion: Despite the discovery of several FOXM1 inhibitors over the years (by our team and others), their therapeutic use is limited by their adverse off-target effects.Newly-discovered proteins regulated by FOXM1 present a promising alternative approach to target its pro-cancer activity. In addition, targeting regulating proteins that take part in the positive feedback loop between FOXM1/AKT has the double advantage of suppressing both, and can lead to developing novel anti-cancer drugs.

Identification of Crucial Genes Associated With Immune Cell Infiltration in Hepatocellular Carcinoma by Weighted Gene Co-expression Network Analysis

The dreadful prognosis of hepatocellular carcinoma (HCC) is primarily due to the low early diagnosis rate, rapid progression, and high recurrence rate. Valuable prognostic biomarkers are urgently needed for HCC. In this study, microarray data were downloaded from GSE14520, GSE22058, International Cancer Genome Consortium (ICGC), and The Cancer Genome Atlas (TCGA). Differentially expressed genes (DEGs) were identified among GSE14520, GSE22058, and ICGC databases. Weighted gene co-expression network analysis (WGCNA) was used to establish gene co-expression modules of DEGs, and genes of key modules were examined to identify hub genes using univariate Cox regression in the ICGC cohort. Expression levels and time-dependent receiver operating characteristic (ROC) and area under the curve (AUC) were determined to estimate the prognostic competence of the hub genes. These hub genes were also validated in the Gene Expression Profiling Interactive Analysis (GEPIA) and TCGA databases. TIMER algorithm and GSCALite database were applied to analyze the association of the hub genes with immunocytotic infiltration and their pathway enrichment. Altogether, 276 DEGs were identified and WGCNA described a unique and significantly DEGs-associated co-expression module containing 148 genes, with 10 hub genes selected by univariate Cox regression in the ICGC cohort (BIRC5, FOXM1, CENPA, KIF4A, DTYMK, PRC1, IGF2BP3, KIF2C, TRIP13, and TPX2). Most of the genes were validated in the GEPIA databases, except IGF2BP3. The results of multivariate Cox regression analysis indicated that the abovementioned hub genes are all independent predictors of HCC. The 10 genes were also confirmed to be associated with immune cell infiltration using the TIMER algorithm. Moreover, four-gene signature was developed, including BIRC5, CENPA, FOXM1, DTYMK. These hub genes and the model demonstrated a strong prognostic capability and are likely to be a therapeutic target for HCC. Moreover, the association of these genes with immune cell infiltration improves our understanding of the occurrence and development of HCC.

The transcription factor FOXM1 regulates the balance between proliferation and aberrant differentiation in head and neck squamous cell carcinoma

Sustained expression of FOXM1 is a hallmark of nearly all human cancers including squamous cell carcinomas of the head and neck (HNSCC). HNSCCs partially preserve the epithelial differentiation program, which recapitulates fetal and adult traits of the tissue of tumor origin but is deregulated by genetic alterations and tumor-supporting pathways. Using shRNA-mediated knockdown, we demonstrate a minimal impact of FOXM1 on proliferation and migration of HNSCC cell lines under standard cell culture conditions. However, FOXM1 knockdown in three-dimensional (3D) culture and xenograft tumor models resulted in reduced proliferation, decreased invasion, and a more differentiated-like phenotype, indicating a context-dependent modulation of FOXM1 activity in HNSCC cells. By ectopic overexpression of FOXM1 in HNSCC cell lines, we demonstrate a reduced expression of cutaneous-type keratin K1 and involucrin as a marker of squamous differentiation, supporting the role of FOXM1 in modulation of aberrant differentiation in HNSCC. Thus, our data provide a strong rationale for targeting FOXM1 in HNSCC. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.