FOX(M1) news--it is cancer

High-level SAE2 promotes malignant phenotype and predicts outcome in gastric cancer

BACKGROUND

The SUMO pathway has been shown to play an important role in tumorigenesis. This report analyzed the involvement of the sole SUMO-Activating Enzyme Subunit 2 (SAE2) in human gastric cancer (GC) progression and prognosis.

METHODS

Expression of SAE2 was examined by Quantigene Plex, western blotting and immunohistochemistry. The expression of SAE2 and c-MYC were detected in parallel in 276 cases. The molecular mechanisms of SAE2 expression and its effects on cell growth, colony formation, migration and invasion were also explored by CCK8 assay, colony formation experiment, transwell chamber assay with or without matrigel, immunoprecipitation and in vivo tumorigenesis and tumor metastasis.

RESULTS

SAE2 was markedly overexpressed in GC cell lines and primary tumor samples of GC, and significantly correlated with deeper tumor depth, distant metastasis, higher pathological stage and stratified survival in human GC. SAE2 positivity was independently associated with a worse outcome in multivariate analysis. Knockdown of SAE2 expression inhibited the proliferation, migration, and invasion of SAE2-overexpressing GC cells. Consistent with the in vitro results, down-regulation of SAE2 in human GC BGC823 cells significantly reduced the tumorigenic and metastatic potential of the cells in vivo. SAE2 protein was significantly associated with the higher expression of c-MYC in primary GC tissues. Moreover, FoxM1 was SUMOylated in GC and that inhibition of SAE2 resulted in a decrease in SUMO1-FoxM1 levels compared with those in the controls.

CONCLUSIONS

These findings suggest that SAE2 has a pivotal role in the aggressiveness of GC, and highlight its usefulness as a prognostic factor in GC.

MDM2 antagonists synergize broadly and robustly with compounds targeting fundamental oncogenic signaling pathways

While MDM2 inhibitors hold great promise as cancer therapeutics, drug resistance will likely limit their efficacy as single agents. To identify drug combinations that might circumvent resistance, we screened for agents that could synergize with MDM2 inhibition in the suppression of cell viability. We observed broad and robust synergy when combining MDM2 antagonists with either MEK or PI3K inhibitors. Synergy was not limited to cell lines harboring MAPK or PI3K pathway mutations, nor did it depend on which node of the PI3K axis was targeted. MDM2 inhibitors also synergized strongly with BH3 mimetics, BCR-ABL antagonists, and HDAC inhibitors. MDM2 inhibitor-mediated synergy with agents targeting these mechanisms was much more prevalent than previously appreciated, implying that clinical translation of these combinations could have far-reaching implications for public health. These findings highlight the importance of combinatorial drug targeting and provide a framework for the rational design of MDM2 inhibitor clinical trials.

High-level SAE2 promotes malignant phenotype and predicts outcome in gastric cancer

BACKGROUND

The SUMO pathway has been shown to play an important role in tumorigenesis. This report analyzed the involvement of the sole SUMO-Activating Enzyme Subunit 2 (SAE2) in human gastric cancer (GC) progression and prognosis.

METHODS

Expression of SAE2 was examined by Quantigene Plex, western blotting and immunohistochemistry. The expression of SAE2 and c-MYC were detected in parallel in 276 cases. The molecular mechanisms of SAE2 expression and its effects on cell growth, colony formation, migration and invasion were also explored by CCK8 assay, colony formation experiment, transwell chamber assay with or without matrigel, immunoprecipitation and in vivo tumorigenesis and tumor metastasis.

RESULTS

SAE2 was markedly overexpressed in GC cell lines and primary tumor samples of GC, and significantly correlated with deeper tumor depth, distant metastasis, higher pathological stage and stratified survival in human GC. SAE2 positivity was independently associated with a worse outcome in multivariate analysis. Knockdown of SAE2 expression inhibited the proliferation, migration, and invasion of SAE2-overexpressing GC cells. Consistent with the in vitro results, down-regulation of SAE2 in human GC BGC823 cells significantly reduced the tumorigenic and metastatic potential of the cells in vivo. SAE2 protein was significantly associated with the higher expression of c-MYC in primary GC tissues. Moreover, FoxM1 was SUMOylated in GC and that inhibition of SAE2 resulted in a decrease in SUMO1-FoxM1 levels compared with those in the controls.

CONCLUSIONS

These findings suggest that SAE2 has a pivotal role in the aggressiveness of GC, and highlight its usefulness as a prognostic factor in GC.

Activation of vitamin D receptor signaling downregulates the expression of nuclear FOXM1 protein and suppresses pancreatic cancer cell stemness

PURPOSE

Dysregulated signaling of nuclear transcription factors vitamin D receptor (VDR) and Forkhead box M1 (FOXM1) plays important roles in transformation and tumorigenesis. In this study, we sought to determine whether VDR signaling causally affected FOXM1 signaling in and pathogenesis of pancreatic ductal adenocarcinoma (PDAC).

EXPERIMENTAL DESIGN

Genetic and pharmacologic approaches were used to manipulate VDR signaling. The impacts of altered VDR signaling on FOXM1 expression and function in PDAC cells were determined using molecular and biochemical methods, whereas those on PDAC cell biology and tumorigenicity were determined using in vitro and in vivo experimental systems. The clinical relevance of our findings was validated by analyzing human PDAC specimens.

RESULTS

There was a striking inverse correlation between reduced expression of VDR and increased expression of FOXM1 in human PDAC cells and tissues. Treatment of PDAC cells with 1,25-dihydroxyvitamin D3 (1,25D), its synthetic analogue EB1089 (EB), and VDR transgenics drastically inhibited FOXM1 signaling and markedly suppressed tumor stemness, growth, and metastasis. Mechanistically, 1,25D and EB repressed FOXM1 transcription and reduced the expression level of nuclear FOXM1 protein.

CONCLUSION

Inactivation of Vitamin D/VDR signaling is a critical contributor to PDAC development and progression via elevated expression and function of FOXM1 and enhanced PDAC cell stemness, invasion, and metastasis.

miR-320 enhances the sensitivity of human colon cancer cells to chemoradiotherapy in vitro by targeting FOXM1

miR-320 expression level is found to be down-regulated in human colon cancer. To date, however, its underlying mechanisms in the chemo-resistance remain largely unknown. In this study, we demonstrated that ectopic expression of miR-320 led to inhibit HCT-116 cell proliferation, invasion and hypersensitivity to 5-Fu and Oxaliplatin. Also, knockdown of miR-320 reversed these effects in HT-29 cells. Furthermore, we identified an oncogene, FOXM1, as a direct target of miR-320. In addition, miR-320 could inactive the activity of Wnt/β-catenin pathway. Finally, we found that miR-320 and FOXM1 protein had a negative correlation in colon cancer tissues and adjacent normal tissues. These findings implied that miR-320-FOXM1 axis may overcome chemo-resistance of colon cancer cells and provide a new therapeutic target for the treatment of colon cancer.

Overexpression of FOXM1 is associated with metastases of nasopharyngeal carcinoma

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Hsp70-Bag3 interactions regulate cancer-related signaling networks

Bag3, a nucleotide exchange factor of the heat shock protein Hsp70, has been implicated in cell signaling. Here, we report that Bag3 interacts with the SH3 domain of Src, thereby mediating the effects of Hsp70 on Src signaling. Using several complementary approaches, we established that the Hsp70-Bag3 module is a broad-acting regulator of cancer cell signaling by modulating the activity of the transcription factors NF-κB, FoxM1, Hif1α, the translation regulator HuR, and the cell-cycle regulators p21 and survivin. We also identified a small-molecule inhibitor, YM-1, that disrupts the Hsp70-Bag3 interaction. YM-1 mirrored the effects of Hsp70 depletion on these signaling pathways, and in vivo administration of this drug was sufficient to suppress tumor growth in mice. Overall, our results defined Bag3 as a critical factor in Hsp70-modulated signaling and offered a preclinical proof-of-concept that the Hsp70-Bag3 complex may offer an appealing anticancer target.

The NF-κB genomic landscape in lymphoblastoid B cells

The nuclear factor κB (NF-κΒ) subunits RelA, RelB, cRel, p50, and p52 are each critical for B cell development and function. To systematically characterize their responses to canonical and noncanonical NF-κB pathway activity, we performed chromatin immunoprecipitation followed by high-throughput DNA sequencing (ChIP-seq) analysis in lymphoblastoid B cell lines (LCLs). We found a complex NF-κB-binding landscape, which did not readily reflect the two NF-κB pathway paradigms. Instead, 10 subunit-binding patterns were observed at promoters and 11 at enhancers. Nearly one-third of NF-κB-binding sites lacked κB motifs and were instead enriched for alternative motifs. The oncogenic forkhead box protein FOXM1 co-occupied nearly half of NF-κB-binding sites and was identified in protein complexes with NF-κB on DNA. FOXM1 knockdown decreased NF-κB target gene expression and ultimately induced apoptosis, highlighting FOXM1 as a synthetic lethal target in B cell malignancy. These studies provide a resource for understanding mechanisms that underlie NF-κB nuclear activity and highlight opportunities for selective NF-κB blockade.

Tumour-suppressive microRNA-24-1 inhibits cancer cell proliferation through targeting FOXM1 in bladder cancer

Here, we found that microRNA-24-1 (miR-24-1) is significantly reduced in bladder cancer (BC) tissues, suggesting that it functions as a tumour suppressor. Restoration of mature miR-24-1 inhibits cancer cell proliferation and induces apoptosis. Forkhead box protein M1 (FOXM1) is a direct target gene of miR-24-1, as shown by genome-wide gene expression analysis and luciferase reporter assay. Overexpressed FOXM1 is confirmed in BC clinical specimens, and silencing of FOXM1 induces apoptosis in cancer cell lines. Our data demonstrate that the miR-24-1-FOXM1 axis contributes to cancer cell proliferation in BC, and elucidation of downstream signalling will provide new insights into the molecular mechanisms of BC oncogenesis.

Suppression of the Oncogenic Transcription Factor FOXM1 by Proteasome Inhibitors

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

Laminins 411 and 421 differentially promote tumor cell migration via α6β1 integrin and MCAM (CD146)

α4-laminins, such as laminins 411 and 421, are mesenchymal laminins expressed by blood and lymphatic vessels and some tumor cells. Laminin-411 promotes migration of leukocytes and endothelial cells, but the effect of this laminin and laminin-421 on tumor cells is poorly understood. In the present study, we demonstrate that laminin-411 and, to a greater extent, laminin-421 significantly promote migration of tumor cells originated from melanomas, gliomas and different carcinomas via α6β1 integrin. In solid-phase binding assays, both laminins similarly bound α6β1 integrin but only laminin-421, among several laminin isoforms, readily bound MCAM (CD146), a cell-surface adhesion molecule strongly associated with tumor progression. Accordingly, a function-blocking mAb to MCAM inhibited tumor cell migration on laminin-421 but not on laminins 411 or 521. In tumor tissues, melanoma cells co-expressed MCAM, laminin α4, β1, β2 and γ1 chains, and integrin α6 and β1 chains. The present data highlight the novel role of α4-laminins in tumor cell migration and identify laminin-421 as a primary ligand for MCAM and a putative mediator of tumor invasion and metastasis.

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

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

FOXM1 modulates cisplatin sensitivity by regulating EXO1 in ovarian cancer

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

Cross-species regulatory network analysis identifies a synergistic interaction between FOXM1 and CENPF that drives prostate cancer malignancy

To identify regulatory drivers of prostate cancer malignancy, we have assembled genome-wide regulatory networks (interactomes) for human and mouse prostate cancer from expression profiles of human tumors and of genetically engineered mouse models, respectively. Cross-species computational analysis of these interactomes has identified FOXM1 and CENPF as synergistic master regulators of prostate cancer malignancy. Experimental validation shows that FOXM1 and CENPF function synergistically to promote tumor growth by coordinated regulation of target gene expression and activation of key signaling pathways associated with prostate cancer malignancy. Furthermore, co-expression of FOXM1 and CENPF is a robust prognostic indicator of poor survival and metastasis. Thus, genome-wide cross-species interrogation of regulatory networks represents a valuable strategy to identify causal mechanisms of human cancer.

Global gene expression analysis of canine cutaneous mast cell tumor: could molecular profiling be useful for subtype classification and prognostication?

Prognosis and therapeutic management of dogs with cutaneous mast cell tumors (MCTs) depend on clinical stage and histological grade. However, the prognostic value of this latter is still questionable. In the present study, MCT transcriptome was analyzed to identify a set of candidate genes potentially useful for predicting the biological behavior of MCTs. Fifty-one canine MCT biopsies were analyzed. Isolated and purified total RNAs were individually hybridized to the Agilent Canine V2 4x44k DNA microarray. The comparison of reference differentiated and undifferentiated MCT transcriptome revealed a total of 597 differentially expressed genes (147 down-regulated and 450 up-regulated). The functional analysis of this set of genes provided evidence that they were mainly involved in cell cycle, DNA replication, p53 signaling pathway, nucleotide excision repair and pyrimidine metabolism. Class prediction analysis identified 13 transcripts providing the greatest accuracy of class prediction and divided samples into two categories (differentiated and undifferentiated), harboring a different prognosis. The Principal Component Analysis of all samples, made by using the selected 13 markers, confirmed MCT classification. The first three components accounted for 99.924% of the total variance. This molecular classification significantly correlated with survival time (p = 0.0026). Furthermore, among all marker genes, a significant association was found between mRNA expression and MCT-related mortality for FOXM1, GSN, FEN1 and KPNA2 (p<0.05). Finally, marker genes mRNA expression was evaluated in a cohort of 22 independent samples. Data obtained enabled to identify MCT cases with different prognosis. Overall, the molecular characterization of canine MCT transcriptome allowed the identification of a set of 13 transcripts that clearly separated differentiated from undifferentiated MCTs, thus predicting outcome regardless of the histological grade. These results may have clinical relevance and warrant future validation in a prospective study.

Signaling of miRNAs-FOXM1 in cancer and potential targeted therapy

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

Prognostic discrimination using a 70-gene signature among patients with estrogen receptor-positive breast cancer and an intermediate 21-gene recurrence score

The Oncotype DX^® recurrence score (RS) predictor has been clinically utilized to appropriately select adjuvant chemotherapy for patients with estrogen receptor (ER)-positive early breast cancer. However, the selection of chemotherapy for patients with intermediate RSs remains controversial. We assessed the prognostic value of a 70-gene signature (70GS) among patients with ER-positive breast cancer and intermediate RSs. In addition, we sought to identify genes associated with poor 70GS scores based on gene expression profiling (GEP). GEP was performed using gene expression data from 186 patients with ER-positive breast cancer. The RS and 70GS score were calculated on the basis of GEP. Among 186 patients, 82 ER-positive patients with intermediate RSs were identified. These patients were stratified by 70GS, overall survival (OS) significantly differed according to 70GS (p = 0.013). In a supervised hierarchical analysis according to 70GS, the expression of several representative genes for cell proliferation was significantly higher in the poor 70GS cluster than in the good 70GS cluster. Furthermore, among these patients, FOXM1, AURKA, AURKB, and BIRC5 displayed prognostic significance for OS. In conclusion, 70GS can help to discriminate survival differences among ER-positive patients with intermediate RSs. FOXM1, AURKA, AURKB, and BIRC5, are associated with poor 70GS scores.

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

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