Forkhead Box K1 Research Articles

Forkhead box K1 regulates the malignant behavior of gastric cancer by inhibiting autophagy.

Forkhead box K1 (FOXK1) is a transcription factor that contributes to cancer development, but it is unclear how FOXK1 regulates the proliferation and migration of gastric cancer (GC) cells. The purpose of this study was to investigate the clinical significance, biological function, and molecular mechanisms of FOXK1 in GC. We conducted bioinformatics assays and western blotting to assess FOXK1 expression. Then, we performed immunohistochemistry (IHC) with tissue microarrays (TMAs) to assess FOXK1 expression in order to identify an association between FOXK1 expression levels and clinical parameters. We used 5-ethynyl-2'-deoxyuridine (EdU), wound healing and Transwell assays to determine whether FOXK1 promotes malignant behaviors in GC. Furthermore, immunofluorescence staining, transmission electron microscopy and western blotting were used to verify an association between FOXK1 and autophagy. We observed high levels of FOXK1 expression in GC tissues, which were associated with the degree of malignancy in GC. FOXK1 promotes the malignant behavior of GC by regulating autophagy via activation of the class I phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway and inhibition of the expression of class III PI3K. These findings provide a new target for the comprehensive treatment of GC by highlighting the relationship between FOXK1 and malignant behaviors in GC.

Circular RNA Circ-ITCH Inhibits the Malignant Behaviors of Cervical Cancer by microRNA-93-5p/FOXK2 Axis.

Growing evidence has been demonstrated that circular RNA circ-ITCH plays an important role in the development of several cancers. However, the role of circ-ITCH in cervical cancer has not been evaluated. The aim of the present study was to investigate the biological function of circ-ITCH in cervical cancer both in vitro and in vivo. Our results showed that circ-ITCH was lowly expressed in both human cervical cancer tissues and cell lines. Overexpression of circ-ITCH in HeLa cells significantly suppressed cell proliferation, migration, and invasion. A xenograft tumor model was established to evaluate the role of circ-ITCH in vivo. The results showed that overexpression of circ-ITCH significantly inhibited tumorigenesis of cervical cancer. Mechanism investigations proved that circ-ITCH executed its tumor suppressive activity through sponging microRNA-93-5p (miR-93-5p) and regulating the expression of forkhead box K2 (FOXK2). These findings suggest that circ-ITCH may be a therapeutic target for the management of cervical cancer.

FOXK1, Regulated by miR-365-3p, Promotes Cell Growth and EMT Indicates Unfavorable Prognosis in Breast Cancer.

BackgroundForkhead box K1 (FOXK1) is members of the FOX transcription factor family. Previous work has found out that FOXK1 promotes cell proliferation, migration and invasion in several cancers, such as gastric cancer, glioma cancer and lung cancer; however, the exact role of FOXK1 in breast cancer is still poorly known.MethodsHere, the association between FOXK1 expression and the clinicopathological characteristics of patients with breast cancer was identified. To further decipher the functional roles of FOXK1, it was overexpressed or knocked down in MCF-7, MDA-MB-231 and MCF-10A cells. Cell Counting Kit-8, colony formation and cell cycle assays were performed to examine the proliferation of breast cancer cells. Moreover, wound-healing and Transwell invasion analyses were carried out to explore the effect of FOXK1 on breast cancer cell migration and invasion.ResultsOur findings discovered that FOXK1 promotes cell proliferation, migration and invasion in breast cancer. In addition, consistent with the previous report, FOXK1 also facilitates EMT in breast cancer. TargetScan was used to predict up-stream of FOXK1, indicating that miR-365-3p could regulate FOXK1 expression in breast cancer.ConclusionThe findings of the present study demonstrated that miR-365-3p-FOXK1 axis plays a key role in breast cancer.

CircUBAP2 Inhibits Proliferation and Metastasis of Clear Cell Renal Cell Carcinoma via Targeting miR-148a-3p/FOXK2 Pathway

Clear cell renal cell carcinoma (ccRCC) is the prominent histological subtype of renal cell carcinoma (RCC) with high incidence of local recurrence and distant metastasis. It has been documented that circular ribonucleic acids (circRNAs) play crucial roles in the development of cancers; however, study on exploring the role of circRNAs in ccRCC still remains limited. In the present study, we aimed to evaluate the biological function of a novel circRNA UBAP2 (circUBAP2) in ccRCC and the underlying mechanism. Our results showed that circUBAP2 expression was significantly down-regulated in ccRCC tissues and cell lines. Overexpression of circUBAP2 significantly inhibited the proliferation, migration, and invasion of ccRCC cells. MiR-148a-3p was a target miRNA of circUBAP2 in ccRCC cells, and its expression levels in ccRCC tissues and cell lines were negatively correlated with circUBAP2 levels. Moreover, miR-148a-3p reversed the inhibitory effects of circUBAP2 on cell proliferation, migration, and invasion in ccRCC cells. Additionally, forkhead box K2 (FOXK2) was found to be a target gene of miR-148a-3p and regulated by miR-148a-3p in ccRCC cells. Furthermore, knockdown of FOXK2 reversed the inhibitory effects of miR-148a-3p inhibitor on ccRCC cells. In conclusion, these findings indicated that circUBAP2 functioned as a novel tumor suppressor in ccRCC through regulating the miR-148a-3p/FOXK2 axis. Therefore, circUBAP2 might serve as a potential therapeutic target for the treatment of ccRCC.

MiR-195-5p Suppresses Lung Cancer Cell Proliferation, Migration, and Invasion Via FOXK1.

Lung cancer remains one of the leading causes of cancer deaths around the world. Previous studies have shown that microRNAs have pivotal functions in tumorigenesis including lung cancer. It is reported that microRNA-195-5p acts as a tumor suppressor role in human cancers. However, the function and molecular mechanism of microRNA-195-5p in lung cancer progression is still unclear. In the present study, the results showed that the expression of microRNA-195-5p was downregulated both in lung cancer tissues and in lung cancer cell lines. Enhanced expression of microRNA-195-5p inhibited cell proliferation, migration, and invasion in lung cancer cells. Furthermore, Forkhead box k1 was identified as the direct target of microRNA-195-5p. Forkhead box k1 overexpression could restore the repressed cell proliferation and metastasis caused by microRNA-195-5p overexpression. Our results demonstrated that a functional mechanism of microRNA-195-5p in regulating lung cancer. It indicates that microRNA-195-5p may regulate lung cancer growth and metastasis through the regulation of Forkhead box k1, highlighting the potential application for the treatment of lung cancer in the future.

Aurora-A/SOX8/FOXK1 signaling axis promotes chemoresistance via suppression of cell senescence and induction of glucose metabolism in ovarian cancer organoids and cells.

Rationale: Cisplatin derivatives are first-line chemotherapeutic agents for epithelial ovarian cancer. However, chemoresistance remains a major hurdle for successful therapy and the underlying molecular mechanisms are poorly understood at present.Methods: RNA sequencing of organoids (PDO) established from cisplatin-sensitive and -resistant ovarian cancer tissue samples was performed. Glucose metabolism, cell senescence, and chemosensitivity properties were subsequently examined. Immunoprecipitation, mass spectrometry, Fӧrster resonance energy transfer-fluorescence lifetime imaging (FRET-FLIM), luciferase reporter assay, ChIP and animal experiments were conducted to gain insights into the specific functions and mechanisms of action of the serine/threonine kinase, Aurora-A, in ovarian cancer.Results: Aurora-A levels were significantly enhanced in cisplatin-resistant PDO. Furthermore, Aurora-A promoted chemoresistance through suppression of cell senescence and induction of glucose metabolism in ovarian cancer organoids and cells. Mechanistically, Aurora-A bound directly to the transcription factor sex determining region Y-box 8 (SOX8) and phosphorylated the Ser327 site, in turn, regulating genes related to cell senescence and glycolysis, including hTERT, P16, LDHA and HK2, through enhancement of forkhead-box k1 (FOXK1) expression.Conclusions: Aurora-A regulates cell senescence and glucose metabolism to induce cisplatin resistance by participating in the SOX8/FOXK1 signaling axis in ovarian cancer. Our collective findings highlight a novel mechanism of cisplatin resistance and present potential therapeutic targets to overcome chemoresistance in ovarian cancer.

FOXK1 promotes malignant progression of breast cancer by activating PI3K/AKT/mTOR signaling pathway.

The aim of this study was to investigate the expression characteristics of forkhead box K1 (FOXK1) in breast cancer (BCa). Meanwhile, its relationship with clinicopathology and prognosis of patients with BCa was also explored. The expression level of FOXK1 in 65 paired BCa tissues and para-cancerous tissues was detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The relationship between FOXK1 expression and BCa pathological parameters as well as the prognosis of patients was analyzed. Meanwhile, the expression of FOXK1 in BCa cells was detected by qRT-PCR. Subsequently, FOXK1 knockdown and overexpression models were constructed by lentivirus transfection in BCa cell lines (including MCF-7 and SKBR3). The effect of FOXK1 on the biological functions of BCa cells was analyzed using Cell Counting Kit-8 (CCK-8), cell cloning assay and flow cytometry, respectively. Finally, whether the role of FOXK1 was achieved via the PI3K/AKT/mTOR signaling pathway was explored. The qRT-PCR results showed that FOXK1 expression in BCa tissues was significantly higher than that of adjacent tissues. Compared with patients with low expression of FOXK1, the pathological grading was markedly higher in those with high expression. Meanwhile, the overall survival rate was remarkably lower in patients with high expression. In addition, compared with the negative control group, the proliferation ability of cells in FOXK1 knockdown group was significantly decreased, while cell apoptosis was markedly up-regulated. Besides, Western blot results revealed that silencing FOXK1 could reduce the levels of key proteins in the PI3K/AKT/mTOR signaling pathway, thereby promoting the malignant progression of BCa. Finally, PI3Kα/mTOR-IN-1, which was the inhibitor of the PI3K/AKT/mTOR signaling pathway, significantly reversed the proliferative capacity of cells in FOXK1 overexpression group, as well as enhanced anti-apoptotic ability. FOXK1 expression was remarkably increased both in BCa tissues and cells. Meanwhile, it was markedly associated with pathological stage and poor prognosis of patients. Besides, FOXK1 might promote the malignant progression of BCa by inhibiting the PI3K/AKT/mTOR signaling pathway.

Epigenetically Upregulated MicroRNA-602 Is Involved in a Negative Feedback Loop with FOXK2 in Esophageal Squamous Cell Carcinoma.

MicroRNA is an endogenous, small RNA controlling multiple target genes and playing roles in various tumorigenesis processes. In this study, our results revealed that miR-602 expression levels in tumor tissues and preoperative serum from esophageal squamous cell carcinoma (ESCC) patients were higher than those in non-tumorous tissues and healthy volunteers. miR-602 overexpression was closely related to lymph node metastasis and TNM stages and correlated short overall, and it acted as an independent prognostic marker of ESCC. The methylation status of the miR-602 gene indicated more frequent hypomethylation of the CpG sites located upstream of the miR-602 gene in the ESCC tissues than in the adjacent normal tissues, and the methylation status of miR-602 correlated inversely with its expression levels. Subsequently, miR-602 overexpression promoted ESCC proliferation and metastasis and regulated cell cycles invitro and invivo. Mechanistically, a dual-luciferase experiment validated that Fork head box (FOX)K2 (FOXK2) was a direct target of miR-602. More importantly, systemic delivery of formulated miR-602 antagomir could reduce tumor growth and increased FOXK2 protein expression in nude mice. This work provides novel insight into the molecular pathogenesis of ESCC.

MicroRNA-652 suppresses malignant phenotypes in glioblastoma multiforme via FOXK1-mediated AKT/mTOR signaling pathway.

PurposeAn increasing number of studies have documented that dysregulation of microRNAs (miRNAs) is common in glioblastoma multiforme (GBM). miR-652 is aberrantly expressed in various human cancers and plays important roles in numerous cancer-related processes. However, the expression profiles and potential roles of miR-652 in GBM remain largely unknown.Patients and methodsReverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed to determine miR-652 expression in GBM tissues and cell lines. The effects of miR-652 upregulation on GBM cell proliferation, clone formation, apoptosis, migration and invasion were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, clone formation, flow cytometry and Transwell® migration and invasion assays, respectively. In vivo xenotransplantation was utilized to determine the effect of miR-652 on GBM tumor growth in vivo. Of note, the molecular mechanisms underlying the tumor-suppressing activity of miR-652 upregulation in GBM cells were also investigated using a series of experiments, including bioinformatics analysis, luciferase reporter assay, RT-qPCR and Western blot analysis.ResultsmiR-652 expression was considerably downregulated in GBM tissues and cell lines. Low miR-652 expression was strongly correlated with Karnofsky performance score and tumor size. Overall survival duration was shorter in GBM patients with low miR-652 expression than in those with high miR-652 expression. miR-652 resumption considerably suppressed the proliferation, clone formation, migration, and invasion and promoted the apoptosis of GBM cells in vitro. In addition, forkhead-box k1 (FOXK1) was demonstrated as the direct target gene of miR-652 in GBM cells. FOXK1 downregulation led to a tumor-suppressing activity similar to that of miR-652 upregulation. Restoration of FOXK1 expression partially neutralized the influence of miR-652 overexpression on GBM cells. Furthermore, ectopic miR-652 expression deactivated the AKT/mTOR pathway in GBM cells via FOXK1 regulation. Moreover, miR-652 impaired GBM tumor growth in vivo, probably caused by miR-652-mediated suppression of FOXK1/AKT/mTOR signaling.ConclusionmiR-652 inhibits FOXK1 and deactivates the AKT/mTOR pathway, thereby resulting in the suppression of malignant phenotypes of GBM cells in vitro and in vivo.

1076 – Forkhead Box K2 (FOXK2) Promotes Human Colorectal Cancer Metastasis by Upregulating Zeb1 and Egfr

1076 – Forkhead Box K2 (FOXK2) Promotes Human Colorectal Cancer Metastasis by Upregulating Zeb1 and Egfr

MiR-186-5p Functions as a Tumor Suppressor in Human Osteosarcoma by Targeting FOXK1.

Aberrantly expressed miRNAs play a vital role in the development of some cancers, such as human osteosarcoma (OS). However, the detailed molecular mechanisms underlying miR-186-5p-involved osteosarcoma are unclear. qRT-PCR and western blot analysis were employed to measure the expressions of miR-186-5p and forkhead box k1 (FOXK1). CCK-8 assay evaluated the effect of miR-186-5p and FOXK1 on cell proliferation. Transwell assay confirmed cell migration and invasion. Eventually, the dual-luciferase reporter assay validated 3'-untranslated region (3'-UTR) of FOXK1 as a direct target of miR-186-5p. Down-regulation of miR-186-5p was identified in OS tissues and cell lines, and negatively correlated with distant metastasis, Enneking stage and poor 5-year prognosis as well as the expression of forkhead box k1 (FOXK1) protein. Further assays demonstrated that miR-186-5p overexpression had inhibitory effects on in-vitro cell proliferation, cell cycle, and in-vivo tumor growth. miR-186-5p overexpression also inhibited the epithelial-tomesenchymal transition (EMT), migration and invasion of OS cells. Importantly, miR-186-5p directly targeted FOXK1 3'-UTR and negatively regulated its expression. Silencing of FOXK1 expression enhanced the inhibitory effects of miR-186-5p on OS cell proliferation, migration and invasion. These findings highlighted miR-186-5p as a tumor suppressor in the regulation of progression and metastatic potential of OS, and may benefit the development of therapies targeting miR-186-5p in patients with OS.

Analysis of the promoter region of the human miR-32 gene in colorectal cancer.

The pathogenesis of colorectal cancer (CRC) is poorly understood. MicroRNA (miR)-32 upregulation in CRC tissues was previously reported, where it increased the proliferation, migration and invasion, and reduced apoptosis of CRC cells by inhibiting the expression of phosphatase and tensin homolog (PTEN). However, the mechanism underlying miR-32 upregulation remains unknown. miR-32 is an intronic miRNA located within intron 14 of the transmembrane protein 245 gene (TMEM245). The present study aimed to elucidate the biological pathways underlying miR-32 regulation in CRC. A truncated promoter containing the 5′-flanking region of TMEM245/miR-32 gene was constructed. The promoter region was analyzed by dual luciferase reporter assay in CRC cells. DNA pull-down assay and mass spectrometry (MS) were used to identify proteins binding to the core promoter. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and transcription factor (TF) analyses were used to identify the binding proteins. The −320 to −1 bp fragment of the 5′-flanking region exhibited the highest luciferase activity. The regions spanning −606 to −320 bp exhibited a significant decrease in luciferase activity, compared with the −320 to −1 bp fragment. DNA pull-down assay and MS revealed 403 potential miR-32 promoter binding proteins. GO and KEGG pathway analysis indicated that these proteins were involved in numerous physiological and biochemical processes, including ‘structural molecule activity’, ‘RNA binding’, ‘small molecule metabolic process’ and ‘biogenesis’. Furthermore, TF analysis revealed 10 potential interacting TFs, including SMAD family member 1 (SMAD1), signal transducer and activator of transcription 1 (STAT1) and forkhead box K1 (Foxk1). These results suggested that the core promoter region may be located within-320 to −1 bp of the 5′-flanking region of TMEM245/miR-32 gene, while the region from −606 to −320 bp may harbor repressive regulatory elements. The TFs SMAD1, STAT1 and Foxk1 may be involved in the transcriptional regulation of miR-32.

Forkhead box K2 promotes human colorectal cancer metastasis by upregulating ZEB1 and EGFR.

Background: Metastasis is the major reason for high recurrence rates and poor survival among patients with colorectal cancer (CRC). However, the underlying molecular mechanism of CRC metastasis is unclear. This study aimed to investigate the role of forkhead box K2 (FOXK2), one of the most markedly increased FOX genes in CRC, and the mechanism by which it is deregulated in CRC metastasis.Methods: FOXK2 levels were analyzed in two independent human CRC cohorts (cohort I, n = 363; cohort II, n = 390). In vitro Transwell assays and in vivo lung and liver metastasis models were used to examine CRC cell migration, invasion and metastasis. Chromatin immunoprecipitation and luciferase reporter assays were used to measure the binding of transcription factors to the promoters of FOXK2, zinc finger E-box binding homeobox 1 (ZEB1) and epidermal growth factor receptor (EGFR). Cetuximab was utilized to treat FOXK2-mediated metastatic CRC.Results: FOXK2 was significantly upregulated in human CRC tissues, was correlated with more aggressive features and indicated a poor prognosis. FOXK2 overexpression promoted CRC migration, invasion and metastasis, while FOXK2 downregulation had the opposite effects. ZEB1 and EGFR were determined to be direct transcriptional targets of FOXK2 and were essential for FOXK2-mediated CRC metastasis. Moreover, activation of EGFR signaling by EGF enhanced FOXK2 expression via the extracellular regulated protein kinase (ERK) and nuclear factor (NF)-κB pathways. The EGFR monoclonal antibody cetuximab significantly inhibited FOXK2-promoted CRC metastasis. In clinical CRC tissues, FOXK2 expression was positively correlated with the expression of p65, ZEB1 and EGFR. CRC patients who coexpressed p65/FOXK2, FOXK2/ZEB1 and FOXK2/EGFR had poorer prognosis.Conclusions: FOXK2 serves as a prognostic biomarker in CRC. Cetuximab can block the EGF-NF-κB-FOXK2-EGFR feedback loop and suppress CRC metastasis.

Peripheral Blood DNA Methylation as Potential Biomarker of Malignant Pleural Mesothelioma in Asbestos-Exposed Subjects

IntroductionMalignant pleural mesothelioma (MPM) is an aggressive tumor strongly associated with asbestos exposure. Patients are usually diagnosed when current treatments have limited benefits, highlighting the need for noninvasive early diagnostic tests to monitor asbestos-exposed people. MethodsWe used a genome-wide methylation array to identify, in asbestos-exposed subjects, novel blood DNA methylation markers of MPM in 163 MPM cases and 137 cancer-free controls (82 MPM cases and 68 controls, training set; replication in 81 MPM cases and 69 controls, test set) sampled from the same areas. ResultsEvidence of differential methylation between MPM cases and controls was found (more than 800 cytosine-guanine dinucleotide sites, false discovery rate p value (pfdr) < 0.05), mainly in immune system–related genes. Considering the top differentially methylated signals, seven single- cytosine-guanine dinucleotides and five genomic regions of coordinated methylation replicated with similar effect size in the test set (pfdr < 0.05). The top hypomethylated single-CpG (cases versus controls effect size less than -0.15, pfdr < 0.05 in both the training and test sets) was detected in FOXK1 (Forkhead-box K1) gene, an interactor of BAP1 which was found mutated in MPM tissue and as germline mutation in familial MPM. In the test set, comparison of receiver operating characteristic curves and the area under the curve (AUC) of two models, including or excluding methylation, showed a significant increase in case/control discrimination when considering DNA methylation together with asbestos exposure (AUC = 0.81 versus AUC = 0.89, DeLong’s test p = 0.0013). ConclusionsWe identified signatures of differential methylation in DNA from whole blood between asbestos exposed MPM cases and controls. Our results provide the rationale to further investigate, in prospective studies, the potential use of blood DNA methylation profiles for the identification of early changes related to the MPM carcinogenic process.

Pyrroline-5-carboxylate reductase 1 promotes cell proliferation via inhibiting apoptosis in human malignant melanoma.

IntroductionHuman malignant melanoma (MM) is a highly malignant tumor of cutaneous melanocytes with a fast progression. We investigated the cellular effects of pyrroline-5- carboxylate reductase 1 (PYCR1) in the MM cell lines, A375 and M14.MethodsCell Counting Kit-8 assay, transwell assay, and flow cytometry analysis were performed to evaluate the proliferation, migration and apoptosis of MM cell lines, respectively. To gain more insight into the role of PYCR1 in tumor growth, we analyzed the AKT phosphorylation level in PYCR1-specific siRNA (siPYCR1) and negative control (NC) cells.ResultsBiochemical analysis revealed a clear increase in PYCR1 expression in human MM samples, and its high expression predicted a poor prognosis. Silencing of PYCR1 suppressed the proliferation and migration of A375 and M14 cells. The percentage of apoptosis in cells transfected with siPYCR1 significantly increased in comparison to that of cells transfected with negative control siRNA (NC). The enhanced apoptosis in PYCR1 knockdown cells was consistent with an increased level of markers of apoptosis. siPYCR1 inhibited AKT phosphorylation, as well as the expression of its downstream protein, P70, suggesting that PYCR1 promoted cell growth of the MM cell lines A375 and M14 through stimulation of the AKT pathway. Moreover, forkhead box K2 and regulatory associated protein of MTOR complex 1 shared a similar expression pattern to that of PYCR1 and were significantly downregulated in PYCR1 knockdown cells.ConclusionPYCR1 promoted tumor progression through the AKT pathway in human MM in vitro. Our results expand the knowledge of PYCR1 functions in solid tumors and provide a potential target for the clinical treatment of human MM.

Long non-coding RNA LINC01503 promotes colorectal cancer cell proliferation and invasion by regulating miR-4492/FOXK1 signaling.

Increasing evidence indicates that long non-coding RNAs (lncRNAs) are closely associated with the progression of human cancer, including colorectal cancer (CRC). A previous study suggested that lncRNA LINC01503 promotes squamous cell carcinoma progression. However, the function of LINC01503 in CRC has remained elusive. The present study indicated that LINC01503 was significantly upregulated in CRC tissues compared with that in adjacent normal tissues as detected by reverse transcription-quantitative polymerase chain reaction. It was demonstrated that knockdown of long intergenic non-protein coding RNA (LINC)01503 markedly inhibited the proliferation and invasion of CRC cells, whereas overexpression of LINC01503 had the opposite effects, as indicated by Cell Counting kit-8 and Transwell assays. Mechanistically, it was revealed that LINC01503 serves as a sponge for microRNA (miR)-4492, which targets forkhead box K1 (FOXK1) in CRC cells. In addition, luciferase reporter assays demonstrated the direct binding of miR-4492 mimics to LINC01503 and to a sequence in the 3'-untranslated region of FOXK1. Furthermore, it was demonstrated that overexpression of LINC01503 reduced the availability of miR-4492 in CRC cells. Furthermore, miR-4492 mimics inhibited FOXK1 expression, while simultaneous overexpression of LINC01503 abolished this effect. Finally, it was demonstrated that restoration of FOXK1 abolished the inhibitory effect of LINC01503 knockdown on CRC cell proliferation and invasion. Taken together, the present results suggested that LINC01503 promotes CRC progression via acting as a competing endogenous RNA for miR-4492/FOXK1.

Downregulation of FOXK2 is associated with poor prognosis in patients with gastric cancer.

Forkhead box (FOX)K2 (FOXK2) is a member of the FOX transcription factor family. It has been suggested previously that FOXK2 is required to suppress tumor growth; however, the exact role of FOXK2 in gastric cancer remains to be elucidated. In the present study, the association between FOXK2 expression and the clinicopathological characteristics of patients with gastric cancer was investigated. The prognostic value of FOXK2 expression and the significance of clinicopathological parameters in the overall survival (OS) and progression-free survival of patients were also determined by survival analysis. To investigate the functional roles of FOXK2, it was downregulated in BGC-823 cells using small interfering (si)RNA, and upregulated using a FOXK2 plasmid. Colony formation, Cell Counting Kit-8 and cell proliferation analyses were conducted to examine the proliferation of gastric cancer cells. Transwell and wound-healing assays were performed to investigate the effect of FOXK2 expression on gastric cancer cell migration and invasion. The clinical data demonstrated that FOXK2 expression was reduced in high-grade gastric cancer tissues, and a low level of FOXK2 expression indicated a poor prognosis. The data obtained from the Human Protein Atlas revealed that patients with gastric cancer and a high level of FOXK2 expression had a longer OS time. The results of colony formation assays, Transwell and wound healing assays demonstrated that FOXK2 repressed the proliferation, invasion and migration of gastric cancer cells, respectively. The findings indicated that FOXK2 may serve as a promising therapeutic target in gastric cancer. Taken together, the findings of the present study demonstrated that FOXK2 functions as a tumor suppressor in gastric cancer; the loss of FOXK2 may induce the growth and invasion of gastric cancer cells.

Nuclear-cytoplasmic shuttling protein PP2AB56 contributes to mTORC1-dependent dephosphorylation of FOXK1.

Mammalian target of rapamycin complex 1 (mTORC1) kinase is a master regulator of the cellular response to nutrition-related signals such as insulin and amino acids. mTORC1 is activated on the lysosomal membrane and induces phosphorylation of a variety of downstream molecules. We previously showed that activated mTORC1 induces protein phosphatase 2A (PP2A)-mediated dephosphorylation of the transcription factor forkhead box K1 (FOXK1). The mechanism underlying the signal transduction from the cytoplasmic mTORC1 to the nuclear FOXK1 has remained unclear, however, we now show that a nuclear-cytoplasmic transport system is necessary for the mTORC1-FOXK1 signal transduction. This reaction is mediated by a shuttling protein B56, which is a regulatory subunit of PP2A and plays an essential role in the mTORC1-dependent dephosphorylation of FOXK1. These results suggest that PP2AB56 phosphatase contributes to the signaling for mTORC1-dependent transcriptional regulation.

FOXK2 suppresses the malignant phenotype and induces apoptosis through inhibition of EGFR in clear-cell renal cell carcinoma.

Forkhead box K2 (FOXK2) belongs to the forkhead box transcription factor family. Recent studies have revealed that FOXK2 plays essential roles in cancer cell proliferation and survival. However, the biological function of FOXK2 in renal cell carcinoma remains unexplored. In our study, we demonstrated that FOXK2 mRNA and protein levels were decreased in clear-cell renal cell carcinoma (ccRCC) tissues compared to those in corresponding non-tumor renal tissues, and decreased FOXK2 levels were associated with poor prognosis in ccRCC patients after nephrectomy. FOXK2 suppressed proliferation, migration and invasion capabilities of ccRCC cells and induced cellular apoptosis in vitro. Moreover, we found that FOXK2 overexpression inhibited xenograft tumor growth and promoted apoptosis in vivo. Genome-wide transcriptome profiling using FOXK2 overexpressed 769-P cells revealed that the epidermal growth factor receptor (EGFR) was a potential downstream gene of FOXK2. Overexpression of EGFR is able to rescue the inhibited proliferation capacity and the enhanced apoptosis capacity due to the overexpression of FOXK2 in 769-P cells. Collectively, our results indicate that FOXK2 inhibits the malignant phenotype of ccRCC and acts as a tumor suppressor possibly through the inhibition of EGFR.

Forkhead box K2 inhibits the proliferation, migration, and invasion of human glioma cells and predicts a favorable prognosis.

PurposeForkhead box K2 (FOXK2) is a member of the forkhead box family of transcription factors. Recently, researchers discovered that overexpression of FOXK2 inhibits the proliferation and metastasis of breast cancer, non-small cell lung cancer, and colorectal cancer, and is related to the clinical prognosis. However, in hepatocellular carcinoma, FOXK2 results in the opposite phenotypes. Currently, the contribution of FOXK2 to glioma pathogenesis is not clear.Patients and methodsWe evaluated the expression of FOXK2 in 151 glioma patients using immunohistochemistry assays. The associations among the expression of FOXK2, clinicopathological parameters, and the prognosis of glioma patients were statistically analyzed. We downregulated and upregulated the level of FOXK2 in glioma cells by transfections with small interfering RNA and plasmids. Then, we investigated the effects on tumor cell behavior in vitro by Cell Counting Kit-8 assays, colony-formation assay, transwell assay, and the epithelial-to-mesenchymal transition (EMT) biomarker levels.ResultsThe clinical data showed that expression of FOXK2 gradually decreased with increasing World Health Organization (WHO) grades and a low level of FOXK2 indicates a poor prognosis. FOXK2 expression is negatively correlated with Ki67 expression and the WHO degree but is not correlated with other clinicopathological parameters, including sex, age, Karnofsky Performance Status, tumor diameter, O-6-methylguanine-DNA methyltransferase, and glutathione S-transferase pi. FOXK2 knockdown enhances glioma cell proliferation, migration, invasion, and EMT process, and, in contrast, FOXK2 overexpression inhibits glioma cell proliferation, migration, invasion, and the EMT process.ConclusionExpression of FOXK2 gradually decreases with increasing WHO grades. FOXK2 inhibits tumor proliferation, migration, and invasion. FOXK2 is a critical mediator of the EMT process.