FOXP1 has a low expression in human gliomas and its overexpression inhibits proliferation, invasion and migration of human glioma U251 cells

The functions of FOXP transcription factors and their regulation by post-translational modifications

The forkhead box subfamily P (FOXP) of transcription factors, consisting of FOXP1, FOXP2, FOXP3, and FOXP4, is involved in the regulation of multisystemic functioning. Disruption of the transcriptional activity of FOXP proteins leads to neurodevelopmental disorders and immunological diseases, as well as the suppression or promotion of carcinogenesis. The transcriptional activities of FOXP proteins are directly or indirectly regulated by diverse post-translational modifications, including phosphorylation, ubiquitination, SUMOylation, acetylation, O-GlcNAcylation, and methylation. Here, we discuss how post-translational modifications modulate the multiple functions of FOXP proteins and examine the implications for tumorigenesis and cancer therapy.

Effect of FOXP2 transcription factor on immune infiltration of thyroid cancer and its potential clinical value

Background

The clinical outcomes are not always favorable in certain thyroid cancer patients. The effect of Forkhead-box family on immune cells infiltration and tumor microenvironment in thyroid cancer was explored. The role of FOXP2 in tumor invasion and recurrence was investigated consequently.

Methods

TIMER and GEPIA were firstly employed to compare FOXPs expression in normal and cancer tissues from multiple human cancers. The results from database were confirmed by quantitative Real Time-PCR and Western blot in matched thyroid cancer and adjacent normal tissues, in addition to a panel of thyroid cancer cell lines and normal thyroid cell. GEPIA platform was employed to discover the possibility of FOXPs as prognostic indicator. TISIBD and UACLCAN were then employed to estimate the influence of FOXPs on lymph node metastasis and tumor staging. GEPIA analysis was initially employed to analyze correlation of FOXPs and tumor immune infiltrating cells, and TIMER dataset was then included for standardization according to tumor purity.

Result

Different member of FOXPs showed divergence in expression in various cancer tissues. Lower FOXP1, FOXP2 and higher FOXP3, FOXP4 levels could be identified in thyroid cancer tissues when compared with matched normal tissue. There was an inverse correlation between FOXP2, FOXP4 and immune invasion, whereas FOXP1 and FOXP3 were positively correlated. FOXPs showed remarkable correlations with multiply immune cells. More importantly, only FOXP2 showed the significant effect on recurrence and tumor staging.

Conclusion

As immune regulatory factor, the reduction of FOXP2 may affect tumor microenvironments and immune cells infiltration, enhance tumor immune escape, and promote recurrence of thyroid cancer. FOXP2 could be a new potential diagnostic and prognostic marker.

Molecular networks of FOXP family: dual biologic functions, interplay with other molecules and clinical implications in cancer progression

Though Forkhead box P (FOXP) transcription factors comprising of FOXP1, FOXP2, FOXP3 and FOXP4 are involved in the embryonic development, immune disorders and cancer progression, the underlying function of FOXP3 targeting CD4 + CD25+ regulatory T (Treg) cells and the dual roles of FOXP proteins as an oncogene or a tumor suppressor are unclear and controversial in cancers to date. Thus, the present review highlighted research history, dual roles of FOXP proteins as a tumor suppressor or an oncogene, their molecular networks with other proteins and noncoding RNAs, cellular immunotherapy targeting FOXP3, and clinical implications in cancer progression.

STAT3 promotes tumour progression in glioma by inducing FOXP1 transcription

Objective

This paper investigated the effects of STAT3 through promoting FOXP1 transcription on proliferation, apoptosis and invasion in glioma cells.

Methods

Quantitative real‐time PCR (qRT‐PCR) and Western blot assay were administered to assess the mRNA and protein expression levels of STAT3 and FOXP1 in glioma tissues and cells, respectively. Luciferase reporter and Chromatin Immunoprecipitation (ChIP) assays were implemented to determine the correlation between STAT3 and FOXP1. MTT and colony formation assays were conducted to identify cell growth. Flow cytometry was run to detect the cell apoptosis rate of glioma cells. Transwell assays were conducted to reveal cell invasion ability.

Results

The mRNA and protein expression levels of STAT3 were highly expressed in glioma tissues and cells. After cells transfected with siRNA of STAT3, both STAT3 and FOXP1 were simultaneously downregulated. STAT3 directly regulated FOXP1 transcription. STAT3 promoted cell proliferation, inhibited cell apoptosis and enhanced cell invasion through promoting FOXP1 transcription in glioma cells.

Conclusion

In summary, STAT3 gene was a transcriptional regulator of FOXP1. Depleted STAT3 restrained cell proliferation and invasion, promoted cell apoptosis in glioma cells. This molecular mechanism between STAT3 and FOXP1 can serve as a therapeutic target for glioma treatment.

FOXP1 enhances tumor cell migration by repression of NFAT1 transcriptional activity in MDA-MB-231 cells

Until now, forkhead box P1 (FOXP1) has been identified as a tumor suppressor in several correlation studies in breast cancer. Although FOXP1 is defined as a transcriptional repressor that interacts with other transcription factors in various mechanistic studies, there is no study that explains its repressor functions in breast cancer biology. This study demonstrated the repressor function of FOXP1 on nuclear factor of activated T cells (NFAT1) and the migratory effect of this repression in MDA-MB-231 breast cancer cells. Co-immunoprecipitation experiments were performed for the investigation of protein-protein interaction between two transcription factors. Protein-protein interaction on DNA was investigated with EMSA and transcriptional effects of FOXP1 on NFAT1, luciferase reporter assay was performed. Wound healing assay was used to analyze the effects of overexpression of FOXP1 on tumor cell migration. This study showed that FOXP1 has protein-protein interaction with NFAT1 on DNA and enhances breast cancer cell migration by repressing NFAT1 transcriptional activity and FOXP1 shows oncogenic function by regulating breast cancer cell motility.

Downregulation of FOXP1 Inhibits Cell Proliferation in Hepatocellular Carcinoma by Inducing G1/S Phase Cell Cycle Arrest

Forkhead box P1 (FOXP1) belongs to a family of winged-helix transcription factors that are involved in the processes of cellular proliferation, differentiation, metabolism, and longevity. FOXP1 can affect cell proliferation and migratory ability in hepatocellular carcinoma (HCC) in vitro. However, little is known about the mechanism of FOXP1 in the proliferation of HCC cells. This study aimed to further explore the function of FOXP1 on the proliferation of HCC cells as well as the relevant mechanism involved. Western blot analysis, tumor xenograft models, and flow cytometry analysis were performed to elucidate the function of FOXP1 in the regulation of cell proliferation in human HCC. We observed that silencing FOXP1 significantly suppressed the growth ability of HCC cells both in vitro and in vivo. In addition, knockdown of FOXP1 induced G1/S phase arrest, and the expression of total and phosphorylated Rb (active type) as well as the levels of E2F1 were markedly decreased at 24 h; however, other proteins, including cyclin-dependent kinase (CDK) 4 and 6 and cyclin D1 did not show noticeable changes. In conclusion, downregulation of FOXP1 inhibits cell proliferation in hepatocellular carcinoma by inducing G1/S phase cell cycle arrest, and the decrease in phosphorylated Rb is the main contributor to this G1/S phase arrest.

Identification of genomic aberrations in hemangioblastoma by droplet digital PCR and SNP microarray highlights novel candidate genes and pathways for pathogenesis

Background

The genetic mechanisms underlying hemangioblastoma development are still largely unknown. We used high-resolution single nucleotide polymorphism microarrays and droplet digital PCR analysis to detect copy number variations (CNVs) in total of 45 hemangioblastoma tumors.

Results

We identified 94 CNVs with a median of 18 CNVs per sample. The most frequently gained regions were on chromosomes 1 (p36.32) and 7 (p11.2). These regions contain the EGFR and PRDM16 genes. Recurrent losses were located at chromosome 12 (q24.13), which includes the gene PTPN11.

Conclusions

Our findings provide the first high-resolution genome-wide view of chromosomal changes in hemangioblastoma and identify 23 candidate genes: EGFR, PRDM16, PTPN11, HOXD11, HOXD13, FLT3, PTCH, FGFR1, FOXP1, GPC3, HOXC13, HOXC11, MKL1, CHEK2, IRF4, GPHN, IKZF1, RB1, HOXA9, and micro RNA, such as hsa-mir-196a-2 for hemangioblastoma pathogenesis. Furthermore, our data implicate that cell proliferation and angiogenesis promoting pathways may be involved in the molecular pathogenesis of hemangioblastoma.

FOXP1 inhibits cell growth and attenuates tumorigenicity of neuroblastoma

BACKGROUND

Segmental genomic copy number alterations, such as loss of 11q or 3p and gain of 17q, are well established markers of poor outcome in neuroblastoma, and have been suggested to comprise tumor suppressor genes or oncogenes, respectively. The gene forkhead box P1 (FOXP1) maps to chromosome 3p14.1, a tumor suppressor locus deleted in many human cancers including neuroblastoma. FoxP1 belongs to a family of winged-helix transcription factors that are involved in processes of cellular proliferation, differentiation and neoplastic transformation.

METHODS

Microarray expression profiles of 476 neuroblastoma specimens were generated and genes differentially expressed between favorable and unfavorable neuroblastoma were identified. FOXP1 expression was correlated to clinical markers and patient outcome. To determine whether hypermethylation is involved in silencing of FOXP1, methylation analysis of the 5' region of FOXP1 in 47 neuroblastomas was performed. Furthermore, FOXP1 was re-expressed in three neuroblastoma cell lines to study the effect of FOXP1 on growth characteristics of neuroblastoma cells.

RESULTS

Low expression of FOXP1 is associated with markers of unfavorable prognosis like stage 4, age >18 months and MYCN amplification and unfavorable gene expression-based classification (P < 0.001 each). Moreover, FOXP1 expression predicts patient outcome accurately and independently from well-established prognostic markers. Array-based CGH analysis of 159 neuroblastomas revealed that heterozygous loss of the FOXP1 locus was a rare event (n = 4), but if present, was associated with low FOXP1 expression. By contrast, DNA methylation analysis in 47 neuroblastomas indicated that hypermethylation is not regularly involved in FOXP1 gene silencing. Re-expression of FoxP1 significantly impaired cell proliferation, viability and colony formation in soft agar. Furthermore, induction of FOXP1 expression led to cell cycle arrest and apoptotic cell death of neuroblastoma cells.

CONCLUSIONS

Our results suggest that down-regulation of FOXP1 expression is a common event in high-risk neuroblastoma pathogenesis and may contribute to tumor progression and unfavorable patient outcome.