The dual role of the X-linked FoxP3 gene in human cancers

FoxP3 expression by retinal pigment epithelial cells: transcription factor with potential relevance for the pathology of age-related macular degeneration

Background

Forkhead-Box-Protein P3 (FoxP3) is a transcription factor and marker of regulatory T cells, converting naive T cells into Tregs that can downregulate the effector function of other T cells. We previously detected the expression of FoxP3 in retinal pigment epithelial (RPE) cells, forming the outer blood–retina barrier of the immune privileged eye.

Methods

We investigated the expression, subcellular localization, and phosphorylation of FoxP3 in RPE cells in vivo and in vitro after treatment with various stressors including age, retinal laser burn, autoimmune inflammation, exposure to cigarette smoke, in addition of IL-1β and mechanical cell monolayer destruction. Eye tissue from humans, mouse models of retinal degeneration and rats, and ARPE-19, a human RPE cell line for in vitro experiments, underwent immunohistochemical, immunofluorescence staining, and PCR or immunoblot analysis to determine the intracellular localization and phosphorylation of FoxP3. Cytokine expression of stressed cultured RPE cells was investigated by multiplex bead analysis. Depletion of the FoxP3 gene was performed with CRISPR/Cas9 editing.

Results

RPE in vivo displayed increased nuclear FoxP3-expression with increases in age and inflammation, long-term exposure of mice to cigarette smoke, or after laser burn injury. The human RPE cell line ARPE-19 constitutively expressed nuclear FoxP3 under non-confluent culture conditions, representing a regulatory phenotype under chronic stress. Confluently grown cells expressed cytosolic FoxP3 that was translocated to the nucleus after treatment with IL-1β to imitate activated macrophages or after mechanical destruction of the monolayer. Moreover, with depletion of FoxP3, but not of a control gene, by CRISPR/Cas9 gene editing decreased stress resistance of RPE cells.

Conclusion

Our data suggest that FoxP3 is upregulated by age and under cellular stress and might be important for RPE function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02620-w.

Epigenetic Alteration and its Association With Downregulated FOXP3 Gene in Indian Breast Cancer Patients

Background:FOXP3 gene, known to be a potential tumor suppressor, has been identified to interact with HER2 in mammary cancer. Moreover, the high expression of FOXP3 serves as a good predictor of the survival of patients in breast cancer, prostate cancer, and gastric cancer. The expression and epigenetic alterations were evaluated in female breast cancer patients.

Material and Methods: Expression studies at the mRNA level and protein level were conducted in 140 breast cancer cases by real-time PCR and immunohistochemistry, respectively. Epigenetic studies were also conducted by analyzing the methylation status at the promoter region of the gene using MS-PCR.

Results:FOXP3 mRNA expression and protein expression were downregulated in breast cancer patients. The absence of FOXP3 protein expression is significantly associated with promoter methylation, where 70 methylated cases exhibited protein loss (70/95, 73.6%). Statistically, we also found a significant correlation between FOXP3 protein expression and TNM stage, promoter methylation, and histological grade. The methylated FOXP3 cases that did not express protein were also significantly associated with positive lymph node metastasis and HER-2 status.

Conclusion: The expression profile of FOXP3 may serve as a prognostic factor. In short, FOXP3 may stand in the most crucial list of biomarkers for breast cancer, bringing compelling results in terms of treatment and management of the disease.

Peritoneal Modulators of Endometriosis-Associated Ovarian Cancer

Ovarian cancer is the 4th largest cause of cancer death in women. Approximately 10-15% of women of childbearing age suffer from endometriosis. Endometriosis is defined by the growth and presence of endometrial tissue (lesions) outside of the uterus. The women with endometriosis also have an increased presence of peritoneal fluid (PF) that comprises of inflammatory cells, growth factors, cytokines/chemokines, etc. Epidemiological studies have shown that >3% of women with endometriosis develop ovarian cancer (low-grade serous or endometrioid types). Our hypothesis is that the PF from women with endometriosis induces transformative changes in the ovarian cells, leading to ovarian cancer development. PF from women with and without endometriosis was collected after IRB approval and patient consent. IOSE (human normal ovarian epithelial cells) and TOV-21G cells (human ovarian clear cell carcinoma cell line) were treated with various volumes of PF (no endometriosis or endometriosis) for 48 or 96 h and proliferation measured. Expression levels of epigenetic regulators and FoxP3, an inflammatory tumor suppressor, were determined. A Human Cancer Inflammation and Immunity Crosstalk RT2 Profiler PCR array was used to measure changes in cancer related genes in treated cells. Results showed increased growth of TOV-21G cells treated with PF from women with endometriosis versus without endometriosis and compared to IOSE cells. Endo PF treatment induced EZH2, H3K27me3, and FoxP3. The RT2 PCR array of TOV-21G cells treated with endo PF showed upregulation of various inflammatory genes (TLRs, Myd88, etc.). These studies indicate that PF from women with endometriosis can both proliferate and transform ovarian cells and hence this microenvironment plays a major mechanistic role in the progression of endometriosis to ovarian cancer.

Forkhead Box Protein P3 (FOXP3) Represses ATF3 Transcriptional Activity

Activating transcription factor 3 (ATF3), a transcription factor and acute stress sensor, is rapidly induced by a variety of pathophysiological signals and is essential in the complex processes in cellular stress response. FOXP3, a well-known breast and prostate tumor suppressor from the X chromosome, is a novel transcriptional repressor for several oncogenes. However, it remains unknown whether ATF3 is the target protein of FOXP3. Herein, we demonstrate that ATF3 expression is regulated by FOXP3. Firstly, we observed that overexpression of FOXP3 reduced ATF3 protein level. Moreover, knockdown FOXP3 by siRNA increased ATF3 expression. Secondly, FOXP3 dose-dependently reduced ATF3 promoter activity in the luciferase reporter assay. Since FOXP3 is regulated by post-translational modifications (PTMs), we next investigated whether PTMs affect FOXP3-mediated ATF3 expression. Interestingly, we observed that phosphorylation mutation on FOXP3 (Y342F) significantly abolished FOXP3-mediated ATF3 expression. However, other PTM mutations on FOXP3, including S418 phosphorylation, K263 acetylation and ubiquitination, and K268 acetylation and ubiquitination, did not alter FOXP3-mediated ATF3 expression. Finally, the FOXP3 binding site was found on ATF3 promoter region by deletion and mutagenesis analysis. Taken together, our results suggest that FOXP3 functions as a novel regulator of ATF3 and that this novel event may be involved in tumor development and progression.

FoxP3-miR-150-5p/3p suppresses ovarian tumorigenesis via an IGF1R/IRS1 pathway feedback loop

Ovarian cancer (OC) causes more deaths than any other gynecological cancer. Many cellular pathways have been elucidated to be associated with OC development and progression. Specifically, the insulin-like growth factor 1 receptor/insulin receptor substrate 1 (IGF1R/IRS1) pathway participates in OC development. Moreover, accumulating evidence has shown that microRNA deregulation contributes to tumor initiation and progression. Here, our study aimed to investigate the molecular functions and regulatory mechanisms of miR-150, specifically, in OC. We found that the expression of miR-150-5p/3p and their precursor, mir-150, was downregulated in OC tissues; lower mir-150 levels were associated with poor OC patient outcomes. Ectopic mir-150 expression inhibited OC cell growth and metastasis in vitro and in vivo. Furthermore, both IRS1 and IGF1R were confirmed as direct targets of miR-150-5p/3p, and the miR-150-IGF1R/IRS1 axis exerted antitumor effects via the PI3K/AKT/mTOR pathway. Forkhead box protein 3 (FoxP3) positively regulated the expression of miR-150-5p/3p by binding to the mir-150 promoter. In turn, the PI3K/AKT/mTOR pathway downregulated FoxP3 and miR-150-5p/3p. Taken together, these findings indicate that a complex FoxP3-miR-150-IGF1R/IRS1-PI3K/AKT/mTOR feedback loop regulates OC pathogenesis, providing a novel mechanism for miR-150 as a tumor suppressor miRNA in OC.

Association of Foxp3 rs3761548 polymorphism with cytokines concentration in gastric adenocarcinoma patients

T regulatory cells (Tregs) and related-cytokines are effectively engaged in the process of tumor immune escape and functionally inhibit immune response against the tumor. This study aimed to investigate the association of Foxp3 gene single nucleotide polymorphism (SNP) (rs3761548) with serum IL-35, IL-10, and TGF-β levels in gastric adenocarcinoma (GA) patients. The blood samples were obtained from 150 GA patients and 166 control subjects. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was done to genotyping of Foxp3 gene polymorphism (rs3761548). The serum cytokines levels were measured using the ELISA method. According to genotyping, the AA, and AC genotypes and A allele demonstrated significantly greater risk of GA. Considering the Lauren classification, our results revealed a greater risk of GA progression in patients with AC + AA genotype compared to CC genotype. Moreover, significantly increased levels of IL-10, IL-35, and TGF-β were observed in GA patients compared to controls and also in diffuse-type compared to the intestinal type of GA patients. The IL-35, IL-10 concentrations in GA patients displayed significant differences between the participants with CC, AC and AA genotypes. Further analysis indicated the prognostic role of serum IL-35, IL-10, and TGF-β levels in GA patients. Our results confirmed that the Foxp3 polymorphism (rs3761548) could influence the predisposition to GA and the serum IL-10, IL-35, and TGF-β levels. Thus, this polymorphism might be involved in the GA progression through influencing Tregs function and the secretion of immunomodulatory cytokines.

FOXP3 in Melanoma with Regression: Between Tumoral Expression and Regulatory T Cell Upregulation

Cutaneous melanoma is a significant immunogenic tumoral model, the most frequently described immune phenomenon being tumor regression, as a result of the interaction of tumoral antigens and stromal microenvironment. We present a retrospective cohort study including 52 cases of melanoma with regression. There were evaluated correlations of the most important prognostic factors (Breslow depth and mitotic index) with FOXP3 expression in tumor cells and with the presence of regulatory T cells and dendritic cells in the tumoral stroma. FOXP3 expression in tumor cells seems an independent factor of poor prognosis in melanoma, while regression areas are characterized by a high number of dendritic cells and a low number of regulatory T cells. FOXP3 is probably a useful therapeutical target in melanoma, since inhibition of FOXP3-positive tumor clones and of regulatory T cells could eliminate the ability of tumor cells to escape the immune defense of the host.

Foxp3 heterozygosity does not overtly affect mammary gland development during puberty or the oestrous cycle in mice

Female mice heterozygous for a genetic mutation in transcription factor forkhead box p3 (Foxp3) spontaneously develop mammary cancers; however, the underlying mechanism is not well understood. We hypothesised that increased cancer susceptibility is associated with an underlying perturbation in mammary gland development. The role of Foxp3 in mammary ductal morphogenesis was investigated in heterozygous Foxp3Sf/+ and wildtype Foxp3+/+ mice during puberty and at specific stages of the oestrous cycle. No differences in mammary ductal branching morphogenesis, terminal end bud formation or ductal elongation were observed in pubertal Foxp3Sf/+ mice compared with Foxp3+/+ mice. During adulthood, all mice underwent normal regular oestrous cycles. No differences in epithelial branching morphology were detected in mammary glands from mice at the oestrus, metoestrus, dioestrus and pro-oestrus stages of the cycle. Furthermore, abundance of Foxp3 mRNA and protein in the mammary gland and lymph nodes was not altered in Foxp3Sf/+ mice compared with Foxp3+/+ mice. These studies suggest that Foxp3 heterozygosity does not overtly affect mammary gland development during puberty or the oestrous cycle. Further studies are required to dissect the underlying mechanisms of increased mammary cancer susceptibility in Foxp3Sf/+ heterozygous mice and the function of this transcription factor in normal mammary gland development.

The forkhead-box family of transcription factors: key molecular players in colorectal cancer pathogenesis

Colorectal cancer (CRC) is the third most commonly occurring cancer worldwide and the fourth most frequent cause of death having an oncological origin. It has been found that transcription factors (TF) dysregulation, leading to the significant expression modifications of genes, is a widely distributed phenomenon regarding human malignant neoplasias. These changes are key determinants regarding tumour’s behaviour as they contribute to cell differentiation/proliferation, migration and metastasis, as well as resistance to chemotherapeutic agents. The forkhead box (FOX) transcription factor family consists of an evolutionarily conserved group of transcriptional regulators engaged in numerous functions during development and adult life. Their dysfunction has been associated with human diseases. Several FOX gene subgroup transcriptional disturbances, affecting numerous complex molecular cascades, have been linked to a wide range of cancer types highlighting their potential usefulness as molecular biomarkers. At least 14 FOX subgroups have been related to CRC pathogenesis, thereby underlining their role for diagnosis, prognosis and treatment purposes.

This manuscript aims to provide, for the first time, a comprehensive review of FOX genes’ roles during CRC pathogenesis. The molecular and functional characteristics of most relevant FOX molecules (FOXO, FOXM1, FOXP3) have been described within the context of CRC biology, including their usefulness regarding diagnosis and prognosis. Potential CRC therapeutics (including genome-editing approaches) involving FOX regulation have also been included. Taken together, the information provided here should enable a better understanding of FOX genes’ function in CRC pathogenesis for basic science researchers and clinicians.

FOXP3 Activates SUMO-Conjugating UBC9 Gene in MCF7 Breast Cancer Cells

Forkhead Box Protein P3 (FOXP3), a transcription factor of the FOX protein family, is essentially involved in the development of regulatory T (Treg) cells, and functions as a tumor suppressor. Although FOXP3 has been widely studied in immune system and cancer development, its function in the regulation of the UBC9 gene (for the sole E2 enzyme of SUMOylation) is unknown. Herein, we find that the overexpression of FOXP3 in human MCF7 breast cancer cells increases the level of UBC9 mRNA. Moreover, the level of UBC9 protein dose-dependently increases in the FOXP3-Tet-off MCF7 cells. Notably, the promoter activity of the UBC9 is activated by FOXP3 in a dose-dependent manner in both the MCF7 and HEK293 cells. Next, by mapping the UBC9 promoter as well as the site-directed mutagenesis and ChIP analysis, we show that the FOXP3 response element at the −310 bp region, but not the −2182 bp region, is mainly required for UBC9 activation by FOXP3. Finally, we demonstrate that the removal of phosphorylation (S418A and Y342F) and the removal of acetylation/ubiquitination (K263R and K263RK268R) of the FOXP3 result in attenuated transcriptional activity of UBC9. Taken together, FOXP3 acts as a novel transcriptional activator of the human UBC9 gene, suggesting that FOXP3 may have physiological functions as a novel player in global SUMOylation, as well as other post-translational modification systems.

Expression of FoxP3 protein plays a key role in thyroid tumors in children

The expression of FoxP3 in tumor cells might play an important role in cancer progression. We evaluated the immunoexpression of FoxP3 in thyroid tumors in children. Studies revealed high nuclear FoxP3 expression in follicular adenoma, papillary carcinoma, follicular carcinoma and low in goiter. Malignant tumors and adenomas, revealed a statistically significant higher expression of FoxP3 compared with the thyroid goiter. High FoxP3 expression in malignant lesions compared with low expression in goiter, may be indirect evidence of its role in carcinogenesis. Revealed high expression of FoxP3 in benign tumor, may suggest a strong activation of oncogenic processes in this lesion.

Study of circulating antibodies against CD25 and FOXP3 in breast cancer

Our recent work suggests that circulating levels of anti-CD25 and anti-FOXP3 antibodies were significantly increased in patients with either lung cancer or esophageal cancer. To confirm if these two autoantibodies are specific for certain types of malignant tumors, the present work was thus undertaken to examine an alteration of anti-CD25 and anti-FOXP3 IgG levels in breast cancer. A total of 152 patients with breast cancer and 112 control subjects were recruited in this study. The levels of circulating anti-CD25 and anti-FOXP3 IgG antibodies were tested using an in-house enzyme-linked immunosorbent assay (ELISA). Student's t test showed no significant differences in the levels of either anti-CD25 IgG or anti-FOXP3 IgG between patients with breast cancer and control subjects, although patients at stage I had increased levels of anti-CD25 IgG compared with control subjects (t = 2.11, P = 0.037); there was no significant association of the anti-FOXP3 IgG levels with stages of breast cancer. In conclusion, circulating IgG autoantibody to CD25 instead of FOXP3 may be a potential biomarker for early diagnosis of breast cancer but further investigation remains needed to replicate this initial finding.

Searching for the Achilles Heel of FOXP3

FOXP3 is a multifaceted transcription factor with a major role in the control of immune homeostasis mediated by T regulatory cells (Treg). The immunoregulatory function of FOXP3 may hinder the induction of immune responses against cancer and infectious agents, and thus, development of inhibitors of its functions might give new therapeutic opportunities for these diseases. But also, FOXP3 is an important tumor suppressor factor in some types of cancers, and therefore, understanding the structure and function of FOXP3 is crucial to gaining insights into the development of FOXP3-targeted therapeutic strategies. FOXP3 homodimerize and likely form supramolecular complexes which might include hundreds of proteins which constitute the FOXP3 interactome. Many of the functions of FOXP3 are clearly regulated by the interactions with these cofactors contributing importantly on the establishment of Treg-cell signature. We summarize here the structural/functional information on this FOXP3 complex, to identify potential opportunities for the development of new strategies to modulate FOXP3 activity.

Circulating autoantibody to FOXP3 may be a potential biomarker for esophageal squamous cell carcinoma

The present study was undertaken to develop a relatively quantitative enzyme-linked immunosorbent assay (ELISA) in-house using human leukocyte antigen class II-restricted epitopes in order to test circulating autoantibodies to human forkhead/winged helix transcription factor (FOXP3) as a biomarker for esophageal cancer. A total of 97 patients with esophageal squamous cell carcinoma (ESCC) and 227 healthy subjects were recruited for this study, and their plasma samples were collected for antibody analysis with the ELISA approach. Student's t test showed that the anti-FOXP3 IgG antibody levels were significantly higher in the patient group than the control group (t=6.23, P<0.0001). Based on a cutoff value determined by the mean+3SD of control IgG levels, the positive rate was 5.15 % in patients with ESCC as compared to 0.88 % in control subjects (X (2) =6.53, P=0.019, OR=5.85, 95 % CI 1.12-30.67), in which patients at stage I had the highest positivity (11.54 %, X (2) =12.15, P=0.0005, OR=13.10, 95 % CI 2.09-82.04). The sensitivity against >95 % specificity was 22.7 % for the IgG assay with an inter-assay deviation of 13.35 %. This work suggests that circulating IgG autoantibody to FOXP3 may be a potential biomarker for early diagnosis of esophageal cancer.

A study of circulating anti-CD25 antibodies in non-small cell lung cancer

PURPOSE

Tumors can trigger specific immune response to tumor-associated antigens but the precise mechanism remains unclear. Since regulatory T-lymphocytes (Treg) play a crucial role in controlling autoimmune responses, the present work was undertaken to test whether dysfunction of Treg cells could be involved in developing autoimmunity in patients with lung cancer.

METHODS

In this study, we developed an in-house enzyme-linked immunosorbent assay to test circulating anti-CD25 autoantibodies among 272 patients with non-small cell lung cancer (NSCLC) and 226 control subjects matched in age, gender and smoking history.

RESULTS

Mann-Whitney U test showed that the anti-CD25 IgG level was significantly higher in patients with NSCLC than control subjects (Z = -7.48, P < 0.001) while the anti-CD25 IgA level was not significantly changed in the patient group as compared with the control group (Z = -1.34, P = 0.181). Spearman correlation analysis failed to reveal a significant correlation between the levels of anti-CD25 IgG and IgA either in patients with NSCLC (r = -0.034, P = 0.578) or in control subjects (r = 0.055, P = 0.429). ROC analysis showed an AUC of 0.70 for anti-CD25 IgG, in which NSCLC at stage III had the highest AUC (0.75). The sensitivity against a specificity of >90 % was 35.0 % for anti-CD25 IgG assay with an inter-assay deviation of 9.4 %, and 4.0 % for anti-CD25 IgA assay with an inter-assay deviation of 13.0 %.

CONCLUSIONS

Circulating anti-CD25 IgG antibody may be a useful biomarker for prognosis of lung cancer.

A study of circulating anti-CD25 antibodies in non-small cell lung cancer

PURPOSE

Tumors can trigger specific immune response to tumor-associated antigens but the precise mechanism remains unclear. Since regulatory T-lymphocytes (Treg) play a crucial role in controlling autoimmune responses, the present work was undertaken to test whether dysfunction of Treg cells could be involved in developing autoimmunity in patients with lung cancer.

METHODS

In this study, we developed an in-house enzyme-linked immunosorbent assay to test circulating anti-CD25 autoantibodies among 272 patients with non-small cell lung cancer (NSCLC) and 226 control subjects matched in age, gender and smoking history.

RESULTS

Mann-Whitney U test showed that the anti-CD25 IgG level was significantly higher in patients with NSCLC than control subjects (Z = -7.48, P < 0.001) while the anti-CD25 IgA level was not significantly changed in the patient group as compared with the control group (Z = -1.34, P = 0.181). Spearman correlation analysis failed to reveal a significant correlation between the levels of anti-CD25 IgG and IgA either in patients with NSCLC (r = -0.034, P = 0.578) or in control subjects (r = 0.055, P = 0.429). ROC analysis showed an AUC of 0.70 for anti-CD25 IgG, in which NSCLC at stage III had the highest AUC (0.75). The sensitivity against a specificity of >90 % was 35.0 % for anti-CD25 IgG assay with an inter-assay deviation of 9.4 %, and 4.0 % for anti-CD25 IgA assay with an inter-assay deviation of 13.0 %.

CONCLUSIONS

Circulating anti-CD25 IgG antibody may be a useful biomarker for prognosis of lung cancer.

The dual role of the X-linked FoxP3 gene in human cancers

The FoxP3 (forkhead box P3) gene is an X-linked gene that is submitted to inactivation. It is an essential transcription factor in CD4(+)CD25(+)FoxP3 regulatory T cells, which are therapeutic targets in disseminated cutaneous melanoma. Moreover, FoxP3 is an important tumor suppressor gene in carcinomas and has putative cancer suppressor gene function in cutaneous melanoma as well. Therefore understanding the structure and function of the FoxP3 gene is crucial to gaining insight into the biology of melanoma to better develop immunotherapeutics and future therapeutic strategies.