FoxO3a mediates glioma cell invasion by regulating MMP9 expression

TRIM6 promotes glioma malignant progression by enhancing FOXO3A ubiquitination and degradation

PURPOSE

TRIM6, an E3 ubiquitin ligase with tripartite motif, directly targets protein substrates for degradation through ubiquitination. Studies have shown that TRIM6 plays a significant role in tumor development in various human malignancies. Thus, the aim of this study was to investigate the importance of TRIM6 and its associated mechanism in promoting the progression of glioma.

METHODS

The expression of TRIM6 and its prognostic value in glioma patients were collected from the TCGA and CGGA databases. The effects of TRIM6 on glioma were investigated in vitro by CCK8, colony formation, wound healing, and transwell assays. Co-IP and western blot analysis were used to detect the interaction between TRIM6 and FOXO3A. The effects of TRIM6 were verified in vivo in subcutaneously xenograft models, and tumor size, and immunohistochemical changes were observed.

RESULTS

Our analysis of TRIM6 expression in glioma tissues revealed a high level of expression, and the heightened expression of TRIM6 showed a positive correlation with the unfavorable prognosis among glioma/GBM patients. Through loss-of-function and gain-of-function experiments, we observed a profound impact on the proliferation, invasion, and migration abilities of glioma cells both in vitro and in vivo upon deletion of TRIM6. Conversely, the overexpression of TRIM6 intensified the malignant characteristics of glioma. Additionally, our findings revealed a significant interaction between TRIM6 and FOXO3A, wherein TRIM6 contributed to the destabilization of FOXO3A protein by promoting its ubiquitination and subsequent degradation. Experiments conducted in the rescue study affirmed that the promotion of glioma cell proliferation, invasion, and migration is facilitated by TRIM6 through the suppression of FOXO3A protein levels.

CONCLUSIONS

These observations imply that the TRIM6-FOXO3A axis could potentially serve as an innovative focus for intervening in glioma.

Forkhead box transcription factors (FOXOs and FOXM1) in glioma: from molecular mechanisms to therapeutics

Glioma is the most aggressive and malignant type of primary brain tumor, comprises the majority of central nervous system deaths, and is categorized into different subgroups according to its histological characteristics, including astrocytomas, oligodendrogliomas, glioblastoma multiforme (GBM), and mixed tumors. The forkhead box (FOX) transcription factors comprise a collection of proteins that play various roles in numerous complex molecular cascades and have been discovered to be differentially expressed in distinct glioma subtypes. FOXM1 and FOXOs have been recognized as crucial transcription factors in tumor cells, including glioma cells. Accumulating data indicates that FOXM1 acts as an oncogene in various types of cancers, and a significant part of studies has investigated its function in glioma. Although recent studies considered FOXO subgroups as tumor suppressors, there are pieces of evidence that they may have an oncogenic role. This review will discuss the subtle functions of FOXOs and FOXM1 in gliomas, dissecting their regulatory network with other proteins, microRNAs and their role in glioma progression, including stem cell differentiation and therapy resistance/sensitivity, alongside highlighting recent pharmacological progress for modulating their expression.

FOXO3A Expression in Upper Tract Urothelial Carcinoma

Background

Epidemiological studies have reported various results regarding whether FOXO3A is related to various carcinomas. However, the prognostic significance of FOXO3A in upper tract urothelial carcinoma (UTUC) remains unclear. The purpose of this study was to validate the correlation between FOXO3A expression and oncological outcomes in UTUC.

Methods

The expression levels of FOXO3A in 107 UTUC patients were examined by immunohistochemistry (IHC). We examined the prognostic role of FOXO3A by using the Cox proportional hazard model.

Results

The results indicated that FOXO3A expression was notably decreased in UTUC tissue compared with control tissue. Decreased expression of FOXO3A was also related to advanced pathologic stage (P = 0.026), lymph node metastasis (P = 0.040), lymphovascular invasion (P < 0.001), and adjuvant therapy (P = 0.048). In addition, UTUC patients with low FOXO3A expression had a significantly shorter survival time, including both overall survival (OS) [hazard ratio (HR) 2.382, P = 0.004] and recurrence-free survival (RFS) (HR 2.385, P = 0.004), than those with high expression. Multivariate analyses showed that FOXO3A was a significant predictor for OS (HR 2.145, P = 0.014) and RFS (HR 2.227, P = 0.010) in UTUC patients.

Conclusion

Our results indicate that FOXO3A may be involved in the recurrence of UTUC and that it has certain clinical value in the therapeutic targeting and prognostic evaluation of UTUC.

Forkhead box protein O3a promotes glioma cell resistance to temozolomide by regulating matrix metallopeptidase and β-catenin

Glioblastoma multiforme (GBM) is the most common type of malignant brain tumor. GBM is currently treated with temozolomide (TMZ), although patients often exhibit resistance to this agent. Although several mechanisms underlying the resistance of GBM to TMZ have been identified, the combination of these mechanisms is not sufficient to fully account for this phenomenon. Our previous study demonstrated that knocking down the Forkhead box protein O3a (FoxO3a) gene, a member of the FoxO subfamily of transcription factors, resulted in glioma cell sensitization to TMZ, accompanied by reduced levels of nuclear β-catenin. The aim of the present study was to specify how FoxO3a and β-catenin are implicated in glioma cell TMZ resistance. Using the U87 and U251 parental cell lines (also designated as sensitive cell lines) and corresponding resistant cell lines (U87-TR and U251-TR, generated by repeated TMZ treatments), coupled with a combined knockdown/overexpression strategy, it was revealed that FoxO3a or β-catenin overexpression in TMZ-treated U87 and U251 cells markedly increased cellular proliferation; co-expression of both FoxO3a and β-catenin resulted in the highest increase. Knockdown of either FoxO3a or β-catenin in U87-TR and U251-TR cells led to a significant decrease in cell viability, which was rescued by the re-expression of FoxO3a in FoxO3a-knockdown cells. Subsequent experiments demonstrated that, in U87-TR and U251-TR cells, FoxO3a knockdown significantly reduced the protein levels of matrix metallopeptidase (MMP)9, while overexpression of FoxO3a in U87 and U251 cells enhanced the nuclear accumulation of β-catenin, concomitantly with an increase in MMP9 levels. Furthermore, MMP9 knockdown markedly reduced the levels of nuclear β-catenin. Collectively, the findings of the present study suggest that FoxO3a may regulate the nuclear accumulation of β-catenin by modulating MMP9 expression, thereby rendering glioblastoma cells resistant to TMZ, and may provide unique molecular insights into the mechanisms underlying the development of TMZ resistance in GBM.

FOXO transcription factor family in cancer and metastasis

Forkhead box O (FOXO) transcription factors regulate diverse biological processes, affecting development, metabolism, stem cell maintenance and longevity. They have also been increasingly recognised as tumour suppressors through their ability to regulate genes essential for cell proliferation, cell death, senescence, angiogenesis, cell migration and metastasis. Mechanistically, FOXO proteins serve as key connection points to allow diverse proliferative, nutrient and stress signals to converge and integrate with distinct gene networks to control cell fate, metabolism and cancer development. In consequence, deregulation of FOXO expression and function can promote genetic disorders, metabolic diseases, deregulated ageing and cancer. Metastasis is the process by which cancer cells spread from the primary tumour often via the bloodstream or the lymphatic system and is the major cause of cancer death. The regulation and deregulation of FOXO transcription factors occur predominantly at the post-transcriptional and post-translational levels mediated by regulatory non-coding RNAs, their interactions with other protein partners and co-factors and a combination of post-translational modifications (PTMs), including phosphorylation, acetylation, methylation and ubiquitination. This review discusses the role and regulation of FOXO proteins in tumour initiation and progression, with a particular emphasis on cancer metastasis. An understanding of how signalling networks integrate with the FOXO transcription factors to modulate their developmental, metabolic and tumour-suppressive functions in normal tissues and in cancer will offer a new perspective on tumorigenesis and metastasis, and open up therapeutic opportunities for malignant diseases.

Downregulated FOXO3a Associates With Poor Prognosis and Promotes Cell Invasion and Migration via WNT/β-catenin Signaling in Cervical Carcinoma

Background: Emerging studies have demonstrated that the Forkhead transcription factor FOXO3a is closely correlated with the progression of multiple tumors. Nevertheless, the biological role and prognostic value of FOXO3a have yet to be fully elucidated in cervical carcinoma. This study was designed to determine the molecular mechanism and prognosis of FOXO3a in cervical carcinoma.

Methods: The protein levels of FOXO3a were detected using immunohistochemistry and Western blotting. The relationships between FOXO3a expression and clinicopathological variables were analyzed. The biological mechanism of FOXO3a in cervical carcinoma cells (HeLa and CaSki) was investigated. We also explored the effect of FOXO3a on WNT/β-catenin signaling with respect to its expression and function.

Results: The results demonstrated that decreased FOXO3a expression was related to increased tumor stage and grade, positive lymph node metastasis, and poor survival outcome in cervical carcinoma. Survival analysis revealed that the FOXO3a level is an independent prognostic factor for cervical carcinoma patients. Furthermore, the data indicated that the downregulation of FOXO3a expression promotes cell invasion and migration, while FOXO3a overexpression exhibited the opposite effects on cervical carcinoma. In addition, FOXO3a acted as a negative regulator of the canonical WNT/ β-catenin pathway in cervical carcinoma. Moreover, overexpression of FOXO3a also inhibited the expression of MMP2 and MMP9.

Conclusion: These results reveal that FOXO3a, serving as a tumor suppressor gene, could suppress cell invasion and migration via the WNT/β-catenin signaling pathway and indicates a good prognosis in cervical carcinoma.

Repaglinide Silences the FOXO3/Lumican Axis and Represses the Associated Metastatic Potential of Neuronal Cancer Cells

The transcription factor FOXO3 is associated with poor outcome in high-stage neuroblastoma (NB), as it facilitates chemoprotection and tumor angiogenesis. In other tumor entities, FOXO3 stimulates metastasis formation, one of the biggest challenges in the treatment of aggressive NB. However, the impact of FOXO3 on the metastatic potential of neuronal tumor cells remains largely unknown. In the present study, we uncover the small leucine-rich proteoglycan family member lumican (LUM) as a FOXO3-regulated gene that stimulates cellular migration in NB. By a drug-library screen we identified the small molecular weight compound repaglinide (RPG) as a putative FOXO3 inhibitor. Here, we verify that RPG binds to the FOXO3-DNA-binding-domain (DBD) and thereby silences the transcriptional activity of FOXO3. Consistent with the concept that the FOXO3/LUM axis enhances the migratory capacity of aggressive NB cells, we demonstrate that stable knockdown of LUM abrogates the FOXO3-mediated increase in cellular migration. Importantly, FOXO3 inhibition by RPG represses the binding of FOXO3 to the LUM promoter, inhibits FOXO3-mediated LUM RNA and protein expression, and efficiently abrogates FOXO3-triggered cellular “wound healing” as well as spheroid-based 3D-migration. Thus, silencing the FOXO3/LUM axis by the FDA-approved compound RPG represents a promising strategy for novel therapeutic interventions in NB and other FOXO3-dependent tumors.

FOXO3a knockdown promotes radioresistance in nasopharyngeal carcinoma by inducing epithelial-mesenchymal transition and the Wnt/β-catenin signaling pathway

Mutations in the forkhead box O 3a (FOXO3a) gene are closely related to the progression of several types of cancers. However, few studies explore the relationship between FOXO3a and nasopharyngeal carcinoma (NPC). Our findings demonstrate that silencing FOXO3a promotes tumor radioresistance of NPC in vitro and in vivo through inducing EMT and activating Wnt/β-catenin signal pathway. These data establish that FOXO3a can be a novel and reliable NPC marker and a potential therapeutic target against NPC.

Arsenic Trioxide Suppressed Migration and Angiogenesis by Targeting FOXO3a in Gastric Cancer Cells

Arsenic trioxide (As₂O₃), a traditional remedy in Chinese medicine, has been used in acute promyelocytic leukemia (APL) research and clinical treatment. Previous studies have shown that As₂O₃ exerts its potent antitumor effects in solid tumors by regulating cell proliferation and survival. The aim of this study was to investigate whether As₂O₃ inhibited gastric cancer cell migration and angiogenesis by regulating FOXO3a expression. We found that As₂O₃ reduced gastric cancer cell viability in a dose-dependent manner and also inhibited cell migration and angiogenesis in vitro. Western blotting and immunofluorescence showed that As₂O₃ downregulated the levels of p-AKT, upregulated FOXO3a expression in the nucleus, and attenuated downstream Vascular endothelial growth factor (VEGF) and Matrix metallopeptidase 9 (MMP9) expression. Moreover, we demonstrated that knockdown of FOXO3a significantly reversed the inhibition of As₂O₃ and promoted cell migration and angiogenesis in vitro. Further, As₂O₃ significantly inhibited xenograft tumor growth and angiogenesis by upregulating FOXO3a expression in vivo. However, knockdown of FOXO3a attenuated the inhibitory effect of As₂O₃ in xenograft tumors, and increased microvessel density (MVD) and VEGF expression. Our results demonstrated that As₂O₃ inhibited migration and angiogenesis of gastric cancer cells by enhancing FOXO3a expression.

High expression of PIWIL2 promotes tumor cell proliferation, migration and predicts a poor prognosis in glioma

Piwi-like RNA-mediated gene silencing 2 (PIWIL2), has been reported as an oncogene tightly associated with the genesis and progression of various malignancies. Nevertheless, the function of the PIWIL2 protein in human gliomas has not yet been clarified. In this study, we sought to investigate the clinical significance of PIWIL2 expression and reveal its function in the pathological process of gliomas. Through western blot and immunohistochemical analyses we found that PIWIL2 was overexpressed in glioma tissues. Moreover, the expression level of PIWIL2 was also significantly correlated with the WHO grades of human gliomas and Ki-67 expression. Kaplan‑Meier curves indicated that PIWIL2 was a prognostic factor for the survival of glioma patients and a high expression of PIWIL2 was correlated with a poor prognosis. In vitro, knockdown of PIWIL2 in glioma cells was shown to induce cell cycle arrest and increase apoptosis. Furthermore, silencing of PIWIL2 expression also obviously suppressed the migration of glioma cells. All the results demonstrated that PIWIL2 plays a significant role in the pathogenesis of human gliomas and may be used as a potential diagnostic marker and a therapeutic target of glioma in the future.