Forkhead box K2 modulates epirubicin and paclitaxel sensitivity through FOXO3a in breast cancer

Emerging roles of FOXK2 in cancers and metabolic disorders

FOXK2, a member of the Forkhead box K (FOXK) transcription factor family, is widely expressed in various tissues and organs throughout the body. FOXK2 plays crucial roles in cell proliferation, differentiation, autophagy, de novo nucleotide biosynthesis, DNA damage response, and aerobic glycolysis. Although FOXK2 is recognized as an oncogene in colorectal cancer and hepatocellular carcinoma, it acts as a tumor suppressor in breast cancer, cervical cancer, and non-small cell lung cancer (NSCLC). This review provides an overview of the recent progress in understanding the regulatory mechanisms of FOXK2 and its downstream targets, highlights the significant impact of FOXK2 dysregulation on cancer etiology, and discusses the potential of targeting FOXK2 for cancer treatment.

Role and regulation of FOXO3a: new insights into breast cancer therapy

Breast cancer is the most common malignancy in the world, particularly affecting female cancer patients. Enhancing the therapeutic strategies for breast cancer necessitates identifying molecular drug targets that effectively eliminate tumor cells. One of these prominent targets is the forkhead and O3a class (FOXO3a), a member of the forkhead transcription factor subfamily. FOXO3a plays a pivotal role in various cellular processes, including apoptosis, proliferation, cell cycle regulation, and drug resistance. It acts as a tumor suppressor in multiple cancer types, although its specific role in cancer remains unclear. Moreover, FOXO3a shows promise as a potential marker for tumor diagnosis and prognosis in breast cancer patients. In addition, it is actively influenced by common anti-breast cancer drugs like paclitaxel, simvastatin, and gefitinib. In breast cancer, the regulation of FOXO3a involves intricate networks, encompassing post-translational modification post-translational regulation by non-coding RNA (ncRNA) and protein-protein interaction. The specific mechanism of FOXO3a in breast cancer urgently requires further investigation. This review aims to systematically elucidate the role of FOXO3a in breast cancer. Additionally, it reviews the interaction of FOXO3a and its upstream and downstream signaling pathway-related molecules to uncover potential therapeutic drugs and related regulatory factors for breast cancer treatment by regulating FOXO3a.

Genetic screening for anticancer genes highlights FBLN5 as a synthetic lethal partner of MYC

BACKGROUND

When ectopically overexpressed, anticancer genes, such as TRAIL, PAR4 and ORCTL3, specifically destroy tumour cells without harming untransformed cells. Anticancer genes can not only serve as powerful tumour specific therapy tools but studying their mode of action can reveal mechanisms underlying the neoplastic transformation, sustenance and spread.

METHODS

Anticancer gene discovery is normally accidental. Here we describe a systematic, gain of function, forward genetic screen in mammalian cells to isolate novel anticancer genes of human origin. Continuing with over 30,000 transcripts from our previous study, 377 cell death inducing genes were subjected to screening. FBLN5 was chosen, as a proof of principle, for mechanistic gene expression profiling, comparison pathways analyses and functional studies.

RESULTS

Sixteen novel anticancer genes were isolated; these included non-coding RNAs, protein-coding genes and novel transcripts, such as ZNF436-AS1, SMLR1, TMEFF2, LINC01529, HYAL2, NEIL2, FBLN5, YPEL4 and PHKA2-processed transcript. FBLN5 selectively caused inhibition of MYC in COS-7 (transformed) cells but not in CV-1 (normal) cells. MYC was identified as synthetic lethality partner of FBLN5 where MYC transformed CV-1 cells experienced cell death upon FBLN5 transfection, whereas FBLN5 lost cell death induction in MCF-7 cells upon MYC knockdown.

CONCLUSIONS

Sixteen novel anticancer genes are present in human genome including FBLN5. MYC is a synthetic lethality partner of FBLN5. Video Abstract.

Current development of cabazitaxel drug delivery systems

The second-generation taxane cabazitaxel has been clinically approved for the treatment of metastatic castration-resistant prostate cancer after docetaxel failure. Compared with the first-generation taxanes paclitaxel and docetaxel, cabazitaxel has potent anticancer activity and is less prone to drug resistance due to its lower affinity for the P-gp efflux pump. The relatively high hydrophobicity of cabazitaxel and the poor aqueous colloidal stability of the commercial formulation, following its preparation for injection, presents opportunities for new cabazitaxel formulations with improved features. This review provides an overview of cabazitaxel drug formulations and hydrophobic taxane drug delivery systems in general, and particularly focuses on emerging cabazitaxel delivery systems discovered in the past 5 years. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Regulation and roles of FOXK2 in cancer

Forkhead box K2 (FOXK2) is a member of the forkhead box transcription factor family that contains an evolutionarily conserved winged-helix DNA-binding domain. Recently, an increasing number of studies have demonstrated that FOXK2 plays an important role in the transcriptional regulation of cancer. Here, we provide an overview of the mechanisms underlying the regulation of FOXK2 expression and function and discuss the roles of FOXK2 in tumor pathogenesis. Additionally, we evaluated the prognostic value of FOXK2 expression in patients with various cancers. This review presents an overview of the different roles of FOXK2 in tumorigenesis and will help inform the design of experimental studies involving FOXK2. Ultimately, the information presented here will help enhance the therapeutic potential of FOXK2 as a cancer target.

PLOD3 contributes to HER-2 therapy resistance in gastric cancer through FoxO3/Survivin pathway

Human epidermal growth factor receptor 2 (HER-2), a famous therapeutic target for breast cancer, is also associated with an increased risk of recurrence and poor outcomes of other malignancies, including gastric cancer. Yet the mechanism of HER-2 therapy resistance remains controversial due to the heterogeneity of gastric adenocarcinoma. We know, Procollagen-Lysine,2-Oxoglutarate 5-Dioxygenase 3 (PLOD3), a key gene coding enzymes that catalyze the lysyl hydroxylation of extracellular matrix collagen, plays an important contributor to HER-2 targeting agent Trastuzumab resistance in gastric cancer. Herein, we analyzed clinical samples of gastric cancer patients and gastric cancer cell lines and identified PLOD3, unveiled that depletion of PLOD3 leads to decreased cell proliferation, tumor growth and Trastuzumab sensitivity in these Trastuzumab resistant GC cell lines. Clinically, increased PLOD3 expression correlates with decreased Trastuzumab therapy responsiveness in GC patients. Mechanistically, we show that PLOD3 represses tumor suppressor FoxO3 expression, therefore upregulating Survivin protein expression that contributes to Trastuzumab resistance in GC. Therefore, our study identifies a new signaling axis PLOD3-FoxO3- Survivin pathway that may be therapeutically targeted in HER-2 positive gastric cancer.

The Function of FoxK Transcription Factors in Diseases

Forkhead box (FOX) transcription factors play a crucial role in the regulation of many diseases, being an evolutionarily conserved superfamily of transcription factors. In recent years, FoxK1/2, members of its family, has been the subject of research. Even though FoxK1 and FoxK2 have some functional overlap, increasing evidence indicates that the regulatory functions of FoxK1 and FoxK2 are not the same in various physiological and disease states. It is important to understand the biological function and mechanism of FoxK1/2 for better understanding pathogenesis of diseases, predicting prognosis, and finding new therapeutic targets. There is, however, a lack of comprehensive and systematic analysis of the similarities and differences of FoxK1/2 roles in disease, prompting us to perform a literature review.

Long non-coding RNA tumor protein 53 target gene 1 promotes cervical cancer development via regulating microRNA-33a-5p to target forkhead box K2

Long non-coding RNA tumor protein 53 target gene 1 (TP53TG1) has been unraveled to exert regulatory effects on cancer progression, while the regulatory function of TP53TG1 on cervical cancer (CC) via regulating microRNA (miR)-33a-5p/Forkhead box K2 (FOXK2) axis remains rarely explored. This study aims to unearth the regulatory mechanism of TP53TG1/miR-33a-5p/FOXK2 axis in CC. The CC clinical samples were collected, and CC cells were cultured. TP53TG1, miR-33a-5p and FOXK2 levels were examined in CC tissues and cells. The CC cells were transfected with high- or low-expressed TP53TG1, FOXK2 or miR-33a-5p to determine the changes of CC cell biological activities and the status of phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway. The tumorigenesis in nude mice was conducted. The relationship among TP53TG1, miR-33a-5p and FOXK2 was validated. TP53TG1 and FOXK2 expression levels were increased and miR-33a-5p expression level was reduced in CC cells and tissues. The silenced TP53TG1 or FOXK2, or elevated miR-33a-5p decelerated the CC cell development and restrained the activation of PI3K/AKT/mTOR signaling pathway. The depleted FOXK2 or elevated miR-33a-5p reversed the effects of decreased TP53TG1 on CC cell progression. TP53TG1 sponged miR-33a-5p, which targeted FOXK2. The experiment in vivo validated the outcomes of the experiment in vitro. TP53TG1 accelerates the CC development via regulating miR-33a-5p to target FOXK2 with the involvement of PI3K/AKT/mTOR signaling pathway. This study provides novel theory basis and distinct therapeutic targets for CC treatment.

FOXK2 transcriptionally activating VEGFA induces apatinib resistance in anaplastic thyroid cancer through VEGFA/VEGFR1 pathway

Anaplastic thyroid carcinoma (ATC) is a rare and extremely aggressive type of thyroid cancer, and the potential mechanisms involved in ATC progression remains unclarified. In this study, we found that forkhead box K2 (FOXK2) was upregulated in ATC tissues, and the expression of FOXK2 was associated with tumor size. Evidenced by RNA-seq and Chromatin immunoprecipitation (ChIP)-seq assays, FOXK2 positively regulated VEGF and VEGFR signaling network, among which only VEGFA could be noticed in both RNA-seq and ChIP-seq results. ChIP, dual-luciferase reporter system and functional experiments further confirmed that FOXK2 promoted angiogenesis by inducing the transcription of VEGFA. On VEGFR2 blockage by specific targeting agent, such as Apatinib, FOXK2 could rapidly trigger therapeutic resistance. Mechanical analyses revealed that VEGFA transcriptionally induced by FOXK2 could bind to VEGFR1 as a compensation for VEGFR2 blockage, which promoted angiogenesis by activating ERK, PI3K/AKT and P38/MAPK signaling in human umbilical vein endothelial cells (HUVECs). Synergic effect on anti-angiogenesis could be observed when VEGFR1 suppressor AF321 was included in VEGFR2 inhibition system, which clarified the pivot role of FOXK2 in VEGFR2 targeting therapy resistance. More importantly, the binding of VEGFA to VEGFR1 could further promoter FOXK2-mediated VEGFA transcription, which consequently constituted a positive feedback loop. Therefore, the novel loop VEGFA/VEGFR1/FOXK2 functioned importantly in resistance to VEGFR2 targeting therapy in FOXK2⁺ ATCs. Altogether, FOXK2 plays critical roles in ATC angiogenesis and VEGFR2 blockage resistance by inducing VEGFA transcription. FOXK2 represents a potentially new therapeutic strategy and biomarker for anti-angiogenic therapy against ATC.

Prognostic Value of the FOXK Family Expression in Patients with Locally Advanced Rectal Cancer Following Neoadjuvant Chemoradiotherapy

Purpose

To assess the role of the expression levels of FOXK family members, FOXK1 and FOXK2, in predicting response to neo-chemoradiotherapy (NCRT) and prognosis in locally advanced rectal cancer (LARC).

Methods

A total of 256 LARC patients who underwent NCRT and radical resection between 2011 and 2017 were enrolled in the present study. The patients were divided into a training dataset (n=169, 2011–2015) and a validation dataset (n=87, 2016–2017). Tumor tissues were collected before NCRT and post-surgery and were used for immunohistochemical analysis.

Results

Oncomine database analysis revealed that FOXK1 and FOXK2 were overexpressed in most cancers especially in colorectal cancer. Additionally, overexpression of FOXK1 and FOXK2 was associated with poorer prognosis by the R2 database. In both our training and validation datasets, the expression of FOXK1 and FOXK2 was lower in the pathological complete response (pCR) group compared with the non-pCR group (P<0.05). Cox regression analysis demonstrated that pathological N stage (HR=1.810, 95% CI 1.159–2.827, P=0.009), FOXK1 expression (HR=5.831, 95% CI 2.925–11.625, P<0.001), and FOXK2 expression (HR=2.390, 95% CI 11.272–4.491, P=0.007) were independent predictors of disease-free survival (DFS). Based on the Cox multivariate analysis, we constructed a risk score model that served as a prognostic biomarker and had a powerful ability to predict pCR in LARC patients upon NCRT in both training and validation groups.

Conclusion

Expression levels of FOXK family members were associated with chemoradiotherapy resistance and prognosis of LARC patients following NCRT and were used to construct a risk score model that is a promising biomarker for LARC.

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.

FOXK2 downregulation suppresses EMT in hepatocellular carcinoma

Forkhead box K2 (FOXK2) was first identified as an NFAT-like interleukin-binding factor. FOXK2 has been reported to act as either oncogene or tumor suppressor. However, functional and regulating mechanisms of FOXK2 in epithelial–mesenchymal transition (EMT) in hepatocellular carcinoma (HCC) remain unclear. An FOXK2-specific siRNA was employed to decrease the endogenous expression of FOXK2. MTT assay, colony formation and transwell assay were used to evaluate proliferation, migration and invasion of Hep3B and HCCLM3 cells, respectively. The protein expression associated with EMT and Akt signaling pathways was evaluated using western blot. FOXK2 downregulation could inhibit cell proliferation and colony formation and suppress migration and invasion in Hep3B and HCCLM3 cells. The expression of E-cadherin was significantly upregulated, and the expression of snail and p-Akt was significantly downregulated in siFOXK2-transfected cells compared with control cells. SF1670 induced the expression of p-Akt and snail and suppressed the expression of E-cadherin in Hep3B and HCCLM3 cells. SF1670 promoted the invasion and colony formation of Hep3B and HCCLM3 cells. SF1670 partly inhibited the effect of FOXK2 suppression on Hep3B and HCCLM3 cells. In conclusion, this study revealed that FOXK2 downregulation suppressed the EMT in HCC partly through inhibition of the Akt signaling pathway.

CircMRPS35 suppresses gastric cancer progression via recruiting KAT7 to govern histone modification

Background

Aberrant expression of circular RNAs contributes to the initiation and progression of cancers, but the underlying mechanism remains elusive.

Methods

RNA-seq and qRT-PCR were performed to screen differential expressed circRNAs between gastric cancer tissues and adjacent normal tissues. Candidate circRNA (circMRPS35) was screened out and validated by qRT-PCR. Cell proliferation and invasion ability were determined by CCK-8 and cell invasion assays. RNA-seq, GO-pathway, RNA pull-down and ChIRP were further applied to search for detailed mechanism.

Results

Here, a novel circRNA named circMRPS35, was screened out by RNA-seq in gastric cancer tissues, whose expression is related to clinicopathological characteristics and prognosis in gastric cancer patients. Biologically, circMRPS35 suppresses the proliferation and invasion of gastric cancer cells in vitro and in vivo. Mechanistically, circMRPS35 acts as a modular scaffold to recruit histone acetyltransferase KAT7 to the promoters of FOXO1 and FOXO3a genes, which elicits acetylation of H4K5 in their promoters. Particularly, circMRPS35 specifically binds to FOXO1/3a promoter regions directly. Thus, it dramatically activates the transcription of FOXO1/3a and triggers subsequent response of their downstream target genes expression, including p21, p27, Twist1 and E-cadherin, resulting in the inhibition of cell proliferation and invasion. Moreover, circMRPS35 expression positively correlates with that of FOXO1/3a in gastric cancer tissues.

Conclusions

Our findings not only reveal the pivotal roles of circMRPS35 in governing histone modification in anticancer treatment, but also advocate for triggering circMRPS35/KAT7/FOXO1/3a pathway to combat gastric cancer.

Regulation of PERK expression by FOXO3: a vulnerability of drug-resistant cancer cells

The major impediment to effective cancer therapy has been the development of drug resistance. The tumour suppressive transcription factor FOXO3 promotes cell cycle arrest, senescence and cell death, and mediates the cytotoxic and cytostatic functions of cancer therapeutics. In consequence, FOXO3 is often downregulated as an adaptive response in cancer and particularly in chemotherapeutic drug-resistant cells. Consistently, we find that FOXO3 expression is attenuated in the drug-resistant MCF-7-Epi^R and MCF-7-Tax^R compared to the parental MCF-7 breast cancer cells. Using ChIP, short-interfering RNA (siRNA) knockdown, and overexpression assays as well as Foxo^1/3/4-/- MEFs, we establish the endoplasmic reticulum (ER)-stress defence modulator PERK (eIF2AK3) as a direct downstream transcriptional target of FOXO3. In agreement, there is also a positive correlation between FOXO3 and PERK expression at the protein and RNA levels in breast cancer patient samples. We uncover that PERK expression is downregulated but its activity constitutively elevated in the drug-resistant cells. With this in mind, we exploit this adaptive response of low FOXO3 and PERK expression, and high PERK activity in drug-resistant breast cancer cells and show that these drug-resistant cells are specifically sensitive to PERK inhibition. In support of this finding, we show that ectopic overexpression of FOXO3 can reduce the sensitivity of the resistant cells to the PERK inhibitor GSK2606414, while the Foxo^1/3/4-/- MEFs expressing lower levels of PERK are more sensitive to PERK inhibition compared to wild-type MEFs. PERK inhibitor-titration and -time course experiments showed that the drug-resistant cells, which express lower expression and higher activity levels of PERK, are more sensitive to the increasing concentrations of PERK inhibitor compared to parental MCF-7 cells. Our present work thus reveals a chemotherapeutic drug-resistant cancer cell vulnerability in PERK and suggests PERK as a potential target for cancer therapy, specifically in the context of drug-resistant cancers.

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.

FOXK transcription factors: Regulation and critical role in cancer

Growing evidence suggests that alterations of gene expression including expression and activities of transcription factors are closely associated with carcinogenesis. Forkhead Box Class K (FOXK) proteins, FOXK1 and FOXK2, are a family of evolutionarily conserved transcriptional factors, which have recently been recognized as key transcriptional regulators involved in many types of cancer. Members of the FOXK family mediate a wide spectrum of biological processes, including cell proliferation, differentiation, apoptosis, autophagy, cell cycle progression, DNA damage and tumorigenesis. Therefore, the deregulation of FOXKs can affect the cell fate and they promote tumorigenesis as well as cancer progression. The mechanisms of FOXKs regulation including post-translational modifications (PTMs), microRNAs (miRNAs) and protein-protein interactions are well demonstrated. However, the detailed mechanisms of FOXKs activation and deregulation in cancer progression are still inconclusive. In this review, we summarize the regulatory mechanisms of FOXKs expression and activity, and their role in the development and progression of cancer. We have discussed whether FOXKs act as tumor suppressors/oncoproteins in tumor cells and their therapeutic applications in malignant diseases are also discussed. This review may assist in designing experimental studies involving FOXKs and it would strength the therapeutic potential of FOXKs as targets for cancers.

Penfluridol overcomes paclitaxel resistance in metastatic breast cancer

Paclitaxel is a first line chemotherapeutic agent for the patients with metastatic breast cancer. But inherited or acquired resistance to paclitaxel leads to poor response rates in a majority of these patients. To identify mechanisms of paclitaxel resistance, we developed paclitaxel resistant breast cancer cell lines, MCF-7 and 4T1 by continuous exposure to paclitaxel for several months. Western blot analysis showed increased expression of HER2 and β-catenin pathway in resistant cell lines as compared to parent cells. Hence, we hypothesized that HER2/β-catenin mediates paclitaxel resistance in breast cancer and suppression of HER2/β-catenin signaling could overcome paclitaxel resistance. Our data showed that penfluridol (PFL) treatment significantly reduced the survival of paclitaxel-resistant cells. Western blot analysis revealed that PFL treatment suppressed HER2, as well as, β-catenin pathway. In vivo data confirmed that PFL significantly potentiated tumor growth suppressive effects of paclitaxel in an orthotropic breast cancer model. In addition, tumors from paclitaxel and PFL-treated mice showed reduced HER2 and β-catenin expression, along with increased apoptosis. Taken together our results demonstrate a novel role of HER2/β-catenin in paclitaxel resistance and open up new avenues for application of PFL as a therapeutic option for overcoming paclitaxel resistance.

FOXK2 Transcription Factor and Its Emerging Roles in Cancer

Forkhead box (FOX) transcription factors compose a large family of regulators of key biological processes within a cell. FOXK2 is a member of FOX family, whose biological functions remain relatively unexplored, despite its description in the early nineties. More recently, growing evidence has been pointing towards a role of FOXK2 in cancer, which is likely to be context-dependent and tumour-specific. Here, we provide an overview of important aspects concerning the mechanisms of regulation of FOXK2 expression and function, as well as its complex interactions at the chromatin level, which orchestrate how it differentially regulates the expression of gene targets in pathophysiology. Particularly, we explore the emerging functions of FOXK2 as a regulator of a broad range of cancer features, such as cell proliferation and survival, DNA damage, metabolism, migration, invasion and metastasis. Finally, we discuss the prognostic value of assessing FOXK2 expression in cancer patients and how it can be potentially targeted for future anticancer interventions.

Adjudin synergizes with paclitaxel and inhibits cell growth and metastasis by regulating the sirtuin 3-Forkhead box O3a axis in human small-cell lung cancer

Background

Small‐cell lung cancer (SCLC), a malignant tumor, is usually widely metastatic when diagnosed. The lack of important therapeutic clinical advances makes it difficult to treat. Previous studies showed that Adjudin had anticancer effects in many other human cancers, and it was synergetic with cisplatin in non‐small cell lung cancer. However, the mechanism on SCLC was unclear.

Methods

We investigated the potential mechanism and effect of Adjudin on SCLC both in vitro and in vivo.

Results

An SCLC xenograft model showed that Adjudin inhibited tumor growth and was significantly synergetic with paclitaxel (in vitro as well). Cell Counting Kit‐8 assays, flow cytometric analysis and western blotting showed that Adjudin effectively suppressed SCLC cell proliferation by inducing S phase arrest and caspase‐dependent apoptosis. Moreover, Transwell and scratch assays showed that Adjudin also effectively inhibited migration and invasion. Furthermore, Adjudin activated the sirtuin 3 (SIRT3)–Forkhead box O3a (FOXO3a) pathway. Downregulating SIRT3 or FOXO3a significantly attenuated Adjudin‐induced anticancer effects. Furthermore, higher expression of SIRT3 and FOXO3a were positively correlated, and both were associated with longer survival in lung cancer patients.

Conclusion

Overall, the present study is the first to show that Adjudin synergizes with paclitaxel and inhibits cell growth and metastasis by regulating the SIRT3–FOXO3a axis in SCLC; thus, Adjudin has great potential to be an anticancer agent.

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.

SUMOylation modulates FOXK2-mediated paclitaxel sensitivity in breast cancer cells

The forkhead transcription factor FOXK2 plays a critical role in suppressing tumorigenesis and mediating cytotoxic drug action in breast cancer. However, the mechanism by which the biological function of FOXK2 is regulated remains poorly understood. Here, we investigated the role of SUMOylation in modulating FOXK2-mediated drug sensitivity. We identified SUMOylation consensus motifs within the FOXK2 sequence and constructed two SUMOylation-defective double mutants by converting lysine 527 and 633 to arginines and glutamic acid 529 and 635 to alanines, respectively. We found that both the FOXK2 SUMOylation-deficient (K527/633 R) and (E529/635 A) mutants were ineffective in mediating the cytotoxic function of paclitaxel when compared to the wild-type (WT) FOXK2. When overexpressed, unlike the wild-type (WT) FOXK2, the K527/633 R mutant had little effect on the sensitivity of MCF-7 and MDA-MB-231 cells to paclitaxel, as examined by cell viability and clonogenic assays. Our results also showed that MCF-7 cells overexpressing the K527/633 R mutant form of FOXK2 or the empty expression vector have lower protein and mRNA levels of its tumour suppressive transcriptional target FOXO3 compared to the wild-type FOXK2. Consistently, ChIP assays revealed that unlike wild-type FOXK2, the SUMOylation-defective (K527/633 R) mutant is unable to bind to the FOXO3 promoter, despite expressing comparable levels of protein and having the same subcellular localization as the wild-type FOXK2 in MCF-7 cells. Interestingly, expression of neither the wild-type nor the K527/633 R mutant FOXK2 had any effect on the proliferation and paclitaxel sensitivity of the MCF-7 TaxR paclitaxel-resistant cells. In agreement, both the wild-type and the (K527/633 R) mutant FOXK2 failed to bind to the endogenous FOXO3 promoter in these cells. Collectively, our results suggest that SUMOylation positively regulates FOXK2 transcriptional activity and has a role in mediating the cytotoxic response to paclitaxel through the tumour suppressor FOXO3.

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

Purpose

Forkhead 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 methods

We 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.

Results

The 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.

Conclusion

Expression of FOXK2 gradually decreases with increasing WHO grades. FOXK2 inhibits tumor proliferation, migration, and invasion. FOXK2 is a critical mediator of the EMT process.

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.

FoxM1: Repurposing an oncogene as a biomarker

The past few decades have witnessed a tremendous progress in understanding the biology of cancer, which has led to more comprehensive approaches for global gene expression profiling and genome-wide analysis. This has helped to determine more sophisticated prognostic and predictive signature markers for the prompt diagnosis and precise screening of cancer patients. In the search for novel biomarkers, there has been increased interest in FoxM1, an extensively studied transcription factor that encompasses most of the hallmarks of malignancy. Considering the attractive potential of this multifarious oncogene, FoxM1 has emerged as an important molecule implicated in initiation, development and progression of cancer. Bolstered with the skill to maneuver the proliferation signals, FoxM1 bestows resistance to contemporary anti-cancer therapy as well. This review sheds light on the large body of literature that has accumulated in recent years that implies that FoxM1 neoplastic functions can be used as a novel predictive, prognostic and therapeutic marker for different cancers. This assessment also highlights the key features of FoxM1 that can be effectively harnessed to establish FoxM1 as a strong biomarker in diagnosis and treatment of cancer.

Sox9 mediated transcriptional activation of FOXK2 is critical for colorectal cancer cells proliferation

FOXK2, which belongs to the fork head DNA binding protein family, has been shown to play a critical role in tumorigenesis. Here, we detected FOXK2 expression and its clinical significance in colorectal cancer, which has not been fully investigated before. Results from public database and our cohort indicated that FOXK2 was transcriptionally activated in colorectal cancer tissues compared to non-cancer tissues. High expression of FOXK2 was significantly correlated with poor survival. In vitro cell experiments suggested that FOXK2 promoted cell proliferation. Furthermore, we found that oncogene SOX9 was responsible for the up-regulation of FOXK2 by directly binding on its promoter. Depletion of FOXK2 attenuated SOX9 induced cell growth. In addition, we observed that the expression of FOXK2 was significantly associated with the expression of SOX9 both in the public database and our colorectal cancer tissues. The patients with SOX9⁺FOXK2⁺ had a poor overall survival (p = 0.0084). In conclusion, our data suggested that SOX9 transcriptionally activated FOXK2 was involved in the pathogenesis of colorectal cancer and might be a novel target for colorectal cancer therapy.