Deregulation of FOXO3A during prostate cancer progression

Casein Kinase 1α-A Target for Prostate Cancer Therapy?

The androgen receptor (AR) is a key driver of prostate cancer (PCa) and, as such, current mainstay treatments target this molecule. However, resistance commonly arises to these therapies and, therefore, additional targets must be evaluated to improve patient outcomes. Consequently, alternative approaches for indirectly targeting the AR are sought. AR crosstalk with other signalling pathways, including several protein kinase signalling cascades, has been identified as a potential route to combat therapy resistance. The casein kinase 1 (CK1) family of protein kinases phosphorylate a multitude of substrates, allowing them to regulate a diverse range of pathways from the cell cycle to DNA damage repair. As well as its role in several signalling pathways that are de-regulated in PCa, mutational data suggest its potential to promote prostate carcinogenesis. CK1α is one isoform predicted to regulate AR activity via phosphorylation and has been implicated in the progression of several other cancer types. In this review, we explore how the normal biological function of CK1 is de-regulated in cancer, the impact on signalling pathways and how this contributes towards prostate tumourigenesis, with a particular focus on the CK1α isoform as a novel therapeutic target for PCa.

Dexamethasone inhibits androgen receptor-negative prostate cancer cell proliferation via the GR-FOXO3a-GAS5 axis

Background

Studies have shown that glucocorticoid receptor (GR) has inconsistent effects on the proliferation of prostate cancer cells, we found dexamethasone inhibited the proliferation of androgen receptor-negative prostate cancer cells, but the underlying mechanisms remain to be illustrated.

Methods

GR expression and its prognosis role were analyzed based on the TCGA dataset. Bioinformatic analysis was performed to identify the candidate of GR downstream, which includes FOXO3a. After overexpressing FOXO3a in PC-3 cells, cell counting kit-8 (CCK-8) and migration assays were performed to evaluate cell proliferation and migration ability. Regulation of FOXO3a on GAS5 was also analyzed by JASPAR and PCR.

Results

GR had low expression in prostate cancer and predicted poor prognosis. FOXO3a was identified as the downstream of GR to inhibit the proliferation of prostate cancer cells. Moreover, FOXO3a directly induces GAS5 expression, forming the GR-FOXO3a-GAS5 signaling pathway.

Conclusion

Our study showed that GR played a role as a tumor suppressor gene in androgen receptor-negative prostate cancer cells via the GR-FOXO3a-GAS5 axis. Our results suggested patients with prostate cancer should be classified and develop a treatment plan according to the expression of AR and GR.

Danlou Tablet Protects Against Cardiac Remodeling and Dysfunction after Myocardial Ischemia/Reperfusion Injury through Activating AKT/FoxO3a Pathway

Myocardial ischemia/reperfusion injury (I/RI) and ventricular remodeling are the critical pathological basis of heart failure. Danlou tablet (Dan) is a kind of Chinese patent medicine used in angina pectoris treatment in China. However, it remains unclear whether and how Dan could protect against cardiac remodeling after myocardial I/RI. In this study, both preventive and therapeutic administration of Dan attenuated ventricular remodeling and cardiac dysfunction at 3 weeks after myocardial I/RI. Dan inhibited Bax/Bcl2 ratio and Caspase3 cleavage in heart tissues and also inhibited apoptosis of human AC16 cells and neonatal rat cardiomyocytes stressed by oxygen and glucose deprivation/reperfusion. Mechanistically, Dan inhibited myocardial apoptosis through phosphorylating AKT and FoxO3a, thereby inhibiting downstream BIM and PUMA expressions. Collectively, these results demonstrate that Dan treatment is effective to protect against cardiac remodeling and dysfunction after myocardial I/RI and provide theoretical basis for its cardioprotection and clinical application in treating ischemic cardiac diseases.

Prognostic Values of Gene Copy Number Alterations in Prostate Cancer

Whilst risk prediction for individual prostate cancer (PCa) cases is of a high priority, the current risk stratification indices for PCa management have severe limitations. This study aimed to identify gene copy number alterations (CNAs) with prognostic values and to determine if any combination of gene CNAs could have risk stratification potentials. Clinical and genomic data of 500 PCa cases from the Cancer Genome Atlas stable were retrieved from the Genomic Data Commons and cBioPortal databases. The CNA statuses of a total of 52 genetic markers, including 21 novel markers and 31 previously identified potential prognostic markers, were tested for prognostic significance. The CNA statuses of a total of 51/52 genetic markers were significantly associated with advanced disease at an odds ratio threshold of ≥1.5 or ≤0.667. Moreover, a Kaplan-Meier test identified 27/52 marker CNAs which correlated with disease progression. A Cox Regression analysis showed that the amplification of MIR602 and deletions of MIR602, ZNF267, MROH1, PARP8, and HCN1 correlated with a progression-free survival independent of the disease stage and Gleason prognostic group grade. Furthermore, a binary logistic regression analysis identified twenty-two panels of markers with risk stratification potentials. The best model of 7/52 genetic CNAs, which included the SPOP alteration, SPP1 alteration, CCND1 amplification, PTEN deletion, CDKN1B deletion, PARP8 deletion, and NKX3.1 deletion, stratified the PCa cases into a localised and advanced disease with an accuracy of 70.0%, sensitivity of 85.4%, specificity of 44.9%, positive predictive value of 71.67%, and negative predictive value of 65.35%. This study validated prognostic gene level CNAs identified in previous studies, as well as identified new genetic markers with CNAs that could potentially impact risk stratification in PCa.

SIRT1/FOXO Signaling Pathway in Breast Cancer Progression and Metastasis

Breast cancer is the second most common cancer in women. The roles of the SIRT and FoxO proteins in tumor progression are known, but their roles in metastasis have not yet been clearly elucidated. In our study, we investigated the roles of SIRT and FoxO proteins their downstream pathways, proteins p21 and p53, in tumor progression and metastasis. We evaluated these proteins in vitro using metastatic 4TLM and 67NR cell lines, as well as their expression levels in tumor-bearing mice. In addition, the regulatory role of SIRT and FoxO proteins in different transduction cascades was examined by IPA core analysis, and clinicopathological evidence was investigated in the TCGA database. In primary tumors, the expression levels of SIRT1, p21, p53, E2F1 and FoxO proteins were higher in 67NR groups. In metastatic tissues, the expression levels of SIRT1, E2F1 and FoxO proteins were found to be enhanced, whereas the levels of p53 and p21 expression were noted to be reduced. IPA analysis also provided empirical evidence of the mechanistic involvement of SIRT and FoxO proteins in tumor progression and metastasis. In conclusion, SIRT1 was found to co-operate with FoxO proteins and to play a critical role in metastasis. Additional research is required to determine why overexpression of SIRT1 in metastatic tissues has oncogenic effects.

FOXO3a-ROS pathway is involved in androgen-induced proliferation of prostate cancer cell

Background

Although FOXO3a can inhibit the cell proliferation of prostate cancer, its relationship with reactive oxygen species (ROS) in prostate cancer (PCa) has not been reported.

Methods

We analyzed the correlation between the expression of FOXO3a and the antioxidant enzyme catalase in prostate cancer with the TCGA and GEPIA databases. We also constructed a PPI network of FOXO3a via the STRING database. The mRNA and protein expression of FOXO3a and catalase were detected by qRT-PCR or western blotting in LNCaP and 22RV1 cells treated with DHT, R1881, or Enzalutamide. The effects of FOXO3a on catalase expression were tested by over-expressing or knocking down FOXO3a in LNCaP cells. Furthermore, the catalase activity and ROS level were detected in LNCaP cells treated with DHT. Cell proliferation and ROS were also analyzed in LNCaP which was treated with antioxidant.

Results

Results showed that the catalase expression was down-regulated in prostate cancer. A positive correlation between FOXO3a and catalase existed. DHT treatment could significantly reduce FOXO3a and catalase expression at mRNA and protein level in LNCaP cells. Catalase expression partly depended on FOXO3a as over-expression and knockdown of FOXO3a could result in the expresssion change of catalase. DHT treatment was found to inhibit catalase activity and increase ROS level in prostate cancer cell. Our study also demonstrated that antioxidant treatment reduced DHT-induced proliferation and ROS production in prostate cancer cell.

Conclusions

We discovered a novel mechanism by which DHT promotes prostate cancer cell proliferation via suppressing catalase activity and activating ROS signaling via a FOXO3a dependent manner.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-022-01020-9.

Targeting Protein Kinases and Epigenetic Control as Combinatorial Therapy Options for Advanced Prostate Cancer Treatment

Prostate cancer (PC), the fifth leading cause of cancer-related mortality worldwide, is known as metastatic bone cancer when it spreads to the bone. Although there is still no effective treatment for advanced/metastatic PC, awareness of the molecular events that contribute to PC progression has opened up opportunities and raised hopes for the development of new treatment strategies. Androgen deprivation and androgen-receptor-targeting therapies are two gold standard treatments for metastatic PC. However, acquired resistance to these treatments is a crucial challenge. Due to the role of protein kinases (PKs) in the growth, proliferation, and metastases of prostatic tumors, combinatorial therapy by PK inhibitors may help pave the way for metastatic PC treatment. Additionally, PC is known to have epigenetic involvement. Thus, understanding epigenetic pathways can help adopt another combinatorial treatment strategy. In this study, we reviewed the PKs that promote PC to advanced stages. We also summarized some PK inhibitors that may be used to treat advanced PC and we discussed the importance of epigenetic control in this cancer. We hope the information presented in this article will contribute to finding an effective treatment for the management of advanced PC.

FOXO3a and Its Regulators in Prostate Cancer

Forkhead box O3 (FOXO3a) is a member of a subfamily of forkhead transcription factors involved in the basic processes within a cell, including proliferation, apoptosis, cell cycle regulation, and DNA damage. As a transcription factor, FOXO3a is involved in the response to cellular stress, UV radiation, or oxidative stress. Its regulation is based on the modification of proteins as well as regulation by other proteins, e.g., growth factors. FOXO3a is commonly deregulated in cancer cells, and its inactivation is associated with initiation and progression of tumorigenesis, suggesting its role as a tumor suppressor; however, its role is still disputed and seems to be dependent on upstream signaling. Nevertheless, FOXO3a serves as an interesting potential target in therapies as it is regulated during treatment with very common anti-cancer drugs such as paclitaxel, cisplatin, docetaxel, and doxorubicin. This review aims to update the reported role of FOXO3a in prostate cancer (PCa), with a focus on its regulators that might serve as potential therapeutic agents in PCa therapy.

Clinicopathological Significance of FOXO4 Expression and Correlation with Prx1 in Head and Neck Squamous Cell Carcinoma

OBJECTIVE

Forkhead box O 4 (FOXO4), a key albumen in the forkhead box O (FOXOs) family, plays crucial roles as a tumor suppressor in the cancer development. In our previous study, Peroxiredoxin1 (Prx1) promoted the development of oral cancer and was predicted to bind to FOXO4. The aim of this study was to investigate the clinicopathological significance of FOXO4 expression and its potential mechanism in head and neck squamous cell carcinomas (HNSCC).

METHODS

The function of FOXO4 correlation with HNSCC prognosis was analyzed via ONCOMINE, UALCAN, Human Protein Atlas, and cBioPortal. The expression of FOXO4 was detected in Prx1 silenced CaL27 and SCC9 cell lines by Western blot. FOXO4 protein expression was observed via immunohistochemistry (IHC) and the binding of Prx1 to FOXO4 measured by Duolink analysis in a 4-nitro-quinoline-1-oxide- (4NQO-) induced tongue carcinogenesis model in Prx1+/+ and Prx1+/- mice.

RESULTS

By the analysis of Bioinformation Databases, there was a significant interaction of FOXO4 down expression to clinical tumor stages and pathological grades in the patients with HNSCC. Reduced mRNA and protein expression of FOXO4 were found to be significantly correlated with the poor overall survival (OS) of HNSCC patients. FOXO4 expression is negatively related to Prx1 significantly in HNSCC tissues. By employing a 4NQO-induced oral carcinogenesis mouse model, we confirmed that FOXO4 expression was reduced in 4NQO-induced squamous cell carcinoma (SCC) tongue tissues compared with those in normal tissues. Prx1 knockdown resulted in the upregulation of FOXO4 expression in the SCC tissues and CaL27 and SCC9 cell lines. Furthermore, the interaction of Prx1 with FOXO4 was observed in mouse tongue tissues by Duolink analysis.

CONCLUSION

FOXO4 plays an important role in the development of HNSCC. The lower expression of FOXO4 is significantly correlated with the shorter OS in patients with HNSCC. FOXO4 is negatively regulated via interaction with Prx1. FOXO4 could be a potential molecular target for the treatment and prognosis of HNSCC.

DNA Damage- But Not Enzalutamide-Induced Senescence in Prostate Cancer Promotes Senolytic Bcl-xL Inhibitor Sensitivity

Cellular senescence is a natural tumor suppression mechanism defined by a stable proliferation arrest. In the context of cancer treatment, cancer cell therapy-induced senescence (TIS) is emerging as an omnipresent cell fate decision that can be pharmacologically targeted at the molecular level to enhance the beneficial aspects of senescence. In prostate cancer (PCa), TIS has been reported using multiple different model systems, and a more systematic analysis would be useful to identify relevant senescence manipulation molecular targets. Here we show that a spectrum of PCa senescence phenotypes can be induced by clinically relevant therapies. We found that DNA damage inducers like irradiation and poly (ADP-ribose) polymerase1 (PARP) inhibitors triggered a stable PCa-TIS independent of the p53 status. On the other hand, enzalutamide triggered a reversible senescence-like state that lacked evidence of cell death or DNA damage. Using a small senolytic drug panel, we found that senescence inducers dictated senolytic sensitivity. While Bcl-2 family anti-apoptotic inhibitor were lethal for PCa-TIS cells harboring evidence of DNA damage, they were ineffective against enzalutamide-TIS cells. Interestingly, piperlongumine, which was described as a senolytic, acted as a senomorphic to enhance enzalutamide-TIS proliferation arrest without promoting cell death. Overall, our results suggest that TIS phenotypic hallmarks need to be evaluated in a context-dependent manner because they can vary with senescence inducers, even within identical cancer cell populations. Defining this context-dependent spectrum of senescence phenotypes is key to determining subsequent molecular strategies that target senescent cancer cells.

FOXO3a‑SIRT6 axis suppresses aerobic glycolysis in melanoma

Melanoma, the most aggressive human skin tumor, has a very short survival time, and there are currently no effective treatments. Alterations in cell metabolism, such as enhanced aerobic glycolysis, have been identified as hallmarks of cancer cells. In the present study, bioinformatics studies using online databases revealed that FOXO3a expression was lower in melanoma tissues compared with normal tissues and nevus. Additionally, Kaplan‑Meier analysis showed that high expression of FOXO3a predicted an improved prognosis for patients with melanoma. Furthermore, Pearson correlation analysis indicated that the expression of FOXO3a was positively correlated with SIRT6 expression and negatively correlated with the expression levels of a number of glycolysis‑associated genes. Chromatin immunoprecipitation and luciferase assays showed that FOXO3a was enriched in the SIRT6 promoter region and promoted its transcription. Then, SIRT6 was overexpressed in FOXO3a‑knockdown MV3 cells and downregulated in FOXO3a‑overexpressing MV3 cells by using lentivirus‑mediated stable infection. The results showed that SIRT6 knockdown or overexpression rescued the effects of FOXO3a overexpression or knockdown, respectively, on glycolysis, as determined by glucose uptake, glucose consumption and lactate production assays, the expression of glycolytic genes and glucose stress flux tests. SIRT6 overexpression also suppressed FOXO3a knockdown‑induced tumor growth in a mouse model. The present findings indicated that the FOXO3a‑SIRT6 regulatory axis inhibited glucose metabolism and tumor cell proliferation in melanoma, and provided novel insight into potential therapeutic strategies to treat this disease.

Downregulation of FOXO3a by DNMT1 promotes breast cancer stem cell properties and tumorigenesis

Breast cancer stem cells (BCSCs) are tumor initiating cells that can self-renew and are highly tumorigenic and chemoresistant. Therefore, the identification of factors critical for BCSC function is vital for the development of therapies. Here, we report that DNMT1-mediated FOXO3a promoter hypermethylation leads to downregulation of FOXO3a expression in breast cancer. FOXO3a is functionally related to the inhibition of FOXM1/SOX2 signaling and to the consequent suppression of BCSCs properties and tumorigenicity. Moreover, we found that SOX2 directly transactivates DNMT1 expression and thereby alters the methylation landscape, which in turn feedback inhibits FOXO3a expression. Inhibition of DNMT activity suppressed tumor growth via regulation of FOXO3a/FOXM1/SOX2 signaling in breast cancer. Clinically, we observed a significant inverse correlation between FOXO3a and FOXM1/SOX2/DNMT1 expression levels, and loss of FOXO3a expression or increased expression of FOXM1, SOX2, and DNMT1 predicted poor prognosis in breast cancer. Collectively, our findings suggest an important role of the DNMT1/FOXO3a/FOXM1/SOX2 pathway in regulating BCSCs properties, suggesting potential therapeutic targets for breast cancer.

Differentially Expressed Genes and Molecular Pathways in an Autochthonous Mouse Prostate Cancer Model

Prostate cancer remains a major public health problem and the second leading cause of cancer-related deaths in men in the United States. The present study aims to understand the molecular pathway(s) of prostate cancer which is essential for early detection and treatment. Dorsolateral prostate from 20 week transgenic adenocarcinoma of the mouse prostate (TRAMP) mice, which spontaneously develops prostate cancer and recapitulates human disease and age-matched non-transgenic littermates were utilized for microarray analysis. Mouse genome network and pathway analyses were mapped to the human genome using the Ingenuity Pathway Analysis (IPA) database for annotation, visualization, and integrated discovery. In total, 136 differentially expressed genes, including 32 downregulated genes and 104 upregulated genes were identified in the dorsolateral prostate of TRAMP, compared to non-transgenic mice. A subset of differentially expressed genes were validated by qRT-PCR. Alignment with human genome database identified 18 different classes of proteins, among these, 36% were connected to the nucleic acid binding, including ribosomal proteins, which play important role in protein synthesis—the most enriched pathway in the development of prostate cancer. Furthermore, the results suggest deregulation of signaling molecules (9%) and enzyme modulators (8%) affect various pathways. An imbalance in other protein classes, including transporter proteins (7%), hydrolases (6%), oxidoreductases, and cytoskeleton proteins (5%), contribute to cancer progression. Our study evaluated the underlying pathways and its connection to human prostate cancer, which may further help assess the risk of disease development and progression and identify potential targets for therapeutic intervention.

CTCF regulates the FoxO signaling pathway to affect the progression of prostate cancer

The present research focuses on the influence of CCCTC‐binding factor (CTCF) on prostate cancer (PC) via the regulation of the FoxO signalling pathway. A bioinformatics analysis was conducted to screen out target genes for CTCF in LNCaP cells and to enrich the relevant pathways in LNCaP cells. It was found that the FoxO pathway was enriched according to the ChIP‐seq results of CTCF. The expression of CTCF, pFoxO1a, FoxO1a, pFoxO3a and FoxO3a was tested by RT‐qPCR and Western blot. Inhibition of CTCF could lead to the up‐regulation of the FoxO signalling pathway. The rates of cell proliferation, cell invasion and apoptosis were examined by MTT assay, cell invasion assay and flow cytometry under different interference conditions. Down‐regulation of CTCF could suppress cell proliferation, cell invasion and facilitate cell apoptosis. Lastly, the effect of CTCF on tumour growth was determined in nude mice. Inhibition of CTCF regulated the FoxO signalling pathway, which retarded tumour growth in vivo. In conclusion, CTCF regulates the FoxO signalling pathway to affect the progress of PC.

Para-Toluenesulfonamide Induces Anti-tumor Activity Through Akt-Dependent and -Independent mTOR/p70S6K Pathway: Roles of Lipid Raft and Cholesterol Contents

Castration-resistant prostate cancer (CRPC) cells can resist many cellular stresses to ensure survival. There is an unmet medical need to fight against the multiple adaptive mechanisms in cells to achieve optimal treatment in patients. Para-toluenesulfonamide (PTS) is a small molecule that inhibited cell proliferation of PC-3 and DU-145, two CRPC cell lines, through p21- and p27-independent G1 arrest of cell cycle in which cyclin D1 was down-regulated and Rb phosphorylation was inhibited. PTS also induced a significant loss of mitochondrial membrane potential that was attributed to up-regulation of both Bak and PUMA, two pro-apoptotic Bcl-2 family members, leading to apoptosis. PTS inhibited the phosphorylation of m-TOR, 4E-BP1, and p70S6K in both cell lines. Overexpression of constitutively active Akt rescued the inhibition of mTOR/p70S6K signaling in PC-3 cells indicating an Akt-dependent pathway. In contrast, Akt-independent effect was observed in DU-145 cells. Lipid rafts serve as functional platforms for multiple cellular signaling and trafficking processes. Both cell lines expressed raft-associated Akt, mTOR, and p70S6K. PTS induced decreases of expressions in both raft-associated total and phosphorylated forms of these kinases. PTS-induced inhibitory effects were rescued by supplement of cholesterol, an essential constituent in lipid raft, indicating a key role of cholesterol contents. Moreover, the tumor xenograft model showed that PTS inhibited tumor growth with a T/C (treatment/control) of 0.44 and a 56% inhibition of growth rate indicating the in vivo efficacy. In conclusion, the data suggest that PTS is an effective anti-tumor agent with in vitro and in vivo efficacies through inhibition of both Akt-dependent and -independent mTOR/p70S6K pathways. Moreover, disturbance of lipid raft and cholesterol contents may at least partly explain PTS-mediated anti-tumor mechanism.

FOXO3a expression and its diagnostic value in pancreatic ductal adenocarcinoma

FOXO3a (FKHRL1) is an important regulator of cell apoptosis, proliferation, metabolic state and longevity. FOXO3a expression can be measured and has been regarded as a tumor suppressor factor in many cancers. However, the expression and role of FOXO3a in PDAC have not been defined. We evaluated the expression of FOXO3a in PDAC and the relationship of its expression with clinicopathological features and patient outcomes. We found that compared with normal tissues, the expression of FOXO3a was significantly higher in tumor tissues (P<0.001). FOXO3a expression correlates significantly with tumor differentiation and with the primary location of the tumor (P<0.001 and P=0.005, respectively). In a univariate analysis, we found that FOXO3a expression has a strong relationship with survival (P=0.013). In addition, Kaplan-Meier survival curves indicated that a low expression of FOXO3a in tumor tissues has a significantly shorter OS compared with patients with high expression of FOXO3a (P=0.013). In conclusion, the expression of FOXO3a is significantly higher in PDAC compared with normal pancreatic tissues and has a low expression or negative staining in poorly differentiated PDAC, which seems to indicate that FOXO3a expression in tumor tissues may be related to the pathological progression stage and may be used as a diagnostic indicator with early tumors.

β-arrestin1-medieated inhibition of FOXO3a contributes to prostate cancer cell growth in vitro and in vivo

Recently, β-arrestin1 has been indicated as a prostate cancer promoter through promoting cell proliferation and epithelial to mesenchymal transition, but its underlying mechanism remains unclear. Here, our data revealed that β-arrestin1 could promote cell growth through inhibiting the transcriptional activity and expression of FOXO3a in prostate cancer cells in vitro and in vivo. We found that β-arrestin1 could promote the cell and tumor growth of prostate cancer, and β-arrestin1 expression represented a negative correlation with FOXO3a expression but not FOXO1 expression in prostate cancer cell lines and tissues. In addition, forced expression of β-arrestin1 induced a significant decrease of FOXO3a expression but had no clear effect on FOXO1 expression. Mechanistically, β-arrestin1 could interact with FOXO3a and MDM2, respectively, and promote the interaction between FOXO3a and MDM2, whereas it had no obvious interaction with FOXO1. Furthermore, β-arrestin1 could inhibit the transcriptional activity of FOXO3a via Akt and ERK1/2 pathways. Together, our results revealed a novel mechanism for β-arrestin1 in the regulation of the prostate cancer procession through inhibiting FOXO3a.

Calcium and Nuclear Signaling in Prostate Cancer

Recently, there have been a number of developments in the fields of calcium and nuclear signaling that point to new avenues for a more effective diagnosis and treatment of prostate cancer. An example is the discovery of new classes of molecules involved in calcium-regulated nuclear import and nuclear calcium signaling, from the G protein-coupled receptor (GPCR) and myosin families. This review surveys the new state of the calcium and nuclear signaling fields with the aim of identifying the unifying themes that hold out promise in the context of the problems presented by prostate cancer. Genomic perturbations, kinase cascades, developmental pathways, and channels and transporters are covered, with an emphasis on nuclear transport and functions. Special attention is paid to the molecular mechanisms behind prostate cancer progression to the malignant forms and the unfavorable response to anti-androgen treatment. The survey leads to some new hypotheses that connect heretofore disparate results and may present a translational interest.

Histone Deacetylase (HDAC) Inhibitor, Suberoylanilide Hydroxamic Acid (SAHA), Induces Apoptosis in Prostate Cancer Cell Lines via the Akt/FOXO3a Signaling Pathway

Background

Histone deacetylase (HDAC) inhibitors are emerging as a new class of anti-cancer drugs that promote cancer cell apoptosis, and include suberoylanilide hydroxamic acid (SAHA). The aim of this study was to investigate the mechanism of SAHA-induced apoptosis in human prostate cancer cell lines, DU145 and PC-3.

Material/Methods

Cell lines, DU145 and PC-3, were studied before and after treatment with SAHA. The effects of SAHA treatment on cell proliferation were studied using the MTT cell proliferation assay. Annexin-V-fluorescein isothiocyanate (FITC) and propidium iodide (PI) staining were used to study the effects of SAHA treatment on cell apoptosis. Western blotting, quantitative polymerase chain reaction (qPCR) and short interfering (si)RNA assays were performed to study the effects of SAHA treatment on apoptotic and cell cycle proteins and the Akt/FOXO3a signaling pathway.

Results

Treatment with SAHA inhibited cell proliferation in human prostate cancer cell lines DU145 and PC-3 cells in a dose-dependent way. Cell cycle analysis and Annexin-V FITC/PI staining showed that treatment with SAHA resulted in G2/M cell cycle arrest and increased cell apoptosis in a dose-dependent way. Also, treatment with SAHA reduced the protein expression levels cyclin B and cyclin A2 and promoted the activation of FOXO3a by inhibiting Akt activation. Western blotting, the siRNA assay, and qPCR showed that FOXO3a, the Bcl-2 family of proteins, survivin, and FasL were involved in SAHA-induced apoptosis in prostate cancer cells grown in vitro.

Conclusions

Treatment with SAHA promoted apoptosis via the Akt/FOXO3a signaling pathway in prostate cancer cells in vitro.

Expression of p-FOXO3/FOXO3 in bladder cancer and its correlation with clinicopathology and tumor recurrence

BACKGROUND

Survey for more accurate biomarkers for predicting and preventing the future recurrence in high risk patients is urgently needed. The transcription factor forkhead box-O3 (FOXO3) is a well-established tumor suppressor. Its phosphorylation (p-FOXO3) as well as deregulation is involved in cancer initiation, progression and drug resistance. Therefore, we proposed that p-FOXO3/FOXO3 ratio change may play important role in the bladder cancer recurrence.

METHODS

Surgical specimens of cancer tissue were obtained from 75 patients with bladder cancer (30 of non-recurrent and 45 of recurrent). The relative expression levels of p-FOXO3/FOXO3 in cancer tissue were measured by immunohistochemistry (IHC) stain and graded according to stain intensity. The correlation p-FOXO3/FOXO3 with clinicopathological parameters and tumor recurrence was analyzed.

RESULTS

For bladder cancer patients with tumor recurrence, higher tumor grade (82% vs 70%, P=0.04) and stage (≥II, 49% vs 33%, P=0.02) in these patients was seen. In IHC study of paired tumor tissues, 39 out of 75 (52%) patients have increased p-FOXO3/FOXO3 ratio and they are closely related to tumor grade (low grade vs high grade =29.4% vs 58.6%, P=0.01) but not related to stage (low stage vs high stage =46.5% vs 59.3%, P=0.26). Regarding to tumor recurrence, the p-FOXO3/FOXO3 ratio is significant higher in recurrent group than non-recurrent group patients (0.78±0.15 vs 1.25±0.11, P=0.03). As comparing the first recurrence and subsequent recurrence group patients, there is no difference in the level of p-FOXO3/FOXO3 ratio (1.25±0.11 vs 1.10±0.09, P=0.25). Interestingly, recurrent tumors in low grade bladder cancer patients have marked increased p-FOXO3/FOXO3 ratio than non-recurrent tumors (0.90±0.22 vs 0.15±0.12, P=0.02).

CONCLUSION

Increased p-FOXO3/FOXO3 ratio has been observed in bladder cancer patients with tumor recurrence and it is closely related to higher tumor grade. Low grade bladder cancer is high risk in recurrence when p-FOXO3/FOXO3 ratio increased. These results implicated that p-FOXO3/FOXO3 ratio can be applied as a useful marker for further treatment decision making and prognostic of tumor recurrence in bladder cancer patients.

The Role and Mechanism of Epithelial-to-Mesenchymal Transition in Prostate Cancer Progression

In prostate cancer (PCa), similar to many other cancers, distant organ metastasis symbolizes the beginning of the end disease, which eventually leads to cancer death. Many mechanisms have been identified in this process that can be rationalized into targeted therapy. Among them, epithelial-to-mesenchymal transition (EMT) is originally characterized as a critical step for cell trans-differentiation during embryo development and now recognized in promoting cancer cells invasiveness because of high mobility and migratory abilities of mesenchymal cells once converted from carcinoma cells. Nevertheless, the underlying pathways leading to EMT appear to be very diverse in different cancer types, which certainly represent a challenge for developing effective intervention. In this article, we have carefully reviewed the key factors involved in EMT of PCa with clinical correlation in hope to facilitate the development of new therapeutic strategy that is expected to reduce the disease mortality.

Molecular signaling cascades involved in nonmelanoma skin carcinogenesis

Nonmelanoma skin cancer (NMSC) is the most common cancer worldwide and the incidence continues to rise, in part due to increasing numbers in high-risk groups such as organ transplant recipients and those taking photosensitizing medications. The most significant risk factor for NMSC is ultraviolet radiation (UVR) from sunlight, specifically UVB, which is the leading cause of DNA damage, photoaging, and malignant transformation in the skin. Activation of apoptosis following UVR exposure allows the elimination of irreversibly damaged cells that may harbor oncogenic mutations. However, UVR also activates signaling cascades that promote the survival of these potentially cancerous cells, resulting in tumor initiation. Thus, the UVR-induced stress response in the skin is multifaceted and requires coordinated activation of numerous pathways controlling DNA damage repair, inflammation, and kinase-mediated signal transduction that lead to either cell survival or cell death. This review focuses on the central signaling mechanisms that respond to UVR and the subsequent cellular changes. Given the prevalence of NMSC and the resulting health care burden, many of these pathways provide promising targets for continued study aimed at both chemoprevention and chemotherapy.

Negative regulation of the FOXO3a transcription factor by mTORC2 induces a pro-survival response following exposure to ultraviolet-B irradiation

Exposure to ultraviolet-B (UVB) irradiation, the principal cause of non-melanoma skin cancer (NMSC), activates both the rapamycin-sensitive mammalian target of rapamycin complex 1 (mTORC1) and the rapamycin-resistant mTORC2. We have previously reported that UVB-induced keratinocyte survival is dependent on mTORC2, though the specific mechanism is not well understood. FOXO3a is an important transcription factor involved in regulating cell survival. The activity of FOXO3a is reduced as a result of protein kinase B (AKT/PKB) activation, which is downstream of mTORC2; however, the specific function of FOXO3a during UVB-induced apoptosis is unclear. In this study, we establish that in cells with wild-type mTORC2 activity, FOXO3a is quickly phosphorylated in response to UVB and sequestered in the cytoplasm. In contrast, loss of mTORC2 causes FOXO3a to be localized to the nucleus and sensitizes cells to UVB-induced apoptosis. Furthermore, this sensitization is rescued by knockdown of FOXO3a. Taken together, these studies provide strong evidence that inhibition of mTORC2 enhances UVB-induced apoptosis in a FOXO3a-dependent manner, and suggest that FOXO3a activation by mTORC2 inhibitors may be a valuable chemopreventive target in NMSC.

Regulation of Bim in Health and Disease

The BH3-only Bim protein is a major determinant for initiating the intrinsic apoptotic pathway under both physiological and pathophysiological conditions. Tight regulation of its expression and activity at the transcriptional, translational and post-translational levels together with the induction of alternatively spliced isoforms with different pro-apoptotic potential, ensure timely activation of Bim. Under physiological conditions, Bim is essential for shaping immune responses where its absence promotes autoimmunity, while too early Bim induction eliminates cytotoxic T cells prematurely, resulting in chronic inflammation and tumor progression. Enhanced Bim induction in neurons causes neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's diseases. Moreover, type I diabetes is promoted by genetically predisposed elevation of Bim in β-cells. On the contrary, cancer cells have developed mechanisms that suppress Bim expression necessary for tumor progression and metastasis. This review focuses on the intricate network regulating Bim activity and its involvement in physiological and pathophysiological processes.

Platycodin D induces tumor growth arrest by activating FOXO3a expression in prostate cancer in vitro and in vivo

Platycodin D (PD), a major saponin derived from Platycodin grandiflorum, exerted cytotoxicity against prostate cancer cell lines (PC3, DU145 and LNCaP cells) with IC₅₀ values in the range of 11.17 to 26.13μmol/L, whereas RWPE-1cells (a non-malignant human prostate epithelial cell line) were not significantly affected. A further study in these cell lines showed that PD could potently affect cell proliferation (indicated by the bromodeoxyuridine assay), induce cell apoptosis (determined by Annexin V-FITC flow cytometry) and cause cell cycle arrest (indicated by PI staining). After being treated with PD for 48 hours, DU145 and LNCaP cells were arrested in the G0 /G1 phase, and PC3 cells were arrested in the G2/M phase. A Western blotting analysis indicated that PD increased the expression of the FOXO3a transcription factor, decreased the expression of p-FOXO3a and MDM2 and increased the expression of FOXO-responsive genes, p21 and p27. MDM2 silencing (transiently by siRNA-MDM2) increased the PD-induced FOXO3a protein expression, while MDM2 overexpression (in cells transiently transfected with a pcDNA3-MDM2 plasmid) decreased the PD-induced expression of the FOXO3a protein. Moreover, PD dose-dependently inhibited the growth of PC3 xenograft tumors in BALB/c nude mice. A Western blotting analysis of the excised xenograft tumors indicated that similar changes in protein expression also occurred in vivo. These results suggest that PD exhibits significant activity against prostate cancer in vitro and in vivo. The FOXO3a transcription factor appears to be involved in the activity of PD. Together, all of these findings provide a basis for the future development of this agent for human prostate cancer therapy.

Expression of microRNA-96 and its potential functions by targeting FOXO3 in non-small cell lung cancer

MicroRNAs are implicated in the regulation of various cellular processes, including proliferation, differentiation, cell death, and cell mobility, and can function either as oncogenes or tumor suppressors in tumor progression. The effects of the expression of miR-96 in non-small cell lung cancer (NSCLC) remain unclear. In our study, qRT-PCR (quantitative reverse transcription PCR) was performed to identify the miR-96 expression level in 68 paired NSCLC and adjacent normal lung tissues. Trans-well, cell counting kit-8, and apoptosis assays were used to evaluate the effects of miR-96 expression on cell invasion, proliferation, and apoptosis. Dual-luciferase reporter assay and Western blotting were used to verify whether FOXO3 was a potential major target gene of miR-96. Finally, the effect of FOXO3 on miR-96-induced cell survival was determined by transfection of the genes expressing FOXO3 lacking 3'UTR and miR-96. The expression level of miR-96 in NSCLC tissues was higher than that in adjacent normal lung tissues, and this increased expression was significantly associated with lymph node metastasis. In contrast to the cells in the blank and negative control groups, the number of cells migrating through the matrigel was significantly lower and the incidence of apoptosis was significantly higher in cells transfected with a miR-96 inhibitor. Western blotting and dual-luciferase reporter assays demonstrated that miR-96 can bind to the putative seed region in FOXO3 mRNA 3'UTR, and can significantly lower the expression of FOXO3. The introduction of FOXO3 cDNA without 3'UTR restored miR-96 induced cell apoptosis and invasion. MiR-96 is up-regulated in NSCLC tissues. Downregulation of miR-96 inhibits invasion and promotes apoptosis in NSCLC cells A549 and SPC-A-1 by targeting FOXO3. Therefore, our study improves our understanding of the mechanisms underlying NSCLC pathogenesis and may promote the development of novel targeted therapies.

Regulation of the tumor suppressor FOXO3 by the thromboxane-A2 receptors in urothelial cancer

The transcription factor FOXO3 is a well-established tumor suppressor whose activity, stability, and localization are regulated by phosphorylation and acetylation. Previous data by our laboratory demonstrated amplified thromboxane-A₂ signaling was associated with poor prognoses in bladder cancer patients and overexpression of the thromboxane-A₂ isoform-β receptor (TPβ), but not TPα, induced malignant transformation of immortalized bladder cells in vivo. Here, we describe a mechanism of TP mediated modulation of FOXO3 activity and localization by phosphorylation and deacetylation in a bladder cancer cell model. In vitro gain and loss of function studies performed in non-transformed cell lines, UROsta and SV-HUC, revealed knockdown of FOXO3 expression by shRNA increased cell migration and invasion, while exogenously overexpressing TPβ raised basal phosphorylated (p)FOXO3-S294 levels. Conversely, overexpression of ERK-resistant, mutant FOXO3 reduced increases in UMUC3 cell migration and invasion, including that mediated by TP agonist (U46619). Additionally, stimulation of UMUC3 cells with U46619 increased pFOXO3-S294 expression, which could be attenuated by treatment with a TP antagonist (PTXA₂) or ERK inhibitor (U0126). Initially U46619 caused nuclear accumulation of pFOXO3-S294; however, prolonged stimulation increased FOXO3 cytoplasmic localization. U46619 stimulation decreased overall FOXO3 transcriptional activity, but was associated with increased expression of its pro-survival target, manganese superoxide dismutase. The data also shows that TP stimulation increased the expression of the histone deacetylase, SIRT1, and corresponded with decreased acetylated-FOXO3. Collectively, the data suggest a role for TP signaling in the regulation of FOXO3 activity, mediated in part through phosphorylation and deacetylation.

Intracellular redox status controls membrane localization of pro- and anti-migratory signaling molecules

Shifts in intracellular Reactive Oxygen Species (ROS) have been shown to contribute to carcinogenesis and to tumor progression. In addition to DNA and cell damage by surges in ROS, sub-lethal increases in ROS are implicated in regulating cellular signaling that enhances pro-metastatic behavior. We previously showed that subtle increases in endogenous H₂O₂ regulate migratory and invasive behavior of metastatic bladder cancer cells through phosphatase inhibition and consequential phosphorylation of p130cas, an adapter of the FAK signaling pathway. We further showed that enhanced redox status contributed to enhanced localization of p130cas to the membrane of metastatic cells. Here we show that this signaling complex can similarly be induced in a redox-engineered cell culture model that enables regulation of intracellular steady state H₂O₂ level by enforced expression of superoxide dismutase 2 (Sod2) and catalase. Expression of Sod2 leads to enhanced p130cas phosphorylation in HT-1080 fibrosarcoma and UM-UC-6 bladder cancer cells. These changes are mediated by H₂O₂, as co-expression of Catalase abrogates p130cas phosphorylation and its interaction with the adapter protein Crk. Importantly, we establish that the redox environment influence the localization of the tumor suppressor and phosphatase PTEN, in both redox-engineered and metastatic bladder cancer cells that display endogenous increases in H₂O₂. Importantly, PTEN oxidation leads to its dissociation from the plasma membrane. This indicates that oxidation of PTEN not only influences its activity, but also regulates its cellular localization, effectively removing it from its primary site of lipid phosphatase activity. These data introduce hitherto unappreciated paradigms whereby ROS can reciprocally regulate the cellular localization of pro- and anti-migratory signaling molecules, p130cas and PTEN, respectively. These data further confirm that altering antioxidant status and the intracellular ROS environment can have profound effects on pro-metastatic signaling pathways.

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Sod2-mediated increases in steady state H₂O₂ enhance phosphorylation of the focal adhesion adapter protein p130cas, which regulates migration.

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Sod2-dependent changes in steady state H₂O₂ increase membrane recruitment of p130cas.

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H₂O₂ controls the oxidation-dependent recruitment of PTEN from the plasma membrane to the cytosol.

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Intracellular shifts in ROS can reciprocally regulate the cellular localization of pro- and anti-migratory signaling molecules, p130cas and PTEN respectively.

Decreased expression of the FOXO3a gene is associated with poor prognosis in primary gastric adenocarcinoma patients

Background

FOXO3a, a member of the forkhead class ‘O’ (FOXO) transcription factor family, controls a wide spectrum of biological processes, such as DNA damage repair, apoptosis, and cell cycle regulation. FOXO3a has been shown to be a tumor suppressor in various cancers. This study investigated the expression of FOXO3a in primary gastric adenocarcinomas and its prognostic value for primary gastric adenocarcinoma patients.

Methods

Real-time quantitative RT-PCR (qRT-PCR), western blotting, and immunohistochemical staining were used to detect FOXO3a expression in primary gastric cancerous surgical specimens and adjacent non-tumorous tissues.

Results

Our data showed that the expression of FOXO3a mRNA (p = 0.03) and protein (p = 0.019) was lower in cancerous tissues compared with their adjacent non-tumorous tissues. In addition, the chi-square test revealed that low FOXO3a expression was significantly correlated with larger tumor size (p = 0.007), poor histopathological classification (p = 0.029), depth of invasion (p = 0.049), local lymph node metastasis (p = 0.013), distant metastasis (p = 0.013) and AJCC staging (p<0.001). Kaplan-Meier survival analysis demonstrated that low expression of FOXO3a was significantly correlated with a poor prognosis for gastric cancer patients (p<0.001). The multivariate analysis showed that FOXO3a expression was an independent prognostic factor of the overall survival rate of patients with primary gastric adenocarcinoma.

Conclusion

Our study suggested that decreased FOXO3a expression may play an important role in the progression of gastric cancer. FOXO3a could be a valuable prognostic marker as well as a potential molecular therapy target for gastric cancer patients.

Deregulation of FoxO3a accelerates prostate cancer progression in TRAMP mice

BACKGROUND

Forkhead box, class "O" (FoxO) transcription factors are involved in multiple signaling pathways and possess tumor suppressor functions. Loss of PTEN and activation of PI3K/Akt is frequently observed in prostate cancer, which may potentially inactivate FoxO activity. We therefore investigated the role of FoxO transcription factors in prostate cancer progression, in particular FoxO3a, in transgenic adenocarcinoma of the mouse prostate (TRAMP) mice, which mimics progressive forms of human disease.

METHODS

Prostate cancer progression in TRAMP mice was followed from 8 to 28 weeks. Expression patterns of Akt, FoxO1a, FoxO3a, FoxO4, and their phosphorylated form, DNA binding activity and downstream signaling molecules during different stages of disease progression were examined by immunoblotting, immunoprecipitation, enzyme-linked immunoabsorbant assay (ELISA), and immunohistochemistry. Inhibition of FoxO3a activity was attained by using FoxO3a peptide treatment to TRAMP mice.

RESULTS

In TRAMP mice, FoxO3a activity is negatively regulated by Akt/PKB through post-translational modification. Progressive increase in Akt activation during prostate cancer progression led to increase phosphorylation of FoxO3a and binding with 14-3-3, which potentially affected its transcriptional activity in age-specific manner. Furthermore, blocking FoxO3a activity resulted in accelerated prostate cancer progression in these mice, which was associated with the loss of cell cycle control and increased proliferation and survival markers.

CONCLUSIONS

Restoration of FoxO3a activity represents an attractive therapeutic target in the chemoprevention and possibly in inhibition of progression of prostate cancer.

Apigenin inhibits prostate cancer progression in TRAMP mice via targeting PI3K/Akt/FoxO pathway

Forkhead box O (FoxO) transcription factors play an important role as tumor suppressor in several human malignancies. Disruption of FoxO activity due to loss of phosphatase and tensin homolog and activation of phosphatidylinositol-3 kinase (PI3K)/Akt are frequently observed in prostate cancer. Apigenin, a naturally occurring plant flavone, exhibits antiproliferative and anticarcinogenic activities through mechanisms, which are not fully defined. In the present study, we show that apigenin suppressed prostate tumorigenesis in transgenic adenocarcinoma of the mouse prostate (TRAMP) mice through the PI3K/Akt/FoxO-signaling pathway. Apigenin-treated TRAMP mice (20 and 50 μg/mouse/day, 6 days/week for 20 weeks) exhibited significant decrease in tumor volumes of the prostate as well as completely abolished distant organ metastasis. Apigenin treatment resulted in significant decrease in the weight of genitourinary apparatus (P < 0.0001), dorsolateral (P < 0.0001) and ventral prostate (P < 0.028), compared with the control group. Apigenin-treated mice showed reduced phosphorylation of Akt (Ser473) and FoxO3a (Ser253), which correlated with its increased nuclear retention and decreased binding of FoxO3a with 14-3-3. These events lead to reduced proliferation as assessed by Ki-67 and cyclin D1, along with upregulation of FoxO-responsive proteins BIM and p27/Kip1. Complementing in vivo results, similar observations were noted in human prostate cancer LNCaP and PC-3 cells after apigenin treatment. Furthermore, binding of FoxO3a with p27/Kip1 was markedly increased after 10 and 20 μM apigenin treatment resulting in G0/G1-phase cell cycle arrest, which was consistent with the effects elicited by PI3K/Akt inhibitor, LY294002. These results provide convincing evidence that apigenin effectively suppressed prostate cancer progression, at least in part, by targeting the PI3K/Akt/FoxO-signaling pathway.

FoxO3a (Forkhead Box O3a) deficiency protects Idiopathic Pulmonary Fibrosis (IPF) fibroblasts from type I polymerized collagen matrix-induced apoptosis via caveolin-1 (cav-1) and Fas

Idiopathic Pulmonary Fibrosis is a lethal fibrotic disease characterized by the unrelenting proliferation and persistence of fibroblasts in a type I collagen-rich matrix that result in an expanding reticular network of fibrotic tissue. However, the underlying mechanism responsible for the persistence of myofibroblasts in IPF remains unclear. During normal tissue repair, unwanted fibroblasts are eliminated during collagen-matrix contraction by a mechanism whereby high PTEN activity suppresses Akt. We have previously found that FoxO3a, a transcriptional activator of apoptosis-inducing proteins, is inactivated in IPF fibroblasts resulting from aberrantly high PI3K/Akt activity due to inappropriately low PTEN activity. Here we demonstrate that this low FoxO3a activity confers IPF fibroblasts with resistance to collagen-mediated apoptosis. We show that the mechanism by which low FoxO3a activity confers IPF fibroblasts with an apoptotic resistant phenotype involves suppression of Fas expression as a result of down regulation of cav-1 expression via a PTEN/Akt-dependent pathway. We demonstrate that PTEN over-expression or Akt inhibition increases FoxO3a expression in IPF fibroblasts, resulting in up-regulation of caveolin-1. We show that FoxO3a binds to the cav-1 promoter region and ectopic expression of FoxO3a transcriptionally increases cav-1 mRNA and protein expression. In turn, we show that overexpression of caveolin-1 increases Fas levels and caspase-3/7 activity and promotes IPF fibroblast apoptosis on polymerized type I collagen. We have found that the expression of caveolin-1, Fas and cleaved caspase-3 proteins in fibroblasts within the fibroblastic foci of IPF patient specimens is low. Our data indicate that the pathologically altered PTEN/Akt axis inactivates FoxO3a down-regulating cav-1 and Fas expression. This confers IPF fibroblasts with an apoptosis-resistant phenotype and may be responsible for IPF progression.

Activation of protein kinase CK2 attenuates FOXO3a functioning in a PML-dependent manner: implications in human prostate cancer

Protein kinase CK2 (also known as Caseine Kinase II) is an ubiquitous Ser/Thr protein kinase present in both the nucleus and cytoplasm of cells, targeting several key enzymes, growth factor receptors, transcription factors and cytoskeletal proteins. It is not only a key player in regulating cellular growth and proliferation, but also behaves as a potent suppressor of apoptosis. CK2 has been frequently found to be deregulated (mostly hyperactivated) in all cancers, prostate cancer being prominent of them. In the recent past, tumor suppressor PML (promyelocytic leukemia) has been shown to be a target of phosphorylation by CK2. This phosphorylation promotes the ubiquitin-mediated proteasomal degradation of PML thereby effectively curbing its role as a tumor suppressor. Among many others, PML has also been established to mediate its tumor suppressive role by mitigating the inactivation of active AKT (pAKT) inside the nucleus by assembling a dephosphorylating platform for nuclear pAKT. One of the immediate consequences, of this inactivation is the stabilization of FOXO3a, another well-established tumor suppressor, inside the nucleus and its downstream activities. Here, we propose a novel signaling axis apexed by deregulated CK2, dismantling the association of PML and PHLPP2 (we also report PHLPP2 to be a novel interacting partner of PML inside the nucleus), ultimately leading to the inactivation and nuclear exclusion of FOXO3a, thereby downregulating p21/p27/Bim in which degradation of PML and the concomitant stabilization of pAKT plays a cardinal part.

Aberrantly activated EGFR contributes to enhanced IL-8 expression in COPD airways epithelial cells via regulation of nuclear FoxO3A

BACKGROUND

Decreased activity of forkhead transcription factor class O (FoxO)3A, a negative regulator of NF-κB-mediated chemokine expression, is implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Previously, we showed that quercetin reduces lung inflammation in a murine model of COPD. Here, we examined the mechanisms underlying decreased FoxO3A activation and its modulation by quercetin in COPD human airway epithelial cells and in a COPD mouse model.

METHODS

Primary COPD and normal human airway epithelial cells were treated with quercetin, LY294002 or erlotinib for 2 weeks. IL-8 was measured by ELISA. FoxO3A, Akt, and epidermal growth factor (EGF) receptor (EGFR) phosphorylation and nuclear FoxO3A levels were determined by Western blot analysis. Effects of quercetin on lung chemokine expression, nuclear FoxO3A levels and phosphorylation of EGFR and Akt were determined in COPD mouse model.

RESULTS

Compared with normal, COPD cells showed significantly increased IL-8, which negatively correlated with nuclear FoxO3A levels. COPD bronchial biopsies also showed reduced nuclear FoxO3A. Decreased FoxO3A in COPD cells was associated with increased phosphorylation of EGFR, Akt and FoxO3A and treatment with quercetin, LY294002 or erlotinib increased nuclear FoxO3A and decreased IL-8 and phosphorylation of Akt, EGFR and FoxO3A, Compared with control, elastase/LPS-exposed mice showed decreased nuclear FoxO3A, increased chemokines and phosphorylation of EGFR and Akt. Treatment with quercetin partially reversed these changes.

CONCLUSIONS

In COPD airways, aberrant EGFR activity increases PI 3-kinase/Akt-mediated phosphorylation of FoxO3A, thereby decreasing nuclear FoxO3A and increasing chemokine expression. Quercetin restores nuclear FoxO3A and reduces chemokine expression partly by modulating EGFR/PI 3-kinase/Akt activity.

Protection against oxidative DNA damage and stress in human prostate by glutathione S-transferase P1

The pi-class glutathione S-transferase (GSTP1) actively protect cells from carcinogens and electrophilic compounds. Loss of GSTP1 expression via promoter hypermethylation is the most common epigenetic alteration observed in human prostate cancer. Silencing of GSTP1 can increase generation of reactive oxygen species (ROS) and DNA damage in cells. In this study we investigated whether loss of GSTP1 contributes to increased DNA damage that may predispose men to a higher risk of prostate cancer. We found significantly elevated (103%; P < 0.0001) levels of 8-oxo-2'-deoxogunosine (8-OHdG), an oxidative DNA damage marker, in adenocarcinomas, compared to benign counterparts, which positively correlated (r = 0.2) with loss of GSTP1 activity (34%; P < 0.0001). Silencing of GSTP1 using siRNA approach in normal human prostate epithelial RWPE1 cells caused increased intracellular production of ROS and higher susceptibility of cells to H2 O2 -mediated oxidative stress. Additionally, human prostate carcinoma LNCaP cells, which contain a silenced GSTP1 gene, were genetically modified to constitutively express high levels of GSTP1. Induction of GSTP1 activity lowered endogenous ROS levels in LNCaP-pLPCX-GSTP1 cells, and when exposed to H2 O2 , these cells exhibited significantly reduced production of ROS and 8-OHdG levels, compared to vector control LNCaP-pLPCX cells. Furthermore, exposure of LNCaP cells to green tea polyphenols caused reexpression of GSTP1, which protected the cells from H2 O2 -mediated DNA damage through decreased ROS production compared to nonexposed cells. These results suggest that loss of GSTP1 expression in human prostate cells, a process that increases their susceptibility to oxidative stress-induced DNA damage, may be an important target for primary prevention of prostate cancer.

Foxo3a drives proliferation in anaplastic thyroid carcinoma through transcriptional regulation of cyclin A1: a paradigm shift that impacts current therapeutic strategies

The Forkhead transcription factor, FoxO3a, is a known suppressor of primary tumor growth through transcriptional regulation of key genes regulating cell cycle arrest and apoptosis. In many types of cancer, in response to growth factor signaling, FoxO3a is phosphorylated by Akt, resulting in its exclusion from the nucleus. Here we show that FoxO3a remains nuclear in anaplastic thyroid carcinoma (ATC). This correlates with lack of Akt phosphorylation at serine473 in ATC cell lines and tissues of ATC patients, providing a potential explanation for nuclear FoxO3a. Mechanistically, nuclear FoxO3a promotes cell cycle progression by transcriptional upregulation of cyclin A1, promoting proliferation of human ATC cells. Silencing FoxO3a with a reverse genetics approach leads to downregulation of CCNA1 mRNA and protein. These combined data suggest an entirely novel function for FoxO3a in ATC promotion by enhancing cell cycle progression and tumor growth through transcriptional upregulation of cyclin A1. This is clinically relevant since we detected highly elevated CCNA1 mRNA and protein levels in tumor tissues of ATC patients. Our data indicate therapeutic inactivation of FoxO3a may lead to attenuation of tumor expansion in ATC. This new paradigm also suggests caution in relation to current dogma focused upon reactivation of FoxO3a as a therapeutic strategy against cancers harboring active PI3-K and Akt signaling pathways.

Computational identification and modeling of crosstalk between phosphorylation, O-β-glycosylation and methylation of FoxO3 and implications for cancer therapeutics

FoxO3 is a member of the forkhead class of transcription factors and plays a major role in the regulation of diverse cellular processes, including cell cycle arrest, DNA repair, and protection from stress stimuli by detoxification of reactive oxygen species. In addition, FoxO3 is a tumor suppressor and has been considered as a novel target for cancer therapeutics. Phosphorylation of FoxO3 via the AKT, IKK, and ERK pathways leads to deregulation, cytoplasmic retention, degradation of FoxO3 and favors tumor progression. Identification of the amino acid residues that are the target of different posttranslational modifications (PTMs) provides a foundation for understanding the molecular mechanisms of FoxO3 modifications and associated outcomes. In addition to phosphorylation, serine and threonine residues of several proteins are regulated by a unique type of PTM known as O-β-glycosylation, which serves as a functional switch. We sought to investigate the crosstalk of different PTMs on the FoxO3 which leads to the onset/progression of various cancers and that could also potentially be targeted as a therapeutic point of intervention. A computational workflow and set of selection parameters have been defined for the identification of target sites and crosstalk between different PTMs. We identified phosphorylation, O-β-GlcNAc modification, and Yin Yang sites on Ser/Thr residues, and propose a potential novel mechanism of crosstalk between these PTMs. Furthermore, methylation potential of human FoxO3 at arginine and lysine residues and crosstalk between methylation and phosphorylation have also been described. Our findings may facilitate the study of therapeutic strategies targeting posttranslational events.

Dual role of FoxA1 in androgen receptor binding to chromatin, androgen signalling and prostate cancer

High androgen receptor (AR) level in primary tumour predicts increased prostate cancer-specific mortality. However, the mechanisms that regulate AR function in prostate cancer are poorly known. We report here a new paradigm for the forkhead protein FoxA1 action in androgen signalling. Besides pioneering the AR pathway, FoxA1 depletion elicited extensive redistribution of AR-binding sites (ARBs) on LNCaP-1F5 cell chromatin that was commensurate with changes in androgen-dependent gene expression signature. We identified three distinct classes of ARBs and androgen-responsive genes: (i) independent of FoxA1, (ii) pioneered by FoxA1 and (iii) masked by FoxA1 and functional upon FoxA1 depletion. FoxA1 depletion also reprogrammed AR binding in VCaP cells, and glucocorticoid receptor binding and glucocorticoid-dependent signalling in LNCaP-1F5 cells. Importantly, FoxA1 protein level in primary prostate tumour had significant association to disease outcome; high FoxA1 level was associated with poor prognosis, whereas low FoxA1 level, even in the presence of high AR expression, predicted good prognosis. The role of FoxA1 in androgen signalling and prostate cancer is distinctly different from that in oestrogen signalling and breast cancer.

Pathological alteration of FoxO3a activity promotes idiopathic pulmonary fibrosis fibroblast proliferation on type i collagen matrix

Idiopathic pulmonary fibrosis (IPF) is a prevalent, progressive, and incurable fibroproliferative lung disease. The phenotype of IPF fibroblasts is characterized by their ability to elude the proliferation-suppressive properties of polymerized type I collagen. The mechanism underlying this pathological response is incompletely understood but involves aberrant activation of the phosphatidylinositol 3-kinase-Akt signaling pathway owing to inappropriately low phosphatase and tensin homolog phosphatase activity. Akt can phosphorylate and inactivate the forkhead box O3a (FoxO3a) transcriptional factor, which, when transcriptionally active, increases the expression of the CDK inhibitor p27 and promotes cell cycle arrest. Herein, we demonstrate that IPF fibroblasts display high levels of inactive FoxO3a compared with nonfibrotic control fibroblasts because of their high Akt activity. We found that p27 levels are decreased in IPF compared with control fibroblasts cultured on polymerized collagen. Furthermore, overexpression of FoxO3a in IPF fibroblasts increases p27 levels and suppresses the ability of IPF fibroblasts to proliferate on polymerized collagen. In contrast, the expression of dominant-negative FoxO3a augmented control fibroblast proliferation. IHC examination of fibroblastic foci in IPF lung tissue demonstrates the presence of inactive FoxO3a in cells within fibroblastic foci. These data indicate that the ability of IPF fibroblasts to circumvent the proliferation-suppressive properties of polymerized collagen involves inactivation of FoxO3a by high Akt activity, resulting in down-regulation of p27.

Characterization of squamous esophageal cells resistant to bile acids at acidic pH: implication for Barrett's esophagus pathogenesis

Barrett's esophagus (BE) is a premalignant condition, where normal squamous epithelium is replaced by intestinal epithelium. BE is associated with an increased risk of developing esophageal adenocarcinoma (EAC). However, the BE cell of origin is not clear. We hypothesize that BE tissue originates from esophageal squamous cells, which can differentiate to columnar cells as a result of repeated exposure to gastric acid and bile acids, two components of refluxate implicated in BE pathology. To test this hypothesis, we repeatedly exposed squamous esophageal HET1A cells to 0.2 mM bile acid (BA) cocktail at pH 5.5 and developed an HET1AR-resistant cell line. These cells are able to survive and proliferate after repeated 2-h treatments with BA at pH 5.5. HET1AR cells are resistant to acidification and express markers of columnar differentiation, villin, CDX2, and cytokeratin 8/18. HET1AR cells have increased amounts of reactive oxygen species, concomitant with a decreased level and activity of manganese superoxide dismutase compared with parental cells. Furthermore, HET1AR cells express proteins and activate signaling pathways associated with inflammation, cell survival, and tumorigenesis that are thought to contribute to BE and EAC development. These include STAT3, NF-κB, epidermal growth factor receptor (EGFR), cyclooxygenase-2, interleukin-6, phosphorylated mammalian target of rapamycin (p-mTOR), and Mcl-1. The expression of prosurvival and inflammatory proteins and resistance to cell death could be partially modified by inhibition of STAT3 signaling. In summary, our study shows that long-term exposure of squamous cells to BA at acidic pH causes the cells to display the same characteristics and markers as BE.