Expression of glutathione peroxidase 2 is associated with not only early hepatocarcinogenesis but also late stage metastasis

Integrative analysis of a novel signature incorporating metabolism and stemness-related genes for risk stratification and assessing clinical outcomes and therapeutic responses in lung adenocarcinoma

BACKGROUND

Metabolism and stemness-related genes (msRGs) are critical in the development and progression of lung adenocarcinoma (LUAD). Nevertheless, reliable prognostic risk signatures derived from msRGs have yet to be established.

METHODS

In this study, we downloaded and analyzed RNA-sequencing and clinical data from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) databases. We employed univariate and multivariate Cox regression analyses, along with least absolute shrinkage and selection operator (LASSO) regression analysis, to identify msRGs that are linked to the prognosis of LUAD and to develop the prognostic risk signature. The prognostic value was evaluated using Kaplan-Meier analysis and log-rank tests. We generated receiver operating characteristic (ROC) curves to evaluate the predictive capability of the prognostic signature. To estimate the relative proportions of infiltrating immune cells, we utilized the CIBERSORT algorithm and the MCPCOUNTER method. The prediction of the half-maximal inhibitory concentration (IC50) for commonly used chemotherapy drugs was conducted through ridge regression employing the "pRRophetic" R package. The validation of our analytical findings was performed through both in vivo and in vitro studies.

RESULTS

A novel five-gene prognostic risk signature consisting of S100P, GPX2, PRC1, ARNTL2, and RGS20 was developed based on the msRGs. A risk score derived from this gene signature was utilized to stratify LUAD patients into high- and low-risk groups, with the former exhibiting significantly poorer overall survival (OS). A nomogram was constructed incorporating the risk score and other clinical characteristics, showcasing strong capabilities in estimating the OS rates for LUAD patients. Furthermore, we observed notable differences in the infiltration of various immune cell subtypes, as well as in responses to immunotherapy and chemotherapy, between the low-risk and high-risk groups. Results from gene set enrichment analysis (GSEA) and in vitro studies indicated that the prognostic signature gene ARNTL2 influenced the prognosis of LUAD patients, primarily through the activation of the PI3K/AKT/mTOR signaling pathway.

CONCLUSIONS

Utilizing this gene signature for risk stratification could help with clinical treatment management and improve the prognosis of LUAD patients.

Selenium-containing compounds, selenium nanoparticles and selenoproteins in the prevention and treatment of lung cancer

THE OBJECTIVE

Is to review the latest data on the role of key organic and inorganic compounds of the essential trace element selenium, selenium-containing nanocomposites and nanoparticles, and selenoproteins in lung cancer therapy.

OBJECT OF RESEARCH

Sodium selenite, methylselenic acid, selenomethionine, selenium nanoparticles, mammalian selenoproteins KEY OBJECTIVES:: To describe the molecular mechanisms of the cytotoxic effect of sodium selenite, methylselenic acid and selenomethionine on lung cancer cells, to discuss the latest advances in lung cancer nanomedicine using selenium-based nanoparticles and nanocomposites and to assess the prospects for creating antitumor drugs based on them, to assess the role of selenoproteins in the progression or inhibition of lung cancer and to study the molecular mechanisms of such regulation CONCLUSIONS:: This review provides a complete picture of the role of selenium and selenium-containing agents of various natures in the regulation of carcinogenesis and therapy of lung cancer, which significantly complements the fundamental data on the functions of these compounds, on the molecular mechanisms of regulation of processes associated with lung cancer. This knowledge provides insight into the latest developments and future prospects in the treatment and prevention of lung cancer with the active participation of the trace element selenium.

Exploring experimental models of prostate cancer in chemoprevention: Oxidative stress as a key pathway to translational research

Prostate cancer (PCa) is the second most common cancer in men globally. Its growth is driven by oxidative stress associated with inflammation, aging, and environmental factors, including diet and lifestyle. These factors contribute to multiple stages of PCa progression, including progression to castration-resistant prostate cancer (CRPC). Therefore, oxidative stress represents an intriguing target for PCa chemoprevention and treatment. In vivo experimental models are crucial for understanding the mechanisms of PCa development, validating chemopreventive and therapeutic approaches, and translating preclinical results into clinical applications. We established a transgenic rat for adenocarcinoma of the prostate (TRAP) model, a transgenic rat that efficiently develops androgen-dependent adenocarcinoma, pathologically and biologically mimicking human PCa progression, to clarify the mechanisms of tumor progression, including the involvement of oxidative stress, and established a system for screening the chemopreventive effects of agents against PCa. Additionally, we derived a CRPC model from the TRAP model and developed a distant metastasis model, providing a comprehensive multistage rat model of prostate carcinogenesis. This review presents findings on the molecular mechanisms of PCa and the chemopreventive effects of natural compounds with antioxidant properties, such as polyphenols. We additionally described the potential for repositioning existing drugs with antiandrogenic activity for PCa chemoprevention.

Development of a prognostic model for hepatocellular carcinoma based on microvascular invasion characteristic genes by spatial transcriptomics sequencing

Microvascular invasion (MVI) is an independent risk factor for the recurrence and metastasis of hepatocellular carcinoma (HCC), associated with poor prognosis. Thus, MVI has significant clinical value for the treatment selection and prognosis assessment of patients with HCC. However, there is no reliable and precise method for assessing the postoperative prognosis of MVI patients. This study aimed to develop a new HCC prognosis prediction model based on MVI characteristic genes through spatial transcriptomics sequencing, distinguishing between high-risk and low-risk patients and evaluating patient prognosis. In this study, four MVI samples with different grades were selected for spatial transcriptomic sequencing to screen for MVI region-specific genes. On this basis, an HCC prognostic model was constructed using univariate Cox regression analysis, LASSO regression analysis, random survival forest, and stepwise multivariate Cox regression analysis methods. We constructed a 7-gene prognostic model based on MVI characteristic genes and demonstrated its applicability for predicting the prognosis of HCC patients in three external validation cohorts. Furthermore, our model showed superior predictive performance compared with three published HCC prediction prognostic models and could serve as an independent prognostic factor for HCC. Additionally, single nucleus RNA sequencing analysis and multiple immunofluorescence images revealed an increased proportion of macrophages in high-risk patient samples, suggesting that HCC tumor cells may promote HCC metastasis through MIF-CD74 cell interactions. To sum up, we have developed a 7-gene biomarker based on MVI that can predict the survival rate of HCC patients at different stages. This predictive model can be used to categorize into high- and low- risk groups, which is of great significance for the prognostic assessment and personalized treatment of HCC patients.

Fullerene and fullerene whisker are not carcinogenic to the lungs and pleura in rat long-term study after 2-week intra-tracheal intrapulmonary administration

Fullerene whiskers (FLW)s are thin rod-like structures composed of C60 and C70 fullerene (FL). The shape of FLWs suggests potential toxic effects including carcinogenicity to the lung and pleura, similar to effects elicited by asbestos and multi-walled carbon nanotubes (MWCNT)s. However, no long-term carcinogenic studies of FL or FLW have been conducted. In the present study we investigated the pulmonary and pleural carcinogenicity of FL and FLW. Twelve-week-old male F344 rats were administered 0.25 or 0.5 mg FL, FLW, MWCNT-7, and MWCNT-N by intra-tracheal intra-pulmonary spraying (TIPS). Acute lung lesions and carcinogenicity were analyzed at 1 and 104 weeks after 8 doses/15 days TIPS administration. At week 1, FLW, MWCNT-7, and MWCNT-N significantly increased alveolar macrophage infiltration. Expression of Ccl2 and Ccl3, reactive oxygen species production, and cell proliferation were significantly increased by administration of MWCNT-7 and MWCNT-N but not FL or FLW. At week 104, the incidence of bronchiolo-alveolar adenoma plus adenocarcinoma was significantly increased in the MWCNT-7 and MWCNT-N groups, and the incidence of mesothelioma was significantly increased in the MWCNT-7 group. No significant induction of pulmonary or pleural tumorigenesis was observed in the FL or FLW groups. The number of 8-OHdG-positive cells in the alveolar epithelium was significantly increased in the MWCNT-7 and MWCNT-N groups but not in the FL or FLW groups. FL and FLW did not exert pulmonary or pleural carcinogenicity in our study. In addition, oxidative DNA damage was implicated in MWCNT-induced lung carcinogenesis, suggesting that it may be a useful initial marker of carcinogenicity.

Immunohistochemical Expression of Glutathione Peroxidase-2 (Gpx-2) and Its Clinical Relevance in Colon Adenocarcinoma Patients

Glutathione peroxidase 2 (Gpx-2) is a selenoenzyme with antioxidant capabilities that may play a role in cancer development. Hence, we investigated the immunohistochemical expression of Gpx-2 protein in colon adenocarcinoma samples derived from patients with colon adenocarcinoma who did not receive any form of treatment prior to the surgical procedure. The associations between the immunohistochemical expression of Gpx-2 and clinical parameters were analysed using the Chi2 test and Fisher's exact test. A Kaplan-Meier analysis and the log-rank test were used to verify the relationship between the intensity of Gpx-2 expression and the 5-year survival rate of patients. In total, 101 (80.80%) samples had strong Gpx-2 protein expression and 24 (19.20%) samples were characterized with low expression. The high expression of Gpx-2 was correlated with the histological grade of the tumour (p < 0.001), PCNA immunohistochemical expression (p < 0.001), depth of invasion (p = 0.001) and angioinvasion (p < 0.001). We can conclude that high expression of Gpx-2 is correlated with reduced survival of colon adenocarcinoma patients (log-rank, p < 0.001).

Dimethylarsinic acid induces bladder carcinogenesis via the amphiregulin pathway

Dimethylarsinic acid (DMA) is a major metabolite in the urine of humans and rats exposed to inorganic arsenicals, and is reported to induce rat bladder carcinogenesis. In the present study, we focused on early pathways of carcinogenesis triggered by DMA that were also active in tumors. RNA expression in the bladder urothelium of rats treated with 0 and 200 ppm DMA in the drinking water for 4 weeks and in bladder tumors of rats treated with 200 ppm DMA for 2 years was initially examined using microarray analysis and Ingenuity Pathway Analysis (IPA). Expression of 160 genes was altered in both the urothelium of rats treated for 4 weeks with DMA and in DMA-induced tumors. IPA associated 36 of these genes with liver tumor diseases. IPA identified the amphiregulin (Areg)-regulated pathway as a Top Regulator Effects Network. Therefore, we focused on Areg and 6 of its target genes: cyclin A2, centromere protein F, marker of proliferation Ki-67, protein regulator of cytokinesis 1, ribonucleotide reductase M2, and topoisomerase II alpha. We confirmed high mRNA expression of Areg and its 6 target genes in both the urothelium of rats treated for 4 weeks with DMA and in DMA-induced tumors. RNA interference of human amphiregulin (AREG) expression in human urinary bladder cell lines T24 and UMUC3 decreased expression of AREG and its 6 target genes and decreased cell proliferation. These data suggest that Areg has an important role in DMA-induced rat bladder carcinogenesis.

GPX2 promotes EMT and metastasis in non-small cell lung cancer by activating PI3K/AKT/mTOR/Snail signaling axis

Lung cancer, with non-small cell lung cancer (NSCLC) being the main subtype, is the leading cause of cancer death worldwide, which is mainly due to the cancer metastasis. Glutathione peroxidase 2 (GPX2), an antioxidant enzyme, is involved in tumor progression and metastasis. Nevertheless, the role of GPX2 in NSCLC metastasis has not been clarified. In this study, we found that GPX2 expression was elevated in NSCLC tissues and high GPX2 expression was correlated with poor prognosis in patients with NSCLC. In addtion, GPX2 expression was related to the patient's clinicopathological features, including lymph node metastasis, tumor size, and TNM stage. Overexpression of GPX2 promoted epithelial-mesenchymal transition (EMT), migration, and invasion of NSCLC cells in vitro. Knockdown of GPX2 showed the opposite effects in vitro and inhibited the metastasis of NSCLC cells in nude mice. Furthermore, GPX2 reduced reactive oxygen species (ROS) accumulation and activated the PI3K/AKT/mTOR/Snail signaling axis. Therefore, our results indicate that GPX2 promotes EMT and metastasis of NSCLC cells by activating the PI3K/AKT/mTOR/Snail signaling axis via the removal of ROS. GPX2 may be an effective diagnostic and prognostic biomarker for NSCLC.

Glutathione peroxidase 2 overexpression promotes malignant progression and cisplatin resistance of KRAS‑mutated lung cancer cells

Kirsten rat sarcoma viral oncogene homolog (KRAS) aberrations frequently occur in patients with lung cancer. Oncogenic KRAS is characterized by excessive reactive oxygen species (ROS) accumulation, thus, ROS detoxification may contribute to KRAS‑driven lung tumorigenesis. In the present study, the influence of glutathione peroxidase 2 (GPX2) on malignant progression and cisplatin resistance of KRAS‑driven lung cancer was explored. The RNA sequencing data from TCGA lung cancer samples and GEO database were downloaded and analyzed. The effects of GPX2 on KRAS‑driven lung tumorigenesis were evaluated by western blotting, cell viability assay, soft agar assay, Transwell assay, tumor xenograft model, flow cytometry, BrdU incorporation assay, transcriptome RNA sequencing, luciferase reporter assay and RNA immunoprecipitation. In the present study, GPX2 was upregulated in patients with non‑small cell lung carcinoma (NSCLC), and positively correlated with poor overall survival. Ectopic GPX2 expression facilitated malignant progression of KRASG12C‑transformed BEAS‑2B cells. Moreover, GPX2 overexpression promoted growth, migration, invasion, tumor xenograft growth and cisplatin resistance of KRAS‑mutated NSCLC cells, while GPX2 knockdown exhibited the opposite effects. GPX2 overexpression reduced ROS accumulation and increased matrix metalloproteinase‑1 (MMP1) expression in KRAS‑mutated NSCLC cells. In addition, GPX2 was directly targeted by miR‑325‑3p, while MMP1 knockdown or miR‑325‑3p overexpression partially abrogated the effects of GPX2 in NSCLC cells. In conclusion, the results indicated that GPX2 facilitated malignant progression and cisplatin resistance of KRAS‑driven lung cancer, and inhibition of GPX2 may be a feasible strategy for lung cancer treatment, particularly in patients with active KRAS mutations.

Association of gut microbiota characteristics and metabolites reveals the regulation mechanisms under cadmium consumption circumstance

BACKGROUND

Cadmium is a non-biodegradable heavy metal with a long biological half-life. Although its negative impact on human health has been previously reported, the association of cadmium consumption overdose with changes in the gut microbiota and its corresponding metabolites has not been fully elucidated so far.

RESULTS

Cadmium consumption overdose led to a reduced body weight gain accompanied by an enhanced level of the proinflammatory cytokine tumor necrosis factor-α, interleukin-6, and histamine in the serum of the rats in comparison with normal rats. Furthermore, hepatotoxicity was also observed to be induced by cadmium, which was consistent with abnormal hepatic activities of alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase and oxidative stress. In contrast, Lactobacillus rhamnosus-fermented Ganoderma lucidum (FGL) slice supplementation improved the aforementioned physiological properties. More importantly, microbiome and metabolites analysis indicated cadmium exposure significantly reduced the generation of short-chain fatty acids in the gut, particularly butyrate. However, rats in the FGL group had the highest level of butyrate in the feces, characterized with significantly enriched probiotics (Lactobacillus, Bifidobacterium) and butyrate-producing bacteria (Roseburia).

CONCLUSION

The targeted regulation of the gut microbial community and its metabolites might be the essential association for attenuating body dysfunction induced by cadmium. The supplementation of FGL, as evidenced in this study, might highlight a novel approach to this field. © 2022 Society of Chemical Industry.

Glutathione peroxidase 2 is a metabolic driver of the tumor immune microenvironment and immune checkpoint inhibitor response

BACKGROUND

The existence of immunologically 'cold tumors' frequently found across a wide spectrum of tumor types represents a significant challenge for cancer immunotherapy. Cold tumors have poor baseline pan-leukocyte infiltration, including a low prevalence of cytotoxic lymphocytes, and not surprisingly respond unfavorably to immune checkpoint (IC) inhibitors. We hypothesized that cold tumors harbor a mechanism of immune escape upstream and independent of ICs that may be driven by tumor biology rather than differences in mutational neoantigen burden.

METHODS

Using a bioinformatic approach to analyze TCGA (The Cancer Genome Atlas) RNA sequencing data we identified genes upregulated in cold versus hot tumors across four different smoking-related cancers, including squamous carcinomas from the oral cavity (OCSCC) and lung (LUSC), and adenocarcinomas of the bladder (BLCA) and lung (LUAD). Biological significance of the gene most robustly associated with a cold tumor phenotype across all four tumor types, glutathione peroxidase 2 (GPX2), was further evaluated using a combination of in silico analyses and functional genomic experiments performed both in vitro and in in vivo with preclinical models of oral cancer.

RESULTS

Elevated RNA expression of five metabolic enzymes including GPX2, aldo-keto reductase family 1 members AKR1C1, AKR1C3, and cytochrome monoxygenases (CP4F11 and CYP4F3) co-occurred in cold tumors across all four smoking-related cancers. These genes have all been linked to negative regulation of arachidonic acid metabolism-a well-established inflammatory pathway-and are also known downstream targets of the redox sensitive Nrf2 transcription factor pathway. In OCSCC, LUSC, and LUAD, GPX2 expression was highly correlated with Nrf2 activation signatures, also elevated in cold tumors. In BLCA, however, GPX2 correlated more strongly than Nrf2 signatures with decreased infiltration of multiple leukocyte subtypes. GPX2 inversely correlated with expression of multiple pro- inflammatory cytokines/chemokines and NF-kB activation in cell lines and knockdown of GPX2 led to increased secretion of prostaglandin E2 (PGE2) and interleukin-6. Conversely, GPX2 overexpression led to reduced PGE2 production in a murine OCSCC model (MOC1). GPX2 overexpressing MOC1 tumors had a more suppressive tumor immune microenvironment and responded less favorably to anti-cytotoxic T-lymphocytes-associated protein 4 IC therapy in mice.

CONCLUSION

GPX2 overexpression represents a novel potentially targetable effector of immune escape in cold tumors.

The beginning of GPX2 and 30 years later

We published the first paper to characterize GPX2 (aka GSHPx-GI) as a selenoenzyme with glutathione peroxidase activity in 1993. Among the four Se-GPX isozymes, GPX1-4, GPX1 and GPX2 are closely related in terms of structure, substrate specificities, and subcellular localization. What sets them apart are distinct patterns of gene regulation, tissue distribution and response to selenium. While we identified the digestive tract epithelium as the main site of GPX2 expression, later work has shown GPX2 is found more widely in epithelial tissues with concentration of expression in stem cell and proliferative compartments. GPX2 expression is regulated over a wide range of levels by many pathways, including NRF2, WNT, p53, RARE and this often results in attaching undue significance to GPX2 as GPX2 is only a part of a system of hydroperoxidase activities, including GPX1, peroxiredoxins and catalase. These other activities may play equal or greater roles, particularly in cell lines cultured without selenium supplementation and often with very low GPX2 levels. This could be assessed by examining levels of mRNA and protein among these various peroxidases at the outset of studies. As an example, it was found that GPX1 responds to the absence of GPX2 in mouse ileum and colon epithelium with higher expression. As such, both Gpx1 and Gpx2 had to be knocked out in mice to produce ileocolitis. However, we note that the actual role of GPX1 and GPX2 in relation to peroxiredoxin function is unclear. There may be an interdependence that requires only low amounts of GPX1 and/or GPX2 in a supporting role to maintain proper peroxiredoxin function. GPX2 levels may be prognostic for cancer progression in colon, breast, prostate and liver, however, there is no consistent trend for higher or lower levels to be favorable.

The Effect of GPX2 on the Prognosis of Lung Adenocarcinoma Diagnosis and Proliferation, Migration, and Epithelial Mesenchymal Transition

Objective

To investigate the expression of glutathione peroxidase 2 (GPX2) in human lung adenocarcinoma tissues and its effect on the biological function of lung adenocarcinoma A549 cells.

Methods

The expression of GPX2 in lung adenocarcinoma and its effect on survival were analyzed by the TCGA database and the GEPIA 2 database. A total of 45 cases of primary lung adenocarcinoma tissue specimens and 45 cases of their paracancerous tissue specimens were collected, and the expression of GPX2 in the two types of tissues was detected by immunohistochemistry. Lung adenocarcinoma A549 cells were divided into the GPX2 overexpression group (GPX2), the GPX2 knockdown group (si-GPX2), the empty vector group (Vector), the siRNA negative control group (si-NC), and the WT group; the mRNA level and protein expression of GPX2 in each group of A549 cells were detected by real-time fluorescence quantitative PCR and Western blotting; the proliferation activity of each group of cells was detected by the CCK-8 assay; the effect of GPX2 on cell migration and invasion ability was detected by the scratch assay and the Transwell invasion assay; the apoptosis of each group of cells was detected by flow cytometry; Western blotting was performed to detect the expression levels of Bax, Bcl-2, E-cadherin, vimentin, and MMP2 and MMP9 proteins in each group of cells.

Results

Bioinformatics analysis showed that the expression of GPX2 was strongly correlated with the prognosis of lung adenocarcinoma patients (P < 0.01). The positive expression rates of GPX2 in lung adenocarcinoma and its paracancerous tissues were 66.0% and 15.7%, respectively (P < 0.05). The results of RT-qPCR and Western blotting showed that the expression level of GPX2 mRNA and protein in A549 cells in the GPX2 group increased, which was significantly higher than that in the WT group (P < 0.05); the expression levels of GPX2 mRNA and protein in A549 cells in the si-GPX2 group were the same, that is, significantly lower than the WT group (P < 0.05). GPX2 overexpression promoted the proliferation, migration, and invasion of A549 cells and inhibited their apoptosis; the results in the si-GPX2 group were opposite to those in the GPX2 group. Compared with the WT group, the expression of Bcl-2, vimentin, and MMP2 and MMP9 protein in the GPX2 group increased (P < 0.05), while the expression of Bax and E-cadherin protein decreased in the GPX2 group (P < 0.05); the results in the si-GPX2 group were opposite to those in the GPX2 group.

Conclusion

The expression of GPX2 in lung adenocarcinoma is related to the prognosis of patients. It is proved that GPX2 can promote the migration and invasion of lung adenocarcinoma cells and is related to the EMT/β-catenin pathway. Thus, GPX2 is expected to be an important target for the diagnosis and treatment of lung adenocarcinoma.

GPX2 is a potential therapeutic target to induce cell apoptosis in lenvatinib against hepatocellular carcinoma

INTRODUCTION

Lenvatinib has recently become available as the first-line therapy for advanced hepatocellular carcinoma (HCC), but its molecular mechanism in HCC remains largely unknown.

OBJECTIVES

The current study aims to identify the molecular mechanisms of lenvatinib in HCC.

METHODS

Gene expression microarrays, flow cytometry, western blot, qRT-PCR, immunohistochemistry and immunofluorescence were used to study the response of HCC cells to lenvatinib. Xenograft tumor of Huh7 cells was also established to detect the effect of lenvatinib in vivo.

RESULTS

Herein, we found that lenvatinib could induce apoptosis via increasing reactive oxygen species (ROS) levels in HCC cells. Then, microarray analysis and qRT-PCR results confirmed that GPX2 was a vital target for lenvatinib against HCC. Loss and gain function of experiment showed that regulating GPX2 levels markedly affected the lenvatinib-induced ROS levels and apoptosis in HCC cells. In addition, analyses of The Cancer Genome Atlas database and the qRT-PCR results in our cohort both showed that GPX2 markedly overexpressed in tumor tissues and correlated with poor overall survival in HCC. Mechanistically, our findings further demonstrated that GPX2 was a downstream gene regulated by β-catenin, while lenvatinib could prevent nuclear translocation of β-catenin and further inhibit GPX2 expression in HCC cells. More importantly, the correlation of GPX2 expression with lenvatinib response was further analyzed in 22 HCC patients who received lenvatinib therapy, and the results showed that the objective response rate (ORR) in patients with low GPX2 expression was 44.4% (4/9), while the ORR in patients with high GPX2 levels was only 7.7% (1/13).

CONCLUSION

Our findings indicated that GPX2 plays an important role in lenvatinib-induced HCC cell apoptosis, which might serve as a biomarker for instruction of lenvatinib therapy in HCC patients.

A pan-cancer study of selenoprotein genes as promising targets for cancer therapy

BACKGROUND

The most important health benefit of selenium (Se) is in the prevention and control of cancer. Glutathione peroxidases (GPXs) and thioredoxin reductases (TXNRDs) are selenoenzymes that are thought to play a role in oxidative stress. The differential expression of genes of the TXNRD and GPX families is closely related to carcinogenesis and the occurrence of cancer. This study comprehensively analyzed the expression profiles of seven genes in the TXNRD and GPX families, in terms of their correlations with patient survival and immune-cell subtypes, tumor microenvironment, and drug sensitivity.

RESULTS

The expression profiles of genes in the TXNRD and GPX families differ between different types of cancer, and also between and within individual cancer cases. The expression levels of the seven analyzed genes are related to the overall survival of patients. The TXNRD1 and TXNRD3 genes are mainly related to poor prognoses, while other genes are related to good or poor prognoses depending on the type of cancer. All of the genes were found to be correlated to varying degrees with immune-cell subtypes, level of mechanistic cell infiltration, and tumor cell stemness. The TXNRD1, GPX1, and GPX2 genes may exert dual effects in tumor mutagenesis and development, while the TXNRD1, GPX1, GPX2, and GPX3 genes were found to be related to drug sensitivity or the formation of drug resistance.

CONCLUSIONS

The results will greatly help in identifying the association between genes and tumorigenesis, especially in the immune response, tumor microenvironment, and drug resistance, and very important when attempting to identify new therapeutic targets.

GPX8 promotes migration and invasion by regulating epithelial characteristics in non-small cell lung cancer

Background

Non‐small cell lung cancer (NSCLC) is the most common cause of cancer‐related death worldwide. The family of glutathione peroxidase (GPX), an important antioxidant enzyme in human tissues, has been discovered to play a key role in the development of cancers. GPX8 is the most promising molecule of the family in a therapeutic strategy against a variety of cancers.

The main purpose of this study was to examine and analyze the function and clinical value of GPX8 in NSCLC.

Methods

Immunohistochemistry (IHC), western blot analysis and quantitative real‐time polymerase chain reaction (qPCR) were used to assess GPX8 expression and its clinical significance in NSCLC. A series of cell biology experiments and bioinformatic analysis tools were further used to study the function of GPX8.

Results

GPX8 expression in tumor tissues was much higher than that in normal lung tissues. High expression of GPX8 in NSCLC was correlated with a worse clinical outcome and prognosis. Furthermore, GPX8 could inhibit the apoptosis of tumor cells and promote its migration and invasion.

Conclusions

Our results conclusively demonstrated that GPX8 could affect the oncogenesis and prognosis of NSCLC via regulating epithelial characteristics. The study also illustrated that GPX8 could serve as a prognostic predictor and potential therapeutic target for NSCLC.

Recruitment of miR-8080 by luteolin inhibits androgen receptor splice variant 7 expression in castration-resistant prostate cancer

A need exists for seeking effective treatments for castration-resistant prostate cancer (CRPC) in response to its emergence following androgen deprivation therapy as a major clinical problem. In the present study, we investigated the chemopreventive and chemotherapeutic potential of luteolin, a flavonoid with antioxidative properties, on prostate cancer, including CRPC. Luteolin inhibited the progression of rat prostate carcinogenesis by induction of apoptosis in a transgenic rat for adenocarcinoma of prostate (TRAP) model. Luteolin decreased cell proliferation in a dose-dependent manner and induced apoptosis with the activation of caspases 3 and 7 in both rat (PCai1, established from a TRAP prostate tumor) and human (22Rv1) CRPC cells. Dietary luteolin also suppressed tumor growth via an increase in apoptosis and inhibition of angiogenesis in PCai1 and 22Rv1 xenografts implanted in castrated nude mice. We also focused on androgen receptor splice variant 7 (AR-V7), which contributes to cell proliferation and therapeutic resistance in CRPC. Luteolin dramatically suppressed AR-V7 protein expression in 22Rv1 cells in vitro and ex vivo. Microarray analysis identified MiR-8080, which contains a possible target sequence for AR-V7 3'-UTR, as a gene upregulated by luteolin. MiR-8080 transfection decreased the AR-V7 expression level and the induction of apoptosis in 22Rv1 cells. Furthermore, miR-8080 knockdown canceled luteolin decreasing AR-V7 and the cell growth of 22Rv1. MiR-8080 induced by luteolin intake enhanced the therapeutic effect of enzalutamide on 22Rv1 xenografts under castration conditions. These results indicate luteolin inhibits CRPC by AR-V7 suppression through miR-8080, highlighting luteolin and miR-8080 as promising therapeutic agents for this disease.

Understanding Metal Dynamics Between Cancer Cells and Macrophages: Competition or Synergism?

Metal ions, such as selenium, copper, zinc, and iron are naturally present in the environment (air, drinking water, and food) and are vital for cellular functions at chemical, molecular, and biological levels. These trace elements are involved in various biochemical reactions by acting as cofactors for many enzymes and control important biological processes by binding to the receptors and transcription factors. Moreover, they are essential for the stabilization of the cellular structures and for the maintenance of genome stability. A body of preclinical and clinical evidence indicates that dysregulation of metal homeostasis, both at intracellular and tissue level, contributes to the pathogenesis of many different types of cancer. These trace minerals play a crucial role in preventing or accelerating neoplastic cell transformation and in modulating the inflammatory and pro-tumorigenic response in immune cells, such as macrophages, by controlling a plethora of metabolic reactions. In this context, macrophages and cancer cells interact in different manners and some of these interactions are modulated by availability of metals. The current review discusses the new findings and focuses on the involvement of these micronutrients in metabolic and cellular signaling mechanisms that influence macrophage functions, onset of cancer and its progression. An improved understanding of "metallic" cross-talk between macrophages and cancer cells may pave the way for innovative pharmaceutical or dietary interventions in order to restore the balance of these trace elements and also strengthen the chemotherapeutic treatment.

Luteolin suppresses bladder cancer growth via regulation of mechanistic target of rapamycin pathway

Luteolin is a natural flavonoid with strong anti–oxidative properties that is reported to have an anti–cancer effect in several malignancies other than bladder cancer. In this study, we describe the effect of luteolin on a human bladder cancer cell line, T24, in the context of the regulation of p21, thioredoxin‐1 (TRX1) and the mechanistic target of rapamycin (mTOR) pathway. Luteolin inhibited cell survival and induced G2/M cell‐cycle arrest, p21 upregulation and downregulation of phospho(p)‐S6, which is downstream of mTOR signaling. Luteolin also upregulated TRX1 and reduced intracellular reactive oxygen species production. In a subcutaneous xenograft mouse model using the rat bladder cancer cell line, BC31, tumor volumes were significantly decreased in mice orally administered luteolin compared to control. Immunohistochemical analysis revealed that increased p21 and decreased p‐S6 expression were induced in the luteolin treatment group. Moreover, in another in vivo N‐butyl‐N‐(4‐hydroxybutyl) nitrosamine (BBN)‐induced rat bladder cancer model, the oral administration of luteolin led to a trend of decreased bladder tumor dimension and significantly decreased the Ki67‐labeling index and p‐S6 expression. Furthermore, the major findings on the metabolism of luteolin suggest that both plasma and urine luteolin‐3ʹ‐O‐glucuronide concentrations are strongly associated with the inhibition of cell proliferation and mTOR signaling. Moreover, a significant decrease in the squamous differentiation of bladder cancer is attributed to plasma luteolin‐3ʹ‐glucuronide concentration. In conclusion, luteolin, and in particular its metabolized product, may represent another natural product‐derived therapeutic agent that acts against bladder cancer by upregulating p21 and inhibiting mTOR signaling.

Control of tumor angiogenesis and metastasis through modulation of cell redox state

Redox reactions pervade all biology. The control of cellular redox state is essential for bioenergetics and for the proper functioning of many biological functions. This review traces a timeline of findings regarding the connections between redox and cancer. There is ample evidence of the involvement of cellular redox state on the different hallmarks of cancer. Evidence of the control of tumor angiogenesis and metastasis through modulation of cell redox state is reviewed and highlighted.

GPX2 silencing relieves epithelial-mesenchymal transition, invasion, and metastasis in pancreatic cancer by downregulating Wnt pathway

Glutathione peroxidase 2 (GPX2) participates in many cancers including pancreatic cancer (PC), and overexpression of GPX2 promotes tumor growth. Herein, we identified the role of GPX2 in epithelial-mesenchymal transformation (EMT), invasion, and metastasis in PC. Bioinformatics prediction was applied to select PC-related genes. The regulatory function of GPX2 in PC was explored by treatment with short hairpin RNA against GPX2 or LiCl (activator of wingless-type MMTV integration site [Wnt] pathway) in PC cells. GPX2 level in PC tissues, the levels of GPX2, β-catenin, Vimentin, Snail, epithelial-cadherin (E-cadherin), matrix metalloproteinase 2 (MMP2), MMP9, and Wnt2 in cells were determined. Subsequently, cell proliferation, invasion, and metastasis were assayed. Bioinformatics analysis revealed that GPX2 was involved in PC development mediated by the Wnt pathway. GPX2 was highly expressed in PC tissues. GPX2 silencing downregulated levels of β-catenin, Vimentin, Snail, MMP2, MMP9, and Wnt2 but upregulated levels of E-cadherin. It was confirmed that GPX2 silencing suppressed PC cell proliferation, metastasis, and invasion. Furthermore, the trend of EMT and invasion and metastasis of PC induced by the LiCl-activated Wnt pathway was reversed when the GPX2 was silenced. GPX2 silencing could inhibit the Wnt pathway, subsequently suppress PC development.

GPX2 promotes development of bladder cancer with squamous cell differentiation through the control of apoptosis

Herein, we elucidated the molecular mechanisms and therapeutic potential of glutathione peroxidase 2 (GPX2) in bladder cancer. GPX2 expression gradually increased during progression from normal to papillary or nodular hyperplasia (PNHP) and urothelial carcinoma (UC) in a rat N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced bladder carcinogenesis model. GPX2 overexpression was more marked in UC with squamous differentiation (SqD) than in pure UC. Clinical intraepithelial lesions of papillary UC and invasive UC with SqD also had strong GPX2 expression in human radical cystectomy specimens. In addition, prognostic analysis using transurethral specimens revealed that low expression level of GPX2 predicted poor prognosis in patients with pure UC. Further, UC cell lines, BC31 and RT4, cultured in vitro also overexpressed GPX2. Knock-down of GPX2 induced significant inhibition of intracellular reactive oxygen species (ROS) production, in addition to significant growth inhibition and increased apoptosis with activation of caspase 3 or 7 in both BC31 and RT4 cells. Interestingly, tumor growth of BC31 cells subcutaneously transplanted in nude mice was significantly caused the induction of apoptosis, as well as inhibition of angiogenesis and SqD by GPX2 down-regulation. Our findings demonstrated that GPX2 plays an important role in bladder carcinogenesis through the regulation of apoptosis against intracellular ROS, and may be considered as a novel biomarker or therapeutic target in bladder cancer.

Selenium and Cancer Stem Cells

Selenium (Se) is an essential micronutrient that functions as "redox gatekeeper" and homeostasis factor of normal and cancer cells. Epidemiology and experimental studies, in the last years suggested that both inorganic and organic forms of Se may have favorable health effects. In this regard, a protective action of Se on cellular systems that may help preventing cancer cell differentiation has been demonstrated, while the hypothesis that Se compounds may cure cancer and its metastatic diffusion appears speculative and is still a matter of investigation. Indeed, the overall actions of Se compounds in carcinogenesis are controversial. The recognition that cancer is a stem cell disease instigated major paradigm shifts in our basic understanding of cancer and attracted a great deal of interest. Although current treatment approaches in cancer are grounded in the need to kill the majority of cancer cells, targeting cancer stem cells (CSCs) may hold great potential in improving cancer treatment. In this respect, Se compounds have been demonstrated modulating numerous signaling pathways involved in CSC biology and these findings are now stimulating further research on optimal Se concentrations, most effective and cancer-specific Se compounds, and inherent pathways involved in redox and metabolic regulation of CSCs. In this review, we summarize the current knowledge about the effects of Se compounds on CSCs, by focusing on redox-dependent pathways and main gene regulation checkpoints that affect self-renewal, differentiation, and migration responses in this subpopulation of cancer cells.

Selenoproteins and Metastasis

Cancer survival is largely impacted by the dissemination of cancer cells from the original tumor site to secondary tissues or organs through metastasis. Targets for antimetastatic therapies have recently become a focus of research, but progress will require a better understanding of the molecular mechanisms driving metastasis. Selenoproteins play important roles in many of the cellular activities underlying metastasis including cell adhesion, matrix degradation and migration, invasion into the blood and extravasation into secondary tissues, and subsequent proliferation into metastatic tumors along with the angiogenesis required for growth. In this review the roles identified for different selenoproteins in these steps and how they may promote or inhibit metastatic cancers is discussed. These roles include selenoenzyme modulation of redox tone and detoxification of reactive oxygen species, calcium homeostasis and unfolded protein responses regulated by endoplasmic reticulum selenoproteins, and the multiple physiological responses influenced by other selenoproteins.

Selenium-Dependent Glutathione Peroxidases During Tumor Development

Five out of eight human glutathione peroxidases (GPxes) are selenoproteins and thus their expression depends on the selenium (Se) supply. Most Se-dependent GPxes are downregulated in tumor cells, while only GPx2 is considerably upregulated. Whether expression profiles of GPxes predict tumor development and patient survival is controversially discussed. Also, results from in vitro and in vivo studies modulating the expression of GPx isoforms provide evidence for both anti- and procarcinogenic mechanisms. GPxes are able to reduce hydroperoxides, which otherwise would damage DNA, possibly resulting in DNA mutations, modulate redox-sensitive signaling pathways affecting proliferation, differentiation, and cellular metabolism or initiate cell death. Considering these different processes, the role and functions of individual Se-dependent GPx isoforms will be discussed herein in the context of tumorigenesis.

GPX2 overexpression indicates poor prognosis in patients with hepatocellular carcinoma

Glutathione peroxidase 2 has important role of tumor progression in lots of carcinomas, yet little is known about the prognosis of glutathione peroxidase 2 in hepatocellular carcinoma. Glutathione peroxidase 2 expression was assessed by immunohistochemistry in hepatocellular carcinoma tissues. The association between glutathione peroxidase 2 expression with clinicopathological/prognostic value was examined. Glutathione peroxidase 2 overexpression was correlated with alpha-fetoprotein level, larger tumor, BCLC stage, and tumor recurrence. Kaplan-Meier analysis showed that glutathione peroxidase 2 was an independent predictor for overall survival and time to recurrence. glutathione peroxidase 2 overexpression was correlated with poor prognosis in patient subgroups stratified by tumor size, differentiation, tumor-node-metastasis, and BCLC stage. Moreover, stratified analysis showed that tumor-node-metastasis stage-I patients with high glutathione peroxidase 2 expression had poor prognosis than those with low glutathione peroxidase 2 expression. Additionally, combination of glutathione peroxidase 2 and serum alpha-fetoprotein was correlated with prognosis in hepatocellular carcinoma. In conclusion, glutathione peroxidase 2 overexpression contributes to poor prognosis of hepatocellular carcinoma patients and helps to identify the high-risk hepatocellular carcinoma patients.

Prognostic significance of glutathione peroxidase 2 in gastric carcinoma

Increasing evidence suggests that the glutathione peroxidase 2 may actually play important roles in tumorigenesis and progression in various human cancers such as colorectal carcinomas and lung adenocarcinomas. However, the role of glutathione peroxidase 2 in gastric carcinoma remains to be determined. In this study, the expression and prognostic significance of glutathione peroxidase 2 in gastric carcinoma were investigated and the well-known prognostic factor Ki-67 labeling index was also assessed as positive control. Glutathione peroxidase 2 expression levels in the tumor tissue specimens, the matched adjacent normal tissue specimens, and the lymph node metastases of 176 patients with gastric carcinoma were evaluated by quantitative polymerase chain reaction, western blotting, and immunohistochemical staining. The associations between glutathione peroxidase 2 expression levels, as determined by immunohistochemical staining, and multiple clinicopathological characteristics were determined by Pearson's chi-square test and Spearman's correlation analysis. The relationships between glutathione peroxidase 2 expression and other clinicopathological variables and patient prognoses were analyzed further by the Kaplan-Meier method, the log-rank test, and Cox multivariate regression. The quantitative polymerase chain reaction, western blotting, and immunohistochemical staining results showed that glutathione peroxidase 2 expression levels were upregulated in both the primary tumor foci and the lymph node metastases of patients with gastric carcinoma (all p values < 0.05). Furthermore, Pearson's chi-square tests, as well as Spearman's correlation analysis, revealed that glutathione peroxidase 2 expression levels were strongly correlated with the Ki-67 labeling index, differentiation, histological patterns, Lauren classifications, lymph node metastasis, vascular invasion, tumor-node-metastasis stages, Helicobacter pylori infection, and overall survival (all p values < 0.05). Kaplan-Meier analysis, as well as the log-rank test and multivariate Cox regression analysis, showed that multiple clinicopathological risk factors and glutathione peroxidase 2 expression were novel independent prognostic factors for gastric carcinoma (all p values < 0.05). Glutathione peroxidase 2 expression is a novel independent prognostic biomarker for gastric carcinoma that may be used to devise personalized therapeutic regimens and precision treatments for this disease.

Selenoproteins in Tumorigenesis and Cancer Progression

Selenium is a micronutrient essential to human health and has long been associated with cancer prevention. Functionally, these effects are thought to be mediated by a class of selenium-containing proteins known as selenoproteins. Indeed, many selenoproteins have antioxidant activity which can attenuate cancer development by minimizing oxidative insult and resultant DNA damage. However, oxidative stress is increasingly being recognized for its "double-edged sword" effect in tumorigenesis, whereby it can mediate both negative and positive effects on tumor growth depending on the cellular context. In addition to their roles in redox homeostasis, recent work has also implicated selenoproteins in key oncogenic and tumor-suppressive pathways. Together, these data suggest that the overall contribution of selenoproteins to tumorigenesis is complicated and may be affected by a variety of factors. In this review, we discuss what is currently known about selenoproteins in tumorigenesis with a focus on their contextual roles in cancer development, growth, and progression.

Clinicopathological and prognostic significance of GPX2 protein expression in esophageal squamous cell carcinoma

BACKGROUND

Chaoshan region, a littoral area of Guangdong province in southern China, has a high incidence of esophageal squamous cell carcinoma (ESCC). At present, the prognosis of ESCC is still very poor, therefore, there is urgent need to seek valuable molecular biomarker for prognostic evaluation to guide clinical treatment. GPX2, a selenoprotein, was exclusively expressed in gastrointestinal tract and has an anti-oxidative damage and anti-tumour effect in the progress of tumourigenesis.

METHODS

We collected 161 ESCC patients samples, among which 83 patients were followed up. We employed immunochemistry analysis, western blotting and quantitative real-time PCR for measuring the expression of GPX2 within ESCC samples. We analysed the relationship between the expression of GPX2 and clinicopathological parameters of 161 patients with ESCC by Chi-square or Fisher's exact test. The survival analysis of GPX2 expression within ESCC tissues was evaluated by the Kaplan-Meier method and Cox-regression.

RESULTS

A significant higher expression level of GPX2 was detected in tumour tissues compared to that in non-tumour tissues (P < 0.001). Moreover, GPX2 expression has statistically significant difference in the tumour histological grade of ESCC (P < 0.001), while there was no statistically significant difference in age, sex, tumour size, tumour location, gross morphology and clinical TNM stages (P > 0.05). Meanwhile, the expression of GPX2 protein was obviously down-regulated within poorly differentiated ESCC. Last, survival analysis revealed that tumour histological grade and clinical TNM stages, both of the clinical pathological parameters of ESCC, were associated with the prognosis of patients with ESCC (respectively, P = 0.009, HR (95 % CI) = 1.885 (1.212 ~ 2.932); P = 0.007, HR (95 % CI) = 2.046 (1.318 ~ 3.177)). More importantly, loss expression of GPX2 protein predicted poor prognosis in patients with ESCC (P < 0.001, HR (95 % CI) = 5.700 (2.337 ~ 13.907)).

CONCLUSIONS

Collectively, these results suggested that the expression of GPX2 was significantly up-regulated within ESCC tumour tissues. GPX2 might be an important predictor for the prognosis of ESCC and a potential target for intervention and treatment of ESCC.

Targeting the expression of glutathione- and sulfate-dependent detoxification enzymes in HepG2 cells by oxygen in minimal and amino acid enriched medium

Cancer cells exhibit specific metabolism allowing them to survive and proliferate in various oxygen conditions and nutrients' availability. Hepatocytes are highly active metabolically and thus very sensitive to hypoxia. The purpose of the study was to investigate the effect of oxygen on the expression of phase II detoxification enzymes in hepatocellular carcinoma cells (HepG2) cultured in minimal and rich media (with nonessential amino acids and GSH). The cells were cultured at 1% hypoxia, 10% tissue normoxia, and 21% atmospheric normoxia. The total cell count was determined by trypan blue exclusion dye and the expression on mRNA level by RT-PCR. The result indicated that the expression of glutathione-dependent enzymes (GSTA, M, P, and GPX2) was sensitive to oxygen and medium type. At 1% hypoxia the enzyme expression (with the exception of GSTA) was higher in minimal compared to rich medium, whereas at 10% normoxia it was higher in the rich medium. The expression was oxygen-dependent in both types of medium. Among phenol sulfotransferase SULT1A1 was not sensitive to studied factors, whereas the expression of SULT1A3 was depended on oxygen only in minimal medium. It can be concluded that in HepG2 cells, the detoxification by conjugation with glutathione and, to a lower extent with sulfate, may be affected by hypoxia and/or limited nutrients' availability. Besides, because the data obtained at 10% oxygen significantly differ from those at 21%, the comparative studies on hypoxia should be performed in relation to 10% but not 21% oxygen.