Down-regulation of the cytoglobin gene, located on 17q25, in tylosis with oesophageal cancer (TOC): evidence for trans-allele repression

SOX7 inhibits the malignant progression of bladder cancer via the DNMT3B/CYGB axis

Bladder cancer (BCa) stands out as a highly prevalent malignant tumor affecting the urinary system. The Sex determining region Y-box protein family is recognized for its crucial role in BCa progression. However, the effect of Sex determining region Y-box 7 (SOX7) on BCa progression has not been fully elucidated. Herein, RNA-sequencing, western blot (WB), immunohistochemistry (IHC), immunofluorescence (IF) and tissue microarray were utilized to assess SOX7 expression in vitro and in vivo. Additionally, SOX7 expression, prognosis, and SOX7 + cytoglobin (CYGB) score were analyzed using R software. In vitro and vivo experiments were performed with BCa cell lines to validate the effect of SOX7 knockdown and overexpression on the malignant progression of BCa. The results showed that SOX7 exhibits low expression in BCa. It functions in diverse capacities, inhibiting the proliferative, migratory, and invasive capabilities of BCa. In addition, the experimental database demonstrated that SOX7 binds to the promoter of DNA methyltransferase 3 beta (DNMT3B), leading to the transcriptional inhibition of DNMT3B. This subsequently results in a reduced methylation of CYGB promoter, ultimately inhibiting the tumor progression of BCa. SOX7 + CYGB scores were significantly linked to patient prognosis. In conclusion, SOX7 inhibits the malignant progression of BCa via the DNMT3B/CYGB axis. Additionally, the SOX7 + CYGB score is capable of predicting the prognostic outcomes of BCa patients. Therefore, SOX7 and CYGB may play an important role in the progression of bladder cancer, and they can be used as prognostic markers of bladder cancer patients.

The cytoglobin-dependent transcriptome in melanoma indicates a protective function associated with oxidative stress, inflammation and cancer-associated pathways

Cytoglobin (CYGB) is a member of the oxygen-binding globin superfamily. In this study we generated stable CYGB overexpressing A375 melanoma cells and performed RNA-sequencing to comprehensively explore the CYGB-dependent transcriptome. Our findings reveal that ectopic expression of CYGB dysregulated multiple cancer-associated genes, including the mTORC1 and AKT/mTOR signaling pathways, which are frequently overactivated in tumors. Moreover, several cancer-associated pathways, such as epithelial-mesenchymal transition (EMT) mediated by CSPG4, were downregulated upon CYGB overexpression. Intriguingly, ectopic expression suggested anti-inflammatory potential of CYGB, as exemplified by downregulation of key inflammasome-associated genes, including NLRP1, CASP1 and CD74, which play pivotal roles in cytokine regulation and inflammasome activation. Consistent with established globin functions, CYGB appears to be involved in redox homeostasis. Furthermore, our study indicates CYGB's association to DNA repair mechanisms and its regulation of NOX4, reinforcing its functional versatility. Additionally, multiple significantly enriched pathways in CYGB overexpressing cells were consistently dysregulated in opposite direction in CYGB depleted cells. Collectively, our RNA-sequencing based investigations illustrate the diverse functions of CYGB in melanoma cells, pointing to its putative roles in cellular protection against oxidative stress, inflammation, and cancer-associated pathways. These findings pave the way for further research into the physiological role of CYGB and its potential as a candidate therapeutic target in melanoma.

Insights into the function of cytoglobin

Since its discovery in 2001, the function of cytoglobin has remained elusive. Through extensive in vitro and in vivo research, a range of potential physiological and pathological mechanisms has emerged for this multifunctional member of the hemoglobin family. Currently, over 200 research publications have examined different aspects of cytoglobin structure, redox chemistry and potential roles in cell signalling pathways. This research is wide ranging, but common themes have emerged throughout the research. This review examines the current structural, biochemical and in vivo knowledge of cytoglobin published over the past two decades. Radical scavenging, nitric oxide homeostasis, lipid binding and oxidation and the role of an intramolecular disulfide bond on the redox chemistry are examined, together with aspects and roles for Cygb in cancer progression and liver fibrosis.

Cytoglobin Silencing Promotes Melanoma Malignancy but Sensitizes for Ferroptosis and Pyroptosis Therapy Response

Despite recent advances in melanoma treatment, there are still patients that either do not respond or develop resistance. This unresponsiveness and/or acquired resistance to therapy could be explained by the fact that some melanoma cells reside in a dedifferentiated state. Interestingly, this dedifferentiated state is associated with greater sensitivity to ferroptosis, a lipid peroxidation-reliant, iron-dependent form of cell death. Cytoglobin (CYGB) is an iron hexacoordinated globin that is highly enriched in melanocytes and frequently downregulated during melanomagenesis. In this study, we investigated the potential effect of CYGB on the cellular sensitivity towards (1S, 3R)-RAS-selective lethal small molecule (RSL3)-mediated ferroptosis in the G361 melanoma cells with abundant endogenous expression. Our findings show that an increased basal ROS level and higher degree of lipid peroxidation upon RSL3 treatment contribute to the increased sensitivity of CYGB knockdown G361 cells to ferroptosis. Furthermore, transcriptome analysis demonstrates the enrichment of multiple cancer malignancy pathways upon CYGB knockdown, supporting a tumor-suppressive role for CYGB. Remarkably, CYGB knockdown also triggers activation of the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome and subsequent induction of pyroptosis target genes. Altogether, we show that silencing of CYGB expression modulates cancer therapy sensitivity via regulation of ferroptosis and pyroptosis cell death signaling pathways.

Cytoglobin attenuates pancreatic cancer growth via scavenging reactive oxygen species

Pancreatic cancer is a highly challenging malignancy with extremely poor prognosis. Cytoglobin (CYGB), a hemeprotein involved in liver fibrosis and cancer development, is expressed in pericytes of all organs. Here, we examined the role of CYGB in the development of pancreatic cancer. CYGB expression appeared predominately in the area surrounding adenocarcinoma and negatively correlated with tumor size in patients with pancreatic cancer. Directly injecting 7, 12-dimethylbenz[a]anthracene into the pancreatic tail in wild-type mice resulted in time-dependent induction of severe pancreatitis, fibrosis, and oxidative damage, which was rescued by Cygb overexpression in transgenic mice. Pancreatic cancer incidence was 93% in wild-type mice but only 55% in transgenic mice. Enhanced CYGB expression in human pancreatic stellate cells in vitro reduced cellular collagen synthesis, inhibited cell activation, increased expression of antioxidant-related genes, and increased CYGB secretion into the medium. Cygb-overexpressing or recombinant human CYGB (rhCYGB) -treated MIA PaCa-2 cancer cells exhibited dose-dependent cell cycle arrest at the G1 phase, diminished cell migration, and reduction in colony formation. RNA sequencing in rhCYGB-treated MIA PaCa-2 cells revealed downregulation of cell cycle and oxidative phosphorylation pathways. An increase in MIA PaCa-2 cell proliferation and reactive oxygen species production by H₂O₂ challenge was blocked by rhCYGB treatment or Cygb overexpression. PANC-1, OCUP-A2, and BxPC-3 cancer cells showed similar responses to rhCYGB. Known antioxidants N-acetyl cysteine and glutathione also inhibited cancer cell growth. These results demonstrate that CYGB suppresses pancreatic stellate cell activation, pancreatic fibrosis, and tumor growth, suggesting its potential therapeutic application against pancreatic cancer.

ΔNp63α promotes Bortezomib resistance via the CYGB-ROS axis in head and neck squamous cell carcinoma

Bortezomib, a proteasome inhibitor, proved potent in the treatment of recurrent multiple myeloma or mantle cell lymphoma. However, slow progress was made when it was applied to treat solid tumors. We discovered that different head and neck squamous cell carcinoma (HNSCC) cell lines had significantly different sensitivities to bortezomib, and also demonstrated that individual relatively sensitive HNSCC cell lines had fewer ΔNp63α expressions. Based on these findings, we speculated that ΔNp63α may be a key factor in the resistance of HNSCC cells to bortezomib. ΔNp63α knockdown made HNSCC more sensitive to bortezomib, while ΔNp63α overexpression made it more resistant. RNA sequencing (RNA-seq) analysis of ΔNp63α-knockdown cells revealed clear alterations in the subset of genes that were associated with oxidative stress and antioxidant defense. The gene CYGB was downregulated significantly. CHIP-seq detection showed that CYGB was the transcriptional regulatory site of ΔNp63α. CHIP-PCR showed evidence of ΔNp63α binding. The detection of the dual-luciferase reporter gene demonstrated that ΔNp63α significantly enhanced the CYGB promoter activity. Furthermore, we confirmed that CYGB plays a role in clearing excess ROS induced by bortezomib to inhibit HNSCC apoptosis. Consequently, ΔNp63α regulated the expression of CYGB in HNSCC. CYGB was the target of transcription regulation of ΔNp63α. It reduced apoptosis by clearing excess ROS produced by bortezomib, and thus exerted drug resistance.

Autoencoded DNA methylation data to predict breast cancer recurrence: Machine learning models and gene-weight significance

Breast cancer is the most frequent cancer in women and the second most frequent overall after lung cancer. Although the 5-year survival rate of breast cancer is relatively high, recurrence is also common which often involves metastasis with its consequent threat for patients. DNA methylation-derived databases have become an interesting primary source for supervised knowledge extraction regarding breast cancer. Unfortunately, the study of DNA methylation involves the processing of hundreds of thousands of features for every patient. DNA methylation is featured by High Dimension Low Sample Size which has shown well-known issues regarding feature selection and generation. Autoencoders (AEs) appear as a specific technique for conducting nonlinear feature fusion. Our main objective in this work is to design a procedure to summarize DNA methylation by taking advantage of AEs. Our proposal is able to generate new features from the values of CpG sites of patients with and without recurrence. Then, a limited set of relevant genes to characterize breast cancer recurrence is proposed by the application of survival analysis and a pondered ranking of genes according to the distribution of their CpG sites. To test our proposal we have selected a dataset from The Cancer Genome Atlas data portal and an AE with a single-hidden layer. The literature and enrichment analysis (based on genomic context and functional annotation) conducted regarding the genes obtained with our experiment confirmed that all of these genes were related to breast cancer recurrence.

Lessons from the post-genomic era: Globin diversity beyond oxygen binding and transport

Vertebrate hemoglobin (Hb) and myoglobin (Mb) were among the first proteins whose structures and sequences were determined over 50 years ago. In the subsequent pregenomic period, numerous related proteins came to light in plants, invertebrates and bacteria, that shared the myoglobin fold, a signature sequence motif characteristic of a 3-on-3 α-helical sandwich. Concomitantly, eukaryote and bacterial globins with a truncated 2-on-2 α-helical fold were discovered. Genomic information over the last 20 years has dramatically expanded the list of known globins, demonstrating their existence in a limited number of archaeal genomes, a majority of bacterial genomes and an overwhelming majority of eukaryote genomes. In vertebrates, 6 additional globin types were identified, namely neuroglobin (Ngb), cytoglobin (Cygb), globin E (GbE), globin X (GbX), globin Y (GbY) and androglobin (Adgb). Furthermore, functions beyond the familiar oxygen transport and storage have been discovered within the vertebrate globin family, including NO metabolism, peroxidase activity, scavenging of free radicals, and signaling functions. The extension of the knowledge on globin functions suggests that the original roles of bacterial globins must have been enzymatic, involved in defense against NO toxicity, and perhaps also as sensors of O₂, regulating taxis away or towards high O₂ concentrations. In this review, we aimed to discuss the evolution and remarkable functional diversity of vertebrate globins with particular focus on the variety of non-canonical expression sites of mammalian globins and their according impressive variability of atypical functions.

Emerging perspectives on cytoglobin, beyond NO dioxygenase and peroxidase

Cytoglobin is an evolutionary ancient hemoglobin with poor functional annotation. Rather than constrained to penta coordination, cytoglobin's heme iron may exist either as a penta or hexacoordinated arrangement when exposed to different intracellular environments. Two cysteine residues at the surface of the protein form an intramolecular disulfide bond that regulates iron coordination, ligand binding, and peroxidase activity. Overall, biochemical results do not support a role for cytoglobin as a direct antioxidant enzyme that scavenges hydrogen peroxide because the rate of the reaction of cytoglobin with hydrogen peroxide is several orders of magnitude slower than metal and thiol-based peroxidases. Thus, alternative substrates such as fatty acids have been suggested and regulation of nitric oxide bioavailability through nitric oxide dioxygenase and nitrite reductase activities has received experimental support. Cytoglobin is broadly expressed in connective, muscle, and nervous tissues. Rational for differential cellular distribution is poorly understood but inducibility in response to hypoxia is one of the most established features of cytoglobin expression with regulation through the transcription factor hypoxia-inducible factor (HIF). Phenotypic characterization of cytoglobin deletion in the mouse have indicated broad changes that include a heightened inflammatory response and fibrosis, increase tumor burden, cardiovascular dysfunction, and hallmarks of senescence. Some of these changes might be reversed upon inhibition of nitric oxide synthase. However, subcellular and molecular interactions have been seldom characterized. In addition, specific molecular mechanisms of action are still lacking. We speculate that cytoglobin functionality will extend beyond nitric oxide handling and will have to encompass indirect regulatory antioxidant and redox sensing functions.

p63 is a key regulator of iRHOM2 signalling in the keratinocyte stress response

Hyperproliferative keratinocytes induced by trauma, hyperkeratosis and/or inflammation display molecular signatures similar to those of palmoplantar epidermis. Inherited gain-of-function mutations in RHBDF2 (encoding iRHOM2) are associated with a hyperproliferative palmoplantar keratoderma and squamous oesophageal cancer syndrome (termed TOC). In contrast, genetic ablation of rhbdf2 in mice leads to a thinning of the mammalian footpad, and reduces keratinocyte hyperproliferation and migration. Here, we report that iRHOM2 is a novel target gene of p63 and that both p63 and iRHOM2 differentially regulate cellular stress-associated signalling pathways in normal and hyperproliferative keratinocytes. We demonstrate that p63-iRHOM2 regulates cell survival and response to oxidative stress via modulation of SURVIVIN and Cytoglobin, respectively. Furthermore, the antioxidant compound Sulforaphane downregulates p63-iRHOM2 expression, leading to reduced proliferation, inflammation, survival and ROS production. These findings elucidate a novel p63-associated pathway that identifies iRHOM2 modulation as a potential therapeutic target to treat hyperproliferative skin disease and neoplasia.

Cell cycle-dependent regulation of cytoglobin by Skp2

Cytoglobin (Cygb) is a cellular haemoprotein belonging to the globin family with ambiguous biological functions. Downregulation of Cygb in many cancers is indicative of its tumour-suppressive role. This is the first report showing the cell cycle regulation of Cygb, which was found to peak at G1 and rapidly decline in S phase. Importantly, Skp2-mediated degradation of Cygb was identified as the key mechanism for controlling its oscillating levels during the cell cycle. Moreover, overexpression of Cygb stimulates hypophosphorylation of Rb causing delayed cell cycle progression. Overall, the study reveals a novel mechanism for the regulated expression of Cygb and also assigns a new role to Cygb in cell cycle control.

COL1A1, PRPF40A, and UCP2 correlate with hypoxia markers in non-small cell lung cancer

Purpose

Collagen 1A1 (COL1A1), RNA-binding and pre-mRNA Processing Factor (PRPF40A), and Uncoupling Protein 2 (UCP2) were identified as downstream effectors of cytoglobin (CYGB), which was shown implicated in tumour biology. Although these three genes have been previously associated with cancer, little is known about their status in lung malignancies.

Methods

Hereby, we investigated the expression and promoter methylation of COL1A1, PRPF40A, and UCP2 in 156 non-small cell lung cancer (NSCLC) and adjacent normal tissues.

Results

We demonstrate that COL1A1 and PRPF40A mRNAs are significantly overexpressed in NSCLC (p < 1 × 10⁻⁴), while UCP2 exhibits a trend of upregulation (p = 0.066). Only COL1A1 promoter revealed hypermethylation in NSCLCs (36%), which was particularly evident in squamous cell carcinomas (p = 0.024) and in the tumours with moderate-to-good differentiation (p = 0.01). Transcript level of COL1A1, as well as PRPF40A and UCP2, exhibited striking association (p ≤ 0.001) with the expression of hypoxia markers. In addition, we demonstrate in lung cancer cell lines exposed to hypoxia or oxidative stress that COL1A1 transcription significantly responds to oxygen depletion, while other genes showed the modest upregulation in stress conditions.

Conclusion

In conclusion, our data revealed that COL1A1, UCP2, and PRPF40A are novel players implicated in the complex network of hypoxia response in NSCLC.

Downregulation of ST6GALNAC1 is associated with esophageal squamous cell carcinoma development

Tylosis is an inherited disorder characterized by abnormal palmoplantar skin thickening and a highly elevated risk of esophageal squamous cell carcinoma (ESCC). Analyses of tylosis in families have localized the responsible gene locus to a region of chromosome 17q25.1. Frequent loss of heterozygosity (LOH) in 17q25.1 was also observed in the sporadic form of ESCC. A putative tumor suppressor gene for ESCC may exist at this locus. We investigated the expression patterns of genes on 17q25.1 in tumor and corresponding normal tissues from patients with sporadic ESCC using RNA sequence analysis. For candidate genes, quantitative real-time reverse transcription-PCR (qRT-PCR), direct sequence, LOH and methylation analyses were performed using 93 clinical ESCC samples and 10 cell lines. A significant downregulation of ST6GALNAC1 was demonstrated in ESCC tissues compared to its expression in normal tissues by qRT-PCR (n=93, p<0.0001). Frequent LOH (17/27, 62.9%) and hyper‑methylation in ST6GALNAC1 were also observed in all cell lines. Our results indicated that ST6GALNAC1 was downregulated in sporadic ESCC via hyper-methylation and LOH, and it may be a candidate responsible gene for ESCC. Furthermore, recent studies suggest that multiple genes on chromosome 17q25 are involved in ESCC development.

Changes in mitochondrial stability during the progression of the Barrett's esophagus disease sequence

Background

Barrett’s esophagus follows the classic step-wise progression of metaplasia-dysplasia-adenocarcinoma. While Barrett’s esophagus is a leading known risk factor for esophageal adenocarcinoma, the pathogenesis of this disease sequence is poorly understood. Mitochondria are highly susceptible to mutations due to high levels of reactive oxygen species (ROS) coupled with low levels of DNA repair. The timing and levels of mitochondria instability and dysfunction across the Barrett’s disease progression is under studied.

Methods

Using an in-vitro model representing the Barrett’s esophagus disease sequence of normal squamous epithelium (HET1A), metaplasia (QH), dysplasia (Go), and esophageal adenocarcinoma (OE33), random mitochondrial mutations, deletions and surrogate markers of mitochondrial function were assessed. In-vivo and ex-vivo tissues were also assessed for instability profiles.

Results

Barrett’s metaplastic cells demonstrated increased levels of ROS (p < 0.005) and increased levels of random mitochondrial mutations (p < 0.05) compared with all other stages of the Barrett’s disease sequence in-vitro. Using patient in-vivo samples, Barrett’s metaplasia tissue demonstrated significantly increased levels of random mitochondrial deletions (p = 0.043) compared with esophageal adenocarcinoma tissue, along with increased expression of cytoglobin (CYGB) (p < 0.05), a gene linked to oxidative stress, compared with all other points across the disease sequence. Using ex-vivo Barrett’s metaplastic and matched normal patient tissue explants, higher levels of cytochrome c (p = 0.003), SMAC/Diablo (p = 0.008) and four inflammatory cytokines (all p values <0.05) were secreted from Barrett’s metaplastic tissue compared with matched normal squamous epithelium.

Conclusions

We have demonstrated that increased mitochondrial instability and markers of cellular and mitochondrial stress are early events in the Barrett’s disease sequence.

Absence of cytoglobin promotes multiple organ abnormalities in aged mice

Cytoglobin (Cygb) was identified in hepatic stellate cells (HSCs) and pericytes of all organs; however, the effects of Cygb on cellular functions remain unclear. Here, we report spontaneous and age-dependent malformations in multiple organs of Cygb(-/-) mice. Twenty-six percent of young Cygb(-/-) mice (<1 year old) showed heart hypertrophy, cystic disease in the kidney or ovary, loss of balance, liver fibrosis and lymphoma. Furthermore, 71.3% (82/115) of aged Cygb(-/-) mice (1-2 years old) exhibited abnormalities, such as heart hypertrophy and cancer development in multiple organs; by contrast, 5.8% (4/68) of aged wild-type (WT) mice had abnormalities (p < 0.0001). Interestingly, serum and urine analysis demonstrated that the concentration of nitric oxide metabolites increased significantly in Cygb(-/-) mice, resulting in an imbalance in the oxidative stress and antioxidant defence system that was reversed by N(G)-monomethyl-L-arginine treatment. A senescent phenotype and evidence of DNA damage were found in primary HSCs and the liver of aged Cygb(-/-) mice. Moreover, compared with HSC(+/+), HSC(-/-) showed high expression of Il-6 and chemokine mRNA when cocultured with mouse Hepa 1-6 cells. Thus, the absence of Cygb in pericytes provokes organ abnormalities, possibly via derangement of the nitric oxide and antioxidant defence system and through accelerated cellular senescence.

The Effect of rhCygb on CCl4-Induced Hepatic Fibrogenesis in Rat

This study aims to investigate whether the use of recombinant human cytoglobin (rhCygb) impact on hepatic fibrogenesis caused by CCl₄. SD (n = 150) rats were randomly divided into three groups of normal, CCl₄ model and rhCygb groups. After model establishment, rats in rhCygb groups were administered daily with rhCygb (2 mg/kg, s.c.). Histological lesions were staged according to metavir. Serum parameters including ALT, AST, HA, LN, Col III and Col IV were determined. The liver proteins were separated by 2-DE and identified. As a result, the stage of hepatic damage and liver fibrosis in rhCygb groups were significantly milder than that in CCl₄ model groups. Meanwhile, rhCygb dramatically reversed serum levels of ALT and AST, and also markedly decreased the liver fibrosis markers levels of LN, HA, Col III and Col IV. In 2-DE, 33 proteins among three groups with the same changing tendency in normal and rhCygb treated groups compared with CCl₄ model group were identified. GO analysis showed that several identified proteins involved in oxidative stress pathway. The study provides new insights and data for administration of rhCygb reversing CCl₄-induced liver fibrosis suggesting that rhCygb might be used in the treatment of liver fibrosis.

Cytoglobin as a Biomarker in Cancer: Potential Perspective for Diagnosis and Management

The search for biomarkers to detect the earliest glimpse of cancer has been one of the primary objectives of cancer research initiatives. These endeavours, in spite of constant clinical challenges, are now more focused as early cancer detection provides increased opportunities for different interventions and therapies, with higher potential for improving patient survival and quality of life. With the progress of the omics technologies, proteomics and metabolomics are currently being used for identification of biomarkers. In this line, cytoglobin (Cygb), a ubiquitously found protein, has been actively reviewed for its functional role. Cytoglobin is dynamically responsive to a number of insults, namely, fibrosis, oxidative stress, and hypoxia. Recently, it has been reported that Cygb is downregulated in a number of malignancies and that an induced overexpression reduces the proliferative characteristics of cancer cells. Thus, the upregulation of cytoglobin can be indicative of a tumour suppressor ability. Nevertheless, without a comprehensive outlook of the molecular and functional role of the globin, it will be most unlikely to consider cytoglobin as a biomarker for early detection of cancer or as a therapeutic option. This review provides an overview of the proposed role of cytoglobin and explores its potential functional role as a biomarker for cancer and other diseases.

ΔNp63 targets cytoglobin to inhibit oxidative stress-induced apoptosis in keratinocytes and lung cancer

During physiological aerobic metabolism, the epidermis undergoes significant oxidative stress as a result of the production of reactive oxygen species (ROS). To maintain a balanced oxidative state, cells have developed protective antioxidant systems, and preliminary studies suggest that the transcriptional factor p63 is involved in cellular oxidative defence. Supporting this hypothesis, the ΔNp63α isoform of p63 is expressed at high levels in the proliferative basal layer of the epidermis. Here we identify the CYGB gene as a novel transcriptional target of ΔNp63 that is involved in maintaining epidermal oxidative defence. The CYGB gene encodes cytoglobin, a member of the globin protein family, which facilitates the diffusion of oxygen through tissues and acts as a scavenger for nitric oxide or other ROS. By performing promoter activity assays and chromatin immunoprecipitation, reverse transcriptase quantitative PCR and western blotting analyses, we confirm the direct regulation of CYGB by ΔNp63α. We also demonstrate that CYGB has a protective role in proliferating keratinocytes grown under normal conditions, as well as in cells treated with exogenous hydrogen peroxide. These results indicate that ΔNp63, through its target CYGB has an important role in the cellular antioxidant system and protects keratinocytes from oxidative stress-induced apoptosis. The ΔNp63-CYGB axis is also present in lung and breast cancer cell lines, indicating that CYGB-mediated ROS-scavenging activity may also have a role in epithelial tumours. In human lung cancer data sets, the p63-CYGB interaction significantly predicts reduction of patient survival.

Cytoglobin deficiency promotes liver cancer development from hepatosteatosis through activation of the oxidative stress pathway

This study was conducted to clarify the role of cytoglobin (Cygb), a globin expressed in hepatic stellate cells (HSCs), in the development of liver fibrosis and cancer in nonalcoholic steatohepatitis (NASH). Cygb expression was assessed in patients with NASH and hepatocellular carcinoma. Mouse NASH model was generated in Cygb-deficient (Cygb(-/-)) or wild-type (WT) mice by giving a choline-deficient amino acid-defined diet and, in some of them, macrophage deletion and N-acetyl cysteine treatment were used. Primary-cultured mouse HSCs isolated from WT (HSCs(Cygb-wild)) or Cygb(-/-) (HSCs(Cygb-null)) mice were characterized. As results, the expression of CYGB was reduced in patients with NASH and hepatocellular carcinoma. Choline-deficient amino acid treatment for 8 weeks induced prominent inflammation and fibrosis in Cygb(-/-) mice, which was inhibited by macrophage deletion. Surprisingly, at 32 weeks, despite no tumor formation in the WT mice, all Cygb(-/-) mice developed liver cancer, which was ameliorated by N-acetyl cysteine treatment. Altered expression of 31 genes involved in the metabolism of reactive oxygen species was notable in Cygb(-/-) mice. Both HSCs(Cygb-null) and Cygb siRNA-transfected-HSCs(Cygb-wild) exhibited the preactivation condition. Our findings provide important insights into the role that Cygb, expressed in HSCs during liver fibrosis, plays in cancer development with NASH.

DNA damage induced activation of Cygb stabilizes p53 and mediates G1 arrest

Cytoglobin (Cygb) is an emerging tumor suppressor gene silenced by promoter hypermethylation in many human tumors. So far, the precise molecular mechanism underlying its tumor suppressive function remains poorly understood. Here, we identified Cygb as a genotoxic stress-responsive hemoprotein upregulated upon sensing cellular DNA damage. Our studies demonstrated that Cygb physically associates with and stabilizes p53, a key cellular DNA damage signaling factor. We provide evidence that Cygb extends the half-life of p53 by blocking its ubiquitination and subsequent degradation. We show that, upon DNA damage, cells overexpressing Cygb displayed proliferation defect by rapid accumulation of p53 and its target gene p21, while Cygb knockdown cells failed to efficiently arrest in G1 phase in response to DNA insult. These results suggest a possible involvement of Cygb in mediating cellular response to DNA damage and thereby contributing in the maintenance of genomic integrity. Our study thus presents a novel insight into the mechanistic role of Cygb in tumor suppression.

Overexpression of cytoglobin gene inhibits hypoxic injury to SH-SY5Y neuroblastoma cells

A plasmid for cytoglobin expression, pAcGFP1-C1-cytoglobin, was transfected into SH-SY5Y cells. Cobalt chloride was used to establish a model of hypoxia. Western blotting indicated that cytoglobin was overexpressed and there was low expression of hypoxia-inducible factor-1α in SH-SY5Y cells after transfection. Following cobalt chloride-induced hypoxia, cytoglobin and hypoxia-inducible factor-1α expression gradually increased in SH-SY5Y cells. Flow cytometry showed that with increasing duration of hypoxia, the proportion of normal cells significantly diminished in the transfected and non-transfected groups. The proportion of cells in the early stages of apoptosis increased. However, the proportion of apoptotic cells was significantly lower in the transfected group compared with the non-transfected group. These results demonstrate that cytoglobin and hypoxia-inducible factor-1α are strongly up-regulated by hypoxia, and that there is a strong relationship between hypoxia-inducible factor-1α and cytoglobin during hypoxic injury.

Cytoglobin in tumor hypoxia: novel insights into cancer suppression

Emerging new and intriguing roles of cytoglobin (Cygb) have attracted considerable attention of cancer researchers in recent years. Hypoxic upregulation of Cygb as well as its altered expression in various human cancers suggest another possible role of this newly discovered globin in tumor cell response under low oxygen tension. Since tumor hypoxia is strongly associated with malignant progression of disease and poor treatment response, it constitutes an area of paramount importance for rational design of cancer selective therapies. However, the mechanisms involved during this process are still elusive. This review outlines the current understanding of Cygb's involvement in tumor hypoxia and discusses its role in tumorigenesis. A better perception of Cygb in tumor hypoxia response is likely to open novel perspectives for future tumor therapy.

Melanoma transition is frequently accompanied by a loss of cytoglobin expression in melanocytes: a novel expression site of cytoglobin

The tissue distribution and function of hemoglobin or myoglobin are well known; however, a newly found cytoglobin (CYGB), which also belongs to the globin family, remains to be characterized. To assess its expression in human malignancies, we sought to screen a number of cell lines originated from many tissues using northern blotting and real time PCR techniques. Unexpectedly, we found that several, but not all, melanoma cell lines expressed CYGB mRNA and protein at much higher levels than cells of other origins. Melanocytes, the primary origin of melanoma, also expressed CYGB at a high level. To verify these observations, immunostaining and immunoblotting using anti-CYGB antibody were also performed. Bisulfite-modified genomic sequencing revealed that several melanoma cell lines that abrogated CYGB expression were found to be epigenetically regulated by hypermethylation in the promoter region of CYGB gene. The RNA interference-mediated knockdown of the CYGB transcript in CYGB expression-positive melanoma cell lines resulted in increased proliferation in vitro and in vivo. Flow cytometric analysis using 2'-, 7'-dichlorofluorescein diacetate (DCFH-DA), an indicator of reactive oxygen species (ROS), revealed that the cellular ROS level may be involved in the proliferative effect of CYGB. Thus, CYGB appears to play a tumor suppressive role as a ROS regulator, and its epigenetic silencing, as observed in CYGB expression-negative melanoma cell lines, might function as an alternative pathway in the melanocyte-to-melanoma transition.

Cytoglobin has bimodal: tumour suppressor and oncogene functions in lung cancer cell lines

Cytoglobin (CYGB) is frequently downregulated in many types of human malignancies, and its exogenous overexpression reduces proliferation of cancer cells. Despite its implied tumour suppressor (TSG) functions, its exact role in carcinogenesis remains unclear as CYGB upregulation is also associated with tumour hypoxia and aggressiveness. In this study, we explore the TSG role of CYGB, its influence on the phenotype of cancerous cells under stress conditions and the clinical significance of CYGB expression and promoter methylation in non-small cell lung cancer (NSCLC). DNA methylation-dependent expression silencing of CYGB is demonstrated in both clinical samples and cell lines. CYGB promoter was more frequently methylated in lung adenocarcinomas (P = 1.4 × 10(-4)). Demethylation by 5'-azadeoxycytidine partially restored CYGB expression in cell lines. Interestingly, trichostatin A triggered upregulation of CYGB expression in cancer cell lines and downregulation in non-tumourigenic ones. CYGB mRNA expression in NSCLC surgical specimens correlated with that of HIF1α and VEGFa (P < 1 × 10(-4)). Overexpression of CYGB in cancer cell lines reduced cell migration, invasion and anchorage-independent growth. Moreover, CYGB impaired cell proliferation, but only in the lung adenocarcinoma cell line (H358). Upon hydrogen peroxide treatment, CYGB protected cell viability, migratory potential and anchorage independence by attenuating oxidative injury. In hypoxia, CYGB overexpression decreased cell viability, augmented migration and anchorage independence in a cell-type-specific manner. In conclusion, CYGB revealed TSG properties in normoxia but promoted tumourigenic potential of the cells exposed to stress, suggesting a bimodal function in lung tumourigenesis, depending on cell type and microenvironmental conditions.

Gene expression profiles and differential cytoglobin expression in atrophy and adenocarcinoma of the prostate

BACKGROUND

Proliferative inflammatory atrophy (PIA) has been proposed as a potential precursor for prostate cancer. The precise molecular abnormalities in prostatic atrophy compared to high-grade prostatic intraepithelial neoplasia (HGPIN) and carcinoma have not been fully defined.

METHODS

We utilized laser capture microdissection and microarray analysis to characterize cells of PIA, HGPIN, invasive prostatic carcinoma, and non-atrophic benign prostatic epithelium (NABE). Cytoglobin was selected for immunohistochemistry (IHC) validation. IHC stains were evaluated for proportion of positive glands, and intensity of cytoglobin staining. An immunoreactive score (IR score) was determined as the product of the percentage of positive staining and intensity.

RESULTS

Microarray analysis revealed probe sets that separated the microdissected cell types. Several genes showed overlapping expression patterns between PIA and PIN, and HGPIN and invasive carcinoma. Cytoglobin protein expression was detected in 57/93 (61%) of NABE and BPH cases, 92/93 atrophy (99%), 3/34 (9%) of PIN, and 23/61 carcinoma (37%) samples. The highest IHC scores were calculated for atrophy foci. A subset (33%) of atrophy cases showed the same low-cytoglobin expression level as PIN and carcinoma.

CONCLUSIONS

Prostatic epithelium can be stratified into normal, atrophic, PIN, and invasive carcinoma categories based on differential genetic signatures. Cytoglobin, a protein that can be induced in response to oxidative stress, was elevated in most atrophy foci, suggesting hypoxic, and/or oxidative damage. The lower level of cytoglobin seen in neoplastic cells and 33% of atrophy foci may indicate a shared susceptibility to oxidative damage for this subset of atrophy cases and prostatic neoplasia.

Protection from intracellular oxidative stress by cytoglobin in normal and cancerous oesophageal cells

Cytoglobin is an intracellular globin of unknown function that is expressed mostly in cells of a myofibroblast lineage. Possible functions of cytoglobin include buffering of intracellular oxygen and detoxification of reactive oxygen species. Previous work in our laboratory has demonstrated that cytoglobin affords protection from oxidant-induced DNA damage when over expressed in vitro, but the importance of this in more physiologically relevant models of disease is unknown. Cytoglobin is a candidate for the tylosis with oesophageal cancer gene, and its expression is strongly down-regulated in non-cancerous oesophageal biopsies from patients with TOC compared with normal biopsies. Therefore, oesophageal cells provide an ideal experimental model to test our hypothesis that downregulation of cytoglobin expression sensitises cells to the damaging effects of reactive oxygen species, particularly oxidative DNA damage, and that this could potentially contribute to the TOC phenotype. In the current study, we tested this hypothesis by manipulating cytoglobin expression in both normal and oesophageal cancer cell lines, which have normal physiological and no expression of cytoglobin respectively. Our results show that, in agreement with previous findings, over expression of cytoglobin in cancer cell lines afforded protection from chemically-induced oxidative stress but this was only observed at non-physiological concentrations of cytoglobin. In addition, down regulation of cytoglobin in normal oesophageal cells had no effect on their sensitivity to oxidative stress as assessed by a number of end points. We therefore conclude that normal physiological concentrations of cytoglobin do not offer cytoprotection from reactive oxygen species, at least in the current experimental model.

Cytoglobin: biochemical, functional and clinical perspective of the newest member of the globin family

Since the discovery of cytoglobin (Cygb) a decade ago, growing amounts of data have been gathered to characterise Cygb biochemistry, functioning and implication in human pathologies. Its molecular roles remain under investigation, but nitric oxide dioxygenase and lipid peroxidase activities have been demonstrated. Cygb expression increases in response to various stress conditions including hypoxia, oxidative stress and fibrotic stimulation. When exogenously overexpressed, Cygb revealed cytoprotection against these factors. Cygb was shown to be upregulated in fibrosis and neurodegenerative disorders and downregulated in multiple cancer types. CYGB was also found within the minimal region of a hereditary tylosis with oesophageal cancer syndrome, and its expression was reduced in tylotic samples. Recently, Cygb has been shown to inhibit cancer cell growth in vitro, thus confirming its suggested tumour suppressor role. This article aims to review the biochemical and functional aspects of Cygb, its involvement in various pathological conditions and potential clinical utility.

Old proteins - new locations: myoglobin, haemoglobin, neuroglobin and cytoglobin in solid tumours and cancer cells

AIM

The unexpected identification of myoglobin (MB) in breast cancer prompted us to evaluate the clinico-pathological value of MB, haemoglobin (HB) and cytoglobin (CYGB) in human breast carcinoma cases. We further screened for the presence of neuroglobin (NGB) and CYGB in tumours of diverse origin, and assessed the O(2) -response of HB, MB and CYGB mRNAs in cancer cell lines, to better elicit the links between this ectopic globin expression and tumour hypoxia.

METHODS

Breast tumours were analysed by immunohistochemistry for HB, MB and CYGB and correlated with clinico-pathological parameters. Screening for CYGB and NGB mRNA expression in tumour entities was performed by hybridization, quantitative PCR (qPCR) and bioinformatics. Hypoxic or anoxic responses of HB, MB and CYGB mRNAs was analysed by qPCR in human Hep3B, MCF7, HeLa and RCC4 cancer cell lines.

RESULTS

78.8% of breast cancer cases were positive for MB, 77.9% were positive for HB and 55.4% expressed CYGB. The closest correlation with markers of hypoxia was observed for CYGB. Compared to the weakly positive status of MB in healthy breast tissues, invasive tumours either lost or up-regulated MB. Breast carcinomas showed the tendency to silence CYGB. HB was not seen in normal tissues and up-regulated in tumours. Beyond breast malignancies, expression levels of NGB and CYGB mRNAs were extremely low in brain tumours (glioblastoma, astrocytoma). NGB was not observed in non-brain tumours. CYGB mRNA, readily detectable in breast cancer and other tumours, is down-regulated in lung adenocarcinomas. Alpha1 globin (α1 globin) and Mb were co-expressed in MCF7 and HeLa cells; CYGB transcription was anoxia-inducible in Hep3B and RCC4 cells.

CONCLUSIONS

This is the first time that HB and CYGB are reported in breast cancer. Neither NGB nor CYGB are systematically up-regulated in tumours. The down-regulated CYGB expression in breast and lung tumours is in line with a tumour-suppressor role. Each of the screened cancer cells expresses at least one globin (i.e. main globin species: CYGB in Hep3B; α1 globin + MB in MCF7 and HeLa). Thus, globins exist in a wide variety of solid tumours. However, the generally weak expression of the endogenous proteins in the cancer argues against a significant contribution to tumour oxygenation. Future studies should consider that cancer-expressed globins might function in ways not directly linked to the binding and transport of oxygen.

Promotion of liver and lung tumorigenesis in DEN-treated cytoglobin-deficient mice

Cytoglobin (Cygb) is a recently discovered vertebrate globin with molecular characteristics that are similar to myoglobin. To study the biological function of Cygb in vivo, we generated Cygb knockout mice and investigated their susceptibility to N,N-diethylnitrosamine (DEN)-induced tumorigenesis. Four-week-old male mice were administered DEN in drinking water at a dose of 25 ppm for 25 weeks or 0.05 ppm for 36 weeks. Cygb deficiency promoted the DEN-induced development of liver and lung tumors. All Cygb(+/-) and Cygb(-/-) mice treated with 25-ppm DEN exhibited liver tumors, compared with 44.4% of their wild-type counterparts. Lung tumors were present only in Cygb-deficient mice. More than 40% of Cygb(-/-) mice developed liver and lung tumors at the nontoxic dose of DEN (0.05 ppm), which did not induce tumors in wild-type mice. Cygb loss was associated with increased cancer cell proliferation, elevated extracellular signal-regulated kinase and Akt activation, overexpression of IL-1β, IL-6, Tnfα, and Tgfβ3 mRNAs, and hepatic collagen accumulation. Cygb-deficient mice also exhibited increased nitrotyrosine formation and dysregulated expression of cancer-related genes (cyclin D2, p53, Pak1, Src, Cdkn2a, and Cebpa). These results suggest that Cygb deficiency induces susceptibility to cancer development in the liver and lungs of mice exposed to DEN. Thus, globins such as Cygb will shed new light on the biological features of organ carcinogenesis.

Neuroglobin and myoglobin in non-small cell lung cancer: expression, regulation and prognosis

Globins are respiratory proteins involved in oxygen metabolism, which is a critical factor in tumor growth and progression. The status of neuroglobin and myoglobin is largely unknown in human malignancies, including lung cancer. The aim of this study was to explore mRNA expression profiles, potential regulatory mechanisms and clinicopathological associations of neuroglobin and myoglobin in non-small cell lung cancer (NSCLC). We screened 208 surgically resected NSCLC specimens and a panel of lung normal and cancer cell lines. The mRNA expression of neuroglobin, myoglobin and hypoxia markers (HIF1α and VEGFa) was measured with qRTPCR, while neuroglobin promoter methylation was assessed with Pyrosequencing. Neuroglobin and myoglobin were upregulated in the tumor samples compared to normal tissue (p=1.3×10(-22) and p=1.9×10(-9), respectively). Neuroglobin was more frequently overexpressed in squamous cell carcinomas (SqCCL) than adenocarcinomas. Overexpression of myoglobin was more profound in adenocarcinomas, which correlated with poor survival (p=0.013). Neuroglobin promoter was hypermethylated in 30.8% of NSCLC cases, which correlated with neuroglobin mRNA downregulation. The epigenetic regulation of neuroglobin was confirmed by treating lung cell lines with 5'azadeoxycytidine and/or trichostatin A. Expression of both genes correlated with the expression of HIF1α (neuroglobin: p=3.8×10(-5), myoglobin: p=1.1×10(-11)). Myoglobin expression was also associated to that of VEGFa (p=2.1×10(-7)). Hypoxia-dependent upregulation of both globins was validated in vitro. In summary, neuroglobin and myoglobin overexpression in NSCLC is associated with histological subtype, hypoxia and, in case of neuroglobin - epigenetic regulation. Myoglobin expression may have potential significance in the prognostication of lung adenocarcinomas.

Upper gastrointestinal cancer predisposition syndromes

Malignancies of the upper gastrointestinal tract form a heterogeneous group of cancers characterized by unique epidemiology and biology. Despite these differences, survival for advanced disease remains poor across the panel of diseases, from cancers of the esophagus, stomach, pancreas, and, until recently, even gastrointestinal stromal tumors. Genetic predisposition syndromes associated with these diseases comprise an emerging subset of these diseases that may provide valuable information on cause and etiology. They may provide insight into molecular drivers for the disease, or disease subtypes, and also insights into novel gene/environment interactions. This review summarizes the current understanding of genetic predisposition syndromes of cancers of the upper gastrointestinal tract.

Cytoglobin is upregulated by tumour hypoxia and silenced by promoter hypermethylation in head and neck cancer

BACKGROUND

Cytoglobin (Cygb) was first described in 2002 as an intracellular globin of unknown function. We have previously shown the downregulation of cytoglobin as a key event in a familial cancer syndrome of the upper aerodigestive tract.

METHODS

Cytoglobin expression and promoter methylation were investigated in sporadic head and neck squamous cell carcinoma (HNSCC) using a cross-section of clinical samples. Additionally, the putative mechanisms of Cygb expression in cancer were explored by subjecting HNSCC cell lines to hypoxic culture conditions and 5-aza-2-deoxycitidine treatment.

RESULTS

In clinically derived HNSCC samples, CYGB mRNA expression showed a striking correlation with tumour hypoxia (measured by HIF1A mRNA expression P=0.013) and consistent associations with histopathological measures of tumour aggression. CYGB expression also showed a marked negative correlation with promoter methylation (P=0.018). In the HNSCC cell lines cultured under hypoxic conditions, a trend of increasing expression of both CYGB and HIF1A with progressive hypoxia was observed. Treatment with 5-aza-2-deoxycitidine dramatically increased CYGB expression in those cell lines with greater baseline promoter methylation.

CONCLUSION

We conclude that the CYGB gene is regulated by both promoter methylation and tumour hypoxia in HNSCC and that increased expression of this gene correlates with clincopathological measures of a tumour's biological aggression.

Non-protein coding RNA biomarkers and differential expression in cancers: a review

Background

In these years a huge number of human transcripts has been found that do not code for proteins, named non-protein coding RNAs. In most cases, small (miRNAs, snoRNAs) and long RNAs (antisense RNA, dsRNA, and long RNA species) have many roles, functioning as regulators of other mRNAs, at transcriptional and post-transcriptional level, and controlling protein ubiquitination and degradation. Various species of npcRNAs have been found differentially expressed in different types of cancer. This review discusses the published data and new results on the expression of a subset of npcRNAs.

Conclusion

These results underscore the complexity of the RNA world and provide further evidence on the involvement of functional RNAs in cancer cell growth control.

Genetics of gastroesophageal cancer: paradigms, paradoxes, and prognostic utility

Hereditary diffuse gastric cancer and tylosis are autosomal dominant cancer susceptibility syndromes. Accumulating evidence also suggests a genetic contribution to Barrett's esophagus and adenocarcinoma, traditionally considered acquired disorders. In this article we review the current knowledge on the genetic mechanisms underlying hereditary diffuse gastric cancer, tylosis, and Barrett's esophagus. Hereditary diffuse gastric cancer is a paradigm for hereditary cancer susceptibility syndromes with E-cadherin implicated as the dominant oncogene in up to one-third of cases. Tylosis in contrast remains the paradox as whilst the putative abnormality has been localized to the long arm of chromosome 17, sequencing of this region has failed to reveal a disease causing mutation. In the case of Barrett's esophagus and adenocarcinoma, although a validated specific disease-associated gene is yet to be identified, the increasing body of evidence of a possible genetic link is paving the way for subsequent prognostic studies such as AspECT (Aspirin Esomeprazole Chemoprevention Trial). For the clinician these advances in understanding are already having implications for practice in terms of improved screening and the stratification of management strategies. As the mechanisms continue to be defined, there is the real possibility that these mechanisms could be exploited or subverted in the design of new therapies. In the meantime, however, clinicians should undertake rigorous biopsy programs to ensure early invasive lesions are detected.

Blood-derived gene-expression profiling in unravelling susceptibility to recessive disease

Identification of new disease predisposition genes with chip-based technologies typically requires extensive financial and sample resources. We have recently shown that combining peripheral blood genome and transcriptome (BGT) information in highly selected materials can be a successful low-cost approach to unravelling dominant tumour susceptibility. In this study, we extended our investigations to recessively inherited tumour predisposition, and identified a homozygous germline mutation in the damage-specific DNA binding protein 2 (DDB2) gene in a patient with several facial tumours, for which doctors had been unable to provide a diagnosis. Our results provide proof of principle that BGT is a powerful approach for both dominant and recessive genes. In addition to tumour susceptibility, the method may be useful in characterising genetic defects underlying other disease phenotypes.

Allogeneic transplantation and the risk for transmission of genetic disease: the heritable cancer disorders

With the development of new approaches to transplantation therapy, such as those building upon the potential found in stem cells, it is vital to pursue a clear understanding of transplantation risks. Allogeneic transplantation presents risk for the transmission of disease of various types, including genetic disease. Predisposition to develop cancer is a feature of numerous genetic disorders, and it may be transmissible by transplantation. Some genetic disorders predisposing to cancer are remarkably common, either worldwide or in specific populations, and they could pose significant risk. Hence, to reduce risk to recipients, there is reason to exclude from donation those potential donors (including embryos) harboring certain germ-line mutations. However, the frequent absence of readily identifiable features might confound the effort to exclude those who harbor mutation. Thus, it is also important to consider the magnitude of risk that they represent. For some disorders, life-threatening cancer is highly likely to develop in those individuals born with germ-line mutation, but whether recipients would face the same risk from transplanted mutation is not always evident. Given the diversity of pathways that lead to cancer, there may be diverse factors that impact the likelihood for cancer to develop in the recipient, with some factors decreasing and others increasing the risk. One factor of special concern is the possibility that manipulation of donor cells, prior to transplantation, might introduce additional genetic or epigenetic abnormality, thereby increasing the risk.

Cytoglobin Up-regulated by Hydrogen Peroxide Plays a Protective Role in Oxidative Stress

Cytoglobin (Cygb) is a recently discovered intracellular respiratory globin, which exists in all types of cells. It has been suggested that Cygb has a role in protecting cells against oxidative stress. In the present study we have tested this hypothesis. The N2a neuroblastoma cells were exposed to various kinds of insults, including hydrogen peroxide (H(2)O(2)), hypoxia, kainic acid, high extracellular CaCl(2), high osmolarity, UV irradiation and heat shock. Among them, only H(2)O(2)-treatment induced a significant up-regulation of cytoglobin mRNA level. We stably transfected N2a cells with Cygb-siRNA vectors and successfully knocked down Cygb. The Cygb-siRNA could exacerbate cell death upon H(2)O(2)-treatment, as demonstrated by MTT cell viability assay. Thus, Cygb in neuronal cells might be specifically induced under oxidative stress to protect them from death.

CpG island methylation phenotype (CIMP) in oral cancer: associated with a marked inflammatory response and less aggressive tumour biology

Studies in several tumour sites highlight the significance of the CpG island methylation phenotype (CIMP), with distinct features of histology, biological aggression and outcome. We utilise pyrosequencing techniques of quantitative methylation analysis to investigate the presence of CIMP in oral squamous cell carcinoma (OSCC) for the first time, and evaluate its correlation with allelic imbalance, pathology and clinical behaviour. Tumour tissue, control tissue and PBLs were obtained from 74 patients with oral squamous cell carcinoma. Pyrosequencing was used to analyse methylation patterns in 75-200 bp regions of the CpG rich gene promoters of 10 genes with a broad range of cellular functions. Allelic imbalance was investigated using a multiplexed panel of 11 microsatellite markers. Corresponding variables, histopathological staging and grading were correlated with these genetic and epigenetic aberrations. A cluster of tumours with a greater degree of promoter methylation than would be predicted by chance alone (P=0.001) were designated CIMP+ve. This group had less aggressive tumour biology in terms of tumour thickness (p=0.015) and nodal metastasis (P=0.012), this being apparently independent of tumour diameter. Further, it seems that these CIMP+ve tumours excited a greater host inflammatory response (P=0.019). The exact mechanisms underlying CIMP remain obscure but the association with a greater inflammatory host response supports existing theories relating these features in other tumour sites. As CIMP has significant associations with other well documented prognostic indicators, it may prove beneficial to include methylation analyses in molecular risk modelling of tumours.

Oxygen-sensing in tumors

PURPOSE OF REVIEW

Tumor hypoxia induces cancer cell treatment resistance, angiogenesis, invasiveness, and overall poor clinical outcome. Cellular adaptations to hypoxia are largely driven by hypoxia-induced alterations in gene transcription, mRNA translation, and protein stability. This review will summarize recent advances in the understanding of mammalian oxygen-sensing mechanisms in normal and cancerous cells.

RECENT FINDINGS

Specific molecular candidates have been identified that are involved in the primary sensing of hypoxia or its secondary consequences. Chief amongst these are the iron and 2-oxoglutarate-dependent dioxygenases that hydroxylate the alpha subunits of hypoxia-inducible transcription factors. This oxygen-dependent reaction, which prevents the transcription of many genes, is relieved under hypoxia. Evidence for the regulated expression and decay of the hypoxia-inducible transcription factor hydroxylating enzymes suggests that the sensitivity of transcriptional responses to hypoxia can be dynamically adjusted. Recent results also argue that these hydroxylating enzymes may be able to sense not only oxygen availability, but also the accumulation of bioenergetic intermediates and reactive oxygen species. In cancer cells, changes in these metabolites may accompany hypoxia or may occur independently. Several organellar compartments including plasma membrane, mitochondria and endoplasmic reticulum also appear to contribute to oxygen sensing through the generation of metabolites or through regulation of protein translation.

SUMMARY

Oxygen-sensing mechanisms induce prominent clinically relevant changes in cancer cells and tumor biology through the control of gene expression. Significant overlap exists between oxygen-sensing mechanisms and other metabolic and cell stress sensing pathways, which allows nonhypoxic cell stresses to activate hypoxia-inducible responses.

Frequent genetic and epigenetic abnormalities contribute to the deregulation of cytoglobin in non-small cell lung cancer

Lung cancer demonstrates the highest mortality in the UK. Previous studies have implicated allelic loss at chromosome 17q in the development of non-small cell lung carcinoma (NSCLC), and a number of known and putative tumour-suppressor genes reside within this region. One candidate tumour-suppressor gene is cytoglobin (CYGB), which is contained entirely within the 42.5 kb tylosis with oesophageal cancer (TOC) minimal region. CYGB abnormalities have been demonstrated only in sporadic head and neck cancers. In this study, we investigated the expression, promoter methylation and allelic imbalance status of this gene in 52 paired (normal/tumour) surgically excised lung tissue samples from patients with NSCLC. CYGB expression in tumour tissue was significantly reduced compared with corresponding adjacent normal in 54% of the examined cases (paired t-test, P<0.001). The CYGB promoter was shown by pyrosequencing to be significantly hypermethylated [2-fold increase of methylation index (MtI) in tumours] in 25/52 (48%) tumour samples compared with normal samples. MtI of the CYGB promoter was associated with CYGB mRNA expression (linear regression analysis, P=0.009), suggesting a primary role for the epigenetic events in CYGB silencing. In addition, frequent LOH was detected at the locus 17q25 in 32/48 (67%) tumours examined. It is of note that the loss of expression intensified when both LOH and hypermethylation coincided in samples (Mann-Whitney, P=0.049). These findings provide the first evidence to suggest the implication of CYGB in the pathogenesis of NSCLCs.