Demethylation of the synuclein gamma gene CpG island in primary gastric cancers and gastric cancer cell lines

Synuclein Proteins in Cancer Development and Progression

Synucleins are a family of small, soluble proteins mainly expressed in neural tissue and in certain tumors. Since their discovery, tens of thousands of scientific reports have been published about this family of proteins as they are associated with severe human diseases. Although the physiological function of these proteins is still elusive, their relationship with neurodegeneration and cancer has been clearly described over the years. In this review, we summarize data connecting synucleins and cancer, going from the structural description of these molecules to their involvement in tumor-related processes, and discuss the putative use of these proteins as cancer molecular biomarkers.

Intragenic β-synuclein rearrangements in malignancy

The synuclein family, consisting of α-, β-, and γ-synuclein, is primarily expressed in neurons. Mutations of α- and β-synuclein have been linked to Parkinson's disease and dementia with Lewy bodies, respectively. Recent studies have shown that synucleins are upregulated in various tumors, including breast, ovarian, meningioma, and melanoma, and high synuclein expression is associated with poor prognosis and drug resistance. We report a novel rearrangement of β-synuclein in a pediatric T-cell acute lymphoblastic leukemia (T-ALL) case, where β-synuclein (SNCB) is fused in-frame with ETS variant transcription factor 6 (ETV6), a gene frequently rearranged in acute leukemia including acute myeloid leukemia (AML), B-cell acute lymphoblastic leukemia (B-ALL), and T-ALL. An additional case of β-synuclein rearrangement was identified in a squamous cell carcinoma of the lung through analysis of the public TCGA database. Both rearrangements involve the C-terminal of β-synuclein. Since β-synuclein shares extensive amino acid similarities with α-synuclein and α-synuclein binds to 14-3-3, an important regulator of apoptosis, the rearranged β-synuclein may contribute to tumorigenesis by deregulating apoptosis. In addition, overexpression of synucleins has been shown to increase cell proliferation, suggesting that the rearranged β-synuclein may also deregulate the cell cycle.

Development of a novel autophagy-related gene model for gastric cancer prognostic prediction

Gastric cancer (GC) is a major global health issue and one of the leading causes of tumor-associated mortality worldwide. Autophagy is thought to play a critical role in the development and progression of GC, and this process is controlled by a set of conserved regulators termed autophagy-related genes (ATGs). However, the complex contribution of autophagy to cancers is not completely understood. Accordingly, we aimed to develop a prognostic model based on the specific role of ATGs in GC to improve the prediction of GC outcomes. First, we screened 148 differentially expressed ATGs between GC and normal tissues in The Cancer Genome Atlas (TCGA) cohort. Consensus clustering in these ATGs was performed, and based on that, 343 patients were grouped into two clusters. According to Kaplan–Meier survival analysis, cluster C2 had a worse prognosis than cluster C1. Then, a disease risk model incorporating nine differentially expressed ATGs was constructed based on the least absolute shrinkage and selection operator (LASSO) regression analysis, and the ability of this model to stratify patients into high- and low-risk groups was verified. The predictive value of the model was confirmed using both training and validation cohorts. In addition, the results of functional enrichment analysis suggested that GC risk is correlated with immune status. Moreover, autophagy inhibition increased sensitivity to cisplatin and exacerbated reactive oxygen species accumulation in GC cell lines. Collectively, the results indicated that this novel constructed risk model is an effective and reliable tool for predicting GC outcomes and could help with individual treatment through ATG targeting.

A new biomarker for the early diagnosis of gastric cancer: gastric juice- and serum-derived SNCG

Aim: To explore the possibility of gastric juice (GJ)- and serum-derived SNCG as a potential biomarker for the early diagnosis of gastric cancer (GC). Materials & methods: GJ and serum samples were collected from 87 patients with GC, 38 patients with gastric precancerous lesions and 44 healthy volunteers. The levels of SNCG in GJ and serum samples were detected by ELISA. Results: The levels of SNCG in GJ and serum were significantly higher in the GC group when compared with the GPL group or the control group. The expression of SNCG in GJ and serum was associated with tumor node metastasis stage, lymph node metastasis, tumor size and drinking, and it is important for the diagnosis and prognosis of GC (p < 0.05). Conclusion: The findings highlight the significance of SNCG in GC diagnosis and prognosis and implicate SNCG as a promising candidate for GC treatment.

Silencing of Synuclein-γ inhibits human cervical cancer through the AKT signaling pathway

BACKGROUND

Synuclein-γ has been demonstrated to be highly expressed in various human cancers including cervical cancer, and has been shown to play a critical role in tumor aggressiveness. We aimed to investigate the role of Synuclein-γ in human cervical cancer in vitro and in vivo.

METHOD

Reverse transcription-quantitative polymerase chain reaction assay and Western blot assay were used to detect the mRNA and protein expression, respectively. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and colony formation assay were performed to measure the viabilities of cancer cells. Flow cytometry assay was used to detect the cell cycle and apoptosis. Moreover, an animal experiment was performed to evaluate the biological behavior of Synuclein-γ in vivo.

RESULTS

In the current study, we found that Synuclein-γ was obviously over-expressed in cervical cancer tissues compared to the adjacent non-cancer tissues. Cervical cancer cells transfected with Synuclein-γ siRNA demonstrated significant inhibition of cancer proliferation (P < 0.01), cell cycle arrest at G0/G1 phase, and cell apoptosis (P < 0.05). Moreover, down-regulation of Synuclein-γ significantly inhibited cervical cancer growth in vivo. In addition, protein levels of AKT, c-Myc and Cyclin D1 were much lower in the Synuclein-γ siRNA-treated groups than that in the control group.

CONCLUSIONS

Synuclein-γ inhibition reduced cervical cancer tumor growth through the AKT pathway. This effect represented a therapeutic opportunity and provided a novel target for cervical cancer treatment.

Epigenetic Mechanisms and Events in Gastric Cancer-Emerging Novel Biomarkers

Gastric cancer is one of the most common malignancy worldwide. The various genetic and epigenetic events have been found to be associated with its carcinogenesis. The epigenetic is a heritable and transient/reversible change in the gene expression that is not accompanied by modification in the DNA sequence. This event is characterized by the alteration in the promoter CpG island of the gene or histone modification. These events are associated with silencing of critical tumor suppressor gene and activation of oncogenes leading to carcinogenesis. The DNA methylation is a chemical change in the DNA sequence that most commonly occurs at cytosine moiety of CpG dinucleotide and histone, primarily on N- terminal tail that ultimately effect the interaction of DNA with chromatin modifying protein.Hypermethylation of tumor suppressor genes and global hypomethylation of oncogenes are widely studied epigenetic modifications. There are large number of publish reports regarding epigenetic events involving gastric cancer. These changes are potentially useful in identifying markers for early diagnosis and management of this lethal malignancy. Also, role of specific miRNAs and long non coding RNAs in regulation of gene expression is gaining interest and is a matter of further investigation. In this review, we aimed to summarize major epigenetic events (DNA methylation) in gastric cancer along with alteration in miRNAs and long non coding RNAs which plays an important role in pathology of this poorly understood malignancy.

Hypoxia, Epithelial-Mesenchymal Transition, and TET-Mediated Epigenetic Changes

Tumor hypoxia is a pathophysiologic outcome of disrupted microcirculation with inadequate supply of oxygen, leading to enhanced proliferation, epithelial-mesenchymal transition (EMT), metastasis, and chemo-resistance. Epigenetic changes induced by hypoxia are well documented, and they lead to tumor progression. Recent advances show that DNA demethylation mediated by the Ten-eleven translocation (TET) proteins induces major epigenetic changes and controls key steps of cancer development. TET enzymes serve as 5mC (5-methylcytosine)-specific dioxygenases and cause DNA demethylation. Hypoxia activates the expression of TET1, which also serves as a co-activator of HIF-1α transcriptional regulation to modulate HIF-1α downstream target genes and promote epithelial-mesenchymal transition. As HIF is a negative prognostic factor for tumor progression, hypoxia-activated prodrugs (HAPs) may provide a favorable therapeutic approach to lessen hypoxia-induced malignancy.

γ-Synuclein Expression Is a Malignant Index in Oral Squamous Cell Carcinoma

Dysregulation of γ-synuclein (SNCG) has been reported in many cancers; however, its role in cancer development is still controversial. Here, we examined the potential involvement of DNA methylation in regulating SNCG and its role in oral squamous cell carcinoma (OSCC). We used 8 OSCC cell lines to investigate SNCG methylation and expression. SNCG methylation was examination by methylation-specific polymerase chain reaction and bisulfate sequencing. Cells showing a high degree of SNCG methylation were treated with 5-aza (methylation inhibitor), and changes in their methylation and expression profiles were analyzed. Functional effects of SNCG in OSCC were examined by its overexpression and knockdown. Additionally, methylation and expression of SNCG in OSCC tissues were investigated and correlated with clinicopathologic features. All OSCC cells showed detectable SNCG expression at the mRNA and protein levels. Methylation-specific polymerase chain reaction and bisulfate sequencing revealed high SNCG expression in SCC25 cells with the unmethylated allele, and their 15 CpG islands were unmethylated. The methylated allele was detected only in OEC-M1 cells exhibiting low SNCG expression, and their CpG islands were partially methylated. 5-aza treatment in OEC-M1 cells attenuated methylation and restored SNCG expression. SNCG overexpression increased colony forming, migration, and invasion abilities in OEC-M1 cells. Silencing SNCG in SCC25 cells suppressed these behaviors. All 25 tumor-adjacent normal tissues were negative for SNCG immunostaining. SNCG upregulation was frequently observed in dysplastic and OSCC tissues. Positive SNCG expression was found in 45% (37 of 82) OSCC tissues. Positive SNCG expression in OSCC significantly correlated with cancer staging and lymph node metastasis. However, SNCG methylation did not correlate with its expression and clinicopathologic variables in OSCC tissues. DNA methylation may participate in regulating SNCG expression in some OSCC cells. SNCG upregulation could be involved in OSCC progression.

Hypoxia-inducible lncRNA-AK058003 promotes gastric cancer metastasis by targeting γ-synuclein

Hypoxia has been implicated as a crucial microenvironmental factor that induces cancer metastasis. We previously reported that hypoxia could promote gastric cancer (GC) metastasis, but the underlying mechanisms are not clear. Long noncoding RNAs (lncRNAs) have recently emerged as important regulators of carcinogenesis that act on multiple pathways. However, whether lncRNAs are involved in hypoxia-induced GC metastasis remains unknown. In this study, we investigated the differentially expressed lncRNAs resulting from hypoxia-induced GC and normoxia conditions using microarrays and validated our results through real-time quantitative polymerase chain reaction. We found an lncRNA, AK058003, that is upregulated by hypoxia. AK058003 is frequently upregulated in GC samples and promotes GC migration and invasion in vivo and in vitro. Furthermore, AK058003 can mediate the metastasis of hypoxia-induced GC cells. Next, we identified γ-synuclein (SNCG), which is a metastasis-related gene regulated by AK058003. In addition, we found that the expression of SNCG is positively correlated with that of AK058003 in the clinical GC samples used in our study. Furthermore, we found that the SNCG gene CpG island methylation was significantly increased in GC cells depleted of AK058003. Intriguingly, SNCG expression is also increased by hypoxia, and SNCG upregulation by AK058003 mediates hypoxia-induced GC cell metastasis. These results advance our understanding of the role of lncRNA-AK058003 as a regulator of hypoxia signaling, and this newly identified hypoxia/lncRNA-AK058003/SNCG pathway may help in the development of new therapeutics.

Epigenetic alterations in gastric cancer (Review)

Gastric cancer is one of the most common types of cancer and the second most common cause of cancer-related mortality worldwide. An increasing number of recent studies have confirmed that gastric cancer is a multistage pathological state that arises from environmental factors; dietary factors in particulary are considered to play an important role in the etiology of gastric cancer. Improper dietary habits are one of the primary concerns as they influence key molecular events associated with the onset of gastric carcinogenesis. In the field of genetics, anticancer research has mainly focused on the various genetic markers and genetic molecular mechanisms responsible for the development of this of this disease. Some of this research has proven to be very fruitful, providing insight into the possible mechamisms repsonsible for this disease and into possible treatment modalities. However, the mortality rate associated with gastric cancer remains relatively high. Thus, epigenetics has become a hot topic for research, whereby genetic markers are bypassed and this research is directed towards reversible epigenetic events, such as methylation and histone modifications that play a crucial role in carcinogenesis. The present review focuses on the epigenetic events which play an important role in the development and progression of this deadly disease, gastric cancer.

Identification of γ-synuclein as a stage-specific marker in bladder cancer by immunohistochemistry

Background

Previous studies have shown that the expression level of γ-synuclein (SNCG) is associated with progression of many different malignant tumors. In this study, we discuss and assess the prognostic ability of SNCG in bladder cancer.

Material/Methods

Medical records (2005–2013) were retrospectively reviewed for the population of interest. SNCG expression was identified immunohistochemically from bladder cancer tissues of 113 bladder cancer patients. The survival rate was calculated by the Kaplan-Meier method. Cox proportional hazard regression model was used for analysis of predictors of bladder cancer.

Results

SNCG was overexpressed in bladder cancer tissues compared with the normal bladder tissues (p<0.0001). SNCG expression in bladder cancer tissue was strongly related to tumor stage. However, SNCG level was not a prognostic factor of survival.

Conclusions

Our results demonstrate that SNCG is highly expressed in bladder cancer tissue and its expression is stage-specific, but it is not helpful for predicting outcome in bladder cancer patients.

Synuclein-gamma predicts poor clinical outcome in esophageal cancer patients

The synuclein gamma (SNCG) protein, a member of neuronal protein family synuclein, has been considered as a promising potential biomarker as an indicator of cancer stage and survival in patients with cancer. The present study was conducted to evaluate the prognostic value of SNCG in patients with esophageal carcinoma (EC). SNCG levels were assessed immunohistochemically in cancer tissues from 73 EC patients. Median age was 57 (range, 29-78) years old. Forty-seven percent of the patients were male. Thirty-seven percent of the patients had upper or middle localized tumor whereas 59 % had epidermoid carcinoma. More than half of the patients (61 %) had undergone operation where 57 % received adjuvant treatment including chemotherapy or chemotherapy plus radiotherapy. Median overall survival was 11.3 ± 1.8 months (95% confidence interval (CI): 7.7-14.9 months). SNCG positivity was significantly associated with the histological type of EC and inoperability (for SNCG positive vs. negative group; epidermoid 80 vs. 53 %; p = 0.05 and inoperable 59 vs.32 %; p = 0.04, respectively). Lymph node metastasis, inoperability and receiving no adjuvant treatment had significantly adverse effect on survival in the univariate analysis (p = 0.01, p < 0.001, and p = 0.001, respectively). SNCG positivity had significantly adverse effect on survival in both univariate and multivariate analysis (p = 0.02 and p = 0.01, respectively). Our results are the first to suggest that SNCG is a new independent predictor for poor prognosis in EC patients in the literature.

DNA methylation regulates expression of VEGF-C, and S-adenosylmethionine is effective for VEGF-C methylation and for inhibiting cancer growth

DNA hypomethylation may activate oncogene transcription, thus promoting carcinogenesis and tumor development. S-adenosylmethionine (SAM) is a methyl donor in numerous methylation reactions and acts as an inhibitor of intracellular demethylase activity, which results in hypermethylation of DNA. The main objectives of this study were to determine whether DNA hypomethylation correlated with vascular endothelial growth factor-C (VEGF-C) expression, and the effect of SAM on VEGF-C methylation and gastric cancer growth inhibition. VEGF-C expression was assayed by Western blotting and RT-qPCR in gastric cancer cells, and by immunohistochemistry in tumor xenografts. VEGF-C methylation was assayed by bisulfite DNA sequencing. The effect of SAM on cell apoptosis was assayed by flow cytometry analyses and its effect on cancer growth was assessed in nude mice. The VEGF-C promoters of MGC-803, BGC-823, and SGC-7901 gastric cancer cells, which normally express VEGF-C, were nearly unmethylated. After SAM treatment, the VEGF-C promoters in these cells were highly methylated and VEGF-C expression was downregulated. SAM also significantly inhibited tumor growth in vitro and in vivo. DNA methylation regulates expression of VEGF-C. SAM can effectively induce VEGF-C methylation, reduce the expression of VEGF-C, and inhibit tumor growth. SAM has potential as a drug therapy to silence oncogenes and block the progression of gastric cancer.

Neural protein gamma-synuclein interacting with androgen receptor promotes human prostate cancer progression

Background

Gamma-synuclein (SNCG) has previously been demonstrated to be significantly correlated with metastatic malignancies; however, in-depth investigation of SNCG in prostate cancer is still lacking. In the present study, we evaluated the role of SNCG in prostate cancer progression and explored the underlying mechanisms.

Methods

First, alteration of SNCG expression in LNCaP cell line to test the ability of SNCG on cellular properties in vitro and vivo whenever exposing with androgen or not. Subsequently, the Dual-luciferase reporter assays were performed to evaluate whether the role of SNCG in LNCaP is through AR signaling. Last, the association between SNCG and prostate cancer progression was assessed immunohistochemically using a series of human prostate tissues.

Results

Silencing SNCG by siRNA in LNCaP cells contributes to the inhibition of cellular proliferation, the induction of cell-cycle arrest at the G1 phase, the suppression of cellular migration and invasion in vitro, as well as the decrease of tumor growth in vivo with the notable exception of castrated mice. Subsequently, mechanistic studies indicated that SNCG is a novel androgen receptor (AR) coactivator. It interacts with AR and promotes prostate cancer cellular growth and proliferation by activating AR transcription in an androgen-dependent manner. Finally, immunohistochemical analysis revealed that SNCG was almost undetectable in benign or androgen-independent tissues prostate lesions. The high expression of SNCG is correlated with peripheral and lymph node invasion.

Conclusions

Our data suggest that SNCG may serve as a biomarker for predicting human prostate cancer progression and metastasis. It also may become as a novel target for biomedical therapy in advanced prostate cancer.

Up-regulated expression of sulfatases (SULF1 and SULF2) as prognostic and metastasis predictive markers in human gastric cancer

Gastric cancer (GC) is the fourth most common cancer worldwide. In spite of the mortality incidence associated with GC, no reliable prognostic biomarkers are currently available for this malignancy. The sulfatases (or SULFs), SULF1 and SULF2, play a critical role in the pathogenesis of a variety of human cancers. We sought to evaluate the potential of SULFs as biomarkers for GC. Thirty pairs of GC and corresponding normal tissues were analysed for the expression and methylation status of SULFs. Furthermore, the functional role of SULF overexpression was investigated in GC cell lines and tumour xenograft animal models. Lastly, we validated the expression of SULF1 protein in a large cohort of 450 GC patients. GC tissues showed conspicuously higher expression of SULF1 (p = 0.0002) and SULF2 (p = 0.001) compared to normal mucosa, which was correlated with its promoter hypomethylation. Furthermore, high expression of SULFs caused marked acceleration in the growth of xenograft tumours in nude mice. The expression of SULF1 protein significantly correlated with higher recurrence rates (p = 0.0002) and worse overall survival (p < 0.0001) in GC patients. Multivariate analysis revealed that SULF1 is an independent prognostic (p = 0.0123) and lymph node metastasis predictive factor (p = 0.0003) in patients with GC. We provide novel evidence that hypomethylation of promoter CpG islands within SULF genes imparts them with oncogenic potential in GC. Moreover, our data suggest that SULF1 may serve as a promising biomarker for patients with GC.

Hypoxia upregulates ovarian cancer invasiveness via the binding of HIF-1α to a hypoxia-induced, methylation-free hypoxia response element of S100A4 gene

Hypoxia is known to play important roles in the development and progression of tumors. We previously demonstrated that S100A4, a critical molecule for metastasis, was upregulated in ovarian cancer cells. Therefore, we examined the mechanisms of the upregulation of S100A4 expression in ovarian carcinoma cells, with particular attention paid to the effects of hypoxia. The expression levels of S100A4 were found to be correlated with the invasiveness of ovarian carcinoma cells in vitro and in vivo, and the upregulation of S100A4 expression was associated with hypomethylation of CpG sites in the first intron of S100A4 in ovarian carcinoma cell lines and tissues. The expression of S100A4 was increased under hypoxia and was associated with elevated invasiveness, which was inhibited by S100A4 small interfering RNA (siRNA). In addition, exposure to hypoxia reduced the methylation of hypoxia-response elements (HRE) of the S100A4 gene in a time-dependent fashion, in association with the increased binding of HIF-1α to a methylation-free HRE in ovarian carcinoma cells. These results indicate that hypoxia-induced hypomethylation plays an essential role in S100A4 overexpression and the epigenetic transformation of ovarian carcinoma cells into the "metastatic phenotype."

Epigenetic inactivation of T-box transcription factor 5, a novel tumor suppressor gene, is associated with colon cancer

T-box transcription factor 5 (TBX5) is a member of a phylogenetically conserved family of genes involved in the regulation of developmental processes. The function of TBX5 in cancer development is largely unclear. We identified that TBX5 was preferentially methylated in cancer using methylation-sensitive arbitrarily primed PCR. We aim to clarify the epigenetic inactivation, biological function and clinical significance of TBX5 in colon cancer. Promoter methylation was evaluated by combined bisulfite restriction analysis and bisulfite genomic sequencing. Cell proliferation was examined by cell viability assay and colony formation assay, apoptosis by flow cytometry and cell migration by wound-healing assay. TBX5 target genes were identified by cDNA microarray analysis. Cox regression model and log-rank test were used to identify independent predictors of prognosis. TBX5 was silenced or downregulated in 88% (7/8) colon cancer cell lines, but was expressed in normal colon tissues. Loss of gene expression was associated with promoter methylation. The biological function of TBX5 in human colon cancer cells was examined. Re-expression of TBX5 in silenced colon cancer cell lines suppressed colony formation (P<0.001), proliferation (P<0.001), migration and induced apoptosis (P<0.01). Induction of apoptosis was mediated through cross-talk of extrinsic apoptosis pathway, apoptotic BCL2-associated X protein and Granzyme A signaling cascades. TBX5 suppressed tumor cell proliferation and metastasis through the upregulation of cyclin-dependent kinase inhibitor 2A, metastasis suppressor 1 and downregulation of synuclein gamma and metastasis-associated protein 1 family member 2. TBX5 methylation was detected in 68% (71/105) of primary colon tumors. Multivariate analysis showed that patients with TBX5 methylation had a significantly poor overall survival (P=0.0007). In conclusion, we identified a novel functional tumor suppressor gene TBX5 inactivated by promoter methylation in colon cancer. Detection of methylated TBX5 may serve as a potential biomarker for the prognosis of this malignancy.

DNA methylation and cancer

DNA methylation is one of the most intensely studied epigenetic modifications in mammals. In normal cells, it assures the proper regulation of gene expression and stable gene silencing. DNA methylation is associated with histone modifications and the interplay of these epigenetic modifications is crucial to regulate the functioning of the genome by changing chromatin architecture. The covalent addition of a methyl group occurs generally in cytosine within CpG dinucleotides which are concentrated in large clusters called CpG islands. DNA methyltransferases are responsible for establishing and maintenance of methylation pattern. It is commonly known that inactivation of certain tumor-suppressor genes occurs as a consequence of hypermethylation within the promoter regions and a numerous studies have demonstrated a broad range of genes silenced by DNA methylation in different cancer types. On the other hand, global hypomethylation, inducing genomic instability, also contributes to cell transformation. Apart from DNA methylation alterations in promoter regions and repetitive DNA sequences, this phenomenon is associated also with regulation of expression of noncoding RNAs such as microRNAs that may play role in tumor suppression. DNA methylation seems to be promising in putative translational use in patients and hypermethylated promoters may serve as biomarkers. Moreover, unlike genetic alterations, DNA methylation is reversible what makes it extremely interesting for therapy approaches. The importance of DNA methylation alterations in tumorigenesis encourages us to decode the human epigenome. Different DNA methylome mapping techniques are indispensable to realize this project in the future.

The reciprocal regulation of gamma-synuclein and IGF-I receptor expression creates a circuit that modulates IGF-I signaling

Insulin-like growth factor (IGF) system plays important roles in carcinogenesis and maintenance of the malignant phenotype. Signaling through the IGF-I receptor (IGF-IR) has been shown to stimulate the growth and motility of a wide range of cancer cells. γ-synuclein (SNCG) is primarily expressed in peripheral neurons but also overexpressed in various cancer cells. Overexpression of SNCG correlates with tumor progression. In the present study we demonstrated a reciprocal regulation of IGF-I signaling and SNCG expression. IGF-I induced SNCG expression in various cancer cells. IGF-IR knockdown or IGF-IR inhibitor repressed SNCG expression. Both phosphatidylinositol 3-kinase and mitogen-activated protein kinase were involved in IGF-I induction of SNCG expression. Interestingly, SNCG knockdown led to proteasomal degradation of IGF-IR, thereby decreasing the steady-state levels of IGF-IR. Silencing of SNCG resulted in a decrease in ligand-induced phosphorylation of IGF-IR and its downstream signaling components, including insulin receptor substrate (IRS), Akt, and ERK1/2. Strikingly, SNCG physically interacted with IGF-IR and IRS-2. Silencing of IRS-2 impaired the interaction between SNCG and IGF-IR. Finally, SNCG knockdown suppressed IGF-I-induced cell proliferation and migration. These data reveal that SNCG and IGF-IR are mutually regulated by each other. SNCG blockade may suppress IGF-I-induced cell proliferation and migration. Conversely, IGF-IR inhibitors may be of utility in suppressing the aberrant expression of SNCG in cancer cells and thereby block its pro-tumor effects.

DNA methylation of cancer genome

DNA methylation plays an important role in regulating normal development and carcinogenesis. Current understanding of the biological roles of DNA methylation is limited to its role in the regulation of gene transcription, genomic imprinting, genomic stability, and X chromosome inactivation. In the past 2 decades, a large number of changes have been identified in cancer epigenomes when compared with normals. These alterations fall into two main categories, namely, hypermethylation of tumor suppressor genes and hypomethylation of oncogenes or heterochromatin, respectively. Aberrant methylation of genes controlling the cell cycle, proliferation, apoptosis, metastasis, drug resistance, and intracellular signaling has been identified in multiple cancer types. Recent advancements in whole-genome analysis of methylome have yielded numerous differentially methylated regions, the functions of which are largely unknown. With the development of high resolution tiling microarrays and high throughput DNA sequencing, more cancer methylomes will be profiled, facilitating the identification of new candidate genes or ncRNAs that are related to oncogenesis, new prognostic markers, and the discovery of new target genes for cancer therapy.

Up-regulation of gamma-synuclein contributes to cancer cell survival under endoplasmic reticulum stress

Previous studies have demonstrated that gamma-synuclein is overexpressed in a variety of human malignancies. Overexpression of gamma-synuclein in human breast cancer cells leads to an increase in cell motility, resistance to chemotherapeutic drugs, and mitotic checkpoint dysfunction. We report in this study that gamma-synuclein is up-regulated by endoplasmic reticulum stress. The up-regulation of gamma-synuclein expression by endoplasmic reticulum stress is mediated, at least in part, by activation transcription factor (ATF) 4. Knockdown of gamma-synuclein sensitized human breast cancer cells to endoplasmic reticulum stress-induced apoptosis. Induction of apoptosis by endoplasmic reticulum stress when gamma-synuclein was inhibited was dependent on JNK or caspase activation, with caspase-3 and caspase-7 being involved. Treatment with the JNK or caspase-3 and caspase-7 inhibitor partially blocked endoplasmic reticulum stress-induced apoptosis in breast cancer cells transfected with or without the siRNA against gamma-synuclein. Taken together, these data suggest that gamma-synuclein may promote cancer progression by suppressing endoplasmic reticulum stress-induced apoptosis.

Relationship of SNCG, S100A4, S100A9 and LCN2 gene expression and DNA methylation in bladder cancer

Microarray analysis of paired cultures of normal and cancerous urothelial cells revealed differences in cytokeratin and adhesion gene expression. Normal cells expressed autocrine growth factor genes more strongly whereas carcinoma cells were distinguished by concomitant expression of urothelial and epidermal differentiation markers. Expression of SNCG, S100A9 and LCN2 was also enhanced. In other cancers, overexpression of SNCG, LCN2 and S100A4 has been ascribed to DNA hypomethylation. We therefore investigated expression and methylation of SNCG, S100A4, S100A9 and LCN2 in urothelial cancer cell lines and tissues. SNCG and S100A4 were overexpressed in some cancer tissues and cell lines, but downregulated in others, whereas LCN2 and S100A9 were upregulated in few cancer cell lines, but regularly in tissues. Normal and cancerous urothelial cells expressing SNCG lacked promoter methylation. SNCG downregulation was associated with hypermethylation and could be reversed by the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine. S100A4 methylation at regulatory intronic sites and in the promoter region was lowest in leukocytes and fibroblasts, and denser in urothelial cells. Gene expression responded to 5-aza-2'-deoxycytidine. LCN2 promoter methylation was variable and even less consistently related to expression. The S100A9 promoter was partially methylated in nonexpressing cells, but 5-aza-2'-deoxycytidine had no effect. Our data indicate that SNCG methylation is cell type-specific and the gene is hypermethylated in some urothelial cancers. S100A4, S100A9 and LCN2 are genes with moderate CpG-density that show a less stringent relationship between DNA methylation and gene expression. Therefore, changes in methylation of these genes in cancer should be interpreted cautiously.

Expression of synuclein g in gastric carcinoma and its relationship with MMP-2 and MMP-9

AIM: To study the expression and significance of synuclein g (SNCG) in gastric cancer, and to explore the relationship between SNCG and MMP-2, and MMP-9 in gastric carcinoma.

METHODS: Expression levels of SNCG protein, MMP-2, MMP-9 in sixty gastric cancer samples were detected using immuno-histochemical analysis and 20 paraffin wax samples of normal gastric mucosa were also detected and compared.

RESULTS: The positive rates of SNCG, MMP-2 and MMP-9 were higher in gastric carcinoma than in neighboring normal tissues (65%, 75%, 68.3% vs 0%, 25%, 20%, all P < 0.05). Their expression was positively correlated with depth of tumor infiltration, lymphatic metastasis, as well as the clinical staging of tumor (all P < 0.05). Expression of SNCG was also positively correlated with that of MMP-2 and MMP-9 (r = 0.383, 0.552, both P < 0.01). In addition, expression of MMP-2 was positively correlated with MMP-9 (r = 0.352, P < 0.01).

CONCLUSION: The aberrant expression of SNCG, MMP-2 and MMP-9 are likely to jointly participate in the process of genesis and development of gastric carcinoma, therefore the detection of SNCG, MMP-2 and MMP-9, which reflect the pathological characteristics of gastric cancer, could be regarded as a reference index.

Aberrant expression and demethylation of gamma-synuclein in colorectal cancer, correlated with progression of the disease

Recent evidence suggests that gamma-synuclein is abnormally expressed in a high percentage of tumor tissues of diversified cancer types, but rarely expressed in tumor-matched non-neoplastic adjacent tissues (NNAT). The molecular mechanism of CpG island demethylation may underlie aberrant gamma-synuclein expression. To fully understand the roles of aberrant gamma-synuclein expression and demethylation in the development of colorectal cancer (CRC), we examined the expression and methylation status of gamma-synuclein in 67 CRC samples, 30 NNAT samples, and five CRC cell lines as well. By using reverse transcription-polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry analyses, gamma-synuclein expression was detected in both HT-29 and HCT116 cells, and was much higher in CRC samples than in NNAT samples (P < 0.05). The demethylating agent, 5-aza-2 cent-deoxycytidine, can induce re-expression of gamma-synuclein in COLO205, LoVo, and SW480 cells. Unmethylated gamma-synuclein alleles were detected in HT-29, HCT116, and LoVo cells by nested methylation-specific PCR, and the demethylated status of gamma-synuclein was much higher in CRC samples than in NNAT samples by real-time quantitative methylation-specific PCR (P < 0.05). The results of genomic bisulfite DNA sequencing further confirmed that the aberrant gamma-synuclein expression in CRC was primarily attributed to the demethylation of CpG island. The protein expression and demethylation status of gamma-synuclein in 67 CRC samples correlated with clinical stage, lymph node involvement, and distant metastasis. These findings suggest an involvement of aberrant gamma-synuclein expression and demethylation in progression of CRC, especially in advanced stages.

Applications of novel monoclonal antibodies specific for synuclein-gamma in evaluating its levels in sera and cancer tissues from colorectal cancer patients

Overexpressions of synuclein-gamma (SNCG) in different cancers display stage-specific patterns. At present, appropriate anti-SNCG monoclonal antibodies (mAbs) with high specificity and affinity are unavailable for different immunoassays in clinical applications. In this study, we generated 10 mAbs against endogenous SNCG and evaluated SNCG levels in several colorectal cancer cell lines, serum samples and tumor tissues from colorectal cancer (CRC) patients. Elevated SNCG levels in cancer cell lines evaluated by a novel sandwich ELISA were consistent with data obtained from Western blot. Secreted SNCG protein levels in sera from CRC patients could be detected by the sandwich ELISA and were further confirmed by Western blot analysis following SNCG enrichment. Immunohistochemical results showed that SNCG was highly expressed in tumor cells of CRC patients, but was undetectable in the adjacent normal epithelium. Taken together, these novel anti-SNCG mAbs specifically recognized endogenous SNCG and were suitable for measuring SNCG levels in cell lysates, human serum samples, and tumor tissues. Elevated serum SNCG and overexpressed SNCG in tumor tissue from CRC patients suggest SNCG is a potential biomarker for CRC.

Advances in γ-Synuclein and progression of tumors

γ-Synuclein with strong tissue specificity, a member of the synuclein family, is mainly located in nervous system. Recently, elevated levels of γ-Synuclein was detected in various types of cancers, such as breast, ovarian, liver, gastric cancers, etc., especially in their advanced stages, which indicated loss of tissue specificity in cancer development and also suggested that γ-Synuclein might serve as a new tumor marker. Additionally, multiple pathways influence the regulation of γ-Synuclein expression. γ-Synuclein has also been shown to promote invasion and metastasis of breast and ovarian cancers and enhance caners' tolerance to some chemotherapies . Overexpression of γ-synuclein also interferes with drug-induced apoptotic responses, which makes it a potential target for treatment.

Targeting synuclein-gamma to counteract drug resistance in cancer

BACKGROUND

Expression of synuclein-gamma (SNCG) protein is elevated in the advanced stages of many types of cancers, including ovarian, lung, liver, esophagus, colon, prostate and, in particular, breast. In breast carcinoma, SNCG is causatively linked to stimulated proliferation, metastasis and drug resistance.

OBJECTIVE

To establish SNCG as a potential therapeutic target and to discuss clinical use of SNCG inhibiting peptide.

METHODS

This review focuses on the plausible mechanisms of SNCG activity, SNCG mediated drug resistance and its inhibition.

RESULTS/CONCLUSION

Evidence based research shows that the aberrant expression of SNCG has a strong correlation with breast cancer progression and poor clinical outcome. A peptide based inhibitor counters activity of SNCG, which may be developed as an adjuvant therapy.

Cytogenetic and molecular aspects of gastric cancer: clinical implications

Gastric cancer is of major importance world-wide being the second most common cause of cancer-related death in the world. According to Lauren's histological classification gastric cancer is divided in two groups, the better differentiated intestinal carcinomas and the poorly differentiated diffuse-type cancers. The genetic changes underlying the initiation and progression of gastric cancer are not well defined. Gastric carcinogenesis is a multistep process involving a number of genetic and epigenetic factors. Although it has been proposed that different genetic pathways exist for differentiated and undifferentiated carcinomas, the two histological subtypes of gastric cancer share some common genetic alterations. Currently, tumor histology and pathologic stage are the major prognostic variables used in the clinical practice for gastric cancer patients. However, it is known that tumors with similar morphology may differ in biological aggressiveness, prognosis and response to treatment. Molecular genetic analysis of gastric cancer revealed a number of associations of certain genetic changes with pathological features, tumor biological behavior and prognosis of gastric cancer patients, suggesting that these genetic abnormalities might play an important role in gastric tumorigenesis. Increasing evidence suggests that the molecular genetic changes could be helpful in the clinical setting, contributing to prognosis and management of patients. Regarding epigenetic events in gastric tumorigenesis, a number of methylating markers have been proposed for risk assessment, prognostic evaluation and as therapeutic targets. However, further research is required in order to systematically investigate the genetic changes in gastric cancer estimating also their usefulness in the clinical practice. A good understanding of the genetic changes underlying gastric carcinogenesis may provide new perspectives for prognosis and screening of high risk individuals. Some of the genetic alterations could definitely improve tumor classification and management of gastric cancer patients. Also, based on molecular data identified in gastric cancer novel therapeutics might help to improve the treatment of this disease.

Cigarette smoke induces demethylation of prometastatic oncogene synuclein-gamma in lung cancer cells by downregulation of DNMT3B

The prometastatic oncogene synuclein-gamma (SNCG) is not expressed in normal lung tissues, but it is highly expressed in lung tumors. Here, we show that cigarette smoke extract (CSE) has strong inducing effects on SNCG gene expression in A549 lung cancer cells through demethylation of SNCG CpG island. CSE treatment also augments the invasive capacity of A549 cells in an SNCG-dependent manner. To elucidate the mechanisms underlying the demethylating effects of CSE, we examined expression levels of DNA methyltransferases (DNMTs), 1, 3A and 3B in CSE-treated cells. We show that the mRNA expression of DNMT3B is specifically downregulated by CSE with a kinetics concurrent to SNCG reexpression. Utilizing siRNA to knockdown DNMT3B expression, we show that inhibition of DNMT3B directly increases SNCG mRNA expression. We further show that exogenous overexpression of DNMT3B in an SNCG-positive lung cancer cell line H292 suppresses SNCG mRNA and protein expression and induces de novo methylation of SNCG CpG island, whereas overexpression of DNMT1 or DNMT3A has no effects. Taken together, these new findings demonstrate that tobacco exposure induces the abnormal expression of SNCG in lung cancer cells through downregulation of DNMT3B. This work sheds light on the molecular understanding of demethylation of this oncogene during cancer progression.

Aberrant DNA methylation in non-neoplastic gastric mucosa of H. Pylori infected patients and effect of eradication

BACKGROUND

Gene promoter methylation is an epigenetic event leading to gene silencing. This mechanism is particularly relevant in cancer since it can interfere with the activity of specific "suppressor" genes.

AIM

To evaluate promoter methylation of CDH1, p16, APC, MLH1, and COX2 in patients with H. pylori (Hp) infection before and after eradication.

METHODS

Fifty-seven dyspeptic outpatients who had never performed previous endoscopy or Hp testing and treatment underwent clinical interview, endoscopy with three paired gastric biopsy specimens from the antrum, angulus, and corpus, and (13)C-urea breath test (UBT). Biopsies were scored for the presence of Hp and intestinal metaplasia (IM). DNA methylation of five tumor-related genes (CDH1, p16, MLH1, APC, and COX2) was evaluated by methylation-specific PCR in each biopsy. Infected patients were given a standard eradicating treatment and, after 1 yr, underwent endoscopy with biopsies and UBT.

RESULTS

Hp infection was found in 45 patients. IM was detected in 17 out of 45 (38%) infected patients. Mean number of methylated genes was 0, 1.1 +/- 0.9, and 1.6 +/- 0.9 among the 12 Hp-/IM-, the 28 Hp+/IM-, and the 17 Hp+/IM+ patients, respectively (P < 0.0001). Specifically, promoter hypermethylation of CDH1, p16, APC, MLH1, and COX2 was found in 68%, 25%, 7%, 0%, and 14% of Hp+/IM- patients and in 71%, 29%, 35%, 12%, and 12% of Hp+/IM+ patients. No significant difference was found among the three groups of patients as far as age, smoking, alcohol, meat and vegetable consumption, and family history of gastric cancer were considered. Twenty-three out of 45 (51%) infected patients underwent the 1-yr follow-up endoscopy: 17 out of 23 (74%) were successfully eradicated. After Hp eradication, CDH1, p16, and APC methylation significantly decreased while COX2 methylation completely disappeared. Conversely, MLH1 methylation did not change significantly in patients with IM.

CONCLUSION

Hp infection is associated with promoter methylation of genes which are relevant in the initiation and progression of gastric carcinogenesis. While CDH1 methylation seems to be an early event in Hp gastritis, MLH1 methylation occurs late along with IM. Hp eradication is able to significantly reduce gene methylation thus delaying or reversing Hp-induced gastric carcinogenesis.

Gamma-synuclein and the progression of cancer

The synucleins are a small, soluble, highly conserved group of neuronal proteins that have been implicated in both neurodegenerative diseases and cancer. The synuclein family consists of alpha-, beta-, and gamma-synucleins (gamma-syn). They are a natively unfolded group of proteins that share sequence homologies and structural properties. So far, the biological functions of the synucleins are still unclear, but their involvement in neurodegenerative diseases and cancer may provide insights into the pathological processes that result from these two groups of debilitating diseases, and present the possibility to use them as potential targets for early diagnosis and treatment. Recently, elevated levels of gamma-syn proteins have been detected in various types of cancer, especially in advanced stages of the disease. Furthermore, studies to date indicate that overexpression of gamma-syn compromises normal mitotic checkpoint controls, resulting in multinucleation as well as faster cell growth. Gamma-syn has also been shown to promote invasion and metastasis in in vitro assays as well as in animal models. Overexpression of gamma-syn also interferes with drug-induced apoptotic responses. These observations raise questions about the involvement of gamma-syn in the process of tumorigenesis and metastasis, and efforts have already been made to use gamma-syn as a marker for assessing breast cancer progression. This review will discuss the involvement of gamma-syn in cancer progression, metastasis and its potential as a marker.

DNA demethylation of vascular endothelial growth factor-C is associated with gene expression and its possible involvement of lymphangiogenesis in gastric cancer

Previous studies have indicated that lymphangiogenesis in solid tumors is associated with lymphatic metastasis. Overexpression of Vascular endothelial growth factor (VEGF)-C plays a major role in lymphangiogenesis in cancers. In the present study, DNA methylation and expression of the VEGF-C gene was investigated in gastric cancer (GC). Four GC cell lines (MKN-45, MKN-74, HSC-39 and HSC-43) showed no expression of VEGF-C, and the VEGF-C gene was found to be methylated in these cells. In contrast, 7 GC cell lines (MKN-1, MKN-7, MKN-28, TMK-1, KATO-III, SH101-P4 and HSC-44PE) expressed VEGF-C, and the VEGF-C gene was found to be unmethylated in these cell lines. In addition, expression of VEGF-C mRNA was retrieved by treatment with a demethylating agent, Aza-2'-deoxycytidine. In GC tissue samples, bisulfite DNA sequencing analysis revealed that VEGF-C was not methylated in 9 (29.0%) of 31 GC samples, whereas demethylation was not observed in corresponding non-neoplastic mucosa samples. Overexpression of VEGF-C mRNA was observed in 16 (51.6%) of 31 GC samples by quantitative reverse transcription-polymerase chain reaction. Of the 9 GC cases with VEGF-C demethylation, 8 (88.9%) overexpressed VEGF-C. In contrast, of the 22 GC cases without VEGF-C demethylation, 8 (36.4%) overexpressed VEGF-C (p = 0.0155). Furthermore, lymphatic vessel density determined by immunostaining of podoplanin in GC tissues was associated with overexpression of VEGF-C (p < 0.0001). These results suggest that demethylation and activation of the VEGF-C gene is likely involved in lymphangiogenesis in GC.

Opa interacting protein 5 (OIP5) is a novel cancer-testis specific gene in gastric cancer

BACKGROUND

Identification of novel cancer-specific antigens is important for the advancement of immunotherapy. Our aim was to identify cancer-specific genes in gastric cancer.

METHODS

Using cDNA microarray analysis, we detected genes overexpressed specifically in gastric cancer cells. The expression levels of selected genes, including OIP5, was confirmed by real time RT-PCR analysis in tumor/normal paired bulk samples of 58 clinical cases. The expression levels of selected genes in normal tissues were also determined with a human total RNA master panel. We also compared the expression status of OIP5 with that of the other known cancer-testis specific genes.

RESULTS

Twenty-two genes were determined to be upregulated in gastric cancer cells. Among these, three genes (CDC6, Exo1, and OIP5) were selected and confirmed to be upregulated in the tumor tissue compared to normal tissue. A human total RNA master panel demonstrated that OIP5, but not Exo1 or CDC6, showed high specificity in testis. Thus OIP5 may be considered a cancer-testis specific gene. In 58 clinical cases of gastric cancer examined, we found OIP5 gene expression in 27 cases (47%). Thirteen of these 27 cases showed no expression of the known cancer specific genes such as MAGE-1, MAGE-3 or NY-ESO-1.

CONCLUSIONS

Using a combination of LMD and microarray, we identified OIP5 as a cancer-testis specific gene. Further expression analysis in a set of clinical cases revealed that OIP5 may be a novel immunotherapy target for patients with gastric cancer.

Regulatory mechanisms for abnormal expression of the human breast cancer specific gene 1 in breast cancer cells

Breast cancer-specific gene 1 (BCSG1), also referred as synuclein y, was originally isolated from a human breast cancer cDNA library and the protein is mainly localized to presynaptic terminals in the nervous system. BCSG1 is not expressed in normal or benign breast lesions, but expressed at an extremely high level in the vast majority of the advanced staged breast carcinomas and ovarian carcinomas. Overexpression of BCSG1 in cancer cells led to significant increase in cell proliferation, motility and invasiveness, and metastasis. To elucidate the molecular mechanism and regulation for abnormal transcription of BCSG1, a variety of BCSG1 promoter luciferase reporters were constructed including 3' end deleted sequences, Sp1 deleted, and activator protein-1 (AP1) domains mutated. Transient transfection assay was used to detect the transcriptional activation of BCSG1 promoters. Results showed that the Sp1 sequence in 5'-flanking region was involved in the basal transcriptional activities of BCSG1 without cell-type specificity. In comparison to pGL3-1249, the reporter activities of pGL3-1553 in BCSG1-negative MCF-7 cells and pGL3-1759 in HepG2 cells were notably decreased. Mutations at AP1 sites in BCSG1 intron 1 significantly reduced the promoter activity in all cell lines. Transcription factors, c-jun, c-fos and cyclin AMP-responsive element binding (CREB) protein, could markedly enhance the promoter activities. Thus, our results suggest that the abnormal expression of BCSG1 in breast cancer cells is likely regulated by multiple mechanisms. The 5' flanking region of BCSG1 provides the basal transcriptional activity without cell type specificity. A critical promoter element involved in abnormal expression of BCSG1 presents in the first exon. The cell type specificity of BCSG1 transcription is probably affected through intronic cis-regulatory sequences. AP1 domains in the first intron play an important role in control of BCSG1 transcription.

DNA demethylation and carcinogenesis

DNA methylation plays an important role in the establishment and maintenance of the program of gene expression. Tumor cells are characterized by a paradoxical alteration of DNA methylation pattern: global DNA demethylation and local hypermethylation of certain genes. Hypermethylation and inactivation of tumor suppressor genes are well documented in tumors. The role of global genome demethylation in carcinogenesis is less studied. New data provide evidence for independence of DNA hypo- and hypermethylation processes in tumor cells. These processes alter expression of genes that have different functions in malignant transformation. Recent studies have demonstrated that global decrease in the level of DNA methylation is related to hypomethylation of repeated sequences, increase in genetic instability, hypomethylation and activation of certain genes that favor tumor growth, and increase in their metastatic and invasive potential. The recent data on the role of DNA demethylation in carcinogenesis are discussed in this review. The understanding of relationships between hypo- and hypermethylation in tumor cells is extremely important due to reversibility of DNA methylation and attempts to utilize for anti-tumor therapy the drugs that modify DNA methylation pattern.

Alterations of tumor suppressor and tumor-related genes in the development and progression of gastric cancer

The development and progression of gastric cancer involves a number of genetic and epigenetic alterations of tumor suppressor and tumor-related genes. The majority of differentiated carcinomas arise from intestinal metaplastic mucosa and exhibit structurally altered tumor suppressor genes, typified by p53, which is inactivated via the classic two-hit mechanism, i.e. loss of heterozygosity (LOH) and mutation of the remaining allele. LOH at certain chromosomal loci accumulates during tumor progression. Approximately 20% of differentiated carcinomas show evidence of mutator pathway tumorigenesis due to hMLH1 inactivation via hypermethylation of promoter CpG islands, and exhibit high-frequency microsatellite instability. In contrast, undifferentiated carcinomas rarely exhibit structurally altered tumor suppressor genes. For instance, while methylation of E-cadherin is often observed in undifferentiated carcinomas, mutation of this gene is generally associated with the progression from differentiated to undifferentiated carcinomas. Hypermethylation of tumor suppressor and tumor-related genes, including APC, CHFR, DAP-kinase, DCC, E-cadherin, GSTP1, hMLH1, p16, PTEN, RASSF1A, RUNX3, and TSLC1, can be detected in both differentiated and undifferentiated carcinomas at varying frequencies. However, the significance of the hypermethylation varies according to the analyzed genomic region, and hypermethylation of these genes can also be present in non-neoplastic gastric epithelia. Promoter demethylation of specific genes, such as MAGE and synuclein γ, can occur during the progressive stages of both histological types, and is associated with patient prognosis. Thus, while the molecular pathways of gastric carcinogenesis are dependent on histological background, specific genetic alterations can still be used for risk assessment, diagnosis, and prognosis.

Loss of epigenetic control of synuclein-gamma gene as a molecular indicator of metastasis in a wide range of human cancers

Metastasis is a major contributing factor to poor prognosis in cancer. Reliable and sensitive biomarkers that indicate the development of metastasis of primary tumors would be of great clinical use. In this study, we show that the neuronal protein synuclein-gamma (SNCG) is abnormally expressed in a high percentage (67.5%) of tumor tissues of diversified cancer types, including liver, esophagus, colon, gastric, lung, prostate, cervical, and breast cancer, but rarely expressed in tumor-matched nonneoplastic adjacent tissues (0.6%). Expressions of SNCG protein in different cancer types all display stage-specific patterns of very low expression in stage I and high expression in stages II to IV. Importantly, we observe a strong association between SNCG protein expression in primary tumors with distant metastasis in patients regardless of the cancer type (60.6%, P < 0.001). By performing genomic sequencing and methylation-specific PCR assays, we identify an inclusive demethylation of CpG sites within the CpG island of SNCG gene in every tumor sample (100%) across all cancer types, illustrating a universal loss of the epigenetic control of SNCG gene expression in tumors and further demonstrating that the demethylation of SNCG CpG island is primarily responsible for the aberrant expression of SNCG protein in cancerous tissues. These new findings strongly suggest that reactivation of SNCG gene expression by DNA demethylation is a common critical contributing factor to malignant progression of many solid tumors and its expression in primary carcinomas is an effective molecular indicator of distant metastasis. Our studies also suggest that the methylation status of SNCG gene can be used as a sensitive molecular tool in early detections of tumorigenesis.

The epigenetics of cancer etiology

Epigenetic dysregulation is central to cancer development and progression. This dysregulation includes hypomethylation leading to oncogene activation and chromosomal instability, hypermethylation and tumor suppressor gene silencing, and chromatin modification acting directly, and cooperatively with methylation changes, to modify gene expression. In addition, disrupted genomic imprinting appears to contribute to colorectal cancer risk, and serves as a gatekeeper in Wilms tumor. A cancer predisposing disorder, Beckwith-Wiedemann syndrome, usually arises from epigenetic errors, solidifying the causal role of epigenetics in cancer. While cancer epigenetics has been reviewed extensively elsewhere, the main focus of this review will be to present the view that epigenetics and genetics are complementary in the area of cancer etiology, the focus of this volume. I propose a hypothesis in which epigenetic alterations contribute to tumor progression, but they also increase the probability that genetic changes, when they occur, will lead to cancer initiation. This hypothesis could contribute to a new understanding of the role of environmental carcinogens that may not be fully explained through a purely genetic view or by tests, such as bacterial mutation frequency, that ignore epigenetic factors.

Identify lymphatic metastasis-associated genes in mouse hepatocarcinoma cell lines using gene chip

AIM: In order to obtain lymphogenous metastasis-associated genes, we compared the transcriptional profiles of mouse hepatocarcinoma cell lines Hca-F with highly lymphatic metastasis potential and Hca-P with low lymphatic metastasis potential.

METHODS: Total RNA was isolated from Hca-F and Hca-P cells and synthesized into double-stranded cDNA. In vitro transcription double-stranded cDNA was labeled with biotin (i.e., biotin-labeled cRNA, used as the probe). The cRNA probes hybridized with Affymetrix GeneChip^® MOE430A (containing 22690 transcripts, including 14500 known mouse genes and 4371 ESTs) respectively and the signals were scanned by the GeneArray Scanner. The results were then analyzed by bioinformatics.

RESULTS: Out of the 14500 known genes investigated, 110 (0.8%) were up regulated at least 2³ fold. Among the total 4371 ESTs, 17 ESTs (0.4%) (data were not presented) were up regulated at least 2³ fold. According to the Gene Ontology and TreeView analysis, the 110 genes were further classified into two groups: differential biological process profile and molecular function profile.

CONCLUSION: Using high-throughput gene chip method, a large number of genes and their cellular functions about angiogenesis, cell adhesion, signal transduction, cell motility, transport, microtubule-based process, cytoskeleton organization and biogenesis, cell cycle, transcription, chaperone activity, motor activity, protein kinase activity, receptor binding and protein binding might be involved in the process of lymphatic metastasis and deserve to be used as potential candidates for further investigation. Cyclin D1, Fosl1, Hsp47, EGFR and AR, and Cav-1 are selected as the possible candidate genes of the metastatic phenotype, which need to be validated in later experiments. ESTs (data were not presented) might indicate novel genes associated with lymphatic metastasis. Validating the function of these genes is helpful to identify the key or candidate gene/pathway responsible for lymphatic metastasis, which might be used as the diagnostic markers and the therapeutic targets for lymphatic metastasis.