Synuclein Gamma Expression Research Articles

Long Noncoding RNA Solute Carrier Family 25 Member 21 Antisense RNA 1 Inhibits Cell Malignant Behaviors and Enhances Radiosensitivity of Gastric Cancer Cells by Upregulating Synuclein Gamma Expression.

Long noncoding RNAs (LncRNAs) were reported to be implicated in the progression of gastric cancer (GC). This study aimed to explore the role of solute carrier family 25 member 21 antisense RNA 1 (SLC25A21-AS1) in radiosensitivity of GC cells. In the present study, reverse transcription quantitative polymerase chain reaction (RT-qPCR) showed that the expression of SLC25A21-AS1 and synuclein gamma (SNCG) was downregulated in GC tissues and cells, while the expression of microRNA-15a-5p (miR-15a-5p) was upregulated in GC tissues and cells. The expression of SLC25A21-AS1 was elevated in GC cells after radiation treatment. SLC25A21-AS1 overexpression enhanced GC cell radiosensitivity, inhibited cell proliferation and promoted apoptosis. SLC25A21-AS1 overexpression also facilitated the DNA damage caused by radiation in GC cells. Mechanically, SLC25A21-AS1 interacted with miR-15a-5p and negatively regulated miR-15a-5p expression in GC cells. SNCG was directly targeted by miR-15a-5p at the 3' untranslated region (3'UTR). In GC tissues, the expression of SNCG was negatively correlated with that of miR-15a-5p, but was positively correlated with that of SLC25A21-AS1. Rescue assays revealed that SNCG silencing rescued the tumor-suppressive effect of overexpressed SLC25A21-AS1 on GC cells. The enhanced radiosensitivity caused by SLC25A21-AS1 overexpression was also reduced by SNCG knockdown. In conclusion, lncRNA SLC25A21-AS1 inhibits cell malignant behaviors and enhances cell radiosensitivity in GC by elevating SNCG expression.

Effect of synuclein-gamma on malignant progression in human prostate cancer

Objective To study the expression and significance of synuclein-gamma (SNCG) in human prostate cancer.Methods SNCG expression in the prostate epithelial cell line (RWPE-1) and the hormone-dependent prostate cancer cell lines (LNCaP,CWR22) was detected by using reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting.The immunohistochemistry was performed to investigate the expression of SNCG in the normal prostate tissue,prostatitis tissue,benign prostatic hyperplasia (BPH) tissue,high-grade prostatic intraepithelial neoplasia,and hormone-dependent prostate cancer (HDPC) tissue.Results The expression of SNCG in hormone-dependent prostate cancer cell line was significantly higher than that in prostate epithelial cell line.Almost no SNCG was detectable in benign prostate specimens (10 normal prostate tissues,10 prostatitis tissues,and 10 BPH tissues),SNCG was partially expressed in high-grade prostatic intraepithelial neoplasia (3/10),and the expression was elevated to a high level in HDPC tissues (the positive rate 60.66％,74/122).Combined with the SNCG stain score and the clinicopathological parameters of the corrresponding PCa patients,we found that SNCG protein expression was associated with middle-high-risk PCa characterized by prostate specific antigen (PSA) ≥ 10 μg/L,Gleason score≥7,and clinical stage≥T2b,and correlated with lymph node metastasis.Conclusion These results suggested that abnormal expression of SNCG may be involved in malignant progression of PCa. Key words: Synuclein-gamma ; Prostate cancer; Immunohistochemistry

Expression of synuclein gamma indicates poor prognosis of triple-negative breast cancer

Synuclein gamma (SNCG), previously identified as breast cancer-specific gene 1, is highly expressed in malignant cells but not in normal epithelium. Studies have demonstrated that the expression of SNCG is an independent predictive marker for recurrence and metastasis in breast cancer. Triple-negative breast cancer (TNBC) is characterized by a lack of expression of both the estrogen receptor and progesterone receptor proteins as well as HER-2 and is often associated with particularly poor outcomes, early development of chemotherapy resistance, and ineffectiveness of targeted therapy. This study aimed to reveal whether SNCG-positive TNBC is more likely than SNCG-negative TNBC to have a more aggressive phenotype. One hundred and two TNBC patients were divided into two groups according to the SNCG protein expression. Clinical and biological features of SNCG-positive tumors were compared with SNCG-negative tumors. Association between survival and SNCG expression was analyzed by the Kaplan-Meier method. Hazard ratios and 95 % confidence intervals (CIs) were calculated using Cox regression. And 34.3 % TNBCs showed moderate to strong positive SNCG expression. Patients whose tumors expressed SNCG had significantly shorter disease-free survival (P = 0.013) and a higher probability of death (P = 0.002) when compared with those whose tumors did not express SNCG. The hazard ratio of metastasis or recurrence based on SNCG expression status was 2.800 (95 % CI 1.193-6.574; P = 0. 018). There was no significant correlation between SNCG expression and age, lymph node involvement, and tumor stage histological type, except tumor size which was significantly associated with SNCG expression (P = 0.032, R = 0.212). This study suggests that SNCG expression indicates [Symbol: see text]correlates with?[Symbol: see text] a much poorer prognosis of TNBC. SNCG is expected to be a useful marker for TNBC progression and a potential target for TNBC treatment.

SNCG gene silencing in gallbladder cancer cells inhibits key tumorigenic activities

We recently determined that synuclein-gamma (SNCG) is highly expressed in human gallbladder cancer (GBC), and its abnormal expression is associated with tumor aggressiveness. To investigate the effects of SNCG gene silencing on the tumorigenic profiles of the GBC cell line, NOZ, short-hairpin RNA (shRNA) interference was employed. Specifically, the SNCG transcript was targeted by SNCG-shRNA lentiviral particles designed to silence SNCG gene expression. Following selection of NOZ cells stably expressing SNCG-shRNA, SNCG expression was examined by western blot and semi-quantitative RT-PCR analyses. Phenotypic hallmarks of gallbladder carcinogenesis were assayed by CCK-8, soft agar (colony formation), modified Boyden-Chamber (invasion), and flow cytometry (cell-cycle and apoptosis) assays. Our results showed that SNCG gene silencing in NOZ cells inhibited cell growth, colony formation, and invasion. In addition, it directly increased the effectiveness of paclitaxel in inducing G2/M cell-cycle arrest and cell apoptosis. Data from our in vivo study showed a decrease in tumor growth and weight in mice injected with SNCG-silenced NOZ cells. Together, these findings suggest that SNCG plays an important role in the progression of GBC.

Synuclein γ Stimulates Membrane-Initiated Estrogen Signaling by Chaperoning Estrogen Receptor (ER)-α36, a Variant of ER-α

Synuclein gamma (SNCG), previously identified as a breast cancer-specific gene, is highly expressed in malignant cancer cells but not in normal epithelium. The molecular targets of SNCG during breast cancer progression have not been fully identified. Here we analyzed the effect of SNCG on stimulation of membrane-initiated estrogen signaling. While SNCG expression enhanced estrogen-induced activation of ERK1/2 and mammalian target of rapamycin, knockdown of endogenous SNCG decreased membrane-initiated estrogen signaling. SNCG functions as a molecular chaperone protein for estrogen receptor (ER)-alpha36, a membrane-based variant of ER-alpha. SNCG bound to ER-alpha36 in the presence and absence of functional molecular chaperone heat shock protein 90. Disruption of heat shock protein 90 with 17-AAG significantly reduced ER-alpha36 expression and membrane-initiated estrogen signaling. However, expression of SNCG prevented ER-alpha36 degradation and completely recovered 17-AAG-mediated down-regulation of estrogen signaling. The function of SNCG in ER-alpha36-mediated estrogen signaling is consistent with its ability to stimulate cell growth in response to estrogen. Expression of SNCG also renders tamoxifen resistance, which is consistent with the clinical observation on the association of ER-alpha36 expression and tamoxifen resistance. The present study indicates that ER-alpha36 is a new member of the ER-alpha family that mediates membrane-initiated estrogen signaling and that SNCG can replace the function of heat shock protein 90, chaperone ER-alpha36 activity, stimulate ligand-dependent cell growth, and render tamoxifen resistance.

Abstract 3548: Role of synuclein-gamma (SNCG) in paclitaxel resistance and mitogen activated protein kinase activation in uterine papillary serous carcinoma(UPSC)

Abstract Objectives: SNCG is a novel prognostic biomarker in UPSC. We have shown that its overexpression correlates with aggressive cellular properties and resistance to paclitaxel in a UPSC cell line (SPEC2) as well as poor prognosis in a pilot set of UPSC patients. The goal of this study was to determine the mechanism of SNCG-associated taxane resistance by evaluating the effect of SNCG on the mitotic checkpoint and its propensity to modulate extracellular signal-regulated protein kinase 1/2 (ERK 1/2) signaling pathways. Methods: A stably transfected SPEC2 cell line was created using shSNCG versus shControl oligonucleotides. Similarly, Ishikawa cells were transiently transfected with an SNCG expression vector versus empty vector. Differences in cell proliferation were measured using a cell viability assay and BrdU incorporation assay after treatment with paclitaxel. Cell cycle analysis was used to study the effect of SNCG on the mitotic checkpoint. Differences in expression of the checkpoint kinase BubR1 due to SNCG were studied using real time PCR, Western blot, 26S ubiquitin-proteasome inhibition, and siRNA to BubR1. ERK and phospho-ERK levels were measured in SPEC2 cells with and without SNCG expression by Western blot. SPEC2 cells were treated with paclitaxel with and without the MEK inhibitor UO126 and apoptosis was measured using cleaved PARP analysis. Results: SNCG overexpression lead to acquired, reversible paclitaxel resistance in endometrial cancer cell lines. SNCG was noted to interfere with mitotic checkpoint function by causing degradation of the critical checkpoint protein BubR1 thereby allowing cells to escape paclitaxel-induced mitotic arrest. SPEC2 cells exhibited sustained activation of ERK which was attenuated by silencing SNCG. When SPEC2 cells were exposed to paclitaxel combined with the MEK inhibitor UO126, decreased cell viability and increased apoptosis was noted compared to either agent alone. SNCG knockdown further enhanced paclitaxel and UO126 sensitivity. Cell cycle analysis revealed that silencing SNCG in SPEC2 cells and adding UO126 acted synergistically in overcoming paclitaxel resistance. Conclusions: SNCG overexpression in UPSC leads to taxane resistance by interacting with the mitotic checkpoint kinase BubR1 causing its degradation. SNCG is also associated with sustained ERK activation. Targeting SNCG in conjunction with MEK inhibition may represent a novel therapeutic strategy to overcome taxane resistance in these cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3548.

Expression of neuronal protein synuclein gamma gene as a novel marker for breast cancer prognosis

Synucleins are emerging as central players in the fundamental neural processes and in the formation of pathologically insoluble deposits characteristic of neurodegenerative diseases. However, synuclein gamma (SNCG), previously identified as a breast cancer specific gene (BCSG1), is also highly expressed in breast carcinomas, but not expressed in normal or benign breast tissues. We analyzed SNCG gene expression in 93 clinical breast specimens and associated it with clinical outcome. Overall SNCG mRNA expression was detectable in 36% breast cancers. However, 81% of stage III/IV breast cancers were positive for SNCG expression, while only 15% of stage I/II breast cancers were positive for SNCG expression. In contrast, SNCG was undetectable in benign breast lesions. Expression of SNCG in the primary tumor also significantly associated with lymph node involvement and metastasis. There was no significant correlation between SNCG gene expression and age, menstruation, and status of ER, PR, PCNA, and HER-2. Patients whose tumors expressed SNCG had a significantly shorter DFS and a high probability of death when compared with those whose tumors did not express SNCG. The hazard ratio of metastasis or recurrence according to the SNCG status was 4.515 (95% CI, 1,188-17.154; P = 0.027). Cox multivariate analysis showed that SNCG had independent prognostic significance above and beyond conventional variables. This study suggests that the expression of SNCG is an independent predictive marker for recurrence and metastasis in breast cancer progression. SNCG is expected to be a useful marker for breast cancer progression and a potential target for breast cancer treatment.

Inhibition of synuclein-γ expression increases the sensitivity of breast cancer cells to paclitaxel treatment

Anti-microtubule drugs that cause mitotic arrest and subsequent apoptosis of cancer cells are frequently used to treat breast cancer patients with advanced or metastatic diseases. However, patient response rates to this class of chemotherapeutic agents vary significantly. Identification of cellular and genetic factors that are associated with the sensitivity to anti-microtubule drug treatment would have great clinical implications. Our previous studies have demonstrated that the neuronal protein, synuclein-gamma (SNCG), plays oncogenic roles in breast carcinogenesis and is abnormally expressed at high levels in advanced and metastatic breast carcinomas but not expressed in normal or benign breast tissues. In this study, we show that responses of 12 breast cancer cell lines to paclitaxel-induced mitotic arrest and cytotoxicity highly correlate with SNCG expression status. SNCG-positive cells exhibit a significant higher resistance to paclitaxel-induced mitotic arrest than SNCG-negative cells (p<0.01). Moreover, we demonstrate that down-regulation of SNCG expression directly increased the effectiveness of anti-microtubule drug-induced cytotoxicity in breast cancer cells without altering cell responses to doxorubicin. These new findings suggest that SNCG expression in breast carcinomas is probably a causal factor contributing to the poor patient response to paclitaxel treatment.

Abnormal activation of the synuclein-gamma gene in hepatocellular carcinomas by epigenetic alteration

Liver cancer is the fifth most common neoplastic disease and the fourth leading cause of cancer-related death. Identification of the key molecular targets involved in hepatocarcinogenesis has significant therapeutic implications. In this study, by conducting immunohistochemistry, we show that the neuronal protein, synuclein-gamma (SNCG), is abnormally expressed in a high percentage of liver cancer (46/70, 65.7%). The expression of SNCG in liver cancer exhibits a clear stage-specific pattern of low expression in stage I (1/19, 5.3%) and high expression in stages III to IV (44/50, 88%). Importantly, all patients with metastatic diseases expressed SNCG in their primary tumors (15/15, 100%). Consistent with the IHC results, RT-PCR assays demonstrate that SNCG mRNA is highly expressed in the tumor tissue of advanced hepatocellular carcinomas. Analyses of the methylation status of the CpG island of the SNCG gene by methylation-specific PCR confirmed that all tumor samples contained the demethylated gene. To determine whether demethylation of SNCG is an early event of genetic abnormality in the process of hepatocarcinogenesis, we examined the methylation status of SNCG in 70 non-malignant cirrhotic liver samples and showed that 64.3% cirrhotic liver samples contained the partially or completely demethylated gene. We further show that SNCG expression in liver cancer is not restricted to HBV- and HCV-infected tumors, implying the involvement of other hepatocarcinogenic risk factors in SNCG gene reactivation. Utilizing human hepatoma-derived cell line HepG2 as an in vitro model, we demonstrate that hepatic carcinogens aflatoxin B1 and N-nitrosodimethylamine (DMN) are strong inducers of SNCG expression. Collectively, these new findings suggest that SNCG protein expression in primary tumors is a strong indicator of distant metastasis and demethylation of SNCG CpG island is an early sign of genetic abnormality in liver cirrhosis preceding hepatocarcinogenesis. Our studies also suggest that inducing demethylation of SNCG by hepatocarcinogens may represent one underlying mechanism for the aberrant expression of SNCG in HCC.

Synuclein Gamma Inhibits the Mitotic Checkpoint Function and Promotes Chromosomal Instability of Breast Cancer Cells

Aberrant expressions of the neuronal protein synuclein gamma (SNCG) in malignant mammary epithelial cells are strongly associated with the progression of breast cancer. SNCG is not expressed in normal breast tissues but abundantly expressed in a high percentage of invasive and metastatic breast carcinomas. Several studies have demonstrated that SNCG expression significantly stimulates proliferation, invasion, and metastasis of breast cancer cells. To elucidate the molecular and cellular mechanisms underlying the tumorigenic functions of SNCG, we investigated the effects of SNCG expression on the mitotic checkpoint function of breast cancer cells. By conducting several different lines of investigations, we now demonstrate that SNCG expression in breast cancer cells overrides the mitotic checkpoint control and confers the cellular resistance to anti-microtubule drug-caused apoptosis. We further show that the inhibitory effects of SNCG on mitotic checkpoint can be overthrown by enforced overexpression of the mitotic checkpoint protein BubR1 in SNCG-expressing cells. These new findings combined with our previous observation that SNCG intracellularly associates with BubR1 together suggest that SNCG expression compromises the mitotic checkpoint control by inhibition of the normal function of BubR1, thereby promoting genetic instability. Genetic instability is recognized as an important contributing factor in tumorigenesis. Hence, our studies gain insight into the mechanisms whereby SNCG expression advances breast cancer disease progression and fasters tumor metastasis.

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

Whereas synuclein gamma (SNCG) gene expression is usually highly tissue-specific and restricted to the nervous system, SNCG is expressed in advanced-stage breast and ovarian cancers. When overexpressed, SNCG stimulates cancer cell proliferation and metastasis. It is thought that the molecular mechanism of CpG island demethylation may underlie aberrant SNCG expression. To determine whether aberrant SNCG expression and demethylation play a role in gastric carcinogenesis, we examined the expression and methylation status of SNCG in primary gastric cancers, gastric cancer cell lines, and non-neoplastic gastric mucosal tissues. Ten gastric cancer cell lines, 105 primary gastric cancers, and 10 non-neoplastic gastric mucosal tissues were examined. SNCG expression and methylation status were examined by reverse transcription-PCR and bisulfite-single-strand conformational polymorphism followed by direct sequencing, respectively. The relationship between SNCG methylation status and various clinicopathological factors of the primary gastric cancers was then analyzed. SNCG mRNA expression was observed in 5 of 10 cell lines. Analysis of cell lines positive for SNCG expression revealed that most of the SNCG CpGs were demethylated. SNCG mRNA was not expressed in the 10 non-neoplastic gastric mucosal tissues, although several CpGs were demethylated. Of the 105 primary gastric cancers, 40 (38.1%) showed apparent SNCG demethylation, similar to the result obtained using cell lines. SNCG demethylation was more frequent in primary gastric cancers positive for lymph node metastasis (51%; 26 of 51) than in cancers without lymph node involvement (26%; 14 of 54; P < 0.05), and also more common in stage II-IV (48%; 27 of 56) than in stage I (27%; 13 of 49) cancers (P < 0.05). Aberrant SNCG gene expression can occur via CpG island demethylation, and tends to occur during the more progressive stages of gastric carcinogenesis.

Transcriptional suppression of synuclein γ (SNCG) expression in human breast cancer cells by the growth inhibitory cytokine oncostatin M

Previously, we have shown that synuclein gamma (SNCG), a member of the brain protein synuclein family, is highly expressed in human infiltrating breast carcinomas but not expressed in normal or benign breast tissues. The SNCG mRNA was also detected in several human breast cancer cell lines with the highest expression found in H3922, a cell line derived from an infiltrating ductal carcinoma. In this study, we show that expression of SNCG mRNA in H3922 cells is significantly decreased by treating cells with the cytokine oncostatin M (OM) who has a growth-inhibitory effect on these cells. A decrease in SNCG mRNA level can be detected as early as 30 min after OM addition. By 4 h OM treatment, the level of SNCG mRNA was decreased to 70% of control, and by 24 h the mRNA was below detectable level. Western blot analysis further demonstrated the suppression of SNCG protein expression by OM. The level of SNCG protein in H3922 cells was reduced more than 90% by OM after 2 days. Since OM-induced growth inhibition occurs after 3-4 days, the down-regulation of SNCG expression appears to proceed the effect of OM on cell growth. Additional experiments to measure the transcriptional rates of SNCG indicate that the observed OM-induced down-regulation of SNCG mRNA occurs mainly at the transcriptional level. In an attempt to examine the role of SNCG gene in the proliferation of breast cancer cells, SNCG cDNA was stably transfected into MCF-7 cells that do not express endogenous SNCG gene. Examination of cell growth under anchorage-dependent and anchorage-independent conditions demonstrates that over expression of SNCG gene significantly stimulated the growth of MCF-7 cells both in monolayer culture and in soft agar. These data together suggest that SNCG may play a role in cell proliferation.