RASSF6 is a novel member of the RASSF family of tumor suppressors

A Bayesian fine-mapping model using a continuous global-local shrinkage prior with applications in prostate cancer analysis

The aim of fine mapping is to identify genetic variants causally contributing to complex traits or diseases. Existing fine-mapping methods employ Bayesian discrete mixture priors and depend on a pre-specified maximum number of causal variants, which may lead to sub-optimal solutions. In this work, we propose a Bayesian fine-mapping method called h2-D2, utilizing a continuous global-local shrinkage prior. We also present an approach to define credible sets of causal variants in continuous prior settings. Simulation studies demonstrate that h2-D2 outperforms current state-of-the-art fine-mapping methods such as SuSiE and FINEMAP in accurately identifying causal variants and estimating their effect sizes. We further applied h2-D2 to prostate cancer analysis and discovered some previously unknown causal variants. In addition, we inferred 369 target genes associated with the detected causal variants and several pathways that were significantly over-represented by these genes, shedding light on their potential roles in prostate cancer development and progression.

The Hippo signaling pathway contributes to the 2,5-Hexadion-induced apoptosis of ovarian granulosa cells

Although n-hexane can induce ovarian damage by inducing ovarian granulosa cell (GC) apoptosis, the mechanism underlying this induction of apoptosis has not been fully elucidated. In this study, rat ovarian GCs were exposed to different concentrations of 2,5-hexanedione (2,5-HD) (the main metabolite of n-hexane) in vitro to observe apoptosis, and the mechanism was further explored via mRNA microarray analysis. Hoechst 33258 staining and flow cytometry suggested that the apoptosis rate of ovarian GC apoptosis was significantly increased in the 2,5-HD-treated group. Subsequently, microarray analysis revealed that a total of 5677 mRNAs were differentially expressed, and further GO and KEGG analyses revealed that the differentially expressed genes were significantly enriched in many signaling pathways, including the Hippo pathway. A total of 7 differentially expressed genes that function upstream of the Hippo signaling pathway (Nf2, Wwc1, Ajuba, Llgl1, Dlg3, Rassf6 and Rassf1) were selected to confirm the microarray results by qRT-PCR, and the expression of these genes did change. Subsequently, the expression of key effector genes (Yap1, Mst1 and Lats1) and target genes (Ctgf and Puma) of the Hippo signaling was measured, and the results suggested that the mRNA and protein levels of Yap1, Mst1, Lats1, and Ctgf were significantly decreased while those of Puma were significantly increased after 2,5-HD treatment. Further CO-IP analysis suggested that the interaction between YAP1 and TEAD was significantly reduced after 2,5-HD treatment, while the interaction between YAP1 and P73 was not affected. In summary, during the 2,5-HD-induced apoptosis of ovarian GCs, the Hippo signaling pathway is inhibited, and downregulation of the pro-proliferation gene Ctgf and upregulated of the pro-apoptosis gene Puma are important. Decreased Ctgf expression was associated with decreased binding of YAP1 to TEAD. However, increased PUMA expression was not associated with YAP1 binding to P73.

Novel Biomarkers for Inflammatory Bowel Disease and Colorectal Cancer: An Interplay between Metabolic Dysregulation and Excessive Inflammation

Persistent inflammation can trigger altered epigenetic, inflammatory, and bioenergetic states. Inflammatory bowel disease (IBD) is an idiopathic disease characterized by chronic inflammation of the gastrointestinal tract, with evidence of subsequent metabolic syndrome disorder. Studies have demonstrated that as many as 42% of patients with ulcerative colitis (UC) who are found to have high-grade dysplasia, either already had colorectal cancer (CRC) or develop it within a short time. The presence of low-grade dysplasia is also predictive of CRC. Many signaling pathways are shared among IBD and CRC, including cell survival, cell proliferation, angiogenesis, and inflammatory signaling pathways. Current IBD therapeutics target a small subset of molecular drivers of IBD, with many focused on the inflammatory aspect of the pathways. Thus, there is a great need to identify biomarkers of both IBD and CRC, that can be predictive of therapeutic efficacy, disease severity, and predisposition to CRC. In this study, we explored the changes in biomarkers specific for inflammatory, metabolic, and proliferative pathways, to help determine the relevance to both IBD and CRC. Our analysis demonstrated, for the first time in IBD, the loss of the tumor suppressor protein Ras associated family protein 1A (RASSF1A), via epigenetic changes, the hyperactivation of the obligate kinase of the NOD2 pathogen recognition receptor (receptor interacting protein kinase 2 [RIPK2]), the loss of activation of the metabolic kinase, AMP activated protein kinase (AMPKα1), and, lastly, the activation of the transcription factor and kinase Yes associated protein (YAP) kinase, that is involved in proliferation of cells. The expression and activation status of these four elements are mirrored in IBD, CRC, and IBD-CRC patients and, importantly, in matched blood and biopsy samples. The latter would suggest that biomarker analysis can be performed non-invasively, to understand IBD and CRC, without the need for invasive and costly endoscopic analysis. This study, for the first time, illustrates the need to understand IBD or CRC beyond an inflammatory perspective and the value of therapeutics directed to reset altered proliferative and metabolic states within the colon. The use of such therapeutics may truly drive patients into remission.

Revealing the Roles of MOAP1 in Diseases: A Review

Modulator of apoptosis protein1 (MOAP1), also known as MAP1 and PNMA4, belongs to the PNMA gene family consisting of at least 15 genes located on different chromosomes. MOAP1 interacts with the BAX protein, one of the most important apoptosis regulators. Due to its critical role in a few of disease-associated pathways, MOAP1 is associated with many diseases such as cancers and neurological diseases. In this study, we introduced MOAP1 and its biological functions and reviewed the associations between MOAP1 and a few diseases including cancers, neurological diseases, and other diseases such as inflammation and heart diseases. We also explained possible biological mechanisms underlying the associations between MOAP1 and these diseases, and discussed a few future directions regarding MOAP1, especially its potential roles in neurodegenerative disorders. In summary, MOAP1 plays a critical role in the development and progression of cancers and neurological diseases by regulating a few genes related to cellular apoptosis such as BAX and RASSF1A and interacting with disease-associated miRNAs, including miR-25 and miR1228.

Analysis of somatic copy number alterations in biliary tract carcinoma using a single nucleotide polymorphism array

Aim:

Biliary tract carcinoma (BTC), including gall bladder carcinoma (GBC) and biliary duct carcinoma (BDC), has a poor prognosis. Comprehensive genomic profiling has important roles in evaluation of the carcinogenesis of BTC.

Materials & methods:

We examined somatic copy number alterations (SCNAs) using a single nucleotide polymorphism array system to analyze 36 BTC samples (11 GBCs and 25 BDCs).

Results:

In hierarchical cluster analysis, two clusters were identified (subgroup 1 with low SCNAs and subgroup 2 with high SCNAs). GBC was predominant in subgroup 1, whereas BDC was predominant in subgroup 2, suggesting that GBC and BDC had different genetic backgrounds in terms of SCNAs.

Conclusion:

These findings could be helpful for establishing the molecular carcinogenesis of BTCs.

Biliary tract carcinoma, including gall bladder carcinoma (GBC) and biliary duct carcinoma (BDC), has a poor prognosis. Comprehensive genomic (single nucleotide polymorphism-array) profiling plays important roles in evaluation of the carcinogenesis of biliary tract carcinoma. In the hierarchical cluster analysis, two clusters were identified (subgroup 1 with low somatic copy number alterations [SCNAs] and subgroup 2 with high SCNAs); GBC was found to be predominant in subgroup 1, whereas BDC was predominant in subgroup 2. These findings suggested that GBC and BDC had different genetic backgrounds in terms of SCNAs.

DNA damage triggers the nuclear accumulation of RASSF6 tumor suppressor protein via CDK9 and BAF53 to regulate p53-target gene transcription

RASSF6, a member of the tumor suppressor Ras-association domain family (RASSF) proteins, regulates cell cycle arrest and apoptosis via p53 and plays a tumor suppressor role. We previously reported that RASSF6 blocks MDM2-mediated p53 degradation and enhances p53 expression. In this study, we demonstrated that RASSF6 has nuclear-localization and nuclear-export signals and that DNA damage triggers the nuclear accumulation of RASSF6. We found that RASSF6 directly binds to BAF53, the component of SWI/SNF complex. DNA damage induces CDK9-mediated phosphorylation of BAF53, which enhances the interaction with RASSF6 and increases the amount of RASSF6 in the nucleus. Subsequently, RASSF6 augments the interaction between BAF53 and BAF60a, another component of SWI/SNF complex, and further promotes the interaction of BAF53 and BAF60a with p53. BAF53 silencing or BAF60a silencing attenuates RASSF6-mediated p53-target gene transcription and apoptosis. Thus, RASSF6 is involved in the regulation of DNA damage-induced complex formation including CDK9, BAF53, BAF60a, and p53.

Characterization of mouse embryonic fibroblasts derived from Rassf6 knockout mice shows the implication of Rassf6 in the regulation of NF-κB signaling

RASSF6 is a member of the tumor suppressor Ras association domain family (RASSF) proteins. We have reported using human cancer cell lines that RASSF6 induces apoptosis and cell cycle arrest via p53 and plays tumor suppressive roles. In this study, we generated Rassf6 knockout mice by CRISPR/Cas technology. Contrary to our expectation, Rassf6 knockout mice were apparently healthy. However, Rassf6-null mouse embryonic fibroblasts (MEF) were resistant against ultraviolet (UV)-induced apoptosis/cell cycle arrest and senescence. UV-induced p53-target gene expression was compromised, and DNA repair was delayed in Rassf6-null MEF. More importantly, KRAS active mutant promoted the colony formation of Rassf6-null MEF but not the wild-type MEF. RNA sequencing analysis showed that NF-κB signaling was enhanced in Rassf6-null MEF. Consistently, 7,12-dimethylbenz(a)anthracene (DMBA) induced skin inflammation in Rassf6 knockout mice more remarkably than in the wild-type mice. Hence, Rassf6 deficiency not only compromises p53 function but also enhances NF-κB signaling to lead to oncogenesis.

A "Janus" face of the RASSF4 signal in cell fate

RASSF4 (Ras-association domain family 4) is a protein-coding gene, regarded as a tumor suppressor regulated by DNA methylation. However, RASSF4 acts as a "Janus" in cell fate: death and survival. This review article focuses on the regulatory mechanisms of RASSF4 on cell death and cell survival and puts forward a comprehensive analysis of the relevant signaling pathways. The participation of RASSF4 in the regulation of intracellular store-operated Ca²⁺ entry also affects cell survival. Moreover, the mechanism of inducing abnormal expression of RASSF4 was summarized. We highlight recent advances in our knowledge of RASSF4 function in the development of cancer and other clinical diseases, which may provide insight into the controversial functions of RASSF4 and its potential application in disease therapy.

Ras Variant Biology and Contributions to Human Disease

Analysis of cancer and RASopathy genetic databases reveals that ~19% of all cancer cases and ~4% of developmental disorders contain Ras mutations. Ras isoform and mutation variants differentially contribute to these diseases and provide an opportunity for deeper understanding of Ras function. The putative mechanisms underpinning these differences, new approaches that are being applied, and some of the key questions and challenges that remain are discussed.

Genome-wide association study and functional analyses for clinical and subclinical ketosis in Holstein cattle

Ketosis is one of the most frequent metabolic diseases in high-yielding dairy cows and is characterized by high concentrations of ketone bodies in blood, urine, and milk, causing high economic losses. The search for polymorphic genes, whose alleles have different effects on resistance to developing the disease, is of extreme importance to help select less susceptible animals. The aims of this study were to identify genomic regions associated with clinical and subclinical ketosis (β-hydroxybutyrate concentration) in North American Holstein dairy cattle and to investigate these regions to identify candidate genes and metabolic pathways associated with these traits. To achieve this, a GWAS was performed for 4 traits: clinical ketosis lactation 1, clinical ketosis lactation 2 to 5, subclinical ketosis lactation 1, and subclinical ketosis lactation 2 to 5. The estimated breeding values from 77,277 cows and 7,704 bulls were deregressed and used as pseudophenotypes in the GWAS. The top-20 genomic regions explaining the largest proportion of the genetic variance were investigated for putative genes associated with the traits through functional analyses. Regions of interest were identified on chromosomes 2, 5, and 6 for clinical ketosis lactation 1; 3, 6, and 7 for clinical ketosis lactation 2 to 5; 1, 2, and 12 for subclinical ketosis lactation 1; and 20, 11, and 25 for subclinical ketosis lactation 2 to 5. The highlighted genes potentially related to clinical and subclinical ketosis included ACAT2 and IGF1. Enrichment analysis of the list of candidate genes for clinical and subclinical ketosis showed molecular functions and biological processes involved in fatty acid metabolism, lipid metabolism, and inflammatory response in dairy cattle. Several genomic regions and SNPs related to susceptibility to ketosis in dairy cattle that were previously described in other studies were confirmed. The novel genomic regions identified in this study aid to characterize the most important genes and pathways that explain the susceptibility to clinical and subclinical ketosis in dairy cattle.

Emerging strategies for sensitization of therapy resistant tumors toward cancer therapeutics by targeting the Bcl-2 family, TGF-β, Wnt/β-Catenin, RASSF and miRNA regulated signaling pathways

Conventional chemotherapy relies on the cytotoxicity of chemo-drugs to inflict destructive effects on tumor cells. However, as most tumor cells develop resistance to chemo-drugs, small doses of chemo-drugs are unlikely to provide significant clinical benefits in cancer treatment while high doses of chemo-drugs have been shown to impact normal human cells negatively due to the non-specific nature and cytotoxicity associated with chemo-drugs. To overcome this challenge, sensitizations of tumor cells with bioactive molecules that specifically target the pro-survival and pro-apoptosis signaling pathways of the tumor cells are likely to increase the therapeutic impacts and improve the clinical outcomes by reducing the dependency and adverse effects associated with using high doses of chemo-drugs in cancer treatment. This review focuses on emerging strategies to enhance the sensitization of tumor cells toward cancer therapies based on our understanding of tumor cell biology and underlying signaling pathways.

RASSF effectors couple diverse RAS subfamily GTPases to the Hippo pathway

Small guanosine triphosphatases (GTPases) of the RAS superfamily signal by directly binding to multiple downstream effector proteins. Effectors are defined by a folded RAS-association (RA) domain that binds exclusively to GTP-loaded (activated) RAS, but the binding specificities of most RA domains toward more than 160 RAS superfamily GTPases have not been characterized. Ten RA domain family (RASSF) proteins comprise the largest group of related effectors and are proposed to couple RAS to the proapoptotic Hippo pathway. Here, we showed that RASSF1-6 formed complexes with the Hippo kinase ortholog MST1, whereas RASSF7-10 formed oligomers with the p53-regulating effectors ASPP1 and ASPP2. Moreover, only RASSF5 bound directly to activated HRAS and KRAS, and RASSFs did not augment apoptotic induction downstream of RAS oncoproteins. Structural modeling revealed that expansion of the RASSF effector family in vertebrates included amino acid substitutions to key residues that direct GTPase-binding specificity. We demonstrated that the tumor suppressor RASSF1A formed complexes with the RAS-related GTPases GEM, REM1, REM2, and the enigmatic RASL12. Furthermore, interactions between RASSFs and RAS GTPases blocked YAP1 nuclear localization. Thus, these simple scaffolds link the activation of diverse RAS family small G proteins to Hippo or p53 regulation.

The RAS-interacting chaperone UNC119 drives the RASSF6-MDM2-p53 axis and antagonizes RAS-mediated malignant transformation

The gene encoding the proto-oncogene GTPase RAS is frequently mutated in human cancers. Mutated RAS proteins trigger antiapoptotic and cell-proliferative signals and lead to oncogenesis. However, RAS also induces apoptosis and senescence, which may contribute to the eradication of cells with RAS mutations. We previously reported that Ras association domain family member 6 (RASSF6) binds MDM2 and stabilizes the tumor suppressor p53 and that the active form of KRAS promotes the interaction between RASSF6 and MDM2. We also reported that Unc-119 lipid-binding chaperone (UNC119A), a chaperone of myristoylated proteins, interacts with RASSF6 and regulates RASSF6-mediated apoptosis. In this study, using several human cancer cell lines, quantitative RT-PCR, RNAi-based gene silencing, and immunoprecipitation/-fluorescence and cell biology assays, we report that UNC119A interacts with the active form of KRAS and that the C-terminal modification of KRAS is required for this interaction. We also noted that the hydrophobic pocket of UNC119A, which binds the myristoylated peptides, is not involved in the interaction. We observed that UNC119A promotes the binding of KRAS to RASSF6, enhances the interaction between RASSF6 and MDM2, and induces apoptosis. Conversely, UNC119A silencing promoted soft-agar colony formation, migration, and invasiveness in KRAS-mutated cancer cells. We conclude that UNC119A promotes KRAS-mediated p53-dependent apoptosis via RASSF6 and may play a tumor-suppressive role in cells with KRAS mutations.

A prognostic 11-DNA methylation signature for lung squamous cell carcinoma

Background

Lung squamous cell carcinoma (LUSC), as the second frequent subtype of lung cancer, causes lots of mortalities primarily due to a lack of precise prognostic markers and timely treatment intervention. Previous studies have constructed several risk prognostic models based on DNA methylation sites in multiple tumors, whereas, DNA methylation signature of LUSC remains to be built, and its predictive value need to be evaluated.

Methods

The genome-wide DNA methylation data of LUSC samples was obtained from The Cancer Genome Atlas dataset. Univariate Cox analysis and the least absolute shrinkage and selection operator (LASSO) were implemented to identify DNA methylation sites related to overall survival of LUSC patients. Thus, we performed multivariate Cox regression to establish a DNA methylation signature. The Kaplan-Meier (K-M) survival curves and time-dependent receiver operating characteristic (ROC) curves were plotted to estimate the prognostic power of the signature. Comparison with other known prognostic biomarkers, our DNA methylation signature showed higher predictive specificity and sensitivity. In addition, multivariate Cox regression screened out independent prognostic factors and constructed a nomogram.

Results

Several statistical methods were performed to construct an 11-DNA methylation signature. LUSC patients were divided into low- and high-risk group based on risk score, and high-risk group had a shorter survival time. According to the results of K-M and ROC analyses, the 11-DNA methylation signature showed significant sensitivity and specificity in predicting the LUSC patients’ overall survival. Finally, we integrated some independent prognostic factors (risk score, metastasis stage, and tobacco smoking history) to construct a nomogram, which has excellent prognostic power and may provide guidance for the therapeutic strategies.

Conclusions

We constructed the first risk prognosis model based on DNA methylation site in LUSC, which showed better predictive ability. In addition, a nomogram integrating the DNA methylation signature, metastasis stage, and tobacco smoking history was developed.

The role of miR-155 in cigarette smoke-induced pulmonary inflammation and COPD

Chronic obstructive pulmonary disease (COPD) is a highly prevalent respiratory disease characterized by airflow limitation and chronic inflammation. MiR-155 is described as an ancient regulator of the immune system. Our objective was to establish a role for miR-155 in cigarette smoke (CS)-induced inflammation and COPD. We demonstrate increased miR-155 expression by RT-qPCR in lung tissue of smokers without airflow limitation and patients with COPD compared to never smokers and in lung tissue and alveolar macrophages of CS-exposed mice compared to air-exposed mice. In addition, we exposed wild type and miR-155 deficient mice to CS and show an attenuated inflammatory profile in the latter. Alveolar macrophages were sorted by FACS from the different experimental groups and their gene expression profile was analyzed by RNA sequencing. This analysis revealed increased expression of miR-155 targets and an attenuation of the CS-induced increase in inflammation-related genes in miR-155 deficient mice. Moreover, intranasal instillation of a specific miR-155 inhibitor attenuated the CS-induced pulmonary inflammation in mice. Finally, elastase-induced emphysema and lung functional changes were significantly attenuated in miR-155 deficient mice. In conclusion, we highlight a role for miR-155 in CS-induced inflammation and the pathogenesis of COPD, implicating miR-155 as a new therapeutic target in COPD.

RASSF6-TRIM16 axis promotes cell proliferation, migration and invasion in esophageal squamous cell carcinoma

Ras-association (RA) domain family number 6 (RASSF6) is a member of the Ras-association domain protein family. It is epigenetically inactive and negatively regulates the malignant progression of some tumors. However, its precise role in esophageal squamous cell carcinoma (ESCC) has not been reported. In this study, we performed immunohistochemistry (IHC) assay. The results show that RASSF6 is upregulated in ESCC and that the elevated expression level of RASSF6 is associated with lymph node metastasis and poor survival of ESCC patients. Consistent with the clinical observations, the upregulation of RASSF6 greatly promotes ESCC cell proliferation, migration and invasion as well as the cell cycle transition to G1/S phase in vitro. According to models in vivo, the downregulation of RASSF6 considerably inhibits ESCC tumor growth and lung metastasis. Mechanistically, RASSF6 negatively regulates the tumor suppressor tripartite-motif-containing protein 16 (TRIM16) by promoting its ubiquitination-dependent degradation and eventually activates pathways associated with the cell cycle and epithelial-mesenchymal transition (EMT). Together, these results indicate that the RASSF6-TRIM16 axis is a key effector in ESCC progression and that RASSF6 serves as a potential target for the treatment of ESCC.

The Role and Function of Ras-association domain family in Cancer: A Review

Ras gene mutation has been observed in more than 30% of cancers, and 90% of pancreatic, lung and colon cancers. Ras proteins (K-Ras, H-Ras, N-Ras) act as molecular switches which are activated by binding to GTP. They play a role in the cascade of cell process control (proliferation and cell division). In the inactive state, transforming GTP to GDP leads to the activation of GTpase in Ras gene. However, the mutation in Ras leads to the loss of internal GTPase activity and permanent activation of the protein. The activated Ras can promote the cell death or stop cell growth, which are facilitated by Ras-association domain family. Various studies have been conducted to determine the importance of losing RASSF proteins in Ras-induced tumors. This paper examines the role of Ras and RASSF proteins. In general, RASSF proteins can be used as a suitable means for targeting a large group of Ras-induced tumors.

The Cross-Talk Between the TNF-α and RASSF-Hippo Signalling Pathways

The regulation of cell death through apoptosis is essential to a number of physiological processes. Defective apoptosis regulation is associated with many abnormalities including anomalies in organ development, altered immune response and the development of cancer. Several signalling pathways are known to regulate apoptosis including the Tumour Necrosis Factor-α (TNF-α) and Hippo signalling pathways. In this paper we review the cross-talk between the TNF-α pathway and the Hippo signalling pathway. Several molecules that tightly regulate the Hippo pathway, such as members of the Ras-association domain family member (RASSF) family proteins, interact and modulate some key proteins within the TNF-α pathway. Meanwhile, TNF-α stimulation also affects the expression and activation of core components of the Hippo pathway. This implies the crucial role of signal integration between these two major pathways in regulating apoptosis.

TCF4 (E2-2) harbors tumor suppressive functions in SHH medulloblastoma

The TCF4 gene encodes for the basic helix-loop-helix transcription factor 4 (TCF4), which plays an important role in the development of the central nervous system (CNS). Haploinsufficiency of TCF4 was found to cause Pitt-Hopkins syndrome (PTHS), a severe neurodevelopmental disorder. Recently, the screening of a large cohort of medulloblastoma (MB), a highly aggressive embryonal brain tumor, revealed almost 20% of adult patients with MB of the Sonic hedgehog (SHH) subtype carrying somatic TCF4 mutations. Interestingly, many of these mutations have previously been detected as germline mutations in patients with PTHS. We show here that overexpression of wild-type TCF4 in vitro significantly suppresses cell proliferation in MB cells, whereas mutant TCF4 proteins do not to the same extent. Furthermore, RNA sequencing revealed significant upregulation of multiple well-known tumor suppressors upon expression of wild-type TCF4. In vivo, a prenatal knockout of Tcf4 in mice caused a significant increase in apoptosis accompanied by a decreased proliferation and failed migration of cerebellar granule neuron precursor cells (CGNP), which are thought to be the cells of origin for SHH MB. In contrast, postnatal in vitro and in vivo knockouts of Tcf4 with and without an additional constitutive activation of the SHH pathway led to significantly increased proliferation of CGNP or MB cells. Finally, publicly available data from human MB show that relatively low expression levels of TCF4 significantly correlate with a worse clinical outcome. These results not only point to time-specific roles of Tcf4 during cerebellar development but also suggest a functional linkage between TCF4 mutations and the formation of SHH MB, proposing that TCF4 acts as a tumor suppressor during postnatal stages of cerebellar development.

The RASSF6 Tumor Suppressor Protein Regulates Apoptosis and Cell Cycle Progression via Retinoblastoma Protein

RASSF6 is a member of the tumor suppressor Ras association domain family (RASSF) proteins. RASSF6 is frequently suppressed in human cancers, and its low expression level is associated with poor prognosis. RASSF6 regulates cell cycle arrest and apoptosis and plays a tumor suppressor role. Mechanistically, RASSF6 blocks MDM2-mediated p53 degradation and enhances p53 expression. However, RASSF6 also induces cell cycle arrest and apoptosis in a p53-negative background, which implies that the tumor suppressor function of RASSF6 does not depend solely on p53. In this study, we revealed that RASSF6 mediates cell cycle arrest and apoptosis via pRb. RASSF6 enhances the interaction between pRb and protein phosphatase. RASSF6 also enhances P16INK4A and P14ARF expression by suppressing BMI1. In this way, RASSF6 increases unphosphorylated pRb and augments the interaction between pRb and E2F1. Moreover, RASSF6 induces TP73 target genes via pRb and E2F1 in a p53-negative background. Finally, we confirmed that RASSF6 depletion induces polyploid cells in p53-negative HCT116 cells. In conclusion, RASSF6 behaves as a tumor suppressor in cancers with loss of function of p53, and pRb is implicated in this function of RASSF6.

RASSF6-mediated inhibition of Mcl-1 through JNK activation improves the anti-tumor effects of sorafenib in renal cell carcinoma

Ras association domain family member 6 (RASSF6) has been shown to act as a tumor suppressor and predictor of poor prognosis in renal cell carcinoma (RCC). However, little is known about the effects of RASSF6 on sorafenib resistance or the underlying mechanism. Here, we show that RASSF6 expression positively correlates with sorafenib sensitivity in RCC cells and human samples. Stable ectopic overexpression of RASSF6 in RCC cell lines reduces resistance to sorafenib in vitro and in vivo. At a molecular level, RASSF6 activates the JNK signaling pathway, which further contributes to Mcl-1 inhibition. Suppression of the JNK pathway can partially restore Mcl-1 expression and sorafenib resistance. Together, these findings suggest that RASSF6 inhibits sorafenib resistance by repressing Mcl-1 through the JNK-dependent pathway. RASSF6 may serve as a novel regulator for sorafenib therapy in RCC.

Tumor suppressor C-RASSF proteins

Human genome has ten genes that are collectedly called Ras association domain family (RASSF). RASSF is composed of two subclasses, C-RASSF and N-RASSF. Both N-RASSF and C-RASSF encode Ras association domain-containing proteins and are frequently suppressed by DNA hypermethylation in human cancers. However, C-RASSF and N-RASSF are quite different. Six C-RASSF proteins (RASSF1-6) are characterized by a C-terminal coiled-coil motif named Salvador/RASSF/Hippo domain, while four N-RASSF proteins (RASSF7-10) lack it. C-RASSF proteins interact with mammalian Ste20-like kinases-the core kinases of the tumor suppressor Hippo pathway-and cross-talk with this pathway. Some of them share the same interacting molecules such as MDM2 and exert the tumor suppressor role in similar manners. Nevertheless, each C-RASSF protein has distinct characters. In this review, we summarize our current knowledge of how C-RASSF proteins play tumor suppressor roles and discuss the similarities and differences among C-RASSF proteins.

DNA methylation is related to the occurrence of breast cancer and is not affected by culture conditions

The present study aimed to explore the relationship between DNA methylation and breast cancer under different cell culture conditions. MCF‑7 breast cancer cells were cultured in two‑dimensional (2D), three‑dimensional (3D) and orthotopic transplantation (Ti) adhesion substrates. Principal component analysis (PCA) was used for global visualization of these three samples. The methylation status of CpG sites was examined by unsupervised clustering analysis. Scatter plots and histograms were constructed from the mean β‑values from 3D vs. 2D, 3D vs. Ti and Ti vs. 2D analysis. In addition, analyses of Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were conducted to explore the putative biological functions in which mutL homolog (MLH), phosphatase and tensin homolog (PTEN), runt‑related transcription factor (RUNX), Ras association domain family (RASSF), cadherin 1 (CDH1), O‑6‑methylguanine‑DNA methyltransferase (MGMT) and P16 may serve a role. Quantitative methylation‑specific polymerase chain reaction (QMSP) was performed to determine the influence of culturing conditions on important gene expression. Results from PCA analysis indicated that the three samples were closely connected with each other. Venn diagrams revealed that certain differential methylation positions were common among the three sample groups, and 116 CpG positions were identified that appeared to be hypermethylated. The methylation patterns were more similar between 3D vs. 2D cultures compared with those between 3D vs. Ti or between Ti vs. 2D. Results of GO term and KEGG pathway analyses indicated that genes were enriched in four pathways, including transporter activity and G‑protein coupled receptor activity. In addition, QMSP analysis identified no notable differences in the methylation status of MLH, PTEN, RUNX, RASSF, CDH1, MGMT and P16 under 2D, 3D and Ti culture conditions. In conclusion, abnormal DNA methylation is related with breast cancer, and the methylation status did not change in breast cancer cells cultured in different conditions.

PNMA family: Protein interaction network and cell signalling pathways implicated in cancer and apoptosis

Paraneoplastic Ma Family (PNMA) comprises a growing number of family members which share relatively conserved protein sequences encoded by the human genome and is localized to several human chromosomes, including the X-chromosome. Based on sequence analysis, PNMA family members share sequence homology to the Gag protein of LTR retrotransposon, and several family members with aberrant protein expressions have been reported to be closely associated with the human Paraneoplastic Disorder (PND). In addition, gene mutations of specific members of PNMA family are known to be associated with human mental retardation or 3-M syndrome consisting of restrictive post-natal growth or dwarfism, and development of skeletal abnormalities. Other than sequence homology, the physiological function of many members in this family remains unclear. However, several members of this family have been characterized, including cell signalling events mediated by these proteins that are associated with apoptosis, and cancer in different cell types. Furthermore, while certain PNMA family members show restricted gene expression in the human brain and testis, other PNMA family members exhibit broader gene expression or preferential and selective protein interaction profiles, suggesting functional divergence within the family. Functional analysis of some members of this family have identified protein domains that are required for subcellular localization, protein-protein interactions, and cell signalling events which are the focus of this review paper.

DNA methylation is a common molecular alteration in colorectal cancer cells and culture method has no influence on DNA methylation

The present study aimed to explore whether culture method had an influence on DNA methylation in colorectal cancer (CRC). In the present study, CRC cells were cultured in two-dimensional (2D), three-dimensional (3D) and mouse orthotopic transplantation (Tis) cultures. Principal component analysis (PCA) was used for global visualization of the three samples. A Venn diagram was applied for intersection and union analysis for different comparisons. The methylation condition of 5′-C-phosphate-G-3′ (CpG) location was determined using unsupervised clustering analysis. Scatter plots and histograms of the mean β values between 3D vs. 2D, 3D vs. Tis and Tis vs. 2D were constructed. In order to explore the biological function of the genes, gene ontology and Kyoto Encyclopedia of Gene and Genomes (KEGG) pathway analyses were utilized. To explore the influence of culture condition on genes, quantitative methylation specific polymerase chain reaction (QMSP) was performed. The three samples connected with each other closely, as demonstrated by PCA. Venn diagram analysis indicated that some differential methylation positions were commonly shared in the three groups of samples and 16 CpG positions appeared hypermethylated in the three samples. The methylation patterns between the 3D and 2D cultures were more similar than those of 3D and Tis, and Tis and 2D. Results of gene ontology demonstrated that differentially expressed genes were involved in molecular function, cellular components and biological function. KEGG analysis indicated that genes were enriched in 13 pathways, of which four pathways were the most evident. These pathways were pathways in cancer, mitogen-activated protein kinase signaling, axon guidance and insulin signaling. Furthermore, QMSP demonstrated that methylation of mutL homolog, phosphatase and tensin homolog, runt-related transcription factor, Ras association family member, cadherin-1, O-6-methylguanine-DNA-methyltransferase and P16 genes had no obvious difference in 2D, 3D and Tis culture conditions. In conclusion, the culture method had no influence on DNA methylation in CRC cells.

The emerging role of Hippo signaling pathway in regulating osteoclast formation

A delicate balance between osteoblastic bone formation and osteoclastic bone resorption is crucial for bone homeostasis. This process is regulated by the Hippo signaling pathway including key regulatory molecules RASSF2, NF2, MST1/2, SAV1, LATS1/2, MOB1, YAP, and TAZ. It is well established that the Hippo signaling pathway plays an important part in regulating osteoblast differentiation, but its role in osteoclast formation and activation remains poorly understood. In this review, we discuss the emerging role of Hippo-signaling pathway in osteoclast formation and bone homeostasis. It is revealed that specific molecules of the Hippo-signaling pathway take part in a stage specific regulation in pre-osteoclast proliferation, osteoclast differentiation and osteoclast apoptosis and survival. Upon activation, MST and LAST, transcriptional co-activators YAP and TAZ bind to the members of the TEA domain (TEAD) family transcription factors, and influence osteoclast differentiation via regulating the expression of downstream target genes such as connective tissue growth factor (CTGF/CCN2) and cysteine-rich protein 61 (CYR61/CCN1). In addition, through interacting or cross talking with RANKL-mediated signaling cascades including NF-κB, MAPKs, AP1, and NFATc1, Hippo-signaling molecules such as YAP/TAZ/TEAD complex, RASSF2, MST2, and Ajuba could also potentially modulate osteoclast differentiation and function. Elucidating the roles of the Hippo-signaling pathway in osteoclast development and specific molecules involved is important for understanding the mechanism of bone homeostasis and diseases.

Downregulation of lncRNA CASC2 facilitates osteosarcoma growth and invasion through miR-181a

OBJECTIVES

Long non-coding RNA cancer susceptibility candidate 2 (CASC2) is a novel lncRNA and has been indicated as playing tumour suppressor gene in several tumours. However, the role of CASC2 in osteosarcoma is still uncovered.

MATERIALS AND METHODS

The CASC2 and miR-181a expressions were measured via qRT-PCR. CCK-8 assay and colony formation assay were performed to determine the cell growth, and transwell assay was performed to assess the cell invasion.

RESULTS

We showed that CASC2 expression was downregulated in osteosarcoma samples and cell lines. Moreover, we showed that downregulated expression of CASC2 was correlated with advanced TNM stage. Furthermore, overexpression of CASC2 inhibited osteosarcoma cell proliferation, colony formation, and invasion. In addition, we indicated that ectopic expression of CASC2 suppressed miR-181a expression and enhanced the expression of Ras association domain family member 6 (RASSF6), PTEN and ATM in osteosarcoma cell, which were the direct target gene of miR-181a. Moreover, we indicated that RASSF6 expression was downregulated in osteosarcoma samples and cell lines and downregulated expression of RASSF6 was correlated with advanced TNM stage. We found that the expression of RASSF6 was positively correlated with the expression of CASC2 in osteosarcoma tissues. Ectopic expression of CASC2 suppressed the osteosarcoma cell proliferation, colony formation and invasion through regulating RASSF6 expression.

CONCLUSIONS

Our data illuminated that CASC2 acted as a tumour suppressor in osteosarcoma progression.

BCL-XL binds and antagonizes RASSF6 tumor suppressor to suppress p53 expression

RASSF6, a member of the tumor suppressor Ras-association domain family proteins, induces apoptosis in the caspase-dependent and caspase-independent manners. RASSF6 interacts with MDM2 and stabilizes p53. BCL-XL is a prosurvival member of BCL-2 family proteins. BCL-XL directly inhibits proapoptotic BAX and BAK. BCL-XL also traps tBID, a proapoptotic activator BH3-only protein, and sequesters p53. In addition, BCL-XL regulates the mitochondrial membrane permeability via voltage-dependent anion channel. In these manners, BCL-XL plays an antiapoptotic role. We report the interaction of BCL-XL with RASSF6. BCL-XL inhibits the interaction between RASSF6 and MDM2 and suppresses p53 expression. Consequently, BCL-XL antagonizes RASSF6-mediated apoptosis. Thus, the inhibition of RASSF6-mediated apoptosis also underlies the prosurvival role of BCL-XL.

Decreased level of RASSF6 in sporadic colorectal cancer and its anti-tumor effects both in vitro and in vivo

Ras-association domain family protein 6 (RASSF6) is a member of tumor suppressor RASSFs family with a wide range of function from RAS interaction, Hippo signaling involvement to cell cycle and apoptosis regulation. RASSF6 is reported inactivated in various types of cancer. However, whether RASSF6 is associated with colorectal cancer and the underlying mechanisms have yet to be investigated. In our previous exome sequencing study, we found a somatic loss-of-function (LoF) mutation in RASSF6 in one sporadic colorectal cancer (sCRC) patient, and two missense mutations in deep sequencing group of sCRC samples, implying the possibility that RASSF6 may be involved in the pathogenesis of sCRC. In this study, we demonstrate that RASSF6 acts as a tumor suppressor in colon cancer cells. Decreased level of RASSF6 was observed in adenocarcinoma compared to normal tissues, especially in advanced tumor cases. Further experiments showed exogenous introduction of RASSF6 into LoVo cells suppressed cell proliferation, migration, invasion, and induced apoptosis in vitro as well as tumor growth in vivo. In contrast, knockdown of RASSF6 in HT-29 cells showed the opposite effects. Taken together, our results suggest, in addition to epigenetics changes, functional somatic mutations may also contribute to the downregulation of RASSF6 and further participate in the pathogenesis of sCRC. RASSF6 may serve as a novel candidate against tumor growth for sCRC.

Relationship between RAS Association Domain Family Protein 1A Promoter Methylation and the Clinicopathological Characteristics in Patients with Ovarian Cancer: A Systematic Meta-Analysis

BACKGROUND

To investigate the relationship between RAS association domain family protein 1A (RASSF1A) promoter methylation and the clinical features, and the survival of ovarian cancer patients.

METHODS

A comprehensive literature search was conducted in the PubMed, Embase, EBSCO, and Cochrane Library databases. The overall ORs with their 95% CIs were calculated in this meta-analysis.

RESULTS

Finally 17 relevant publications with 1,108 ovarian cancer samples were available for the current meta-analysis. RASSF1A promoter methylation had a significantly higher level in ovarian cancer than in low malignant potential (LMP) tumors. No significant relationship was observed between RASSF1A promoter methylation and the clinicopathological characteristics in ovarian cancer. Two studies reported that RASSF1A promoter methylation was not correlated with the survival of patients with ovarian cancer.

CONCLUSIONS

Our findings suggest that the use of RASSF1A promoter methylation could distinguish ovarian cancer and LMP tumors. -RASSF1A promoter methylation may not be correlated with the clinical features and the survival of ovarian cancer patients. More studies with large sample sizes are essential in the future.

Differential proteomic analysis of white adipose tissues from T2D KKAy mice by LC-ESI-QTOF

Type 2 diabetes (T2D) has become a worldwide increasingly social health burden for its high morbidity and heightened prevalence. As one of the main tissues involved in uptake of glucose under the stimulation of insulin, WAT plays very important role in metabolic and homeostasis regulation. We performed a differential proteomics study to investigate alterations in epididymis fat pad of high fat diet fed T2D KKAy mice compared to normal fed C57BL/6J mice, by ¹⁸ O-labeling relative quantitative technique. Among 329 confidently identified proteins, 121 proteins showed significant changes with CV ≤ 20% (fold changes of >2 or <0.5 as threshold). According to GO classification, we found that altered proteins contained members of biological processes of metabolic process, oxidative stress, ion homeostasis, apoptosis and cell division. In metabolic, proteins assigned to fatty acid biosynthesis (FAS etc.) were decreased, the key enzyme (ACOX3) in β-oxidation process was increased. Increased glycolysis enzymes (ENOB etc.) and decreased TCA cycle related enzymes (SCOT1 etc.) suggested that glucose metabolism in mitochondria of T2D mice might be impaired. Elevated oxidative stress was observed with alterations of a series of oxidordeuctase (QSOX1 etc.). Besides, alterations of ion homeostasis (AT2C1 etc.) proteins were also observed. The enhancement of cell proliferation associated proteins (ELYS etc.) and inhibition of apoptosis associated proteins (RASF6 etc.) in WAT might contributed to the fat pad and body weight gain. Overall, these changes in WAT may serve as a reference for understanding the functional mechanism of T2D.

TET1 inhibits cell proliferation by inducing RASSF5 expression

Tet methylcytosine dioxygenases (TETs) catalyze the oxidative reactions of 5-methylcytosine to 5-hydroxymethylcytosine (5hmC). However, TET1 roles in ovarian cancer cell growth are unknown. Here, we show that ectopic expression of TET1 increased 5hmC levels, and inhibited proliferation and colony formation in ovarian cancer cell lines. Furthermore, in vitro and in vivo functional studies demonstrated that TET1 overexpression is necessary for the suppression of ovarian cancer growth, whereas depletion of TET1 expression had the opposite effect. Furthermore, the results of RNA-seq and qRT-PCR analyses identified a tumor suppressor, Ras association domain family member 5 (RASSF5), as the key downstream target of TET1. TET1 promotes RASSF5 expression by demethylating a CpG site within RASSF5 promoter. Up-regulated RASSF5 expression leads to the suppression of ovarian cancer cells growth. Additionally, we demonstrated that inhibition of CUL4-DDB1 ubiquitin ligase complex decrease 5hmC levels in ovarian cancer cells. These results provide new insights into the understanding of how ovarian cancers develop and grow, and identify TET1 as a key player in this process.

Meta-analysis of promoter methylation in eight tumor-suppressor genes and its association with the risk of thyroid cancer

Promoter methylation in a number of tumor-suppressor genes (TSGs) can play crucial roles in the development of thyroid carcinogenesis. The focus of the current meta-analysis was to determine the impact of promoter methylation of eight selected candidate TSGs on thyroid cancer and to identify the most important molecules in this carcinogenesis pathway. A comprehensive search was performed using Pub Med, Scopus, and ISI Web of Knowledge databases, and eligible studies were included. The methodological quality of the included studies was evaluated according to the Newcastle Ottawa scale table and pooled odds ratios (ORs); 95% confidence intervals (CIs) were used to estimate the strength of the associations with Stata 12.0 software. Egger's and Begg's tests were applied to detect publication bias, in addition to the "Metatrim" method. A total of 55 articles were selected, and 135 genes with altered promoter methylation were found. Finally, we included eight TSGs that were found in more than four studies (RASSF1, TSHR, PTEN, SLC5A, DAPK, P16, RARβ2, and CDH1). The order of the pooled ORs for these eight TSGs from more to less significant was CDH1 (OR = 6.73), SLC5 (OR = 6.15), RASSF1 (OR = 4.16), PTEN (OR = 3.61), DAPK (OR = 3.51), P16 (OR = 3.31), TSHR (OR = 2.93), and RARβ2 (OR = 1.50). Analyses of publication bias and sensitivity confirmed that there was very little bias. Thus, our findings showed that CDH1 and SCL5A8 genes were associated with the risk of thyroid tumor genesis.

DNA hypermethylation of tumor suppressor genes RASSF6 and RASSF10 as independent prognostic factors in adult acute lymphoblastic leukemia

BACKGROUND

The Hypermethylation of Ras association domain family (RASSF) often plays a key role in malignant progression of solid tumors; however, their impact on the prognosis and survival of adult ALL patients remain elusive.

METHODS

The frequency of the promoter methylation pattern of RASSF6 and RASSF10 were analyzed in the peripheral blood (PB) samples taken at the time of diagnosis of 45 ALL patients. The methylation-specific PCR (MSP) assay was used to detect the DNA methylation patterns.

RESULTS

RASSF6 was frequently hypermethylated in patients diagnosed with pre-B-ALL (90.9%) and B-ALL (87.5%), followed by T-ALL (66.7%); whereas, RASSF10 methylation was more confined to T-ALL (80%) as compared to B-ALL (25%) and pre-B ALL (9.1%) patients. Moreover, hypermethylation of RASSF6 was significantly associated with a poor prognosis and shorter overall survival (OS) in patients with pre-B-ALL (log-rank test; P=0.041).

CONCLUSION

RASSF6 and RASSF10 were frequently hypermethylated in the samples at the time of diagnosis of adult ALL patients. Our study represents the first report of methylation of RASSF6 at a high frequency in patients with pre-B ALL. Furthermore, hypermethylation of RASSF6 was significantly associated with inferior overall survival in pre-B ALL patients. It may suggest that the frequent epigenetic inactivation of RASSF6 plays an important role in the pathogenesis and progression of pre-B-ALL.

Diagnostic Capacity of RASSF1A Promoter Methylation as a Biomarker in Tissue, Brushing, and Blood Samples of Nasopharyngeal Carcinoma

Methylation of the RAS association domain family protein 1A (RASSF1A) promoter has been observed in nasopharyngeal carcinoma (NPC). This study investigated the correlation of RASSF1A promoter methylation with clinicopathological features and its utility as a diagnostic biomarker in NPC. A total of 926 patients with NPC and 495 non-tumor controls were analyzed in this study. RASSF1A promoter methylation was notably higher in NPC compared with non-tumor tissue, brushing and blood samples. RASSF1A promoter methylation was associated with clinical stage, lymph node status, distant metastasis, and T classification of patients with NPC, although it was not linked to age and sex. The pooled sensitivity, specificity, and AUC (area under the curve) of RASSF1A promoter methylation were determined in NPC samples vs. non-tumor samples (tissue: sensitivity=0.72, specificity=0.99, AUC=0.98; brushing: sensitivity=0.56, specificity=1.00, AUC=0.94; blood: sensitivity=0.11, specificity=0.98, AUC=0.97). Our findings show that RASSF1A promoter methylation may be correlated with the development, progression and metastasis of NPC. RASSF1A promoter methylation is a promising noninvasive biomarker for the diagnosis of NPC from tissue and brushing samples.

Diagnostic value of selected markers and apoptotic pathways for pancreatic cancer

Pancreatic cancer occupies the fourth place as a cause of death from cancer, and the mortality rate is similar to the number of newly detected cases. Due to the late diagnosis, only 5-6% of patients with pancreatic cancer survive for five years. Given that early diagnosis is critical for improving patients' survival rates, there is an urgent need for the discovery and validation of new biomarkers with sufficient sensitivity and specificity to help diagnose pancreatic cancer early. Detection of serum tumor markers (CA19-9, CEA, CA125 and CA242) is conducive to the early diagnosis of pancreatic cancer. The combination of miR-16, miR-196a and CA19-9 plasma level was more effective, especially in early tumor screening. Furthermore, recent studies reported that mainly miR-21, miR-155 and miR-196 were dysregulated in IPMN (intraductal papillary mucinous neoplasms) and PanIN (pancreatic intraepithelial neoplasia) lesions, suggesting their usefulness as early biomarkers of these diseases. The reduced rate of apoptosis plays a crucial role in carcinogenesis, and it is one of the most important characteristics acquired by pancreatic cancer cells, which protects them from attack by the immune system and reduces the effectiveness of pharmacological treatment. This review summarizes the data concerning the clinical utility of selected biomarkers in pancreatic cancer patients. The review mainly focuses on the genetic aspects of signaling pathway disorders associated with apoptosis in the pathogenesis and diagnosis of pancreatic cancer.

RASSF1A promoter methylation is associated with increased risk of thyroid cancer: a meta-analysis

Objective

Previous studies have reported that Ras-associated domain family 1A (RASSF1A), the most commonly silenced tumor suppressor via promoter methylation, played vital roles in the development of carcinogenesis. The purpose of this meta-analysis was to determine whether RASSF1A promoter methylation increased the risk of thyroid cancer.

Methods

PubMed, Embase, ISI Web of Knowledge, and Chinese National Knowledge Infrastructure databases were searched to obtain eligible studies. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to estimate the strength of the associations, using Stata 12.0 software. The methodological quality of included studies was evaluated using Newcastle–Ottawa scale table. Egger’s test and Begg’s test were applied to detect publication biases. TSA 0.9 software was used to calculate the required information size and whether the result was conclusive.

Results

A total of 10 articles with 12 studies that included 422 thyroid cancer patients, identifying the association of RASSF1A promoter methylation with thyroid cancer risk, were collected in this meta-analysis. Overall, RASSF1A promoter methylation significantly increased the risk of thyroid cancer (total, OR=8.27, CI=4.38–15.62, P<0.05; Caucasian, OR=9.25, CI=3.97–21.56, P<0.05; Asian, OR=7.01, CI=2.68–18.38, P<0.05). In the subgroup analysis based on sample type, a significant association between thyroid cancer group and control group was found (normal tissue, OR=9.55, CI=4.21–21.67, P<0.05; adjacent tissue, OR=6.80, CI=2.49–18.56, P<0.05). The frequency of RASSF1A promoter methylation in follicular thyroid carcinoma was higher than in control group (OR=11.88, CI=5.80–24.32, P<0.05). In addition, the results indicated that the RASSF1A promoter methylation was correlated with papillary thyroid carcinoma in Caucasians and Asians (total, OR=8.07, CI=3.54–18.41, P<0.05; Caucasian, OR=11.35, CI=2.39–53.98, P<0.05; Asian, OR=6.67, CI=2.53–17.64, P<0.05). On the basis of the trial sequential analysis, the significant association of RASSF1A promoter methylation with thyroid cancer risk was found, and there was no need to perform further studies.

Conclusion

This meta-analysis confirms that RASSF1A promoter methylation is a risk factor for thyroid tumor.

miR-181a-5p promotes the progression of gastric cancer via RASSF6-mediated MAPK signalling activation

We previously discovered that Ras association domain family member 6 (RASSF6) was downregulated and predicted poor prognosis in GC patients. However, the mechanisms of the down regulation of RASSF6 in GC remained unclear. Increasing evidence indicates that dysregulation of microRNAs promotes the progression of cancer through the repression of tumour suppressors. Here, we identified miR-181a-5p as a novel regulator of RASSF6 in GC. Functionally, ectopic expression or silencing of miR-181a-5p, respectively, promoted or inhibited GC cell proliferation, colony formation and cell cycle transition, as well as enhanced or prevented the invasion, metastasis of GC cells and epithelial to mesenchymal transition of GC cells in vitro and in vivo. Molecularly, miR-181a-5p functioned as an onco-miRNA by activating the RASSF6-regulated MAKP pathway. Overexpression or silencing of RASSF6 could partially reverse the effects of the overexpression or repression of miR-181a-5p on GC progress caused by activation of the MAKP pathway in vitro and in vivo. Clinically, high miR-181a-5p expression predicted poor survival in GC patients, especially combined with low RASSF6 expression. Collectively, we identified miR-181a-5p as an onco-miRNA, which acts by directly repressing RASSF6 in GC.

HPV16 integration probably contributes to cervical oncogenesis through interrupting tumor suppressor genes and inducing chromosome instability

Background

The integration of human papilloma virus (HPV) into host genome is one of the critical steps that lead to the progression of precancerous lesion into cancer. However, the mechanisms and consequences of such integration events are poorly understood. This study aims to explore those questions by studying high risk HPV16 integration in women with cervical intraepithelial neoplasia (CIN) and cervical squamous cell carcinoma (SCC).

Methods

Specifically, HPV integration status of 13 HPV16-infected patients were investigated by ligation-mediated PCR (DIPS-PCR) followed by DNA sequencing.

Results

In total, 8 HPV16 integration sites were identified inside or around genes associated with cancer development. In particular, the well-studied tumor suppressor genes SCAI was found to be integrated by HPV16, which would likely disrupt its expression and therefore facilitate the migration of tumor. On top of that, we observed several cases of chromosome translocation events coincide with HPV integration, which suggests the existence of chromosome instability. Additionally, short overlapping sequences were observed between viral derived and host derived fragments in viral-cellular junctions, indicating that integration was mediated by micro homology-mediated DNA repair pathway.

Conclusions

Overall, our study suggests a model in which HPV16 might contribute to oncogenesis not only by disrupting tumor suppressor genes, but also by inducing chromosome instability.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0454-4) contains supplementary material, which is available to authorized users.

RASSF8 regulates progression of cutaneous melanoma through nuclear factor-κb

Our group previously demonstrated that the RASSF1 gene has a significant tumor suppressor role in cutaneous melanoma. The RASSF8 gene is a member of the N-terminal RASSF gene family. Previously, we identified RASSF8 (HOJ1, NCBI Gene ID:11228) expression in cutaneous melanoma; however the functional role of RASSF8 in melanoma is not known. RASSF8 expression was assessed in melanoma cell lines and tumors of different AJCC stages. Results indicated that RASSF8 expression was low in metastatic melanoma lines and decreased with melanoma progression. We then explored the mechanism of RASSF8 downregulation in melanoma by assessing methylation of RASSF8 and demonstrated that methylation of RASSF8 gene promoter was higher in advanced than in early stages melanomas. Functional activity of RASSF8 in melanoma lines by knockdown and overexpression of RASSF8 demonstrated that RASSF8 expression significantly inhibited cell growth, cell migration and invasion, whereas knockdown of RASSF8 expression significantly increased cell growth, cell migration and invasion of melanoma cells by increasing expression of P65 and its downstream target IL-6. Moreover RASSF8 was found to induce apoptosis in melanoma cells by activating the P53-P21 pathway, and also in vivo studies demonstrated that inhibiting RASSF8 increases the tumorigenic properties of human melanoma xenografts. These results suggest that RASSF8 plays a significant role in suppressing the progression of cutaneous melanoma.

Distinct functional domains of PNMA5 mediate protein-protein interaction, nuclear localization, and apoptosis signaling in human cancer cells

PURPOSE

Members of paraneoplastic Ma (PNMA) family have been identified as onconeuronal antigens, which aberrant expressions in cancer cells of patients with paraneoplastic disorder (PND) are closely linked to manifestation of auto-immunity, neuro-degeneration, and cancer. The purpose of present study was to determine the role of PNMA5 and its functional relationship to MOAP-1 (PNMA4) in human cancer cells.

METHODS

PNMA5 mutants were generated through deletion or site-directed mutagenesis and transiently expressed in human cancer cell lines to investigate their role in apoptosis, subcellular localization, and potential interaction with MOAP-1 through apoptosis assays, fluorescence microscopy, and co-immunoprecipitation studies, respectively.

RESULTS

Over-expressed human PNMA5 exhibited nuclear localization pattern in both MCF-7 and HeLa cells. Deletion mapping and mutagenesis studies showed that C-terminus of PNMA5 is responsible for nuclear localization, while the amino acid residues (391KRRR) within the C-terminus of PNMA5 are required for nuclear targeting. Deletion mapping and co-immunoprecipitation studies showed that PNMA5 interacts with MOAP-1 and N-terminal domain of PNMA5 is required for interaction with MOAP-1. Furthermore, co-expression of PNMA5 and MOAP-1 in MCF-7 cells significantly enhanced chemo-sensitivity of MCF-7 to Etoposide treatment, indicating that PNMA5 and MOAP-1 interact synergistically to promote apoptotic signaling in MCF-7 cells.

CONCLUSIONS

Our results show that PNMA5 promotes apoptosis signaling in HeLa and MCF-7 cells and interacts synergistically with MOAP-1 through its N-terminal domain to promote apoptosis and chemo-sensitivity in human cancer cells. The C-terminal domain of PNMA5 is required for nuclear localization; however, both N-and C-terminal domains of PNMA5 appear to be required for pro-apoptotic function.

Ras-association domain family 10 acts as a novel tumor suppressor through modulating MMP2 in hepatocarcinoma

Ras-Association Domain Family 10 (RASSF10) is the last identified member of the RASSF family. The functional characteristics of this new gene in human cancers remain largely unclear. Here, we examined RASSF10 for the biological functions and related molecular mechanisms in hepatocellular carcinoma (HCC). We found that RASSF10 is expressed in normal human liver tissue, but is silenced or down-regulated in 62.5% (5/8) of HCC cell lines. The mean expression level of RASSF10 was significantly lower in primary HCCs compared with their adjacent normal tissues (P<0.005, n=52). The promoter methylation contributes to the inactivation of RASSF10 as demonstrated by bisulfite genomic sequencing and demethylation treatment analyses. Transgenic expression of RASSF10 in silenced HCC cell lines suppressed cell viability, colony formation and inhibited tumor growth in nude mice (QGY7703, P<0.01; HepG2, P<0.05). Furthermore, RASSF10 was shown to induce the cell accumulation in G1 phase with the increase of p27, as well as the decrease of cyclinD1 and CDK2/CDK4. Over-expression of RASSF10 also inhibited HCC cells migration (P<0.01) or invasion (P<0.05). Adhesion genes array revealed that Matrix Metalloproteinase 2 (MMP2) was a downstream effector of RASSF10. RASSF10 acting as a tumor suppressor to inhibit HCC invasion partially mediated by Focal Adhesion Kinase or p38 MAPK to decrease the accumulation of MMP2. Our study suggests that RASSF10 acts as a tumor suppressor for HCC.

Ras signaling through RASSF proteins

There are six core RASSF family proteins that contain conserved Ras Association domains and may serve as Ras effectors. They lack intrinsic enzymatic activity and appear to function as scaffolding and localization molecules. While initially being associated with pro-apoptotic signaling pathways such as Bax and Hippo, it is now clear that they can also connect Ras to a surprisingly broad range of signaling pathways that control senescence, inflammation, autophagy, DNA repair, ubiquitination and protein acetylation. Moreover, they may be able to impact the activation status of pro-mitogenic Ras effector pathways, such as the Raf pathway. The frequent epigenetic inactivation of RASSF genes in human tumors disconnects Ras from pro-death signaling systems, enhancing Ras driven transformation and metastasis. The best characterized members are RASSF1A and RASSF5 (NORE1A).

Comparative Modeling, Molecular Docking, and Revealing of Potential Binding Pockets of RASSF2; a Candidate Cancer Gene

RASSF2, potential tumor suppressor gene, acts as a KRAS-specific effectors protein and may promote apoptosis and cell cycle arrest. It stabilizes STK3/MST2 by protecting it from proteasomal degradation. RASSF2 plays a significant role against the inhibition of cancer. MODELLER (9v15) and online servers (I-Tasser, SwissModel, 3D-JigSaw, ModWeb) were utilized to generate 3D structures of the RASSF2 based on homology modeling. A comparison between models predicted by MODELLER (9v15) and Web servers had been checked through utilized evaluation tools. The most potent model for RASSF2 was analyzed and selected for molecular docking studies. The binding pockets were revealed for binding studies through Site Hound. AutoDock Vina and AutoDock4 were utilized for molecular docking, and the attempt of this experiment was to identify the ligands for RASSF2. The selected compounds may act as regulators and regulate the normal activity of RASSF2. It was also analyzed and observed that the selected compounds showed least binding energy and high-affinity binding in predicted top binding domain. The determination of protein function is based on accurate identification of binding sites in protein structures. The binding site is known, and it may allow the ligand type and protein function to be determined by performing in silico and experimental procedures. The detection, comparison, and analysis of binding pockets are pivotal to drug discovery. It proposed that predicted structure is reliable for the structural insights and functional studies. The predicted binding pockets may lead to further analysis (drug discovery), used against cancer study.

RASSF6; the Putative Tumor Suppressor of the RASSF Family

Humans have 10 genes that belong to the Ras association (RA) domain family (RASSF). Among them, RASSF7 to RASSF10 have the RA domain in the N-terminal region and are called the N-RASSF proteins. In contradistinction to them, RASSF1 to RASSF6 are referred to as the C-RASSF proteins. The C-RASSF proteins have the RA domain in the middle region and the Salvador/RASSF/Hippo domain in the C-terminal region. RASSF6 additionally harbors the PSD-95/Discs large/ZO-1 (PDZ)-binding motif. Expression of RASSF6 is epigenetically suppressed in human cancers and is generally regarded as a tumor suppressor. RASSF6 induces caspase-dependent and -independent apoptosis. RASSF6 interacts with mammalian Ste20-like kinases (homologs of Drosophila Hippo) and cross-talks with the Hippo pathway. RASSF6 binds MDM2 and regulates p53 expression. The interactions with Ras and Modulator of apoptosis 1 (MOAP1) are also suggested by heterologous protein-protein interaction experiments. RASSF6 regulates apoptosis and cell cycle through these protein-protein interactions, and is implicated in the NF-κB and JNK signaling pathways. We summarize our current knowledge about RASSF6 and discuss what common and different properties RASSF6 and the other C-RASSF proteins have.

Decreased expression and frequent promoter hypermethylation of RASSF2 and RASSF6 correlate with malignant progression and poor prognosis of gastric cardia adenocarcinoma

The RAS-association domain family (RASSF) consists of 10 members, and several members act as tumor suppressor genes and epigenetically inactivated in different tumor types. The present study investigated the role and methylation status of RASSF2, RASSF3, RASSF4, and RASSF6 in the pathogenesis and prognosis of GCA. Quantitative real-time RT-PCR, Western blot, and immunohistochemistry (IHC) methods were used respectively to detect the expression of RASSF2, RASSF3, RASSF4, and RASSF6 in 135 GCA cases and BS-MSP method was used to clarify the methylation status of these four genes. Decreased mRNA and protein expression of RASSF2, RASSF3, RASSF4, and RASSF6 were detected in GCA tumor tissues. Aberrant CpG island methylation of RASSF2, RASSF4, and RASSF6 were detected in GCA tumor tissues and were inversely correlated with the expression levels of these genes. Both of RASSF2 and RASSF6 expression and methylation were associated with TNM stage, depth of invasion, LN metastasis, distant metastasis or recurrence, and UGIC family history. GCA patients with simultaneous negative protein expression of RASSF2 and RASSF6 or with simultaneous methylation of both genes demonstrated poor patient survival. These results suggest that down-regulation of RASSF2, RASSF3, RASSF4, and RASSF6 is a tumor-specific phenomenon and the inactivation of RASSF2 and RASSF6 may be associated with tumor progression. Inactivation of RASSF2, RASSF4, and RASSF6 through CpG island methylation may play important roles in GCA carcinogenesis. A combination of RASSF2 and RASSF6 expression or hypermethylation may serve as useful prognostic biomarker for GCA. © 2015 Wiley Periodicals, Inc.

Pro-survival function of MEF2 in cardiomyocytes is enhanced by β-blockers

β1-Adrenergic receptor (β1-AR) stimulation increases apoptosis in cardiomyocytes through activation of cAMP/protein kinase A (PKA) signaling. The myocyte enhancer factor 2 (MEF2) proteins function as important regulators of myocardial gene expression. Previously, we reported that PKA signaling directly represses MEF2 activity. We determined whether (a) MEF2 has a pro-survival function in cardiomyocytes, and (b) whether β-adrenergic/PKA signaling modulates MEF2 function in cardiomyocytes. Initially, we observed that siRNA-mediated gene silencing of MEF2 induces cardiomyocyte apoptosis as indicated by flow cytometry. β1-AR activation by isoproterenol represses MEF2 activity and promotes apoptosis in cultured neonatal cardiomyocytes. Importantly, β1-AR mediated apoptosis was abrogated in cardiomyocytes expressing a PKA-resistant form of MEF2D (S121/190A). We also observed that a β1-blocker, Atenolol, antagonizes isoproterenol-induced apoptosis while concomitantly enhancing MEF2 transcriptional activity. β-AR stimulation modulated MEF2 cellular localization in cardiomyocytes and this effect was reversed by β-blocker treatment. Furthermore, Kruppel-like factor 6, a MEF2 target gene in the heart, functions as a downstream pro-survival factor in cardiomyocytes. Collectively, these data indicate that (a) MEF2 has an important pro-survival role in cardiomyocytes, and (b) β-adrenergic signaling antagonizes the pro-survival function of MEF2 in cardiomyocytes and β-blockers promote it. These observations have important clinical implications that may contribute to novel strategies for preventing cardiomyocyte apoptosis associated with heart pathology.