Diagnostic value of RASSF1A hypermethylation in colorectal cancer: a meta-analysis

RASSF1 is identified by transcriptome coordination analysis as a target of ATF4

Evaluation of gene co-regulation is a powerful approach for revealing regulatory associations between genes and predicting biological function, especially in genetically diverse samples. Here, we applied this strategy to identify transcripts that are co-regulated with unfolded protein response (UPR) genes in cultured fibroblasts from outbred deer mice. Our analyses showed that the transcriptome associated with RASSF1, a tumor suppressor involved in cell cycle regulation and not previously linked to UPR, is highly correlated with the transcriptome of several UPR-related genes, such as BiP/GRP78, DNAJB9, GRP94, ATF4, DNAJC3, and CHOP/DDIT3. Conversely, gene ontology analyses for genes co-regulated with RASSF1 predicted a previously unreported involvement in UPR-associated apoptosis. Bioinformatic analyses indicated the presence of ATF4-binding sites in the RASSF1 promoter, which were shown to be operational using chromatin immunoprecipitation. Reporter assays revealed that the RASSF1 promoter is responsive to ATF4, while ablation of RASSF1 mitigated the expression of the ATF4 effector BBC3 and abrogated tunicamycin-induced apoptosis. Collectively, these results implicate RASSF1 in the regulation of endoplasmic reticulum stress-associated apoptosis downstream of ATF4. They also illustrate the power of gene coordination analysis in predicting biological functions and revealing regulatory associations between genes.

Potential of RASSF1A promoter methylation as a biomarker for colorectal cancer: Meta-analysis and TCGA analysis

The RAS association domain family protein 1A (RASSF1A) is a tumor suppressor in colorectal cancer (CRC), and is often inactived by hypermethylation. Therefore, we evaluated the association between RASSF1A hypermethylation and the risk and prognosis in CRC. We identified literature through searching PubMed and China National Knowledge Infrastructure databases, and then validated and supplemented the meta-analysis with TCGA analysis. Twenty-three studies involving 2886 subjects of CRC were examined. The meta-analysis showed that RASSF1A promoter methylation inferred high CRC risk (odds ratio, 6.53, 95% confidence interval 3.88-11.01, P < .001) and poor overall survival (hazard ratio 2.85, 95% CI 1.88-4.31, P < .001). The TCGA analysis suggested that effect of RASSF1A promotor methylation was affected by tumor localization (colon vs. rectum). RASSF1A promoter methylation was a predictor of high risk (OR 2.38, 95%CI 1.02-5.6, P = .046) and poor disease free survival(HR 2.25, 95%CI 1.27-3.99, P = .006)in colon adenocarcinoma, but the association was statistically insignificant in rectum adenocarcinoma(HR 1.58, 95% CI 0.69-3.59, P = .28). These results suggested RASSF1A hypermethylation is a risk and a potential prognostic biomarker in CRC.

RASSF1A: A promising target for the diagnosis and treatment of cancer

The Ras association domain family 1 isoform A (RASSF1A), a tumor suppressor, regulates several tumor-related signaling pathways and interferes with diverse cellular processes. RASSF1A is frequently demonstrated to be inactivated by hypermethylation in numerous types of solid cancers. It is also associated with lymph node metastasis, vascular invasion, and chemo-resistance. Therefore, reactivation of RASSF1A may be a viable strategy to block tumor progress and reverse drug resistance. In this review, we have summarized the clinical value of RASSF1A for screening, staging, and therapeutic management of human malignancies. We also highlighted the potential mechanism of RASSF1A in chemo-resistance, which may help identify novel drugs in the future.

RASSF-1A modulates proliferation-mediated oral squamous cell carcinoma progression

Background

To investigate the expression of RASSF-1A in oral squamous cell carcinoma (OSCC) and adjacent tissues, and to explore its mechanism of action in the development of OSCC.

Methods

RASSF-1A and proliferation-related protein expression in clinical and OSCC mouse models were detected by qPCR and western blot. In vitro experiments were used siRNA knockdown of RASSF-1A gene in SCC9 cells to detect cell proliferation, migration and apoptosis. In vivo experiments were performed using adenovirus overexpressing RASSF-1A gene in mice and observing tumor growth.

Results

The results of qPCR and western blot showed that the expression of RASSF-1A gene was decreased in OSCC, and the expression of CyclinD1 protein was increased. The results of co-immunoprecipitation showed that the two proteins were significantly combined in the oral cancer cell line. Knocking down the RASSF-1A gene in SCC9 cells promotes cell migration and proliferation, while reducing apoptosis and increasing CyclinD1 protein expression. Overexpression of RASSF-1A gene in mice reduces tumor volume and inhibits CyclinD1 protein expression.

Conclusions

Low expression of RASSF-1A gene in OSCC promotes the expression of CyclinD1 protein and tumor growth.

The Hippo and Wnt signalling pathways: crosstalk during neoplastic progression in gastrointestinal tissue

The Hippo and Wnt signalling pathways play crucial roles in maintaining tissue homeostasis and organ size by orchestrating cell proliferation, differentiation and apoptosis. These pathways have been frequently found to be dysregulated in human cancers. While the canonical signal transduction of Hippo and Wnt has been well studied, emerging evidence shows that these two signalling pathways contribute to and exhibit overlapping functions in gastrointestinal (GI) tumorigenesis. In fact, the core effectors YAP/TAZ in Hippo signalling pathway cooperate with β-catenin in Wnt signalling pathway to promote GI neoplasia. Here, we provide a brief review to summarize the molecular mechanisms underlying the crosstalk between these two pathways and elucidate their involvement in GI tumorigenesis, particularly focusing on the intestine, stomach and liver.

Interrelations of Apoptotic and Cellular Senescence Genes Methylation in Inflammatory Bowel Disease Subtypes and Colorectal Carcinoma in Egyptians Patients

Ras-related domain family member 1 transcript variant A (RASSF1A) controls apoptosis and cell proliferation while p14/ARF gene has a regulatory role in cellular senescence. Failure of apoptosis and cellular senescence occurs during inflammatory bowel disease (IBD) and colorectal cancer (CRC). To reveal the role of peripheral leukocyte promoter methylation of RASSF1A and p14/ARF in the pathogenesis of IBD subtypes and CRC we investigated the methylation state of the two genes by methylation-specific polymerase chain reaction (MSP-PCR) in 60 CRC patients, 60 patients with IBD; 27 with ulcerative colitis and 33 had Crohn's disease and also in 30 healthy subjects. Methylated RASSF1A and p14/ARF genes were detected in 55% and 60% of CRC, while the frequency of the methylated RASSF1A and p14/ARF genes was 23.3% and 43.3% in IBD patients and 3.3% and 13.3% in the control group (P = 0.000 each). Also, the frequency of methylated RASSF1A gene was significantly higher in ulcerative colitis than in Crohn's disease, while a non-significant frequency of methylated p14/ARF was detected between ulcerative colitis and Crohn's disease. Furthermore, methylated RASSF1A and p14/ARF were associated with the grade of CRC but not associated with the age of patients, family history, or tumor location. Results suggest that methylated RASSF1A and p14/ARF are related to CRC and IBD pathogenesis and may be used as molecular biomarkers for early detection of CRC and IBD.

Identification of Cross Talk between FoxM1 and RASSF1A as a Therapeutic Target of Colon Cancer

Metastatic colorectal cancer (mCRC) is characterized by the expression of cellular oncogenes, the loss of tumor suppressor gene function. Therefore, identifying integrated signaling between onco-suppressor genes may facilitate the development of effective therapy for mCRC. To investigate these pathways we utilized cell lines and patient derived organoid models for analysis of gene/protein expression, gene silencing, overexpression, and immunohistochemical analyses. An inverse relationship in expression of oncogenic FoxM1 and tumor suppressor RASSF1A was observed in various stages of CRC. This inverse correlation was also observed in mCRC cells lines (T84, Colo 205) treated with Akt inhibitor. Inhibition of FoxM1 expression in mCRC cells as well as in our ex vivo model resulted in increased RASSF1A expression. Reduced levels of RASSF1A expression were found in normal cells (RWPE-1, HBEpc, MCF10A, EC) stimulated with exogenous VEGF₁₆₅. Downregulation of FoxM1 also coincided with increased YAP phosphorylation, indicative of tumor suppression. Conversely, downregulation of RASSF1A coincided with FoxM1 overexpression. These studies have identified for the first time an integrated signaling pathway between FoxM1 and RASSF1A in mCRC progression, which may facilitate the development of novel therapeutic options for advanced colon cancer therapy.