Loss of the Ras regulator RASAL1: another route to Ras activation in colorectal cancer

miR-130b-5p promotes proliferation, migration and invasion of gastric cancer cells via targeting RASAL1

The aim of the present study was to investigate the targeted interaction between microRNA (miR)-130b-5p and RAS protein activator like 1 (RASAL1) gene and elucidate the function of miR-130b-5p in cell proliferation, migration and invasion in gastric cancer. Expression of miR-130b-5p and RASAL1 in seven gastric cell lines was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). MGC803 cells were selected for further study since they exhibited a marked increase in expression of miR-130b-5p accompanied by decreased expression of RASAL1. MGC803 cells were transfected with miR-130b-5p mimics and miR-130b-5p inhibitor using Lipofectamine 2000 for over- and underexpression, respectively, with cells transfected with negative control (NC) sequence as the control. In addition, a luciferase reporter gene assay was performed to evaluate the targeted interaction between miR-130b-5p and RASAL1. Then, alterations in RASAL1 expression were detected by RT-qPCR and western blot analysis following transfection with miR-130b-5p mimics and miR-130b-5p inhibitor. Cell proliferation, colony formation, and migration and invasion ability were detected by MTT, colony formation and Transwell assays, respectively. RASAL1 was demonstrated to be a target gene of miR-130b-5p by luciferase reporter gene assay. In addition, the expression of RASAL1 was significantly lower in MGC803 cells that were transfected with miR-130b-5p mimics and significantly higher in cells transfected with miR-130b-5p inhibitor in comparison with cells transfected with NC (P<0.05). Furthermore, the experimental group transfected with miR-130b-5p mimics manifested significantly higher cell proliferation, increased colony formation and increased migratory and invasive capacities (P<0.05). By contrast, cells transfected with miR-130b-5p inhibitor exhibited significantly lower cell proliferation, decreased colony formation and decreased migratory and invasive capacities, compared with cells transfected with NC (P<0.05). In conclusion, RASAL1 was demonstrated to be a target gene of miR-130b-5p. Overexpression of miR-130b-5p results in promoted proliferation, colony formation and migration and invasion abilities through targeted modulation of RASAL1.

RASAL1 influences the proliferation and invasion of gastric cancer cells by regulating the RAS/ERK signaling pathway

The aim of this study was to investigate the biological characteristics of the RASAL1 gene in a well-differentiated gastric cancer cell line MKN-28 and a poorly differentiated gastric cancer cell line BGC-823 cells, using RNA interference and gene transfection technology, respectively. MKN-28 cells were transfected with the shRNA of RASAL1 and BGC-823 cells were transfected with the pcDNA 3.1 plasmid vector containing RASAL1. RT-PCR and western blotting were then used to detect the expression of RASAL1 mRNA and protein. The activities of RAS and extracellular signal-regulated kinase 1/2 were analyzed by the pull-down method and western blotting. The proliferate capacity, apoptosis rate, invasive and migratory potentials of MKN-28 or BGC-823 cells were also measured by Cell Counting Kit-8 cell proliferation assay, propidium iodide/Annexin V staining coupled with flow cytometry, and transwell chamber assays, respectively. Measurement of RASAL1 mRNA and protein expression in two cells revealed successful transfection of the shRNA of RASAL1 and RASAL1-pcDNA3.1 plasmid into these two cells. Moreover, decreased expression of RASAL1 in MKN-28 cells resulted in increased expression of RAS-GTP and p-ERK1/2. Interestingly, decreased expression of RASAL1 inhibited apoptosis and facilitated cell proliferation, invasion and migration. The increased expression of RASAL1 in BGC-823 cells caused declined expression of RAS-GTP and p-ERK1/2, as well as promoted apoptosis and restrained cell proliferation, invasion and migration. The down-regulation of RASAL1 promoted the proliferation, invasion and migration of gastric cancer MKN-28 cells, and up-regulation of RASAL1 inhibited the proliferation, invasion and migration of BGC-823 gastric cancer cells by regulating the RAS/ERK signaling pathway. Thus, our results suggest that RASAL1 may play an important role as a tumor suppressor gene in gastric cancer.

Deregulation of the miRNAs expression in cervical cancer: human papillomavirus implications

MicroRNAs (miRNAs) are a class of small non coding RNAs of 18-25 nucleotides in length. The temporal or short-lived expression of the miRNAs modulates gene expression post transcriptionally. Studies have revealed that miRNAs deregulation correlates and is involved with the initiation and progression of human tumors. Cervical cancer (CC) displays notably increased or decreased expression of a large number of cellular oncogenic or tumor suppressive miRNAs, respectively. However, understanding the potential role of miRNAs in CC is still limited. In CC, the high-risk human papillomaviruses (HR-HPVs) infection can affect the miRNAs expression through oncoprotein E6 and E7 that contribute to viral pathogenesis, although other viral proteins might also be involved. This deregulation in the miRNAs expression has an important role in the hallmarks of CC. Interestingly, the miRNA expression profile in CC can discriminate between normal and tumor tissue and the extraordinary stability of miRNAs makes it suitable to serve as diagnostic and prognostic biomarkers of cancer. In this review, we will summarize the role of the HR-HPVs in miRNA expression, the role of miRNAs in the hallmarks of CC, and the use of miRNAs as potential prognostic biomarkers in CC.

New advances of DNA methylation in liver fibrosis, with special emphasis on the crosstalk between microRNAs and DNA methylation machinery

Epigenetics refers to the study of heritable changes in the pattern of gene expression that is controlled by a mechanism specifically not due to changes the primary DNA sequence. Well-known epigenetic mechanisms include DNA methylation, post-translational histone modifications and RNA-based mechanisms including those controlled by small non-coding RNAs (miRNAs). Recent studies have shown that epigenetic modifications orchestrate the hepatic stellate cell (HSC) activation and liver fibrosis. In this review we focus on the aberrant methylation of CpG island promoters of select genes is the prominent epigenetic mechanism to effectively silence gene transcription facilitating HSC activation and liver fibrosis. Furthermore, we also discuss epigenetic dysregulation of tumor-suppressor miRNA genes by promoter DNA methylation and the interaction of DNA methylation with miRNAs involved in the regulation of HSC activation and liver fibrosis. Recent advances in epigenetics alterations in the pathogenesis of liver fibrosis and their possible use as new therapeutic targets and biomarkers.

Clinical significance of RASAL1 promoter methylation and ras activity in colorectal carcinoma

AIM: To detect RASAL1 (ras GTPase-activating-like protein 1) promoter methylation and ras activity in colorectal carcinoma (CRC) and to analyze their correlation with clinical and pathological parameters.

METHODS: Methylation-specific PCR (MSP) was used to detect RASAL1 promoter methylation in forty CRC specimens and matched normal colorectal tissue specimens. Co-immunoprecipitation was used to detected ras activity in tumor and normal tissues. The correlation of RASAL1 promoter methylation and ras activity with clinical and pathological parameters was analyzed.

RESULTS: RASAL1 promoter methylation was detected in 67.5% (26/40) of colorectal cancer tissues and in 30% (12/40) of normal tissues, and the positive rate of RASAL1 promoter methylation in tumor tissues was significantly higher than that in normal tissues (P = 0.0017). The median ras activity was significantly higher in colorectal cancer tissues than in normal tissues (1.07 vs 0.52, P < 0.001). RASAL1 promoter methylation and ras activity were both positively correlated with degree of tumor differentiation, invasion depth, lymph node metastasis, and TNM stage (all P < 0.05).

CONCLUSION: High ras activity is related to RASAL1 promoter methylation, which may play an important role in the oncogenesis of CRC. RASAL1 methylation and ras activity may be novel therapeutic targets for CRC.

In vivo and in vitro expression of the RASAL1 gene in human gastric adenocarcinoma and its clinicopathological significance

Recent studies have suggested that the RAS protein activator like-1 (RASAL1) is a potential tumor suppressor, which is found to be reduced in certain human cancers. Its downregulation is involved in the progression of malignancies. However, whether or not RASAL1 plays a role in the development of gastric cancer remains to be determined. Our study aimed to clarify the role of RASAL1 in the progression of gastric adenocarcinoma. The expression of RASAL1 in primary gastric adenocarcinoma tissue specimens was determined by immunohistochemistry. The expression of RASAL1 mRNA and protein was detected by RT-PCR and western blotting in gastric adenocarcinoma cell lines with varying differentiation statuses, including well-differentiated MKN-28, moderately differentiated SGC-7901 and poorly differentiated BGC-823, respectively. A normal gastric epithelial cell line, GES-l, was used as the control line. The immunohistochemical results revealed that the expression of the RASAL1 protein was mainly observed in the cytoplasm. Among 50 cases of gastric adenocarcinoma tissues, 12 cases were identified as (-), 23 cases (+), 13 cases (++) and 2 cases (+++). Among 50 cases of normal gastric tissues, 16 cases were (++) and 34 cases (+++). The expression of the RASAL1 protein was found to be decreased in the gastric adenocarcinoma tissue compared with normal gastric tissue (p<0.01). Moreover, in the gastric carcinoma tissues, the expression of RASAL1 was correlated with carcinoma diameter, differentiation grades, invasive depth, lymph node metastasis and TNM. Additionally, the RASAL1 mRNA and proteins were decreased in the three gastric adenocarcinoma cell lines compared with the normal gastric epithelial cell line GES-l. In addition, the downregulation of RASAL1 correlated with the differentiation status of cancer cell lines. Based on the above investigation, we conclude that expression of the RASAL1 gene is decreased in gastric carcinoma tissues and cell lines. The results indicate that RASAL1 may be important in the tumorigenesis and development of gastric carcinoma.

Clinical significance of expression of RASAL1 in gastric cancer

AIM: To detect the expression of Ras protein activator like 1 (RASAL1) in gastric cancer and to analyze its clinicopathological significance.

METHODS: Immunohistochemistry was used to detect RASAL1 expression in 50 cases of normal gastric tissue, 50 cases of low intraepithelial neoplasia, 50 cases of high intraepithelial neoplasia and early gastric carcinoma, and 50 cases of advanced gastric carcinoma. The correlation between RASAL1 expression and clinicopathological features of gastric cancer was then analyzed.

RESULTS: The positive rate of RASAL1 expression had significant differences among each group. The positive rate of RASAL1 expression was 94.0% (47/50) in normal gastric tissue, 70.0% (35/50) in low intraepithelial neoplasia, 42.0% (21/50) in intraepithelial neoplasia and early gastric carcinoma, and 18.0% (9/50) in advanced gastric carcinoma. The positive rate of RASAL1 expression was not correlated with sex, age, or tumor site, but was correlated with tumor size, differentiation, invasive depth and lymph node metastasis in high intraepithelial neoplasia and early gastric carcinoma and advanced gastric carcinoma (all P < 0.05).

CONCLUSION: Decreased expression of RASAL1 correlates with the development of gastric cancer. The lower expression of RASAL1 underlies bigger tumor size, lower degree of differentiation, deeper invasion, and more metastatic lymph nodes in patients with gastric cancer.

Clinical significance of RASAL1 expression in colorectal carcinoma

AIM: To investigate the expression of RASAL1 (Ras GTPase-activating-like protein 1) mRNA and protein in human colorectal carcinoma (CRC) and to analyze its correlation with tumor clinicopathological features.

METHODS: Fifty paraffin-embedded surgical CRC specimens, matched tumor-adjacent tissue specimens, and normal colorectal tissue specimens were used to detect the distribution of RASAL1 by immunohistochemistry (IHC). Twenty fresh CRC specimens, matched tumor-adjacent tissue specimens, and normal colorectal tissue specimens were used to determine the levels of RASAL1 mRNA expression by RT-PCR. The correlation between RASAL1 expression and tumor clinicopathological parameters was analyzed.

RESULTS: RASAL1 was mainly localized in the cytoplasm of glands cells. The positive rate of RASAL1 protein expression in CRC was significantly lower than those in tumor-adjacent tissue and normal colorectal tissue [46% (23/50) vs 85% (17/20), 96% (48/50), both P < 0.05]. The positive rate of RASAL1 mRNA expression was also significantly lower in CRC than in tumor-adjacent tissue and normal colorectal tissue [50% (10/20) vs 90% (18/20), 95% (19/20), both P < 0.05]. The expression of RASAL1 protein was positively related with that of RASAL1 mRNA (r = 0.686, P < 0.01), but negatively with tumor differentiation degree (P < 0.05), invasive depth (P < 0.01), lymph node metastasis (P < 0.05), and TNM stage (P < 0.05).

CONCLUSION: The expression of RASAL1 mRNA and protein is reduced in CRC. RASAL1 expression is negatively related to tumor progression. RASAL1 may be a novel therapeutic target for CRC.

Transcriptional signature of human macrophages exposed to the environmental contaminant benzo(a)pyrene

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed immunotoxic and carcinogenic environmental contaminants, known to affect macrophages. In order to identify their molecular targets in such cells, we have analyzed gene expression profile of primary human macrophages treated by the prototypical PAH benzo(a)pyrene (BaP), using pangenomic oligonucleotides microarrays. Exposure of macrophages to BaP for 8 and 24 h resulted in 96 and 1100 genes, differentially expressed by at least a twofold change factor, respectively. Some of these targets, including the chemokine receptor CXCR5, the G protein-coupled receptor 35 (GPR35), and the Ras regulator RASAL1, have not been previously shown to be affected by PAHs, in contrast to others, such as interleukin-1beta and the aryl hydrocarbon receptor (AhR) repressor. These BaP-mediated gene regulations were fully validated by reverse transcription-quantitative polymerase chain reaction assays for some selected genes. Their bioinformatic analysis indicated that biological functions linked to immunity, inflammation, and cell death were among the most affected by BaP in human macrophages and that the AhR and p53 signaling pathways were the most significant canonical pathways activated by the PAH. AhR and p53 implications were moreover fully confirmed by the prevention of BaP-related upregulation of some selected target genes by AhR silencing or the use of pifithrin-alpha, an inhibitor of PAH bioactivation-related DNA damage/p53 pathways. Overall, these data, through identifying genes and signaling pathways targeted by PAHs in human macrophages, may contribute to better understand the molecular basis of the immunotoxicity of these environmental contaminants.