Gene Summary

Gene:RASAL1; RAS protein activator like 1
Aliases: RASAL
Summary:The protein encoded by this gene is member of the GAP1 family of GTPase-activating proteins. These proteins stimulate the GTPase activity of normal RAS p21 but not its oncogenic counterpart. Acting as a suppressor of RAS function, the protein enhances the weak intrinsic GTPase activity of RAS proteins resulting in the inactive GDP-bound form of RAS, thereby allowing control of cellular proliferation and differentiation. This particular family member contains domains which are characteristic of the GAP1 subfamily of RasGAP proteins but, in contrast to the other GAP1 family members, this protein is strongly and selectively expressed in endocrine tissues. Alternatively spliced transcript variants that encode different isoforms have been described [provided by RefSeq, Jul 2010]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:rasGAP-activating-like protein 1
Source:NCBIAccessed: 31 August, 2019


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 31 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: RASAL1 (cancer-related)

Gorlov I, Orlow I, Ringelberg C, et al.
Identification of gene expression levels in primary melanoma associated with clinically meaningful characteristics.
Melanoma Res. 2018; 28(5):380-389 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Factors influencing melanoma survival include sex, age, clinical stage, lymph node involvement, as well as Breslow thickness, presence of tumor-infiltrating lymphocytes based on histological analysis of primary melanoma, mitotic rate, and ulceration. Identification of genes whose expression in primary tumors is associated with these key tumor/patient characteristics can shed light on molecular mechanisms of melanoma survival. Here, we show results from a gene expression analysis of formalin-fixed paraffin-embedded primary melanomas with extensive clinical annotation. The Cancer Genome Atlas data on primary melanomas were used for validation of nominally significant associations. We identified five genes that were significantly associated with the presence of tumor-infiltrating lymphocytes in the joint analysis after adjustment for multiple testing: IL1R2, PPL, PLA2G3, RASAL1, and SGK2. We also identified two genes significantly associated with melanoma metastasis to the regional lymph nodes (PIK3CG and IL2RA), and two genes significantly associated with sex (KDM5C and KDM6A). We found that LEF1 was significantly associated with Breslow thickness and CCNA2 and UBE2T with mitosis. RAD50 was the gene most significantly associated with survival, with a higher level of expression associated with worse survival.

Angelousi A, Settas N, Faucz FR, et al.
Medullary thyroid cancer, leukemia, mesothelioma and meningioma associated with germline APC and RASAL1 variants: a new syndrome?
Hormones (Athens). 2017; 16(4):423-428 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor hereditary in 35% of cases. The most common syndromic form is in the context of the multiple endocrine neoplasia type 2 (MEN 2) syndromes in association with other tumors and due to germline RET mutations. We describe a 57-year-old female patient diagnosed with sporadic MTC. The patient had a history of other neoplasias, such as acute myeloid leukemia, for which she had received chemotherapy, and two other solid tumors, peritoneal mesothelioma and meningioma. Genetic analyses were carried out including whole exome and Sanger sequencing (WES and SS) and loss-of-heterozygosity (LOH) testing for the respective loci. Immunohistochemistry (IHC) was used for the detection of proteins of interest. WES showed two germline variants in the APC and RASAL1 genes confirmed by SS. In MTC tissue only there was a RETvariant identified by SS; germline studies did not show any RETsequence changes. The pattern of tumors in this patient is unusual for either one of the APC- orRASAL1-associated neoplasms and her non-MEN 2-associated MTC contained a RET variant like other sporadic MTCs. As in other patients with more than one genetic variant predisposing to tumors, it is possible that this case represents a unique association.

Jin W, Chen L, Cai X, et al.
Long non-coding RNA TUC338 is functionally involved in sorafenib-sensitized hepatocarcinoma cells by targeting RASAL1.
Oncol Rep. 2017; 37(1):273-280 [PubMed] Related Publications
Development of novel targeted therapy holds promise for conquering chemotherapy resistance, one of major hurdles in current liver cancer treatment. We found that long non-coding RNA TUC338 is involved in the development of hepatocellular carcinoma (HCC) and sorafenib resistance. HCC cell lines were transfected with siTUC338, then cell proliferation and invasion ability were investigated by MTT and Transwell assay. Sorafenib resistance HepG2 cells were generated to test the role of TUC338 in sorafenib sensitivity. Intratumoral delivering of siTUC338 was used to analyze the sorafenib treatment response in HepG2/Sor xenografts in vivo. Higher levels of TUC338 were found both in HCC tissues and cell lines, knockdown of TUC338 was accompanied with increased expression of RASAL1 in HCC cell line with increased proliferation and invasion ability, knockdown of TUC338 could activate the RASAL1 pathway and inhibit tumor growth genes by directly targeting RASAL1 3'-UTR. Furthermore, knockdown of TUC338 in HepG2 sorafenib sensitized its reaction to the treatment of sorafenib, which was accompanied by increased expression RASAL1; intratumoral delivering of siTUC338 could also restore sorafenib treatment response in HepG2/Sor xenografts in vivo. These findings provide direct evidence that the TUC338/RASAL1 axis might play an essential role in sorafenib-resistance of liver cancer cells, suggesting the signaling cohort could serve as a novel therapeutic target for the treatment of chemotherapy resistant liver cancer.

Guérin M, Thariat J, Ouali M, et al.
A new subtype of high-grade mandibular osteosarcoma with RASAL1/MDM2 amplification.
Hum Pathol. 2016; 50:70-8 [PubMed] Related Publications
In contrast to long bone osteosarcoma, mandibular osteosarcoma is highly heterogeneous and morphologically overlaps with benign tumors, obscuring diagnosis and treatment selection. Molecular characterization is difficult due to the paucity of available specimens of this rare disease. We aimed to characterize the spectrum of mandibular osteosarcoma using immunohistochemistry and molecular techniques (quantitative polymerase chain reaction and sequencing) and compare them with benign fibro-osseous lesions. Forty-nine paraffin-embedded mandible osteosarcoma tissue samples were collected retrospectively and compared with 10 fibrous dysplasia and 15 ossifying fibroma cases. These were analyzed for molecular markers thought to differ between the different diseases and subtypes: MDM2 (murine double-minute type 2) overexpression, GNAS (guanine nucleotide-binding protein/α subunit) mutations, and amplification of MDM2 and/or RASAL1 (RAS protein activator like 1). Five fibroblastic high-grade osteosarcoma subtypes showed MDM2 amplification, including 2 with a microscopic appearance of high-grade osteosarcoma with part low-grade osteosarcoma (differentiated/dedifferentiated osteosarcoma) and MDM2 overexpression. The other 3 contained a coamplification of MDM2 and RASAL1, a signature also described for juvenile ossifying fibroma, with no overexpression of MDM2. These were of the giant cell-rich high-grade osteosarcoma, with areas mimicking juvenile ossifying fibroma (ossifying fibroma-like osteosarcoma). Our results show that some diagnosed high-grade osteosarcomas are differentiated/dedifferentiated osteosarcomas and harbor an overexpression and amplification of MDM2. In addition, juvenile ossifying fibromas can potentially evolve into giant cell-rich high-grade osteosarcomas and are characterized by a RASAL1 amplification (osteosarcoma with juvenile ossifying fibroma-like genotype). Thus, the presence of a RASAL1 amplification in ossifying fibroma may indicate a requirement for closer follow-up and more aggressive management.

Jeon MJ, Chun SM, Kim D, et al.
Genomic Alterations of Anaplastic Thyroid Carcinoma Detected by Targeted Massive Parallel Sequencing in a BRAF(V600E) Mutation-Prevalent Area.
Thyroid. 2016; 26(5):683-90 [PubMed] Related Publications
BACKGROUND: Anaplastic thyroid carcinoma (ATC), the most aggressive type of thyroid cancer, has no effective therapy. Due to its dismal prognosis, it is vital to understand the genetic alterations of ATC and identify effective molecular targets. Targeted next-generation sequencing was performed to investigate the mutational profile of ATC using a massive parallel sequencing approach.
METHODS: DNA from formalin-fixed, paraffin-embedded archival samples of 11 ATCs and normal matched pairs were used. A total of 48 genetic alterations were identified by targeted exome sequencing. These alterations were validated by mass spectrometric genotyping and direct Sanger sequencing.
RESULTS: The most commonly mutated gene was BRAF, identified in 10 samples (91%), all showing the V600E point mutation. A KRAS point mutation was observed in the one sample (9%) without the BRAF(V600E) mutation. All 11 ATCs harbored BRAF or RAS mutations, reflecting the possibility that differentiated thyroid carcinomas progress to ATCs after the accumulation of mutations. A loss of function mutation of TP53 was observed in eight samples (73%), a PIK3CA mutation was observed in two samples (18%), and a frameshift mutation of PTEN was observed in one sample (9%). Twenty-eight novel mutated genes were found that had not previously been associated with ATC. Of these, loss of function mutations of NF2, KMT2D, and PKHD1 were repeatedly seen in three samples (27%), two samples (18%), and two samples (18%), respectively. Using direct Sanger sequencing, two samples (18%) were also found with a RASAL1 mutation. KMT2D and RASAL1 mutations were significantly associated with shorter ATC patient survival.
CONCLUSIONS: This comprehensive analysis of ATCs using targeted massive parallel sequencing identified several novel mutations in ATCs, such as loss of function mutations of NF2 or KMT2D. Future studies are needed to confirm the role of these novel mutations as independent drivers of ATC development.

Buffet C, Groussin L
Molecular perspectives in differentiated thyroid cancer.
Ann Endocrinol (Paris). 2015; 76(1 Suppl 1):1S8-15 [PubMed] Related Publications
Progress in understanding the molecular genetics of thyroid cancer in the last 20 years has accelerated recently with the advent of high-throughput sequencing technologies known as Next-Generation Sequencing. Besides classical molecular abnormalities involving the MAPK (Mitogen Activated Protein Kinase) and PI3K (PhosphoInositide 3-Kinase) pathways that play a key role in follicular-derived thyroid tumorigenesis, new molecular abnormalities have been discovered. The major advances in recent years have been the discovery of new somatic driver gene point mutations (such as RASAL1 [RAS protein activator Like 1] mutations in follicular cancer) and/or mutations that have prognostic value (such as TERT [Telomerase reverse transcriptase] promoter mutations); new chromosomal rearrangements, usually having close connection with exposure to ionizing radiation (such as ALK [Anaplastic Lymphoma Kinase] rearrangements); and deregulation of some gene or microRNA expression representing a molecular signature. Progress made in understanding the molecular mechanisms of thyroid cancer offers new perspectives for the diagnosis of the benign or malignant status of a thyroid nodule, to refine prognosis and offer new perspectives of targeted therapy for radioiodine-refractory cancers.

Liu H, Li Z, Li L, et al.
EBP1 suppresses growth, migration, and invasion of thyroid cancer cells through upregulating RASAL expression.
Tumour Biol. 2015; 36(11):8325-31 [PubMed] Related Publications
Ebp1, a protein identified by its interactions with the ErbB3 receptor, has been characterized as a negative regulator of cancers. RAS GTPase-activating protein (RasGAP), RASAL1, was recently identified as a major tumor suppressor in thyroid cancer. In this study, we examined EBP1 expression in papillary and follicular thyroid cancer cells. We found that compared with normal thyroid cells, TPC1, WRO, and FTC133 thyroid tumor cells exhibited lower EBP1 expression at messenger RNA (mRNA) and protein levels. We then investigated the effects of forced EBP1 expression on growth, migration, and invasiveness of thyroid tumor cells. By using MTT and Boyden chamber assays, we showed that EBP1 overexpression dramatically reduced growth rate, migration, and invasiveness of K1 and FTC133 thyroid tumor cells. Furthermore, we explored the molecular mechanism underlying the effects of EBP1 on the cells by disclosing the correlation of EBP1 and RASAL1 expression. RASAL expression was elevated in thyroid tumor cells overexpressing EBP1. Knockdown RASAL by transduction of RASAL1 shRNA lentiviral particles markedly reduced RASAL levels with restoration of EBP1, and RASAL1 knockdown abrogated the effects of forced EBP1 expression on cell growth, migration, and invasiveness of thyroid tumor cells. These findings suggest that Ebp1 suppressed thyroid cancer cell lines by upregulating RASRAL expression.

Tabareau-Delalande F, Collin C, Gomez-Brouchet A, et al.
Chromosome 12 long arm rearrangement covering MDM2 and RASAL1 is associated with aggressive craniofacial juvenile ossifying fibroma and extracranial psammomatoid fibro-osseous lesions.
Mod Pathol. 2015; 28(1):48-56 [PubMed] Related Publications
To evaluate the diagnostic value of MDM2 status in craniofacial fibro-osseous lesions, we investigated MDM2 expression by immunohistochemistry and analyzed MDM2 amplification by qPCR in 30 cases of ossifying fibroma (including 13 cases of the juvenile variant) and 17 cases of fibrous dysplasia. Two cases of uncommon extragnathic psammomatoid fibrous dysplasia and a mixed control group of 15 cases of low-grade osteosarcoma and 15 cases of well-differentiated/dedifferentiated liposarcoma were included. MDM2 amplification was found in 33% of ossifying fibromas (peak of 69% for the juvenile variant) and in 12% of fibrous dysplasia, in none of which was MDM2 overexpressed. All control cases exhibited MDM2 amplification and overexpression. To investigate possible polysomy of chromosome 12, we studied RASAL1 amplification, a gene telomeric to MDM2 on the long arm of chromosome 12. RASAL1 amplification was reported in all benign fibro-osseous lesions exhibiting MDM2 amplification but not in controls. Simultaneous amplification of these two genes was significantly higher in juvenile ossifying fibromas compared with fibrous dysplasia (P=0.004), non-juvenile ossifying fibromas (P=0.001), and all other benign craniofacial fibro-osseous lesions combined (P=0.0001). Of the nine cases of juvenile ossifying fibroma exhibiting amplification, three were locally invasive and four were recurrent, suggesting aggressive disease. The two cases of extragnathic psammomatoid fibrous dysplasia also showed MDM2 and RASAL1 amplification with no MDM2 overexpression. This large chromosome 12 rearrangement, spanning MDM2 and RASAL1, is the first recurrent molecular abnormality to be reported in juvenile ossifying fibroma. It may represent both a molecular diagnostic marker and a characteristic of more aggressive forms with a higher risk of recurrence. Finally, the presence of this rearrangement in extragnathic psammomatoid fibro-osseous lesions mimicking ossifying fibromas might reflect a common molecular pathway in their pathogenesis and calls into question the classification of such lesions within fibrous dysplasia.

Ngeow J, Ni Y, Tohme R, et al.
Germline alterations in RASAL1 in Cowden syndrome patients presenting with follicular thyroid cancer and in individuals with apparently sporadic epithelial thyroid cancer.
J Clin Endocrinol Metab. 2014; 99(7):E1316-21 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
CONTEXT: RASAL1 has recently been identified as an important tumor suppressor for sporadic thyroid tumorigenesis, particularly for follicular thyroid cancer (FTC) and anaplastic thyroid cancer. Thyroid cancer is an important component of Cowden syndrome (CS). Patients with germline PTEN mutations have an overrepresentation of FTC over other histological subtypes.
OBJECTIVE: To determine the prevalence of germline RASAL1 mutations in PTEN mutation-positive and wild type CS patients.
SETTING AND DESIGN: We reviewed our prospective database of more than 3000 CS/CS-like patients and retrospectively identified a subset of patients who presented with thyroid cancer for RASAL1 mutation analysis. We reviewed data from The Cancer Genome Atlas (TCGA) sporadic papillary thyroid cancer (PTC) database with germline data for RASAL1 mutations to determine the prevalence of germline RASAL1 mutations in CS-related thyroid cancer patients.
RESULTS: We scanned 155 CS/CS-like patients with thyroid cancer for germline RASAL1 mutations. Of the 155 patients, 39 had known germline pathogenic PTEN mutations (PTEN(mut+)) and 116 were PTEN mutation negative (PTEN(WT)). Among these 155 patients, we identified RASAL1 germline alterations suspected as being deleterious in two patients. Both were patients with PTEN(WT) who had FTC (2/48, 4.1%). This was in contrast to patients with PTEN(mut+) who had thyroid cancer (0/39). Of 339 sporadic patients with PTC from the TCGA study, 62 (18%) had germline RASAL1 variants predicted to be deleterious. TCGA patients with follicular-variant PTC were statistically overrepresented (21/62, 34%) among patients with deleterious RASAL1 variants compared with those without (57/277, 21%).
CONCLUSIONS: Germline RASAL1 alterations are uncommon in patients with CS but may not be infrequent in patients with apparently sporadic follicular-variant PTC.

Chen H, Cheng ZY, Pan Y, et al.
RASAL1 influences the proliferation and invasion of gastric cancer cells by regulating the RAS/ERK signaling pathway.
Hum Cell. 2014; 27(3):103-10 [PubMed] Related Publications
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.

Chen H, Pan Y, Cheng ZY, et al.
Hypermethylation and clinicopathological significance of RASAL1 gene in gastric cancer.
Asian Pac J Cancer Prev. 2013; 14(11):6261-5 [PubMed] Related Publications
BACKGROUND: Recent studies have suggested that expression of the RAS protein activator like-1 gene (RASAL1) is decreased in gastric carcinoma tissues and cell lines, indicated a role in tumorigenesis and development of gastric cancer. Reduced expression of RASAL1 could result in aberrant increase of activity of RAS signaling pathways in cancer cells. However, the exact mechanism which induces down-regulation of the RASAL1 gene remains unclear. This study aimed to determine the methylation status and regulation of RASAL1 in gastric cancer.
MATERIALS AND METHODS: Using the methylation-specific polymerase chain reaction (MSP), the methylation status of CpG islands in the RASAL1 promoter in gastric cancers and paired adjacent non-cancerous tissues from 40 patients was assessed and its clinicopathological significance was analyzed. The methylation status of RASAL1 in gastric cancer lines MKN-28, SGC-790l, BGC-823, as well as in normal gastric epithelial cell line GES-l was also determined after treatment with a DNA methyltransferase inhibitor, 5-aza-2'-doexycytidine (5-Aza-CdR). RAS activity (GAS-GTP) was assessed through a pull-down method, while protein levels of ERK1/2, a downstream molecule of RAS signaling pathways, were determined by Western blotting.
RESULTS: The frequencies of RASAL1 promoter methylation in gastric cancer and paired adjacent non-cancerous tissues were 70% (28/40) and 30% (12/40) respectively (P<0.05). There were significantly correlations between RASAL1 promoter methylation with tumor differentiation, tumor size, invasive depth and lymph node metastasis in patients with gastric cancer (all P<0.05), but no correlation was found for age or gender. Promoter hypermethylation of the RASAL1 gene was detected in MKN-28, SGC-790l and BGC-823 cancer cells, but not in the normal gastric epithelial cell line GES-1. Elevated expression of the RASAL1 protein, a decreased RAS-GTP and p-ERK1/2 protein were detected in three gastric cancer cell lines after treatment with 5-Aza-CdR.
CONCLUSIONS: Aberrant hypermethylation of the RASAL1 gene promoter frequently occurs in gastric cancer tissues and cells. In addition, the demethylating agent 5-Aza-CdR can reverse the hypermethylation of RASAL1 gene and up-regulate the expression of RASAL1 significantly in gastric cancer cells in vivo. Our study suggests that RASAL1 promoter methylation may have a certain relationship with the reduced RASAL1 expression in gastric cancer.

Liu D, Yang C, Bojdani E, et al.
Identification of RASAL1 as a major tumor suppressor gene in thyroid cancer.
J Natl Cancer Inst. 2013; 105(21):1617-27 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
BACKGROUND: RAS-coupled MAPK and PI3K pathways play a fundamental role in thyroid tumorigenesis, and classical genetic alterations upregulating these pathways are well characterized. We hypothesized that gene abnormality of negative modulators of these signaling pathways might be an important alternative genetic background for thyroid cancer.
METHODS: By examining gene expression patterns of negative modulators of RAS signaling, we attempted to identify potential tumor suppressor genes. We then analyzed the methylation and mutation patterns of the identified gene in 101 thyroid tumors and tested its functions in vitro and in vivo to establish the tumor suppressor role in thyroid cancer.
RESULTS: Among 13 negative modulators of the RAS pathway screened, RASAL1, encoding a RAS GTPase-activating protein, was frequently hypermethylated in thyroid cancers, which was coupled to its silencing in thyroid cancer cells. We also, for the first time, identified the presence of RASAL1 mutations, with a prevalence of 4.88% (n = 2 of 41) in follicular thyroid cancer (FTC) and 16.67% (n = 5 of 30) in anaplastic thyroid cancer (ATC). RASAL1 displayed MAPK- and PI3K-suppressing and thyroid tumor-suppressing activities, which were all impaired by the mutations. Hypermethylation and mutations of RASAL1 were mutually exclusive and collectively found in zero of 20 benign thyroid tumors, 3.22% (n = 1 of 31) of papillary thyroid cancers, 31.70% (n = 13 of 41) of FTCs, and 33.33% (n = 10 of 30) of ATCs. A rate of 20.83% (n = 5 of 24) of tumors carrying RASAL1 mutation or methylation at high levels (>50%) vs 44.16% (n = 34 of 77) of tumors carrying no RASAL1 mutation or methylation at low levels (< 50%) harbored any of the classical mutations (two-sided P = .02, Fisher exact test) in RAS, BRAF, PTEN, and PIK3CA genes in the MAPK and PI3K pathways, revealing a largely mutually exclusive relationship.
CONCLUSIONS: We identified RASAL1 as a major tumor suppressor gene that is frequently inactivated by hypermethylation and mutations, providing a new alternative genetic background for thyroid cancer, particularly FTC and ATC.

Qiao F, Su X, Qiu X, et al.
Enforced expression of RASAL1 suppresses cell proliferation and the transformation ability of gastric cancer cells.
Oncol Rep. 2012; 28(4):1475-81 [PubMed] Related Publications
RAS protein activator like 1 (RASAL1) is a member of the RAS GTPase-activating protein (GAP) family, and it is an important molecule in the regulation of RAS activation. In the present study, we investigated the role of RASAL1 in gastric carcinogenesis. Decreased expression pattern of RASAL1 in gastric cancer tissues and cell lines was found in protein and RNA levels, although there was no statistically significant relationship between RASAL1 and clinicopathological features. Restored expression of RASAL1 induced by DNA methylation inhibitor 5-aza-2'-deoxycytidine (5'-AZA) and HDAC inhibitor trichostatin A (TSA) implied that RASAL1 expression is regulated by epigenetic mechanisms. The biological role of RASAL1 in gastric carcinogenesis was determined by in vitro tumorigenicity assays. Overexpression of RASAL1 showed suppression of cell proliferation due to cell apoptosis. Subsequently, enforced expression of RASAL1 repressed significantly the gastric cancer cell transformation ability. These findings demonstrated that decreased RASAL1 expression is a characteristic of gastric cancer and regulated by epigenetic mechanisms. RASAL1 may be a functional tumor suppressor involved in gastric cancer. This study provides novel insights into the biological role of RASAL1 in gastric carcinogenesis.

Zhu J, Jiang Z, Gao F, et al.
A systematic analysis on DNA methylation and the expression of both mRNA and microRNA in bladder cancer.
PLoS One. 2011; 6(11):e28223 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
BACKGROUND: DNA methylation aberration and microRNA (miRNA) deregulation have been observed in many types of cancers. A systematic study of methylome and transcriptome in bladder urothelial carcinoma has never been reported.
METHODOLOGY/PRINCIPAL FINDINGS: The DNA methylation was profiled by modified methylation-specific digital karyotyping (MMSDK) and the expression of mRNAs and miRNAs was analyzed by digital gene expression (DGE) sequencing in tumors and matched normal adjacent tissues obtained from 9 bladder urothelial carcinoma patients. We found that a set of significantly enriched pathways disrupted in bladder urothelial carcinoma primarily related to "neurogenesis" and "cell differentiation" by integrated analysis of -omics data. Furthermore, we identified an intriguing collection of cancer-related genes that were deregulated at the levels of DNA methylation and mRNA expression, and we validated several of these genes (HIC1, SLIT2, RASAL1, and KRT17) by Bisulfite Sequencing PCR and Reverse Transcription qPCR in a panel of 33 bladder cancer samples.
CONCLUSIONS/SIGNIFICANCE: We characterized the profiles between methylome and transcriptome in bladder urothelial carcinoma, identified a set of significantly enriched key pathways, and screened four aberrantly methylated and expressed genes. Conclusively, our findings shed light on a new avenue for basic bladder cancer research.

Delahanty RJ, Beeghly-Fadiel A, Xiang YB, et al.
Association of obesity-related genetic variants with endometrial cancer risk: a report from the Shanghai Endometrial Cancer Genetics Study.
Am J Epidemiol. 2011; 174(10):1115-26 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Obesity is a well-established risk factor for endometrial cancer, the most common gynecologic malignancy. Recent genome-wide association studies (GWAS) have identified multiple genetic markers for obesity. The authors evaluated the association of obesity-related single nucleotide polymorphisms (SNPs) with endometrial cancer using GWAS data from their recently completed study, the Shanghai Endometrial Cancer Genetics Study, which comprised 832 endometrial cancer cases and 2,049 controls (1996-2005). Thirty-five SNPs previously associated with obesity or body mass index (BMI; weight (kg)/height (m)(2)) at a minimum significance level of ≤5 × 10(-7) in the US National Human Genome Research Institute's GWAS catalog (http://genome.gov/gwastudies) and representing 26 unique loci were evaluated by either direct genotyping or imputation. The authors found that for 22 of the 26 unique loci tested (84.6%), the BMI-associated risk variants were present at a higher frequency in cases than in population controls (P = 0.0003). Multiple regression analysis showed that 9 of 35 BMI-associated variants, representing 7 loci, were significantly associated (P ≤ 0.05) with the risk of endometrial cancer; for all but 1 SNP, the direction of association was consistent with that found for BMI. For consistent SNPs, the allelic odds ratios ranged from 1.15 to 1.29. These 7 loci are in the SEC16B/RASAL, TMEM18, MSRA, SOX6, MTCH2, FTO, and MC4R genes. The associations persisted after adjustment for BMI, suggesting that genetic markers of obesity provide value in addition to BMI in predicting endometrial cancer risk.

Bell A, Bell D, Weber RS, El-Naggar AK
CpG island methylation profiling in human salivary gland adenoid cystic carcinoma.
Cancer. 2011; 117(13):2898-909 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
BACKGROUND: DNA methylation is a fundamental epigenetic event associated with physiologic and pathologic conditions, including cancer. Hypermethylation of CpG islands at active gene promoters leads to transcriptional repression, whereas hypomethylation is associated with gene overexpression. The aim of this study was to identify genes in adenoid cystic carcinoma (ACC) of salivary gland strongly deregulated by epigenetic CpG island methylation, to validate selected genes by conventional techniques, and to correlate the findings with clinicopathologic factors.
METHODS: The authors analyzed 16 matched normal and tumor tissues for aberrant DNA methylation using the methylated CpG island amplification and microarray method and the pyrosequencing technique.
RESULTS: Microarray analysis showed hypomethylation in 7 and hypermethylation in 32 CpG islands. Hypomethylation was identified in CpG islands near FBXO17, PHKG1, LOXL1, DOCK1, and PARVG. Hypermethylation was identified near genes encoding predominantly transcription factors (EN1, FOXE1, GBX2, FOXL1, TBX4, MEIS1, LBX2, NR2F2, POU3F3, IRX3, TFAP2C, NKX2-4, PITX1, NKX2-5), and 13 genes with different functions (MT1H, EPHX3, AQPEP, BCL2L11, SLC35D3, S1PR5, PNLIPRP1, CLIC6, RASAL, XRN2, GSTM5, FNDC1, INSRR). Four CpG islands by EN1, FOXE1, TBX4, and PITX1 were validated by pyrosequencing.
CONCLUSIONS: The highly methylated genes in tumor versus normal tissue are linked to developmental, apoptotic, and other fundamental cellular pathways, suggesting that down-regulation of these genes is associated with ACC development and progression. With EN1 hypermethylation showing potential as a possible biomarker for ACC in salivary gland, the biological and therapeutic implications of these findings require further preclinical investigations.

Calvisi DF, Ladu S, Conner EA, et al.
Inactivation of Ras GTPase-activating proteins promotes unrestrained activity of wild-type Ras in human liver cancer.
J Hepatol. 2011; 54(2):311-9 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
BACKGROUND & AIMS: Aberrant activation of the RAS pathway is ubiquitous in human hepatocarcinogenesis, but the molecular mechanisms leading to RAS induction in the absence of RAS mutations remain under-investigated. We defined the role of Ras GTPase activating proteins (GAPs) in the constitutive activity of Ras signaling during human hepatocarcinogenesis.
METHODS: The mutation status of RAS genes and RAS effectors was assessed in a collection of human hepatocellular carcinomas (HCC). Levels of RAS GAPs (RASA1-4, RASAL1, nGAP, SYNGAP1, DAB2IP, and NF1) and the RASAL1 upstream inducer PITX1 were determined by real-time RT-PCR and immunoblotting. The promoter and genomic status of RASAL1, DAB2IP, NF1, and PITX1 were assessed by methylation assays and microsatellite analysis. Effects of RASAL1, DAB2IP, and PITX1 on HCC growth were evaluated by transfection and siRNA analyses of HCC cell lines.
RESULTS: In the absence of Ras mutations, downregulation of at least one RAS GAP (RASAL1, DAB2IP, or NF1) was found in all HCC samples. Low levels of DAB2IP and PITX1 were detected mostly in a HCC subclass from patients with poor survival, indicating that these proteins control tumor aggressiveness. In HCC cells, reactivation of RASAL1, DAB2IP, and PITX1 inhibited proliferation and induced apoptosis, whereas their silencing increased proliferation and resistance to apoptosis.
CONCLUSIONS: Selective suppression of RASAL1, DAB2IP, or NF1 RAS GAPs results in unrestrained activation of Ras signaling in the presence of wild-type RAS in HCC.

Aytekin T, Ozaslan M, Cengiz B
Deletion mapping of chromosome region 12q13-24 in colorectal cancer.
Cancer Genet Cytogenet. 2010; 201(1):32-8 [PubMed] Related Publications
Colorectal cancer is one of the most common cancers in the world. Colorectal cancer develops after a long and multistep process of carcinogenesis. Inactivation of tumor suppressor genes is among the most important steps in development of colorectal cancer. Analysis of loss of heterozygosity (LOH) is an effective method to determine the localization of tumor suppressor genes. In this study, we used five microsatellite markers to analyze the region 12q13-24 among 47 patients with colorectal cancer. The frequency of LOH and the clinicopathological data were compared using logistic regression and a chi-square test. In 34 of 47 tumor tissues (72%), LOH was detected at least in one marker. The highest LOH frequency was 34%, on the D12S129 locus; the lowest frequency was 23%, on the D12S78 locus. Loss of heterozygosity was detected as 32% on D12S83, 30% on D12S346, and 26% on D12S1660. No statistically significant correlation was found between the frequency of LOH and clinicopathological features (P > 0.05). Chromosome region 12q13-24 contains several known genes that may be candidate tumor suppressor genes, including RASAL1, ITGA7, STAB2, GLIPR1, and SLC5A8. Although the exact roles of these genes in colorectal cancer formation remain to be clarified, the present data point to a tumor suppressor role.

Seto M, Ohta M, Ikenoue T, et al.
Reduced expression of RAS protein activator like-1 in gastric cancer.
Int J Cancer. 2011; 128(6):1293-302 [PubMed] Related Publications
RAS signaling is frequently deregulated in human neoplasms. However, RAS mutations have been found in only a small proportion of human gastric cancers, implicating other mechanisms in the activation of RAS signaling in gastric tumorigenesis. We have previously reported that decreased expression of RAS protein activator like-1 (RASAL1), a member of the RAS-GTPase-activating proteins that switch off RAS activity, contributes to colon tumor progression. In our study, we explored the involvement of decreased RASAL1 expression in gastric tumorigenesis. RASAL1 expression was reduced in 6 of 10 gastric cancer cell lines examined by immunoblotting. Knockdown of RASAL1 increased mitogen-activated protein kinase signaling in response to growth factor stimulation, and the forced expression of RASAL1 reduced proliferation of gastric cancer cells. Immunohistochemical analyses in primary gastric tumors showed that RASAL1 expression was reduced in 23 of 48 (48%) of the gastric cancers but in none of the adenomas (0/10). Methylation of the RASAL1 promoter region and loss of heterozygosity (LOH) at the RASAL1 locus were examined to investigate the causes of RASAL1 silencing. All cell lines with reduced RASAL1 had RASAL1 methylation, and two had LOH. In primary gastric cancers, methylation or LOH was detected in 50% (6/12) of those with reduced RASAL1. Furthermore, RASAL1 expression was restored in some cell lines by histone deacetylase inhibitor treatment. Our findings demonstrate that reduced RASAL1 expression, partly due to genetic and epigenetic changes, contributes to gastric carcinogenesis, and also re-emphasize the importance of RAS signaling in gastric cancer development.

Ma BB, Sung F, Tao Q, et al.
The preclinical activity of the histone deacetylase inhibitor PXD101 (belinostat) in hepatocellular carcinoma cell lines.
Invest New Drugs. 2010; 28(2):107-14 [PubMed] Related Publications
The activity of the histone deacetylase inhibitor PXD101 was investigated in three hepatocellular carcinoma (HCC) cell lines. PXD101 was found to inhibit cell growth at a dose-dependent manner and induce histone acetylation in PLC/PRF/5, Hep3B and HepG2 cells. In PLC/PRF/5 and Hep3B cells which express hepatitis B-related genes (HBx, HBc and HBc), treatment with PXD101 resulted in apoptosis without a significant effect on viral gene expression. Exposure to PXD101 for up to 48 h had varying effects on the expression of 12 cellular genes with tumor suppressor functions, including p21, SOCS1, CMTM5, RASAL1, DLEC1, SFRP (-1, -2, -4 and -5), ADAMTS (-8 and -9). This study provided the basis for a phase II clinical trial of PXD101 in inoperable hepatitis-B associated HCC.

Ohta M, Seto M, Ijichi H, et al.
Decreased expression of the RAS-GTPase activating protein RASAL1 is associated with colorectal tumor progression.
Gastroenterology. 2009; 136(1):206-16 [PubMed] Related Publications
BACKGROUND & AIMS: Although colorectal cancer (CRC) progression has been associated with alterations in KRAS and RAS signaling, not all CRC cells have KRAS gene mutations. RAS activity is modulated by RAS-GTPase-activating proteins (RASGAPs), so we investigated the role of RASGAPs in CRC progression.
METHODS: The level of RASGAP expression in CRC cells was analyzed using quantitative real-time polymerase chain reaction. The expression of the RAS protein activator like-1 (RASAL1) was examined in clinical colorectal neoplasms using immunohistochemistry. The clinicopathologic (age, sex, and tumor site and grade) and molecular (KRAS gene mutation, as well as CTNNB1 and TP53 expression patterns) factors that could affect RASAL1 expression were examined.
RESULTS: Of 12 RASGAPs examined, expression levels of only RASAL1 decreased in CRC cells; RASAL1 expression decreased in most CRC cells with wild-type KRAS gene but rarely in those with mutant KRAS gene. A transfection assay showed that RASAL1 repressed RAS/mitogen-activated protein kinase signaling in response to growth factor stimulation and reduced proliferation of CRC cells that contained wild-type KRAS gene. RASAL1 expression was detected in 46.9% (30/64) of adenocarcinoma, 17.4% (8/46) of large adenoma, and no (0/42) small adenoma samples. RASAL1 expression levels were correlated with the presence of wild-type KRAS gene in CRC tumor samples (P= .0010), distal location (P= .0066), and abnormal expression of TP53 (P= .0208).
CONCLUSIONS: RASAL1 expression is reduced in CRC cells that contain wild-type KRAS gene. Reductions in RASAL1 expression were detected more frequently in advanced lesions than in small adenomas, suggesting that RASAL1 functions in the progression of benign colonic neoplasms.

Jin H, Wang X, Ying J, et al.
Epigenetic silencing of a Ca(2+)-regulated Ras GTPase-activating protein RASAL defines a new mechanism of Ras activation in human cancers.
Proc Natl Acad Sci U S A. 2007; 104(30):12353-8 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Ras has achieved notoriety as an oncogene aberrantly activated in multiple human tumors. Approximately 30% of all human tumors express an oncogenic form of this GTPase that is locked in an active conformation as a result of being insensitive to Ras GTPase-activating proteins (GAPs), proteins that normally regulate the inactivation of Ras by enhancing its intrinsic GTPase activity. Besides oncogenic mutations in Ras, signaling by wild-type Ras is also frequently deregulated in tumors through aberrant coupling to activated cell surface receptors. This indicates that alternative mechanisms of aberrant wild-type Ras activation may be involved in tumorigenesis. Here, we describe another mechanism through which aberrant Ras activation is achieved in human cancers. We have established that Ras GTPase-activating-like protein (RASAL), a Ca(2+)-regulated Ras GAP that decodes the frequency of Ca(2+) oscillations, is silenced through CpG methylation in multiple tumors. With the finding that ectopic expression of catalytically active RASAL leads to growth inhibition of these tumor cells by Ras inactivation, we have provided evidence that epigenetically silencing of this Ras GAP represents a mechanism of aberrant Ras activation in certain cancers. Our demonstration that RASAL constitutes a tumor suppressor gene has therefore further emphasized the importance of Ca(2+) in the regulation of Ras signaling and has established that deregulation of this pathway is an important step in Ras-mediated tumorigenesis.

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