Promoter Methylation Status Of RASSF1A Research Articles

Promoter methylation status of RASSF1A and RASSF2A tumor suppressor genes in endometrial endometrioid carcinomas

We aimed to investigate the promoter methylation status of RASSF1A and RASSF2A tumor suppressor genes in endometrial endometrioid carcinomas with p53 wild type and mismatch repair proficient. Genomic DNAs were isolated from 50 specimens (15 formalin-fixed paraffin embedded tumor tissues, 15 paired blood samples and 20 normal endometrial tissues). Bisulfide modification and methylation-specific polymerase chain reaction were performed. As a result of the study, while no significance was found for RASSF1A gene (p = 0.08), a statistically significance was found for RASSF2A gene (p < 0.001), RASSF2A gene methylation status was also found higher in high grade tumors, advanced age (≥50) and nonsmokers groups. Our results indicate that RASSF2A gene may play a role in the carcinogenesis of endometrioid and it could be potential biomarker for early detection for endometrioid carcinoma. Further and larger investigations are needed to confirm our results.

Association between SOX17, Wif-1 and RASSF1A promoter methylation status and response to chemotherapy in patients with metastatic gastric cancer.

Article Association between SOX17, Wif-1 and RASSF1A promoter methylation status and response to chemotherapy in patients with metastatic gastric cancer was published on February 1, 2021 in the journal Clinical Chemistry and Laboratory Medicine (CCLM) (volume 59, issue 2).

The Relationship Between Promoter Methylation of RASSF1A Gene and Prognosis of Patients Affected with Breast Cancer in Khuzestan Province

Background DNA methylation is one of the most frequent molecular changes that are associated with human cancers. Tumor suppressor genes are the important targets of hypermethylation in breast cancer and thus may result in cancer by deregulation of cell growth and division.Objectives The purpose of this research was to compare the methylation pattern of the RASSF1A gene in cancerous and normal tissues.Methods Twenty breast cancer patients with known clinicopathologic characteristics and 20 healthy women as control were studied for analysis of the methylation status of the RASSF1A gene promoter by methylation-specific polymerase chain reaction (MS-PCR) technique.Results The findings showed that the frequency of RASSF1A promoter methylation was in 15% of tumor tissues and 5% of normal tissues. These results indicate that there is no statistically significant relationship between the RASSF1A promoter methylation status of tumor tissues and normal tissues (P > 0.05).Conclusions Until now, the evidence for powerful methylation biomarkers is still incomplete and the recognized biomarkers require further validation.

Prognostic role of APC and RASSF1A promoter methylation status in cell free circulating DNA of operable gastric cancer patients

Gastric carcinogenesis is a multistep process including not only genetic mutations but also epigenetic alterations. The best known and more frequent epigenetic alteration is DNA methylation affecting tumor suppressor genes that may be involved in various carcinogenetic pathways. The aim of the present study was to investigate the methylation status of APC promoter 1A and RASSF1A promoter in cell free DNA of operable gastric cancer patients.Using methylation specific PCR, we examined the methylation status of APC promoter 1A and RASSF1A promoter in 73 blood samples obtained from patients with gastric cancer.APC and RASSF1A promoters were found to be methylated in 61 (83.6%) and 50 (68.5%) of the 73 gastric cancer samples examined, but in none of the healthy control samples (p<0.001). A significant association between methylated RASSF1A promoter status and lymph node positivity was observed (p=0.005). Additionally, a significant correlation between a methylated APC promoter and elevated CEA (p=0.033) as well as CA-19.9 (p=0.032) levels, was noticed. The Kaplan–Meier estimates of survival, significantly favored patients with a non-methylated APC promoter status (p=0.008). No other significant correlations between APC and RASSF1A methylation status and different tumor variables examined was observed.Serum RASSF1A and APC promoter hypermethylation is a frequent epigenetic event in patients with early operable gastric cancer. The observed correlations between APC promoter methylation status and survival as well as between a hypermethylated RASSF1A promoter and nodal positivity may be indicative of a prognostic role for those genes in early operable gastric cancer. Additional studies, in a larger cohort of patients are required to further explore whether these findings could serve as potential molecular biomarkers of survival and/or response to specific treatments.

RASSF1A promoter hypermethylation is a strong biomarker of poor survival in patients with salivary adenoid cystic carcinoma in a Chinese population.

In addition to the clinicopathological parameters, molecular biomarkers are becoming increasingly important in the prognostic evaluation of cancer patients. This study aimed to determine the molecular alterations in the RAS association domain family protein1A gene (RASSF1A) in salivary adenoid cystic carcinoma (ACC) and to evaluate the potential of such alterations as prognostic markers. One hundred and sixty-seven ACC tumor tissues and 50 samples of matched normal salivary gland tissues from the same patients were analyzed for RASSF1A promoter methylation status by bisulfite sequencing PCR (BSP) and/or methylation-specific PCR (MSP). Fifty ACC tumor tissues and matched normal salivary gland tissues were analyzed for loss of heterozygosity (LOH) by examining two microsatellite markers (D3S1478, D3S1621) at 3p21. RASSF1A gene mutations were detected by direct sequencing of all six exons in 50 tumor and normal tissue specimens. Over-all, RASSF1A promoter hypermethylation was detected in 35.3% (59/167) of ACC tissues and was associated with histologically solid tumor pattern (P = 0.002) and advanced TNM stage (P = 0.014). RASSF1A LOH was observed in 18.0% (9/50) of cases, and no somatic mutation of RASSF1A was detected in any cases. RASSF1A promoter methylation was associated with the poor over-all survival (Log-rank test, P <0.001) and disease-free survival (Log-rank test, P <0.001) and identified as an independent predicator of over-all patient survival (P = 0.009) and disease-free survival (P <0.001). It was concluded that RASSF1A methylation is involved in the development, differentiation and progression of ACC and is a strong independent biomarker of poor survival in ACC patients in a Chinese population.

The prognostic role of RASSF1A promoter methylation in breast cancer: a meta-analysis of published data.

PurposeEpigenetic alterations have been investigated as prognostic indicators in breast cancer but their translation into clinical practice has been impeded by a lack of appropriate validation. We present the results of a meta-analysis of the associations between RASSF1A promoter methylation status and both disease free survival (DFS) and overall survival (OS) in female breast cancer.MethodsEligible studies were identified through searching the PubMed, Web of Science and Embase databases. Studies were pooled and summary hazard ratios (HR) with corresponding confidence intervals (CIs) were calculated. Funnel plots were also carried out to evaluate publication bias.ResultsA total of 1795 patients from eight studies were included in the meta-analysis. There are eight studies which investigated DFS in 1795 cases. The relative hazard estimates ranged from 1.77–5.64 with a combined HR of 2.75 (95%CI 1.96–3.84). The HR of RASSF1A promoter methylation on DFS adjusted for other potential prognostic factors was 2.54 (95%CI 1.77–3.66). There has been five trials which analyzed the associations of RASSF1A promoter methylation status with OS in 1439 patients. The hazard estimates ranged from 1.21–6.90 with a combined random-effects estimates of 3.47 (95%CI 1.44–8.34). OS reported in multivariate analysis was evaluated in four series comprising 1346 cases and the summarized random-effects HR estimate was 3.35 (95%CI 1.14–9.85). Additionally, no publication bias was detected for both OS and DFS.ConclusionThe results of this meta-analysis suggest that RASSF1A promoter hypermethylation confers a higher risk of relapse and a worse survival in patients with breast cancer. Large prospective studies are now needed to establish the clinical utility of RASSF1A promoter methylation.

Promoter hypermethylation of DNA damage response genes in hepatocellular carcinoma

Aberrant methylation of promoter CpG islands is a major inactivation mechanism of tumour-related genes that play a crucial role in the progression of silencing in human cancers, including HCC (hepatocellular carcinoma). We have examined the promoter methylation status of five important DNA damage response genes in fresh-frozen HCC tissues and cell lines, as well as the possible correlation between methylation patterns and clinical features of the carcinoma. Promoter methylation status of RASSF1A (Ras association domain family 1), CHFR (checkpoint with forkhead and ring finger domains), GSTP1 (glutathione-S-transferase-pi gene), MGMT [O(6)-methylguanine-DNA methyltransferase] and hMLH1 (human mutL homologue 1) were examined by the MSP (methylation-specific PCR) in 70 HCC tissues and five HCC cell lines. The mRNA expression levels of these genes were measured by RT-PCR (reverse transcription-PCR). Methylation frequencies of these genes tested in HCC were 54 (78%) for RASSF1A, 30 (43%) for CHFR, 26 (38%) for GSTP1 and 22 (32%) for MGMT. No hypermethylation was detected for hMLH1 in any case of HCC or HCC cell lines. Moreover, promoter hypermethylation of RASSF1A, CHFR and GSTP1 in both HepG2 and SNU398 cells, and hypermethylation of MGMT in Huh7 cells, were detected. Treatment of three cell lines with 5Aza-dC (5-aza-20-deoxycytidine) restored or increased the expression of these genes, implicating aberrant DNA methylation in transcriptional silencing. Hypermethylation of RASSF1A and patient age were significantly associated. CHFR methylation status showed a statistically significant correlation with HCC progression. Methylation of the RASSF1A, CHFR, GSTP1 and MGMT genes seem therefore to play an important role in the pathogenesis of HCC. These epigenetic changes may have prognostic importance for patients with HCC.

Prolonged sampling of spontaneous sputum improves sensitivity of hypermethylation analysis for lung cancer

AimsThe adequacy of lung cancer diagnosis with sputum cytology depends on duration of sputum sampling. The aim of this methodological study was to determine whether the hypermethylation detection rate of...

Hepatitis C virus core upregulates the methylation status of the RASSF1A promoter through regulation of SMYD3 in hilar cholangiocarcinoma cells

Increasing evidence has been accumulated indicating the important role of epigenetic regulation in tumor genesis. Previously, we observed that the transfection of hepatitis C virus core (HCVc) protein led to malignant transformation in normal biliary cells, and that tumor suppressor gene RASSF1A was downregulated in many hilar cholangiocarcinoma patients by hypermethylation in the promoter region. In the present study, we found SET and MYND domain-containing protein 3 (SMYD3), a novel histone methyltransferase, was overexpressed in cholangiocarcinoma patients especially in those with HCV infection. Transfection of HCVc into hilar cholangiocarcinoma cell lines QBC939 and FRH0201 could upregulate the expression of SMYD3 and promote cell growth, which was consistent with the results of our clinical research. This phenomenon indicated that SMYD3 was related to the epigenetic regulation of cholangiocarcinoma genesis with HCV infection. Overexpression of SMYD3 could inhibit RASSF1A expression, whereas inhibition of SMYD3 by siRNA improved its expression. Methylation-specific polymerase chain reaction (MS-PCR) results showed the methylation status of RASSF1A promoter was regulated by SMYD3. In conclusion, HCVc could upregulate the methylation status of the RASSF1A promoter through regulation of SMYD3, and histone methylation may affect the DNA methylation of downstream gene by an unknown mechanism.

Prognostic value of methylation status of RASSF1A gene as an independent factor of non-small cell lung cancer

背景与目的研究发现在很多肿瘤中都存在RASSF1A基因启动子区域高甲基化状态导致基因表达失活的现象，本研究就RASSF1A基因启动子的甲基化状态与非小细胞肺癌预后的关系进行探讨。方法采用甲基化特异的PCR检测150例非小细胞肺癌和20例肺部良性病变RASSF1A启动子甲基化状态。结果150例非小细胞肺癌中58例发现RASSF1A启动子存在甲基化（58/158, 38.7%），20例肺部良性病变中无一例发现RASSF1A启动子甲基化。存在RASSF1A启动子高甲基化的病例预后较未发现RASSF1A甲基化的病例差（P=0.004），Cox回归分析显示RASSF1A启动子的甲基化状态是非小细胞肺癌术后的一个预后相关因素（RR=1.584, 95%CI: 1.040-2.411, P=0.032）。结论MSP法检测RASSF1A启动子甲基化状态可以作为非小细胞肺癌术后的一个预后评价指标。

Value of promoter methylation of RASSF1A, p16, and DAPK genes in induced sputum in diagnosing lung cancers

To determine the aberrant methylation status of RASSF1A,p16 and DAPK gene promoter region in induced sputum from lung cancer patients and the value of their combined detection in diagnosing lung cancers. Methylation-specific PCR (MSP) was used to detect the promoter methylation status of RASSF1A, p16, and DAPK genes in induced sputum and pathological tissues from 82 patients with lung cancers and 25 patients with pulmonary benign lesion. We also analyzed the relation between methylation status and clinical pathological data. The positive rates of promoter methylation of RASSF1A, p16, and DAPK genes in pathological tissues from patients with lung cancers were 63.4%, 59.8%, and 58.5%, respectively,and those in induced sputum were 54.9%, 48.8%, and 51.2%, respectively. The promoter methylation of RASSF1A,p16, and DAPK genes were not detected in patients with pulmonary benign lesion. There was a significant difference between the lung cancer group and pulmonary benign lesion group (P<0.05). The methylation rate of RASSF1A gene was significantly lower in the middle and high differentiation and non-metastastic lymph node of lung cancer tissues than that in the poor differentiation and the metastatic lymph node of lung cancer tissues(P<0.05), and was not correlated with age, sex, smoking index, clinical stage, and pathological types.The methylation rate of p16, and DAPK genes was not significantly correlated with all the above mentioned factors (P>0.05). The methylation rate of joint detecting RASSF1A, p16, and DAPK genes was 73.2%. Joint detection for promoter hypermethylation of RASSF1A, p16, and DAPK genes in induced sputum may be used as a simple and effective index of the diagnosis and prognose of lung cancers, and can improve the positive rate.

Prognostic significance of RASSF1A promoter methylation in operable breast cancer

Objectives The aim of our study was to evaluate the prognostic significance of RASSF1A promoter methylation status in operable breast cancer. Design and methods By using Methylation Specific PCR, we evaluated the specificity of RASSF1A promoter methylation in 10 breast tumors and matching normal tissues, 10 breast fibroadenomas and 11 normal breast tissues. The prognostic significance of RASSF1A methylation was validated in 93 formalin fixed paraffin-embedded (FFPE) tissues obtained from patients with operable breast cancer. Results Methylation of RASSF1A promoter was observed in 1/31 (3.2%) non-cancerous breast tissues and 53/93 (57.0%) early stage breast tumors. The only positive sample in the non-cancerous breast tissues group was found in a histological normal tissue surrounding the tumor. During the follow-up period, 24/93 (25.8%) patients relapsed and 19/93 (20.4%) died. Disease-Free-Interval (DFI) was significantly associated with RASSF1A methylation ( p = 0.028). Conclusions RASSF1A promoter methylation provides important prognostic information in early stage breast cancer patients.

Immunohistochemical and Molecular Characteristics of Follicular Patterned Thyroid Nodules with Incomplete Nuclear Features of Papillary Thyroid Carcinoma

Background : Follicular patterned thyroid nodules with incomplete nuclear features of papillary thyroid carcinoma (FTN-INPTCs) are difficult to diagnose, and their biological behavior and association with follicular variants of PTC (FVPTCs) have not yet been established. The aim of this study is to determine immunohistochemical and molecular characteristics of FTNINPTCs. Methods : We investigated immunohistochemical features (galectin-3, HBME-1, CK19, fibronectin-1, CITED1), BRAF V600E mutation and RASSF1A promoter methylation status in 30 FTN-INPTC cases, along with 26 FVPTCs, 21 follicular adenomas (FAs) and 14 nodular hyperplasias (NHs). Results : Expression of galectin-3, HBME-1, CK19 and CITED1 was significantly higher in FTN-INPTCs than in FAs or NHs, but expression of galectin-3, CK19 and fibronectin-1 was lower in FTN-INPTCs than in FVPTCs. The BRAF V600E mutation was not detected in the benign nodules or FTN-INPTCs, whereas 57% of FVPTCs had the mutation. RASSF1A promoter methylation was higher in FTN-INPTCs than in benign nodules but there was no difference between FTN-INPTCs and FVPTCs. Conclusions : Our results represent the borderline immunohistochemical and molecular characteristics of FTN-INPTC. We conclude that FTN-INPTC is an intermediate lesion between a benign nodule and a FVPTC, and that it is pathogenetically related to FVPTC.

Critical role of ΔDNMT3B4/2 in regulating RASSF1A promoterspecific DNA methylation in non-small cell lung cancer

DeltaDNMT3B (a new DNMT3B subfamily) expression is initiated through a novel promoter. We identified at least 7 transcription variants of deltaDNMT3B as a result of alternative pre-mRNA processing. The aim of this study was to detect the expression pattern of deltaDNMT3B variants in non-small cell lung cancer (NSCLC) and to explore the role of deltaDNMT3B variants in regulating the promoter-specific DNA methylation. Specific polymerase chain reaction (PCR) primer sets were designed to distinguish individual deltaDNMT3B variants according to their splicing patterns. The expressions of seven deltaDNMT3B variants were measured in 13 cell lines, 109 NSCLC patients, and the corresponding normal lung tissues using reverse transcription-PCR (RT-PCR). The status of the p16 and RASSF1A promoter methylations in the tumors was detected using a methylation specific PCR (MSP). The relationships of the expression patterns of the deltaDNMT3B variants were analyzed by observing the status of p16 and RASSF1A promoter methylations in the tumors. The siRNA and the anti-sense oligo-dioxynucleotide specifically targeting the junction of exon 5 and 7 of deltaDNMT3B were designed and transfected by lipofectmane 2000 into H1299 and H358 cell lines. RASSF1A promoter methylation from cells treated by siRNA-deltaDNMT3B4/2 was detected using MSP and Bisulfite sequencing, and Western blotting was used to detect the protein expression of DNMT3B and ADNMT3B. Cell growth and cell cycle distribution were measured by applying real-time cell growth analysis and flowcytometry, respectively. ADNMT3B variants, not DNMT3B, were the predominant transcripts in both NSCLC cell lines and primary tumors. The expression of deltaDNMT3B4 strongly correlated to the promoter methylation status of RASSF1A in a primary NSCLC. The knockdown of deltaDNMT3B4/2 by RNA-interference or anti-sense approaches resulted in a complete demethylation of RASSF1A promoter with the reactivation of a RASSF1A gene expression in less than 12 hours, but no effect resulted from the p16(INK4a) promoter in the NSCLC cell lines. These results demonstrate an important role of deltaDNMT3B4/2 in the maintenance of promoter-specific DNA methylation in a cell type specific manner and provide a novel cell model for the study of the regulation of replication-independent DNA methylation.

Clinical study of methylation status of RASSF1A promoter in non-small cell lung cancer

目的 探讨非小细胞肺癌(NSCLC)中RASSF1A启动子的甲基化状态及临床意义.方法 采用甲基化特异的PCR(MSP)检测150例NSCLC、34例癌旁正常组织和20例肺部良性病变中RASSF1A启动子甲基化状态.结果 150例NSCLC中58例发现RASSF1A启动子存在甲基化(38.7%),34例癌旁正常组织和20例肺部良性病变无一例发现RASSF1A启动子甲基化.RASSF1A启动子甲基化与年龄、性别、吸烟指数、组织类型、TNM临床分期均无关(P＞0.05),与开始吸烟年龄、肿瘤分化程度相关(P＜0.05).结论 RASSF1A启动子甲基化状态可以作为NSCLC诊断的一个候选分子标志。

Detection of RASSF1A promoter hypermethylation in serum from gastric and colorectal adenocarcinoma patients

To evaluate the diagnostic role of serum RASSF1A promoter hypermethylation in gastric and colorectal adenocarcinoma. Methylation-specific polymerase chain reaction (MSPCR) was used to examine the promoter methylation status of the serum RASSF1A gene in 47 gastric adenocarcinoma patients, 45 colorectal adenocarcinoma patients, 60 patients with benign gastrointestinal disease (30 with benign gastric disease and 30 with benign colorectal disease), and 30 healthy donor controls. A paired study of RASSF1A promoter methylation status in primary tumor, adjacent normal tissue, and postoperative serum were conducted in 25 gastric and colorectal adenocarcinoma patients who later were underwent surgical therapy. The frequencies of detection of serum RASSF1A promoter hypermethylation in gastric (34.0%) and colorectal (28.9%) adenocarcinoma patients were significantly higher than those in patients with benign gastric (3.3%) or colorectal (6.7%) disease or in healthy donors (0%) (P < 0.01). The methylation status of RASSF1A promoter in serum samples was consistent with that in paired primary tumors, and the MSPCR results for RASSF1A promoter methylation status in paired preoperative samples were consistent with those in postoperative serum samples. The serum RASSF1A promoter hypermethylation did not correlate with patient sex, age, tumor differentiation grade, surgical therapy, or serum carcinoembryonic antigen level. Although the serum RASSF1A promoter hypermethylation frequency tended to be higher in patients with distant metastases, there was no correlation between methylation status and metastasis. Aberrant CpG island methylation within the promoter region of RASSF1A is a promising biomarker for gastric and colorectal cancer.

Identification of epigenetic aberrant promoter methylation of RASSF1A in serum DNA and its clinicopathological significance in lung cancer

21014 Objective: To detect the hypermethylation status of RASSF1A promoter in serum DNA of lung cancer patients and to analyze its correlation with clinicopathological features. Methods: Serum DNA was extracted from peripheral blood from 80 primary lung cancer patients, 35 benign pulmonary disease patients and 15 healthy donors. The methylation status of RASSF1A promoter was determined using methylation-specific PCR technique, and the correlation between methylation profiles and clinicopathological parameters was statistically analyzed. Results: Aberrant methylation of RASSF1A was detected in 27 of the 80 (33.8%) patients with lung cancer but no benign pulmonary disease patients or healthy donors (p&lt;0.001). RASSF1A was preferentially observed in small cell lung cancer (p=0.042), while no statistical difference was found among methylation frequencies of different subtypes of non-small cell lung cancer. The methylation status was also found to be associated with relative poor differentiation (p=0.009) and late stage (p=0.013), but not with gender, age or treatment. Conclusion: RASSF1A promoter is frequently hypermethylated in serum DNA of primary lung cancer patients, and RASSF1A is a promising novel biomarker for lung cancer diagnosis. No significant financial relationships to disclose.

Hypermethylation of the RASSF1A tumor suppressor gene in Japanese clear cell renal cell carcinoma

Hypermethylation associated inactivation of RASSF1A tumor suppressor gene at chromosome 3p21.3 has been observed in several human malignancies. Relatively high (91%) or low (23%) frequencies were reported in the methylation status of promoter region of the RASSF1A gene in clear cell renal carcinoma (RCC) depending on the country the report was from. To clarify exact contribution of the hypermethylation of RASSF1A gene in the development of RCC in Japan, we analyzed the methylation status of the RASSF1A promoter region in 50 Japanese clear cell RCC and RCC cell lines. Although relatively high frequency of hypermethylation in RASSF1A promoter (39 of 50 tumors, 78%) was observed, most of matched proximal normal tissue DNA also showed weak methylation. By comparison with methylation level of adapted normal kidney tissue DNA, tumor preferential hypermethylation in RASSF1A promoter was recognized as 40% (20/50 matched sets) of primary clear cell RCCs. Hypermethylation in RASSF1A promoter was observed in 36% (15/42) and 64% (5/8) of stage I-II or III-IV tumors, and also observed in 42% (11/26) and 38% (9/24) of our tumor samples with pathological grade I or II, respectively. In addition, 16 of 19 RCC cell lines (84%) showed complete or partial methylation of RASSF1A promoter region. There was no association between the frequency of RASSF1A methylation and inactivation of VHL tumor suppressor gene in either primary RCCs or RCC cell lines. Our results showed tumor specific RASSF1A promoter hypermethylation in up to 40% of low grade or low stage clear cell RCCs. It is essential to compare the methylation status of RASSF1A promoter in tumor with normal tissue to understand tumor specific hypermethylation. Since considerable cases of normal kidney are hypermethylated, contribution of the RASSF1A for the development and progression of kidney cancer may be more complex than expected.

RASSF1A Promoter Methylation and Kras2 Mutations in Non Small Cell Lung Cancer

In the present studies, we investigated the correlation between RASSF1A promoter methylation status and Kras2 mutations in 65 primary non small cell lung cancer (NSCLC) including 33 adenocarcinomas, 12 large cell carcinomas, and 20 squamous cell carcinomas. Mutational analysis of Kras2 showed: 30% (10 of 33) of adenocarcinomas, 25% (3 of 12) of large cell carcinomas, and only 5% (1 of 20) of squamous cell carcinomas contained activated Kras2 mutation at codon 12 or 13. RASSF1A promoter region CpG island methylation was detected in adenocarcinomas (55%), large cell carcinomas (25%), and squamous cell carcinomas (25%). Interestingly, combined RASSF1A methylation and Kras2 mutation data show that only ~7% adenocarcinomas/large cell carcinomas exhibited both KRASSF1A promoter methylation and Kras2 mutation, whereas 24% adenocarcinomas, 50% large cell carcinomas, and 70% squamous cell carcinomas showed neither Kras2 mutation nor RASSF1A promoter methylation. These results showed that the majority of the primary NSCLCs with Kras2 mutations lack RASSF1A inactivation, and both RASSF1A inactivation and Kras2 mutation events occur frequently in adenocarcinomas and large cell carcinomas. Our results indicate a trend of inverse relationship between Kras2 activation and RASSF1A promoter methylation in the majority of human lung adenocarcinomas and large cell carcinomas.

Frequent epigenetic inactivation of the RASSF1A tumour suppressor gene in testicular tumours and distinct methylation profiles of seminoma and nonseminoma testicular germ cell tumours.

Testicular germ cell tumours (TGCTs) are histologically heterogeneous neoplasms with variable malignant potential. Previously, we demonstrated frequent 3p allele loss in TGCTs, and recently we and others have shown that the 3p21.3 RASSF1A tumour suppressor gene (TSG) is frequently inactivated by promoter hypermethylation in a wide range of cancers including lung, breast, kidney and neuroblastoma. In order to investigate the role of epigenetic events in the pathogenesis of TGCTs, we analysed the promoter methylation status of RASSF1A and nine other genes that may be epigenetically inactivated in cancer (p16(INK4A), APC, MGMT, GSTP1, DAPK, CDH1, CDH13, RARbeta and FHIT) in 24 primary TGCTs (28 histologically distinct components). RASSF1A methylation was detected in four of 10 (40%) seminomas and 15 of 18 (83%) nonseminoma TGCT (NSTGCT) components (P=0.0346). None of the other nine candidate genes were methylated in seminomas, but MGMT (44%), APC (29%) and FHIT (29%) were frequently methylated in NSTGCTs. Furthermore, in two mixed germ cell tumours, the NSTGCT component for one demonstrated RASSF1A, APC and CDH13 promoter methylation, but the seminoma component was unmethylated for all genes analysed. In the second mixed germ cell tumour, the NSTGCT component was methylated for RASSF1A and MGMT, while the seminoma component was methylated only for RASSF1A. In all, 61% NSTGCT components but no seminoma samples demonstrated promoter methylation at two or more genes (P=0.0016). These findings are consistent with a multistep model for TGCT pathogenesis in which RASSF1A methylation occurs early in tumorigenesis and additional epigenetic events characterize progression from seminoma to NSTGCTs.