BRCA1 promoter methylation & its immunohistochemical correlation in sporadic breast cancer

Background & objectives: Studies have shown that apart from hereditary breast carcinomas, breast cancer susceptibility gene 1 (BRCA1) mutations conferring to its loss are seen in sporadic breast carcinomas (SBC) as well. The aim of the present study was to assess BRCA1 methylation in females presenting at King George’s Medical University, Lucknow, with SBC by both immunohistochemistry (IHC) and methylation PCR with respect to hormonal profile and various morphological prognostic parameters. The primary objective was to look for the association between BRCA1 protein expression and DNA promoter methylation. Methods: 81 mastectomy specimens from SBC of invasive breast carcinoma (no special type) were included in this study. After a detailed morphological assessment, formalin fixed paraffin embedded tissue from a representative tumour area was selected for BRCA1 IHC by heat-mediated antigen retrieval under high pH and DNA extraction and further bisulphate treatment. BRCA1 was studied for methylation by methylated and unmethylated PCR-specific primers. Results: BRCA1 promoter methylation was present in 42/81 (51.9%) participants, with significant BRCA1 protein loss (72.7%; P=0.002). A significant association between BRCA1 loss and hormonal profile was found (P=0.001); maximum in triple negative breast carcinoma (TNBC) (72%; 18/25). Most of the TNBC also harboured methylation (68%). Although not significant grade II and III tumours, lymph vascular invasion, ductal carcinoma in situ, and nodal metastasis (?3) were seen in a higher percentage in methylated tumours. Mortality in SBC was significantly associated with BRCA1 loss (30.3%; P=0.024). Interpretation & conclusions: Study results highlight the concept of “BRCAness” in SBC as well. Hence, we can confer that identification of BRCA1 loss in SBC can make it a perfect candidate for poly ADP- ribose polymerase inhibitors or cisplatin-based therapy like hereditary ones.

The clinical significance of MGMT promoter methylation in the treatment and progno-sis of glioma patients / 中国肿瘤临床

Adjuvant temozolomide-based chemotherapy has become the standard of care for most postoperative glioma patients. However, a large proportion of these patients do not respond to temozolomide. DNA repair enzyme O6-methylguanine-DNA methyl-transferase (MGMT) promoter methylation has emerged as an important molecular marker in patients with gliomas. It is associated with prognosis and resistance to alkylated drugs such as temozolomide. MGMT promoter methylation is the key mechanism of MGMT gene silencing, thereby inhibiting DNA repair and increasing the sensitivity of chemotherapy. We reviewed current data on the prog-nostic and predictive relevance of MGMT testing and clinical trials, summarized the clinical application of MGMT promoter methyla-tion, in order to provide reference for the individualized treatment of glioma patients.

Chemoradiation therapy induces in vivo changes in gene promoter methylation & gene transcript expression in patients with invasive cervical cancer

Background & objectives: Invasive cervical cancer patients are primarily treated with chemoradiation therapy. The overall and disease-free survival in these patients is variable and depends on the tumoral response apart from the tumour stage. This study was undertaken to assess whether in vivo changes in gene promoter methylation and transcript expression in invasive cervical cancer were induced by chemoradiation. Hence, paired pre- and post-treatment biopsy samples were evaluated for in vivo changes in promoter methylation and transcript expression of 10 genes (ESR1, BRCA1, RASSF1A, MYOD1, MLH1, hTERT, MGMT, DAPK1, BAX and BCL2L1) in response to chemoradiation therapy. Methods: In patients with locally advanced invasive cervical cancer, paired pre- and post-treatment biopsies after 10 Gy chemoradiation were obtained. DNA/RNA was extracted and gene promoter methylation status was evaluated by custom-synthesized methylation PCR arrays, and the corresponding gene transcript expression was determined by absolute quantification method using quantitative reverse transcription PCR. Results: Changes in the gene promoter methylation as well as gene expression following chemoradiation therapy were observed. BAX promoter methylation showed a significant increase (P<0.01) following treatment. There was a significant increase in the gene transcript expression of BRCA1 (P<0.01), DAPK1 and ESR1 (P<0.05), whereas MYOD1 and MLH1 gene transcript expression was significantly decreased (P<0.05) following treatment. Interpretation & conclusions: The findings of our study show that chemoradiation therapy can induce epigenetic alterations as well as affect gene expression in tissues of invasive cervical cancer which may have implications in determining radiation response.

Tissue-specific Changes of Clock DNA Promoter Methylation with Aging / 中国康复理论与实践

@#Objective To investigate the role of the clock gene promoter methylation in aging. Methods C57BL mice of 4- (young, n=9) and 20- (old, n=10) month-old were determined the promoter methylation level of clock genes (Per1/2, Bmal1/2, Cry1/2, Clock, Npas2) in the stomach, spleen, vascular, kidney and striatum with methylation-specific polymerase chain reaction (MSP). Results The incidence of promoter methylation of Cry1, Bmal2 and Npas2 in spleen increased in old mice (P<0.05), while the promoter methylation of Per1 in stomach decreased (P<0.05), and the promoter methylation of Bmal1 in vascular increased (P<0.05). Conclusion Promoter methylation of some clock genes is involved in process of aging in a tissue-specific way.

Primary Spinal Cord Oligodendroglioma with Postoperative Adjuvant Radiotherapy: A Case Report

Primary spinal cord oligodendrogliomas are rare tumors comprising two percent of all spinal cord tumors. Although a treatment guideline has yet to be established, maximal surgical resection is primary in the treatment of spinal cord oligodendrogliomas. Adjuvant radiotherapy has remained controversial, and it is unclear whether chemotherapy adds any benefit. In this case report, the authors present a 24-year-old male who had a seven-year history of left leg weakness and a radiating pain in both legs. Magnetic resonance image (MRI) showed an intramedullary mass at the T4-T8 level. He underwent subtotal removal of the tumor and pathologic diagnosis revealed a WHO grade II oligodendroglioma. The patient was treated with radiotherapy postoperatively and followed up with MRI annually. Clinical and radiological status of the patient had been stationary for four years after the surgery. The five-year follow-up MRI showed an increase in the size and extent of the residual tumor. Despite radiological progression, considering that symptoms and the performance status of the patient had remained unchanged, further treatment has not been performed. Given the clinical outcome of this patient, close observation after subtotal removal with adjuvant radiotherapy is one of the acceptable treatment options for WHO grade II spinal cord oligodendrogliomas.

Tissue-specific Changes of Clock DNA Promoter Methylation with Aging / 中国康复理论与实践

Objective To investigate the role of the clock gene promoter methylation in aging. Methods C57BL mice of 4-(young, n=9) and 20-(old, n=10) month-old were determined the promoter methylation level of clock genes (Per1/2, Bmal1/2, Cry1/2, Clock, Npas2) in the stomach, spleen, vascular, kidney and striatum with methylation-specific polymerase chain reaction (MSP). Results The incidence of promoter methylation of Cry1, Bmal2 and Npas2 in spleen increased in old mice (P<0.05), while the promoter methylation of Per1 in stom-ach decreased (P<0.05), and the promoter methylation of Bmal1 in vascular increased (P<0.05). Conclusion Promoter methylation of some clock genes is involved in process of aging in a tissue-specific way.

Relationship between promoter methylation & tissue expression of MGMT gene in ovarian cancer.

Background & objectives: Epigenetic alterations, in addition to multiple gene abnormalities, are involved in the genesis and progression of human cancers. Aberrant methylation of CpG islands within promoter regions is associated with transcriptional inactivation of various tumour suppressor genes. O6-methyguanine-DNA methyltransferase (MGMT) is a DNA repair gene that removes mutagenic and cytotoxic adducts from the O6-position of guanine induced by alkylating agents. MGMT promoter hypermethylation and reduced expression has been found in some primary human carcinomas. We studied DNA methylation of CpG islands of the MGMT gene and its relation with MGMT protein expression in human epithelial ovarian carcinoma. Methods: A total of 88 epithelial ovarian cancer (EOC) tissue samples, 14 low malignant potential (LMP) tumours and 20 benign ovarian tissue samples were analysed for MGMT promoter methylation by nested methylation-specific polymerase chain reaction (MSP) after bisulphite modification of DNA. A subset of 64 EOC samples, 10 LMP and benign tumours and five normal ovarian tissue samples were analysed for protein expression by immunohistochemistry. Results: The methylation frequencies of the MGMT gene promoter were found to be 29.5, 28.6 and 20 per cent for EOC samples, LMP tumours and benign cases, respectively. Positive protein expression was observed in 93.8 per cent of EOC and 100 per cent in LMP, benign tumours and normal ovarian tissue samples. Promoter hypermethylation with loss of protein expression was seen only in one case of EOC. Interpretation & conclusions: Our results suggest that MGMT promoter hypermethylation does not always reflect gene expression.

Modulation of p21, DAPK1 and COX-2 during the DMBA/TPA-induced mouse skin tumorigenesis and its prevention by phytic acid.

Chemoprevention by naturally occurring agents is gaining much attention as a newer dimension in the management of cancer. Many naturally occurring agents have shown cancer chemopreventive potential in a variety of bioassay systems and animal models, having relevance to human disease. Phytic acid or Inositol hexaphosphate (IP6), an antioxidant, is a naturally occurring polyphosphorylated carbohydrate that has shown a strong anticancer activity in several experimental models. We assessed the protective effects of Phytic acid against the 7, 12-dimethylbenz [a] anthracene (DMBA)/ 12-O-tetradecanoylphorbol-13- acetate (TPA) induced mouse skin tumorigenesis at 4 and 16 weeks, the time before and after the tumor development. At molecular level we studied expression and promoter CpG methylation status of p21, DAPK1 and COX-2. Our data suggests exposure of DMBA/TPA methylated the promoter region of p21 and DAPK1 genes in time dependent manner that could be the cause of down regulation of their expression with time, which were reversed by administration of phytic acid. But we did not observe methylation in COX-2 whereas upregulation of COX-2 was observed at protein level in mice treated with DMBA followed by TPA in time dependent manner. Administration of phytic acid prevented theses DMBA/TPA induced molecular changes. Study provides a rationale for cancer chemoprevention by natural occurring compounds like Phytic acid.

Correlation of MGMT promoter methylation status with gene and protein expression levels in glioblastoma

OBJECTIVES: 1) To correlate the methylation status of the O6-methylguanine-DNA-methyltransferase (MGMT) promoter to its gene and protein expression levels in glioblastoma and 2) to determine the most reliable method for using MGMT to predict the response to adjuvant therapy in patients with glioblastoma. BACKGROUND: The MGMT gene is epigenetically silenced by promoter hypermethylation in gliomas, and this modification has emerged as a relevant predictor of therapeutic response. METHODS: Fifty-one cases of glioblastoma were analyzed for MGMT promoter methylation by methylation-specific PCR and pyrosequencing, gene expression by real time polymerase chain reaction, and protein expression by immunohistochemistry. RESULTS: MGMT promoter methylation was found in 43.1 percent of glioblastoma by methylation-specific PCR and 38.8 percent by pyrosequencing. A low level of MGMT gene expression was correlated with positive MGMT promoter methylation (p = 0.001). However, no correlation was found between promoter methylation and MGMT protein expression (p = 0.297). The mean survival time of glioblastoma patients submitted to adjuvant therapy was significantly higher among patients with MGMT promoter methylation (log rank = 0.025 by methylation-specific PCR and 0.004 by pyrosequencing), and methylation was an independent predictive factor that was associated with improved prognosis by multivariate analysis. DISCUSSION AND CONCLUSION: MGMT promoter methylation status was a more reliable predictor of susceptibility to adjuvant therapy and prognosis of glioblastoma than were MGMT protein or gene expression levels. Methylation-specific polymerase chain reaction and pyrosequencing methods were both sensitive methods for determining MGMT promoter methylation status using DNA extracted from frozen tissue.

Promoter Methylation in the Genesis of Gastrointestinal Cancer

Colorectal cancers (CRC)-and probably all cancers-are caused by alterations in genes. This includes activation of oncogenes and inactivation of tumor suppressor genes (TSGs). There are many ways to achieve these alterations. Oncogenes are frequently activated by point mutation, gene amplification, or changes in the promoter (typically caused by chromosomal rearrangements). TSGs are typically inactivated by mutation, deletion, or promoter methylation, which silences gene expression. About 15% of CRC is associated with loss of the DNA mismatch repair system, and the resulting CRCs have a unique phenotype that is called microsatellite instability, or MSI. This paper reviews the types of genetic alterations that can be found in CRCs and hepatocellular carcinoma (HCC), and focuses upon the epigenetic alterations that result in promoter methylation and the CpG island methylator phenotype (CIMP). The challenge facing CRC research and clinical care at this time is to deal with the heterogeneity and complexity of these genetic and epigenetic alterations, and to use this information to direct rational prevention and treatment strategies.

Role of DCC(Deleted in Colorectal Cancer) Gene in Oral Squamous Cell Carcinoma

Chromosome 18q alteration plays a key role in colorectal tumorigenesis, and loss of heterozygosity at 18q is associated with a poor prognosis in colon cancer. DCC(Deleted in Colorectal Cancer) is a putative tumor- suppressor gene at 18q21 that encodes a transmembrane protein with structural similarity to neural cell adhesion molecule that is involved in both epithelial and neuronal cell differentiation. DCC is implicated in regulation of cell growth, survival and proliferation. Thus, tumor progression in squamous cell carcinoma, stomach cancer, colorectal cancer correlates with downregulation of DCC expression. The mechanism for DCC suppression is associated with hypermethylation of the DCC gene promoter region. Hence, the goal of this study is to identify the promoter methylation responsible for the down-regulation of DCC expression in oral squamous cell carcinoma. 12 of tissue specimens for the study are excised and gathered from 12 patients who are diagnosed as SCC in department of OMS, dental hospital, dankook university. To find expression of DCC in each tissue samples, immunohistochemical staining, RT-PCR gene analysis and methylation specific PCR are processed. The results are as follows. 1. In the DCC gene RT-PCR analysis, 5(41.6%) of 12 specimens of oral squamous cell carcinoma did not expressed DCC gene. 2. In the promoter methylation specific PCR analysis, 5(41.6%) of 12 specimens showed promoter methylation of DCC gene. 3. In the immunohistochemical staining of poor differentiated and invasive oral squamous cell carcinoma, loss of DCC expression was observed. These findings suggest that methylation of the DCC gene may play a role in loss of gene expression in invasive oral squamous cell carcinoma.

Promoter Methylation of the CDH-13 Gene in the Oral Squamous Cell Carcinoma

CDH-13(T-cadherin), which is one of a kind among the 20 cadherins, can be found mainly in wall of aorta, neuron, spleen, blood vessel etc. It is also called H-cadherin. This structural difference can explain that CDH-13 is thought to play a key role in maintaining mutual relation between extra and intra-cellular environment rather than in cell adhesion. The main function of CDH-13 is to participate in blood vessel function. Additionally, it is known to regulate cell growth and cell contact inhibition. When cells are proliferating, cell surface perceives other cells so that substance such as CDH-13 can inhibit their growth or proliferation resulting in homeostasis without endless proliferation or invasion of connective tissue boundaries. However, tumor cell itself appears to be different from normal cells' growth, invasion or transmission. Therefore, it can be diagnosed that these characteristics are closely related to expression of CDH-13 in tumor cells. This study is to investigate expression of CDH-13 in SCC and its correlation with promoter methylation. 20 of tissue species for the study are excised and gathered from 20 patients who are diagnosed as SCC in department of OMS, dental hospital, dankook university. To find development of CDH-13 in each tissue samples, immunohistochemical staining, RT-PCR gene analysis and methylation specific PCR are processed. The results are as follows. 1.Immunohistochemical staining: In normal oral squamous epithelial tissue, strong expression of CDH-13 was found in cell plasma membrane of basal cell layer. On the other hand, in case of low-differentiated oral SCC, development of CDH-13 was hardly seen. 2.The development of CDH-13 gene: In 9 of samples, expression of CDH-13 gene could be seen and 2 of them showed low expression compared to the others. And rest of the 11 samples showed no expression of CDH-13 gene. 3.Methylation of CDH-13 gene: Among 9 samples which expressed CDH-13 gene, 7 of them showed unmethylation. In addition, among 11 samples without CDH-13 gene expression, 10 showed methylation. According to the results stated above, promoter methylation were found in 13 samples(65%) among 20 of oral SCC samples. In low-differentiated SCC, suppression of gene expression could be seen accompanying promoter methylation. These phenomenon of gene expression was proved by immunohistochemical investigation. Finally, for development of oral SCC, conclusions can be made that suppression of CDH-13 played a main role and suppression of gene expression was originated from promoter methylation. Considering this, it is expected that suppression of CDH-13 from promoter methylation to be utilized as a good diagnostic marker of oral SCC.

AKAP12alpha is Associated with Promoter Methylation in Lung Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Promoter methylation is an important mechanism for silencing tumor-suppressor genes in cancer and it is a promising tool for the development of molecular biomarkers. The purpose of the present study was to investigate whether inactivation of the A Kinase Anchoring Protein 12 (AKAP12) gene is associated with promoter methylation in lung cancer. MATERIALS AND METHODS: The AKAP12 expression was examined by reverse transcription-polymerase chain reaction (RT-PCR) in ten lung cancer cell lines. The methylation status of the AKAP12alpha promoter was analyzed by performing bisulfite sequencing analysis in ten lung cancer cell lines, twenty four lung tissues and matched normal tissues. RESULTS: The AKAP12alpha expression was reduced in 6 of 10 (60%) lung cancer cell lines, whereas the AKAP12beta expression was absent in 1 of 10 (10%) lung cancer cell lines. The AKAP12alpha expression was restored after treatment with the demethylating agent 5-aza-2'-deoxycytidine in three lung cancer cell lines. Methylation of CpG island 1 in the AKAP12alpha promoter was detected in 30% of the lung cancer cell lines, whereas methylation of CpG island 2 in the AKAP12alpha promoter was observed in the immortalized bronchial cell line and in all the lung cancer cell lines. In lung tumors, the CpG island 1 in the AKAP12alpha promoter was infrequently methylated. However, CpG island 2 in the AKAP12alpha promoter was highly methylated in lung tumors compared with the surrounding normal tissues, and this was statistically significant (p=0.0001). CONCLUSION: Our results suggest that inactivation of the AKAP12alpha expression is associated with DNA methylation of the promoter region in lung cancer, and that AKAP12alpha may play an important role in lung cancer carcinogenesis.

Expression of Sodium/iodide Symporter Transgene in Neural Stem Cells / 대한핵의학회잡지

PURPOSE: The ability to noninvasively track the migration of neural progenitor cells would have significant clinical and research implications. We generated stably transfected F3 human neural progenitor cells with human sodium/iodide symporter (hNIS) for noninvasively tracking F3. In this study, the expression patterns of hNIS gene in F3-NIS were examined according to the cultured time and the epigenetic modulation. MATERIALS AND METHODS: F3 human neural stem cells had been obtained from Dr. Seung U. Kim (Ajou University, Suwon, Korea). hNIS and hygromycin resistance gene were linked with IRES (Internal Ribosome Entry Site) under control of CMV promoter. This construct was transfected to F3 with Liposome. To investigate the restoration of hNIS gene expression in F3-NIS, cells were treated with demethylating agent (5-Azacytidine) and Histone deacetylase inhibitor (Trichostatin A: TSA). The expression of hNIS was measured by I-125 uptake assay and RT-PCR analysis. RESULTS: The iodide uptake of the F3-NIS was higher 12.86 times than F3 cell line. According to the cell passage number, hNIS expression in F3-NIS gradually diminished. After treatment of 5-Azacytidine and TSA with serial doses (up to 20micro M, up to 62.5nM, respectively) for 24 hours, I-125 uptake and mRNA of hNIS in F3-NIS were increased. CONCLUSION: These results suggest that hNIS transfected F3 might undergo a change in its biological characters by cell passage. Therefore, the gene expression of exogenous gene transferred human stem cell might be affected to the epigenetic modulation such as promoter methylation and Histone deacetylation and to the cell culture conditions.

Inactivation patterns of p16/INK4A in oral squamous cell carcinomas

The p16/INK4A is one of the major target genes in carcinogenesis and its inactivation has frequently been reported in other types of tumors. The purpose of this study is to evaluate inactivation patterns of p16/INK4A in oral squamous cell carcinoma. Six different oral cancer cell lines, SCC-4, SCC-9, SCC-15, SCC-25, KB, and SNUDH- 379 were examined for inactivation of p16/INK4A genes. In the analysis of p16/INK4A gene inactivation, PCR amplification, direct sequencing, and methylation-specific PCR methods were adopted for evaluation of homozygous deletion, point mutation, and promoter hypermethylation, respectively. Homozygous deletion was detected in SCC-25 and SCC-9. SCC-15 showed hypermethylated promoter region within p16/INK4A gene. It is suggestive in the present study that inactivation patterns of p16/INK4A were mainly homozygous deletion, promoter methylation rather than point mutation in oral squamous cancer cell lines, so treatment modalities of oral squamous cell carcinoma should be focused on these types of inactivation.

Microsatellite Instability and Promoter Methylation of hMLH1 in Sporadic Gastric Carcinoma

BACKGROUND: An aberrant function of the mismatch repair system has been reported to underlie carcinogenesis in several tumors, including colorectal and gastric carcinomas, and to induce the typical genotype of microsatellite instability (MSI). PURPOSE: We aimed to determine the frequency of MSI in early-onset sporadic gastric carcinoma and elucidate the role of promoter methylation in hMLH1 as the mechanism of MSI. MATENRIALS AND METHODS: Thirty-six early-onset sporadic gastric carcinomas were analyzed to determine the status of MSI and the frequency of methylation of the promoter region in hMLH1. MSI was determined using five markers recommended by NCI: MSI-H (high), MSI-L (low), and MSS (Microsatellite stable). Methylation specific PCR (MSP) and direct automated genomic sequencing analysis with DNA modified by sodium bisulfite have been performed to confirm promoter region methylation. All the data were analyzed regarding characteristics of molecular changes, and clinicopathologic variables. RESULTS: The microsatellite status was determined as MSI-H in five cases (13.8%), MSI-L in 13 cases (36.1%), and MSS in 18 cases (50.0%). hMLH1 was methylated in seven cases (19.4%). In all cases of MSI-H, promoter of hMLH1 was methylated, and in two of the 13 cases of MSI-L, hMLH1 promoter methylation was identified. Methylation was not found in any cases of MSS. Promoter methylation in hMLH1 was significantly correlated with MSI status (P<0.001). We could not find any relationship between MSI and clinicopathologic parameters. CONCLUSION: These results suggest that an abnormal function of the mismatch repair system may be associated with gastric carcinogenesis in more than 10% of early-onset gastric carcinomas and MSI appeared to be closely related to the promoter methylation in hMLH1.

Methylation of DNA mismatch repair gene MLH1 and MSH2 in acquired multidrug-resistance of human small cell lung cells H446 / 第三军医大学学报

Objective To investigate the role of methylated DNA mismatch repair gene MLH1 and MSH2 in the acquired multidrug-resistance of human small cell lung cancer cells H446.Methods The reverse transcription polymerase chain reaction(RT-PCR)and Western blot were applied to measure MLH1 and MSH2 mRNA and protein expressions of the multidrug-resistant cells H446/DDP and its parental cells H446.The promoter methylation status of the genes was assessed by methylation-specific PCR(MSP).Results The expressions of MLH1 and MSH2 significantly decreased both in mRNA level and protein level.Promoter methylation of MLH1 was observed in H446/DDP cells but not in H446 cells.Promoter semi-methylation of MSH2 in H446 cells was transformed to methylation in H446/DDP cells.Conclusion The downregulation of DNA mismatch repair gene MLH1 and MSH2 induced by its promoter methylation may play an important role in the acquired multidrug resistance of human small cell lung cancer.

A study on regulation of DNA mismatch repair genes MLH1 and MSH2 in human SCLC cell line H446 under hypoxic condition / 中国癌症杂志

Background and purpose:Regulation of MMR activity under hypoxia may play an important role in genetic instability of cancer,but the mechanism is still unclear.We investigated the expression of DNA mismatch repair genes MLH1 and MSH2 in human SCLC cell line H446 under hypoxic condition and explore the role of promoter methylation of genes in hypoxia.Methods:RT-PCR and Western blot were applied to detect MLH1 and MSH2 expression in human SCLC cell line H446 at the mRNA and the protein level,respectively,under either hypoxic condition or after 5-Aza-CdR treatment.Meanwhile,methylation-specific PCR(MSP)was used to determine promoter methylation of MLH1 and MSH2.Results:The expression of MLH1 and MSH2 in H446 cells significantly decreased both at the mRNA and the protein level under hypoxic condition.5-Aza-CdR treatment led to the restoration of MLH1 and MSH2 expression,while,both MLH1 and MSH2 were down-regulated again after removing 5-Aza-CdR.Conclusions:The promoter methylation of MLH1 and MSH2 may play an important role in its defective expression in H446 cells under hypoxic condition.And 5-Aza-CdR could restore MLH1 and MSH2 expression.

Relationship between mismatching repair gene hMLH1 mutation and promoter methylation and genetic instability in gastric cancer / 中华消化杂志

Objective To evaluate the relationship between hMLH1 mutation and promoter methylation and genetic instability in gastric carcinomas. Methods hMLH1 mutation was measured by two dimentional DNA electrophoresis and DNA sequencing. The methylation of hMLH1 promoter was measured with methylation specific PCR. MSI was analyzed by PCR based methods. Results Sixty eight cases of sporadic gastric carcinoma were studied for hMLH1 mutation and promoter methylation. hMLH1 mutaions were detected in three cases (4.4%) of gastric cancer. No association was observed between hMLH1 mutation and tumor size, differentiation, histological type, depth of invasion, metastasis or stages. Methylation of hMLH1 promoter was detected in 11 cases (16.2%) of gastric cancer. By using five microsatellite markers, MSI in at least one locus was detected in 17 of 68 (25%) cases of the tumors analyzed. hMLH1 mutations were all detected in MSI H(≥2 loci, n =8), but no mutation was found in MSI L (only one locus, n =9) or MSS (tumor lacking MSI or stable, n =51). Methylation frequence of hMLH1 in MSI H was significantly higher than that in MSI L or MSS ( P 0.05). Conclusion hMLH1 mutation and promoter methylation may be involved in MSI pathway in gastric cancer.