Aberrant methylation patterns in cancer: a clinical view

Effects of R type and S type ginsenoside Rg3 on DNA methylation in human hepatocarcinoma cells

Ginsenoside Rg3, a bioactive constituent isolated from Panax ginseng, exhibits antitumorigenic, antioxidative, antiangiogenic, neuroprotective and other biological activities are associated with the regulation of multiple genes. DNA methylation patterns, particularly those in the promoter region, affect gene expression, and DNA methylation is catalyzed by DNA methylases. However, whether ginsenoside Rg3 affects DNA methylation is unknown. High performance liquid chromatography assay, MspI/HpaII polymerase chain reaction (PCR) and reverse transcription‑quantitative PCR were performed to assess DNA methylation. It was demonstrated that 20(S)‑ginsenoside Rg3 treatment resulted in increased inhibition of cell growth, compared with treatment with 20(R)‑ginsenoside Rg3 in the human HepG2 hepatocarcinoma cell line. It was additionally revealed that treatment with 20(S)‑ginsenoside Rg3 reduced global genomic DNA methylation, altered cystosine methylation of the promoter regions of P53, B cell lymphoma 2 and vascular endothelial growth factor, and downregulated the expression of DNA methyltransferase (DNMT) 3a and DNMT3b more than treatment with 20(R)‑ginsenoside Rg3 in HepG2 cells. These results revealed that the modulation of DNA methylation may be important in the pharmaceutical activities of ginsenoside Rg3.

Aberrant gene-specific DNA methylation signature analysis in cervical cancer

Multicomponent molecular modifications such as DNA methylation may offer sensitive and specific cervical intraepithelial neoplasia and cervical cancer biomarkers. In this study, we tested cervical tissues at various stages of tumor progression for 5-methylcytosine and 5-hydroxymethylcytosine levels and also DNA promoter methylation profile of a panel of genes for its diagnostic potential. In total, 5-methylcytosine, 5-hydroxymethylcytosine, and promoter methylation of 33 genes were evaluated by reversed-phase high-performance liquid chromatography, enzyme-linked immunosorbent assay based technique, and bisulfate-based next generation sequencing. The 5-methylcytosine and 5-hydroxymethylcytosine contents were significantly reduced in squamous cell carcinoma and receiver operating characteristic curve analysis showed a significant difference in (1) 5-methylcytosine between normal and squamous cell carcinoma tissues (area under the curve = 0.946) and (2) 5-hydroxymethylcytosine levels among normal, squamous intraepithelial lesions and squamous cell carcinoma. Analyses of our next generation sequencing results and data from five independent published studies consisting of 191 normal, 10 low-grade squamous intraepithelial lesions, 21 high-grade squamous intraepithelial lesions, and 335 malignant tissues identified a panel of nine genes ( ARHGAP6, DAPK1, HAND2, NKX2-2, NNAT, PCDH10, PROX1, PITX2, and RAB6C) which could effectively discriminate among the various groups with sensitivity and specificity of 80%-100% (p < 0.05). Furthermore, 12 gene promoters (ARHGAP6, HAND2, LHX9, HEY2, NKX2-2, PCDH10, PITX2, PROX1, TBX3, IKBKG, RAB6C, and DAPK1) were also methylated in one or more of the cervical cancer cell lines tested. The global and gene-specific methylation of the panel of genes identified in our study may serve as useful biomarkers for the early detection and clinical management of cervical cancer.

Octreotide inhibits the proliferation of gastric cancer cells through P300-HAT activity and the interaction of ZAC and P300

Somatostatin (SST) exhibits a wide range of physiological functions, including the regulation of tumor cell growth. Octreotide (OCT) is a synthetic analogue of SST that can be used to slow gastrointestinal bleeding, inhibit the release of growth hormone and impede gastrointestinal tumor growth. The aim of the present study was to investigate the molecular mechanism of OCT underlying the inhibition of gastric cancer cell proliferation. Proteins of interest were detected using western blotting, and the zinc finger protein (ZAC)-P300 complex was quantified using co-immunoprecipitation. P300-histone acetyltransferase (P300-HAT) activity was determined spectrophotometrically. The results showed that OCT decreased the phosphorylation of Akt which caused the level of ZAC to increase. In turn, the interaction between ZAC and P300 increased the activity of P300-HAT; ultimately, the phosphorylation of serine 10 in histone H3 (pS10-H3) was decreased and the acetylation of lysine 14 in histone H3 (acK14-H3) was increased. These results suggest that OCT attenuates SGC-7901 cell proliferation by enhancing P300-HAT activity through the interaction of ZAC and P300, causing a reduction in pS10-H3 and an increase in acK14-H3. These findings provide insight for future research on OCT and further demonstrate the potential of OCT to be used as a therapeutic agent for gastric cancer.

Graphene Nanopores for Electronic Recognition of DNA Methylation

We investigate theoretically the ability of graphene nanopore membranes to detect methylated sites along a DNA molecule by electronic sheet current along the two-dimensional (2D) materials. Special emphasis is placed on the detection sensitivity changes due to pore size, shape, position, and the presence of defects around the nanopore in a membrane with constricted geometry. Enhanced sensitivity for detecting methylated CpG sites, labeled by methyl-CpG binding domain (MBD) proteins along a DNA molecule, is obtained for electronic transport through graphene midgap states caused by the constriction. A large square deviation from the graphene conductance with respect to the open nanopore is observed during the translocation of MBD proteins. This approach exhibits superior resolution in the detection of multiple methylated sites along the DNA compared to conventional ionic current blockade techniques.

Pharmacogenomics of genes involved in antifolate drug response and toxicity in osteosarcoma

INTRODUCTION

Antifolates are structural analogs of folates, which have been used as antitumor drugs for more than 60 years. The antifolate drug most commonly used for treating human tumors is methotrexate (MTX), which is utilized widely in first-line treatment protocols of high-grade osteosarcoma (HGOS). In addition to MTX, two other antifolates, trimetrexate and pemetrexed, have been tested in clinical settings for second-line treatment of recurrent HGOS with patients unfortunately showing modest activity. Areas covered: There is clinical evidence which suggsest that, like other chemotherapeutic agents, not all HGOS patients are equally responsive to antifolates and do not have the same susceptibility to experience adverse drug-related toxicities. Here, we summarize the pharmacogenomic information reported so far for genes involved in antifolate metabolism and transport and in MTX-related toxicity in HGOS patients. Expert opinion: Identification and validation of genetic biomarkers that significantly impact clinical antifolate treatment response and related toxicity may provide the basis for a future treatment modulation based on the pharmacogenetic and pharmacogenomic features of HGOS patients.

Hypermethylated APC in serous carcinoma based on a meta-analysis of ovarian cancer

Background

The reduced expression of the Adenomatous polyposis coli (APC) gene, a tumor suppressor gene, through promoter hypermethylation has been reported to play a key role in the carcinogenesis. However, the correlation between APC promoter hypermethylation and ovarian cancer (OC) remains to be clarified.

Methods

A comprehensive literature search was carried out in related research databases. The overall odds ratio (OR) and corresponding 95 % confidence interval (CI) were used to evaluate the effects of APC promoter hypermethylation on OC and clinicopathological characteristics.

Results

Ultimately, 12 eligible studies were used in our study, including 806 OC samples, 429 normal controls, 109 benign lesions and 75 LMP samples. The pooled OR showed that APC promoter hypermethylation was significantly higher in OC than in normal and benign controls (OR = 6.18 and OR = 3.26, respectively). No significant correlation was observed between OC and low malignant potential (LMP) tumors (P = 0.436). In the comparison of OC and normal controls, subgroup analysis based on race showed that the overall OR of APC promoter hypermethylation was significant and similar in Asians and Caucasians (OR = 8.34 and OR = 5.39, respectively). A subgroup analysis based on sample type found that the pooled OR was significantly higher in blood than in tissue (OR = 18.71 and OR = 5.74, respectively). A significant association was not observed between APC promoter hypermethylation and tumor grade or tumor stage. The pooled OR indicated that APC promoter hypermethylation was significantly lower in serous carcinoma than in non-serous carcinoma (OR = 0.56, P = 0.02). No obvious publication bias was detected by Egger’s test (all P > 0.05).

Conclusions

APC promoter hypermethylation may be linked to the increased risk of OC. It was associated with histological type, but not with tumor grade or tumor stage. Moreover, hypermethylated APC may be a noninvasive biomarker using blood samples. Future studies are required to validate these results.

Increased expression of SET domain-containing proteins and decreased expression of Rad51 in different classes of renal cell carcinoma

Because of scant availability of tissue samples, we did not perform elaborate examination of chromatin immunoprecipitation and specific binding of SET domain-containing proteins to the promoters of Rad51. These remain avenues for future investigations.

In the present study, we aimed to examine whether SET domain-containing methyltransferases are up-regulated in different classes of renal cell carcinoma. We immunoblotted against SET domain and quantified the expression of these modular domains. Furthermore, we examined the expression of Rad51, the key protein that confers genomic stability. There was enhanced expression of SET domain-containing histone methyltransferases in whole lysates of all classes of renal carcinoma. In metastatic high grade clear cell carcinoma, this expression was more pronounced. Though we could not demonstrate direct correlation, we showed that epigenetic modification by methylation is associated with decreased genomic translation of Rad51.

Efficiency of methylated DNA immunoprecipitation bisulphite sequencing for whole-genome DNA methylation analysis

AIMS

We compared four common methods for measuring DNA methylation levels and recommended the most efficient method in terms of cost and coverage.

MATERIALS & METHODS

The DNA methylation status of liver and stomach tissues was profiled using four different methods, whole-genome bisulphite sequencing (WG-BS), targeted bisulphite sequencing (Targeted-BS), methylated DNA immunoprecipitation sequencing (MeDIP-seq) and methylated DNA immunoprecipitation bisulphite sequencing (MeDIP-BS). We calculated DNA methylation levels using each method and compared the results.

RESULTS

MeDIP-BS yielded the most similar DNA methylation profile to WG-BS, with 20 times less data, suggesting remarkable cost savings and coverage efficiency compared with the other methods.

CONCLUSION

MeDIP-BS is a practical cost-effective method for analyzing whole-genome DNA methylation that is highly accurate at base-pair resolution.

Effects of paclitaxel on permanent head and neck squamous cell carcinoma cell lines and identification of anti-apoptotic caspase 9b

PURPOSE

Paclitaxel is an effective chemotherapeutic agent against various human tumors inducing apoptosis via binding to β-tubulin of microtubules and arresting cells mainly in the G2/M phase of the cell cycle. However, the underlying specific molecular mechanisms of paclitaxel on head and neck squamous cell carcinoma (HNSCC) have not been identified yet.

METHODS

The apoptotic effects and mechanisms of paclitaxel on different permanent HPV-negative HNSCC cell lines (UT-SCC-24A, UT-SCC-24B, UT-SCC-60A and UT-SCC-60B) were determined by flow cytometry assays, polymerase chain reaction analysis, immunofluorescence-based assays and sequencing studies.

RESULTS

Paclitaxel induced a G2/M arrest in HNSCC cell lines followed by an increased amount of apoptotic cells. Moreover, the activation of caspase 8, caspase 10 and caspase 3, and the loss of the mitochondrial outer membrane potential could be observed, whereas an activation of caspase 9 could barely be detected. The efficient activation of caspase 9 was not affected by altered methylation patterns. Our results can show that the promoter region of apoptotic protease activating factor 1 (Apaf-1) was not methylated in the HNSCC cell lines. By sequencing analysis two isoforms of caspase 9, the pro-apoptotic caspase 9 and the anti-apoptotic caspase 9b were identified. The anti-apoptotic caspase 9b is missing the catalytic site and acts as an endogenous inhibitor of apoptosis by blocking the binding of caspase 9 to Apaf-1 to form the apoptosome.

CONCLUSION

Our data indicate the presence of anti-apoptotic caspase 9b in HNSCC, which may serve as a promising target to increase chemotherapeutic apoptosis induction.

Methylation analysis of DNA repair genes in Alzheimer's disease

There is substantial evidence of impaired DNA repair activities in Alzheimer's disease (AD) neurons and peripheral tissues, inducing some investigators to speculate that this could partially result from promoter hypermethylation of DNA repair genes, resulting in gene silencing in those tissues. In the present study a screening cohort composed by late-onset AD (LOAD) patients and healthy matched controls was evaluated with a commercially available DNA methylation array for the assessment of the methylation levels of a panel of 22 genes involved in major DNA repair pathways in blood DNA. We then applied a cost-effective PCR based methylation-sensitive high-resolution melting (MS-HRM) technique, in order to evaluate the promoter methylation levels of the following DNA repair genes: OGG1, PARP1, MRE11A, BRCA1, MLH1, and MGMT. The analysis was performed in blood DNA from 56 LOAD patients and 55 matched controls, including the samples previously assessed with the DNA methylation array as validating samples. Both approaches revealed that all the investigated genes were largely hypomethylated in LOAD and control blood DNA, and no difference between groups was observed. Collectively, present data do not support an increased promoter methylation of some of the major DNA repair genes in blood DNA of AD patients.

Methods for genome-wide DNA methylation analysis in human cancer

Aberrant DNA methylation is considered to be one of the most common hallmarks of cancer. Several recent advances in assessing the DNA methylome provide great promise for deciphering the cancer-specific DNA methylation patterns. Herein, we present the current key technologies used to detect high-throughput genome-wide DNA methylation, and the available cancer-associated methylation databases. Additionally, we focus on the computational methods for preprocessing, analyzing and interpreting the cancer methylome data. It not only discusses the challenges of the differentially methylated region calling and the prediction model construction but also highlights the biomarker investigation for cancer diagnosis, prognosis and response to treatment. Finally, some emerging challenges in the computational analysis of cancer methylome data are summarized.

A 2015 survey of established or potential epigenetic biomarkers for the accurate detection of human cancers

Context The silencing or activation of cancer-associated genes by epigenetic mechanisms can ultimately lead to the clonal expansion of cancer cells. Objective The aim of this review is to summarize all relevant epigenetic biomarkers that have been proposed to date for the diagnosis of some prevalent human cancers. Methods A Medline search for the terms epigenetic biomarkers, human cancers, DNA methylation, histone modifications and microRNAs was performed. Results One hundred fifty-seven relevant publications were found and reviewed. Conclusion To date, a significant number of potential epigenetic cancer biomarkers of human cancer have been investigated, and some have advanced to clinical implementation.

Aberrant Promoter Methylation of the Tumour Suppressor RASSF10 and Its Growth Inhibitory Function in Breast Cancer

Breast cancer is the most common cancer in women, with 1.7 million new cases each year. As early diagnosis and prognosis are crucial factors in cancer treatment, we investigated potential DNA methylation biomarkers of the tumour suppressor family Ras-association domain family (RASSF). Promoter hypermethylation of tumour suppressors leads to their inactivation and thereby promotes cancer development and progression. In this study we analysed the tumour suppressors RASSF1A and RASSF10. Our study shows that RASSF10 is expressed in normal breast but inactivated by methylation in breast cancer. We observed a significant inactivating promoter methylation of RASSF10 in primary breast tumours. RASSF10 is inactivated in 63% of primary breast cancer samples but only 4% of normal control breast tissue is methylated (p < 0.005). RASSF1A also shows high promoter methylation levels in breast cancer of 56% vs. 8% of normal tissue (p < 0.005). Interestingly more than 80% of breast cancer samples harboured a hypermethylation of RASSF10 and/or RASSF1A promoter. Matching samples exhibited a strong tumour specific promoter methylation of RASSF10 in comparison to the normal control breast tissue. Demethylation treatment of breast cancer cell lines MCF7 and T47D reversed RASSF10 promoter hypermethylation and re-established RASSF10 expression. In addition, we could show the growth inhibitory potential of RASSF10 in breast cancer cell lines MCF7 and T47D upon exogenous expression of RASSF10 by colony formation. We could further show, that RASSF10 induced apoptotic changes in MCF7 and T47D cells, which was verified by a significant increase in the apoptotic sub G1 fraction by 50% using flow cytometry for MCF7 cells. In summary, our study shows the breast tumour specific inactivation of RASSF10 and RASSF1A due to DNA methylation of their CpG island promoters. Furthermore RASSF10 was characterised by the ability to block growth of breast cancer cell lines by apoptosis induction.

Aberrant HOXA10 Methylation in Patients With Common Gynecologic Disorders: Implications for Reproductive Outcomes

HomeoboxA10 (HOXA10) is a transcription factor that is crucial for the development and patterning of the uterus during embryogenesis. In the adult endometrium, HOXA10 expression is regulated by steroid hormones and embryonic signals. Expression of sufficient HOXA10 messenger RNA is essential to endometrial receptivity and embryo implantation. Aberrant methylation is believed to alter the expression of HOXA10. Methylation of this gene may be associated with decreased fertility, implantation defects, and/or reproductive wastage seen in certain disease states that affect the female reproductive tract. This study describes the differences in methylation patterns of HOXA10 gene in uterine myomas, endometriosis, uterine septum, Asherman syndrome, or uterine polyps of women undergoing hysteroscopic surgery. In the endometrium of uteri with polyps, submucosal myomas, and intramural myomas, there were CpG sites within the HOXA10 gene that were highly methylated compared to controls. The HOXA10 gene in women with endometriosis was hypomethylated compared to controls. DNA methylation may be a common molecular mechanism that results in reproductive dysfunction seen in gynecologic disease.

Effect of MTHFR Gene Polymorphism Impact on Atherosclerosis via Genome-Wide Methylation

BACKGROUND

Atherosclerosis seriously threats human health. Homocysteine is an independent risk factor closely related to DNA methylation. MTHFR C667T loci polymorphism is closely associated with homocysteine level. This study aimed to investigate the relationship among MTHFR C667T loci polymorphism, genome-wide methylation, and atherosclerosis.

MATERIAL/METHODS

Blood sample was collected from 105 patients with coronary atherosclerosis and 105 healthy controls. Pyrosequencing methylation was used to detect LINE-1 methylation level. Polymerase chain reaction-restriction enzyme fragment length polymorphism (PCR-RFLP) was used to test MTHFR.

RESULTS

LINE-1 methylation level in the patient group was significantly lower than in the controls (t=5.007, P<0.001). MTHFR C667T genotype distribution presented marked differences in the 2 groups. TT genotype carriers had significantly increased risk of atherosclerosis (OR=3.56, P=0.009). Three different genotypes of MTHFR C667T loci showed different LINE-1 methylation level between the 2 groups (P<0.01). LINE-1 methylation level in TT and CT genotype carriers was obviously lower than in CC genotype carriers (P<0.05).

CONCLUSIONS

MTHFR C667T loci polymorphism may affect atherosclerosis by regulating genome methylation level.

Emerging Proteomic Technologies Provide Enormous and Underutilized Potential for Brain Cancer Research

High-throughput technologies present immense opportunities to characterize brain cancer biology at a systems level. However, proteomic studies of brain cancers are still relatively scarce. Here we discuss the latest proteomic technologies, their application to profiling and quantitation of brain proteomes and how we expect these technologies will be applied to study brain cancer proteomes in the future. Mass spectrometry based proteomics with increased specificity, coverage and throughput will be pervasive in proteomics investigations of brain. Generated data needs to be captured by the curation of databases, and application of creative data analysis strategies is needed to provide meaningful insights into brain functions and associated pathologies. Overall, proteomics applications to brain cancers are in the earliest stages and the expanded use of these technologies holds enormous potential to improve our understanding of brain functions and pathologies.

Colorectal cancer detection in an asymptomatic population: fecal immunochemical test for hemoglobin vs. fecal M2-type pyruvate kinase

INTRODUCTION

Screening programs for colorectal cancer (CRC) are mainly based on a first-line fecal immunochemical test for hemoglobin (FIT). Fecal M2-type pyruvate kinase (M2-PK) has been evaluated in clinical settings showing promising results for early CRC detection. However, the impact of fecal M2-PK assessment on the performance of first-round CRC screening programs is not known. We investigated whether fecal M2-PK alone or in combination with FIT may improve CRC screening efficacy in the general population.

MATERIALS AND METHODS

A total of 1027 asymptomatic subjects (median age 66 [59-74] years; females 504 [49.1%]), identified through the general practitioners' rosters, were invited for the collection of 2 fecal samples for FIT and M2-PK evaluation. Participants with at least positive one fecal test were referred for colonoscopy. Quality indicators for screening performance were calculated and analyzed using Fisher's exact test.

RESULTS

Overall, 572 subjects underwent both FIT and M2-PK assessment (participation rate 55.7%): 93 participants showed positive results for at least one test (positivity rate 16.3%). Only 10 patients were positive for both tests. Attendance rate to colonoscopy was 86.0% and a total of 65 adenomas and 7 cancers were detected. Combined use of FIT and fecal M2-PK permitted the identification of 18 more neoplasm (25%) without improving colonoscopy workload, as deduced by the comparable number needed to scope (P = 0.402).

CONCLUSION

The addition of M2-PK testing to FIT offers the potential to detect additional neoplasms that either do not bleed or only bleed intermittently without reducing participation rate and without increasing endoscopy workload.

Aberrant Protocadherin17 (PCDH17) Methylation in Serum is a Potential Predictor for Recurrence of Early-Stage Prostate Cancer Patients After Radical Prostatectomy

Background

Prostate cancer is a one of the most common malignant diseases in men worldwide. Now it is a challenge to identify patients at higher risk for relapse and progression after surgery, and more novel prognostic biomarkers are needed. The aim of this study was to investigate the clinical significance of protocadherin17 (PCDH17) methylation in serum and its predictive value for biochemical recurrence (BCR) after radical prostatectomy.

Material/Methods

We evaluated the methylation status of PCDH17 in serum samples of 167 early-stage prostate cancer patients and 44 patients with benign prostatic hyperplasia (BPH) using methylation-specific PCR (MSP), and then evaluated the relationship between PCDH17 methylation and clinicopathologic features. Kaplan-Meier survival analysis and Cox analysis were used to evaluate its predictive value for BCR.

Results

The ratio of PCDH17 methylation in prostate cancer patients was higher than in patients with BPH. Moreover, PCDH17 methylation was significantly associated with advanced pathological stage, higher Gleason score, higher preoperative PSA levels, and BCR. Kaplan-Meier survival analysis indicated that patients with methylated PCDH17 had shorter BCR-free survival time compared to patients with unmethylated PCDH17. Cox regression analysis indicated that PCDH17 methylation was an independent predictive factor for the BCR of patients after radical prostatectomy.

Conclusions

PCDH17 methylation in serum is a frequent event in early-stage prostate cancer, and it is an independent predictor of BCR after radical prostatectomy.

DAPK1, MGMT and RARB promoter methylation as biomarkers for high-grade cervical lesions

Gene promoter methylation may be used a potential biomarker for detecting solid tumor including cervical cancer. Here, we used methylation sensitive-high resolution melting (MS-HRM) analysis to detecting promoter methylation ratios of DAPK1, MGMT and RARB gene in patients with different cervical disease grade. The detection of gene promoter methylation was conducted in two hundred fifty patients' samples including normal cytology (n=48), cervical intraepithelial neoplasia grade 1 (CIN1, n=54), cervical intraepithelial neoplasia grade 2 (CIN2, n=47), cervical intraepithelial neoplasia grade 3 (CIN3, n=56) and cervical squamous cell carcinomas (SCS, n=45). We found there were a significant positive correlation between the promoter methylation status of DAPK1 and cervical disease grade (P=0.022). In addition, the methylated promoters of DAPK1 combined with MGMT, MGMT combined with RARB, DAPK1 combined with RARB were positive correlated with cervical disease grade (P < 0.05). All three genes promoters methylated were positive correlated with cervical disease grade (P < 0.001). Receiver operating characteristic (ROC) curves was conducted to evaluate whether the three genes methylation could be used to be a potential marker for diagnosing high grade cervical disease (HSIL and SCC). The cutoff values for the methylation rates of all these genes were 0-5%. Regrettably, only the methylation of MGMT combined with DAPK1 gave 43.4% sensitivity and 68.6% specificity. The current results indicated that MS-HRM-based testing for DNA methylations of MGMT plus DAPK1 genes holds some promise for high grade cervical disease screening.

DNA methylation of RAMP1 gene in migraine: an exploratory analysis

Background

Receptor activity modifying protein 1(RAMP1) is a key receptor subunit of calcitonin gene related peptide (CGRP) playing a critical role in migraine. But variations in RAMP1 gene have not been found to link with migraine. Still it is elusive that DNA methylation at RAMP1 promoter is associated with migraine.

Methods

A total of 51 blood DNA samples from 26 patients with migraine and 25 matched healthy controls were collected, extracted and treated with bisulfate. Subsequently DNA methylation levels at RAMP1 promoter region were measured using Sequenom Mass ARRAY systems.

Results

Among 13 detected CpG sites or units at RAMP1 promoter region, there were no significant differences between the migraine and control groups, but indicating a low methylation trend overall in migraine group (total average methylation level: 8.41 % ±1.92 % vs. 9.90 % ± 3.88 %, p = 0.197). Stratification analysis showed that methylation level at (+25, +27, +31, related to the transcription start site) CpG unit was higher in migraineurs with migraine family history compared to those without (13.92 % ± 5.97 % vs. 8.77 % ± 6.61 %, p = 0.034), and methylation level at (+89, +94, +96) CpG unit was lower in migraine female than that in healthy female (2.18 % ± 1.91 % vs. 5.85 % ± 5.41 %, p = 0.02). For female with methylation level at (+89, +94, +96) CpG unit below 3.50 %, the probability of being a migraine patient was significantly higher than those with methylation level above the threshold (OR: 7.313; 95%CI: 1.439-37.164).

Conclusions

This study provides the first evidence that DNA methylation at RAMP1 promoter might play a role in migraine. A low methylation trend overall was presented in migraine subjects, and two CpG units were observed to link with positive migraine family history and female migraine, respectively. Lower methlytion level at (+89, +94, +96) CpG unit may be a risk of migraine in females.