LINE-1 Methylation Research Articles

Early maternal care restores LINE-1 methylation and enhances neurodevelopment in preterm infants

BackgroundPreterm birth affects almost 9–11% of newborns and is one of the leading causes of childhood neurodevelopmental disabilities; the underlying molecular networks are poorly defined. In neurons, retrotransposons LINE-1 (L1) are an active source of genomic mosaicism that is deregulated in several neurological disorders; early life experience has been shown to regulate L1 activity in mice.MethodsVery preterm infants were randomized to receive standard care or early intervention. L1 methylation was measured at birth and at hospital discharge. At 12 and 36 months, infants’ neurodevelopment was evaluated with the Griffiths Scales. L1 methylation and CNVs were measured in mouse brain areas at embryonic and postnatal stages.ResultsHere we report that L1 promoter is hypomethylated in preterm infants at birth and that an early intervention program, based on enhanced maternal care and positive multisensory stimulation, restores L1 methylation levels comparable to healthy newborns and ameliorates neurodevelopment in childhood. We further show that L1 activity is fine-tuned in the perinatal mouse brain, suggesting a sensitive and vulnerable window for the L1 epigenetic setting.ConclusionsOur results open the field on the inspection of L1 activity as a novel molecular and predictive approach to infants’ prematurity-related neurodevelopmental outcomes.Trial registrationClinicalTrial.gov (NCT02983513). Registered on 6 December 2016, retrospectively registered.

Invasive and Noninvasive Nonfunctioning Gonadotroph Pituitary Tumors Differ in DNA Methylation Level of LINE-1 Repetitive Elements.

Purpose: Epigenetic dysregulation plays a role in pituitary tumor pathogenesis. Some differences in DNA methylation were observed between invasive and noninvasive nonfunctioning gonadotroph tumors. This study sought to determine the role of DNA methylation changes in repetitive LINE-1 elements in nonfunctioning gonadotroph pituitary tumors. Methods: We investigated LINE-1 methylation levels in 80 tumors and normal pituitary glands with bisulfite-pyrosequencing. Expression of two LINE-1 open reading frames (L1-ORF1 and L1-ORF2) was analyzed with qRT-PCR in tumor samples and mouse gonadotroph pituitary cells treated with DNA methyltransferase inhibitor. Immunohistochemical staining against L1-ORF1p was also performed in normal pituitary glands and tumors. Results: Hypomethylation of LINE-1 was observed in pituitary tumors. Tumors characterized by invasive growth revealed lower LINE-1 methylation level than noninvasive ones. LINE-1 methylation correlated with overall DNA methylation assessed with HM450K arrays and negatively correlated with L1-ORF1 and L1-ORF2 expression. Treatment of αT3-1 gonadotroph cells with 5-Azacytidine clearly increased the level of L1-ORF1 and L1-ORF2 mRNA; however, its effect on LβT2 cells was less pronounced. Immunoreactivity against L1-ORF1p was higher in tumors than normal tissue. No difference in L1-ORF1p expression was observed in invasive and noninvasive tumors. Conclusion: Hypomethylation of LINE-1 is related to invasive growth and influences transcriptional activity of transposable elements.

Global DNA hypomethylation of Alu and LINE-1 transposable elements as an epigenetic biomarker of anti-tuberculosis drug-induced liver injury

ABSTRACT Despite being highly effective, anti-tuberculosis (TB) drugs often induce adverse liver injury, anti-TB drug-induced liver injury (ATDILI), leading to treatment failure given no sensitive and selective ATDILI markers. Herein, we conducted a case–control association study to determine whether global DNA methylation of Alu and LINE-1 transposable elements responsible for genomic stability and transcriptional regulation was correlated with clinical parameters indicating ATDILI in TB patients and might serve as an ATDILI biomarker. Alu and LINE-1 methylation levels in blood leukocyte of 130 TB patients (80 ATDILI cases and 50 non-ATDILI cases) and 100 healthy controls were quantified using quantitative combined bisulfite restriction analysis. Both TB patients with and without ATDILI had significantly lower methylation levels of Alu and LINE-1 elements than healthy controls. Compared with non-ATDILI patients, Alu methylation levels were significantly decreased in ATDILI patients, commensurate with LINE-1 methylation analysis. Hypomethylation of Alu and LINE-1 measured within 1–7 days of TB treatment was independently associated with raised levels of serum aminotransferases assessed within 8–60 days of TB treatment. Receiver operating characteristic curve analysis uncovered that Alu and LINE-1 methylation levels were both more sensitive and specific for differentiating ATDILI cases from non-ATDILI cases than serum aminotransferases after starting TB treatment within 1–7 days. Kaplan-Meier analysis displayed a significant association between hypomethylation of Alu and LINE-1 elements and an increased rate of ATDILI occurrence in TB patients. Collectively, global DNA hypomethylation of Alu and LINE-1 elements would reflect ATDILI progression and might serve as novel sensitive and specific ATDILI biomarkers.

RETRACTED ARTICLE: Aging-associated distinctive DNA methylation changes of LINE-1 retrotransposons in pure cell-free DNA from human blood

LINE-1 hypomethylation of cell-free DNA has been described as an epigenetic biomarker of human aging. However, in the past, insufficient differentiation between cellular and cell-free DNA may have confounded analyses of genome-wide methylation levels in aging cells. Here we present a new methodological strategy to properly and unambiguously extract DNA methylation patterns of repetitive, as well as single genetic loci from pure cell-free DNA from peripheral blood. Since this nucleic acid fraction originates mainly in apoptotic, senescent and cancerous cells, this approach allows efficient analysis of aged and cancerous cell-specific DNA methylation patterns for diagnostic and prognostic purposes. Using this methodology, we observe a significant age-associated erosion of LINE-1 methylation in cfDNA suggesting that the threshold of hypomethylation sufficient for relevant LINE-1 activation and consequential harmful retrotransposition might be reached at higher age. We speculate that this process might contribute to making aging the main risk factor for many cancers.

Impact of Tumor LINE-1 Methylation Level and Neoadjuvant Treatment and Its Association with Colorectal Cancer Survival.

Recent studies suggest that long-interspersed nucleotide element-1 (LINE-1) hypomethylation is commonly found in colorectal cancer (CRC), and is associated with worse prognosis. However, the utility of LINE-1 methylation on the prognosis of CRC is still controversial, and may be due to the fact that some clinical and pathological features may affect LINE-1 methylation. Thus, the aim of this study was to assess the prognostic value of tumor LINE-1 methylation in CRC, through their association with the CRC clinical and pathological characteristics. Survival of sixty-seven CRC patients was evaluated according to the median of tumor LINE-1 methylation, as well as pathological and oncological variables. We also studied the association between LINE-1 methylation and pathological features, and finally, we assessed the overall and disease-free survival of LINE1 methylation, stratified by neoadjuvant treatment and further checked by multivariate Cox regression to assess the statistical interactions. LINE-1 was hypomethylated in the CRC tumor with respect to the tumor adjacent-free area (p < 0.05), without association with any other clinical and oncological features, nor with overall and disease-free survival rates for CRC. Relevantly, in neoadjuvant treatment, LINE-1 methylation was associated with survival rates. Thus, disease-free and overall survival rates of treated CRC patients were worse in the hypomethylated LINE-1 tumors than those with normal LINE-1 methylation (p = 0.004 and 0.0049, respectively). Indeed, LINE-1 was hypermethylated more in the treated patients than in the non-treated patients (p < 0.05). The present study showed that tumor LINE-1 hypomethylation was associated with worse survival rates in only treated patients. Our data suggest an interactive effect of neoadjuvant treatment and tumor LINE-1 methylation, which could be a specific-tissue biomarker to predict survival of the treated patients, and help to personalize treatment in CRC.

PO-0802: Impact of LINE-1 methylation on survival in patients with locally advanced oropharyngeal carcinoma.

PO-0802: Impact of LINE-1 methylation on survival in patients with locally advanced oropharyngeal carcinoma.

Fasting and fasting mimetic supplementation address sirtuin expression, miRNA and microbiota composition

Background: Fasting and fasting mimetics - bioactive compounds mimicking fasting effects, are of growing interest as potential means to slow down the aging process and increase health span. Sirtuins are known as enzymes that interfere with mitochondrial energy metabolism and molecular pathways involved in longevity. Although their activation is determined as a response to stress i.e. caloric restriction. Sirtuin activating nutraceuticals are believed to mimic the effects of nutrient deprivation, thus activating signaling pathways correlated to an improved health span. In this study, we compare 5 days periodic buchinger fasting intervention with 3 months shot supplementation, a drink formula, containing secondary plant ingredients considered to activate sirtuins.Methods: We analyzed pathways in response to fasting and a sirtuins activating drink. Genetic and epigenetic biomarkers including telomere length, LINE1 methylation, and a set of mRNAs and miRNAs were assessed using qPCR analysis. Gut composition and metabolites were compared using Illumnia sequencing and mass spectrometry.Results: Fasting, but also the fasting mimetic could increase expression of FoxO1, SIRT1, and MLH1 mRNA, all genes discussed in aspects of longevity. A positive correlation between telomere length and both SIRT1, and SIRT6 was observed. Furthermore, a significant change in the gut composition was measured. Actinobacteria increased in the supplementation group, whereas after buchinger fasting a rise in the distribution of Proteobacteria could be observed. Firmicutes/Bacteroidetes ratio decreased and correlated with the body mass index (BMI).Conclusions: Our results confirm the effects of fasting on longevity associated mechanisms but also suggest that SIRTFOOD shot intervention addresses some of these effects.

Human Endogenous Retroviruses Long Terminal Repeat Methylation, Transcription, and Protein Expression in Human Colon Cancer.

Colon cancer is the fourth most common malignancy in both incidence and mortality in developed countries. Infectious agents are among the risk factors for colon cancer. Variations in human endogenous retrovirus (HERV) transcript and protein levels are associated with several types of cancers, but few studies address HERV expression in colon cancer. Fifty-eight patients with advanced-stage colon cancer were enrolled in this study. HERV-H, -K (HML-2), -P LTRs, Alu, and LINE-1 methylation levels and transcription of HERV-H, -K (HML-2), and -P env and HERV-K pol genes in normal adjacent and tumor tissues were investigated by pyrosequencing and RT-qPCR, respectively. Expression of the HERV-K (HML-2) Pol and Env proteins in selected tissues was examined by Western blotting. Associations between HERV transcript expression and methylation levels and between clinical characteristics and HERV expression were evaluated. Compared to adjacent normal tissues, LINE-1 was hypomethylated in tumor tissues (p < 0.05), whereas Alu, HERV-K (HML-2), and -H LTRs showed a decreasing trend in tumor tissue compared to normal tissue, though without a significant difference. The transcription levels of HERV env and pol genes were similar. However, the HERV-K (HML-2) Pol protein was more highly expressed (p < 0.01) in surrounding normal tissues, but the HERV-K (HML-2) Env protein was only expressed in tumor tissues. Although HERV LTR methylation and gene expression did not show significant differences between tumor and normal tissues, HERV protein expression differed greatly. Pol protein expression in normal cells may induce reverse transcription and subsequent integration into the host genome, likely favoring cell transformation; in contrast, the Env protein in tumor tissue may contribute to cancer progression through cell-to-cell fusion.

LINE1 methylation is differentially associated with lead exposure and job-tasks performed by electronic waste workers

Background/Aim: Electronic waste (e-waste) is a pressing global public health concern due to high production volumes and inadequate management practices, which often occur in developing countries without appropriate recycling infrastructure. Exposure to a variety of chemical mixtures during informal e-waste recycling processes has been associated with adverse health outcomes affecting respiratory, cardiovascular, neurological, and reproductive systems. DNA methylation has been associated with toxic chemical exposures including heavy metals in epidemiological studies. Although e-waste contains a myriad of toxic chemicals with known health effects, DNA methylation profile of e-waste recyclers has not been studied. This study assessed the associations between cadmium (Cd), lead (Pb), and arsenic (As) concentration and methylation levels of the LINE1 gene among e-waste workers and non e-waste workers in Ghana.Methods: The study included 100 males e-waste workers and 51 males non e-waste workers. The participants provided extensive demographic and work-related data and biological samples. The metals were measured in blood and urine using Inductively Coupled Plasma Mass Spectrometry while LINE1 methylation levels were determined by pyrosequencing of bisulfite-converted DNA from whole blood.Results: There was no significant difference in LINE1 methylation between e-waste workers and non-e-waste workers (85.16% ±1.32 vs 85.17% ±1.11, p = 0.950). However, CpG1 showed significantly lower mean methylation among non-e-waste workers compared to the e-waste workers (81.70% ±1.86 vs 82.48% ±2.20, p = 0.034). In linear regression models, blood lead (B-Pb) level was significantly inversely associated with overall LINE1 methylation (β = -0.004; 95%CI: -0.008, -0.0002; p = 0.038), while e-waste collectors showed significantly reduced LINE1 methylation levels (β = -1.068; 95%CI: -2.040, -0.095; p = 0.032) when comparing across job-task for e-waste workers.Conclusion: Our results suggest that lead exposure may alter LINE1 methylation levels, and collectors, in particular, maybe at an increased risk of epigenetic alteration due to lead exposure.

Nonsyndromic orofacial clefts in Chile: LINE-1 methylation and MTHFR variants.

Aim: To evaluate the risk of nonsyndromic orofacial clefts (NSOFCs) associated withLINE-1 methylation, as amarker of global DNA methylation, and the effect of MTHFR functional variants on this variable. Patients & methods: LINE-1 methylation was evaluated by bisulfite modification coupled to DNA pyrosequencing in 95 NSOFC cases and 95 controls. In these subjects, MTHFR genotypes for variants c.C677T (rs1801133) and c.A1298C (rs1801131) were obtained. Results: Middle levels (second tertile) of LINE-1 methylation increase the risk of NSOFCs. In addition, LINE-1 methylation depends on c.A1298C genotypes in controls but not in cases. Conclusion: A nonlinear association between global DNA methylation and NSOFCs was detected in this Chilean population, which appears to be influenced by MTHFR functional variants.

Aberrant Methylation of LINE-1 Transposable Elements: A Search for Cancer Biomarkers.

Cancer remains one of the main causes of human mortality despite significant progress in its diagnostics and therapy achieved in the past decade. Massive hypomethylation of retrotransposons, in particular LINE-1, is considered a hallmark of most malignant transformations as it results in the reactivation of retroelements and subsequent genomic instability. Accumulating data on LINE-1 aberrant methylation in different tumor types indicates its significant role in cancer initiation and progression. However, direct evidence that LINE-1 activation can be used as a cancer biomarker is still limited. The objective of this review was to critically evaluate the published results regarding the diagnostic/prognostic potential of the LINE-1 methylation status in cancer. Our analysis indicates that LINE-1 hypomethylation is a promising candidate biomarker of cancer development, which, however, needs validation in both clinical and laboratory studies to confirm its applicability to different cancer types and/or stages. As LINE-1 is present in multiple cell-free copies in blood, it has advantages over single-copy genes regarding perspectives of using its methylation status as an epigenetic cancer biomarker for cell-free DNA liquid biopsy.

Promoter methylation, transcription, and retrotransposition of LINE-1 in colorectal adenomas and adenocarcinomas

BackgroundThe methylation of the CpG islands of the LINE-1 promoter is a tight control mechanism on the function of mobile elements. However, simultaneous quantification of promoter methylation and transcription of LINE-1 has not been performed in progressive stages of colorectal cancer. In addition, the insertion of mobile elements in the genome of advanced adenoma stage, a precancerous stage before colorectal carcinoma has not been emphasized. In this study, we quantify promoter methylation and transcripts of LINE-1 in three stages of colorectal non-advanced adenoma, advanced adenoma, and adenocarcinoma. In addition, we analyze the insertion of LINE-1, Alu, and SVA elements in the genome of patient tumors with colorectal advanced adenomas.MethodsLINE-1 hypomethylation status was evaluated by absolute quantitative analysis of methylated alleles (AQAMA) assay. To quantify the level of transcripts for LINE-1, quantitative RT-PCR was performed. To find mobile element insertions, the advanced adenoma tissue samples were subjected to whole genome sequencing and MELT analysis.ResultsWe found that the LINE-1 promoter methylation in advanced adenoma and adenocarcinoma was significantly lower than that in non-advanced adenomas. Accordingly, the copy number of LINE-1 transcripts in advanced adenoma was significantly higher than that in non-advanced adenomas, and in adenocarcinomas was significantly higher than that in the advanced adenomas. Whole-genome sequencing analysis of colorectal advanced adenomas revealed that at this stage polymorphic insertions of LINE-1, Alu, and SVA comprise approximately 16%, 51%, and 74% of total insertions, respectively.ConclusionsOur correlative analysis showing a decreased methylation of LINE-1 promoter accompanied by the higher level of LINE-1 transcription, and polymorphic genomic insertions in advanced adenoma, suggests that the early and advanced polyp stages may host very important pathogenic processes concluding to cancer.

Adherence to the Mediterranean diet partially mediates socioeconomic differences in leukocyte LINE-1 methylation: evidence from a cross-sectional study in Italian women

Although previous research demonstrated that socioeconomic status (SES) might affect DNA methylation, social inequalities alone do not completely explain this relationship. We conducted a cross-sectional study on 349 women (Catania, Italy) to investigate whether behaviors might mediate the association between SES and long interspersed nuclear elements (LINE-1) methylation, a surrogate marker of global DNA methylation. Educational level, used as an indicator of SES, and data on behaviors (i.e. diet, smoking habits, physical activity, and weight status) were collected using structured questionnaires. Adherence to Mediterranean diet (MD) was assessed by the Mediterranean Diet Score (MDS). Leukocyte LINE-1 methylation was assessed by pyrosequencing. Mediation analysis was conducted using the procedure described by Preacher and Hayes. Women with high educational level exhibited higher MDS (β = 0.669; 95%CI 0.173–1.165; p < 0.01) and LINE-1 methylation level (β = 0.033; 95%CI 0.022–0.043; p < 0.001) than their less educated counterpart. In line with this, mediation analysis demonstrated a significant indirect effect of high educational level on LINE-1 methylation through the adherence to MD (β = 0.003; 95%CI 0.001–0.006). Specifically, the mediator could account for 9.5% of the total effect. To our knowledge, this is the first study demonstrating the mediating effect of diet in the relationship between SES and DNA methylation. Although these findings should be confirmed by prospective research, they add value to the promotion of healthy dietary habits in social disadvantaged people.

The mediating effect of lifestyles on the association between social factors and DNA methylation

Abstract Background Social disadvantage and unhealthy lifestyles may induce molecular changes associated with aging and age-related diseases. For instance, previous studies reported socioeconomic difference in DNA methylation, which in turn led to aberrant gene expression and genome instability. Socioeconomic status (SES) alone, however, does not completely explain this difference, and further studies are needed to unveil what factors contribute to it. Methods We conducted a cross-sectional study on 349 Italian women, aged 25-64 years, to assess SES differences in LINE-1 methylation level - a surrogate marker of global DNA methylation - and to examine the mediating effect of lifestyles (i.e. diet, smoking habits, physical activity, and weight status). Educational level was used as SES indicator. The adherence to Mediterranean diet (MD) was assessed by the Mediterranean Diet Score (MDS). Leukocyte LINE-1 methylation was assessed by pyrosequencing. Mediation analysis was conducted using the PROCESS macro for the SPSS software. Results We first observed that women with high educational level were more likely to be normal weight (p &amp;lt; 0.001) and to adhere to MD (p = 0.018), and less likely to perform physical activity (p = 0.012) than their less educated counterpart. Moreover, age-adjusted linear regression demonstrated that LINE-1 methylation level increased with increasing educational level (β = 0.016; SE = 0.003; p &amp;lt; 0.001). In line, mediation analysis demonstrated an indirect effect of high educational level on LINE-1 methylation through the adherence to MD (β = 0.003; 95%CI=0.001-0.006). Specifically, the mediator could account for 9.5% of the total effect. None of the other lifestyles, instead, exhibited a significant mediating effect. Conclusions To our knowledge, this is the first study demonstrating the mediation of diet in the relationship between SES and DNA methylation. Thus, our findings add even more value to the promotion of healthy dietary habits among social disadvantaged people. Key messages Social disadvantage is associated with epigenetic changes related to aging and age-related diseases. Adherence to the Mediterranean diet might mediate the association between socioeconomic status and DNA methylation.

Abstract 1265: The effects of ancestry and histology on the lung tumor methylome

Abstract Methylation-based biomarkers can provide molecular insight on the contribution of ancestry and histology to lung tumor biology. Loss of global methylation is a benchmark of aging and a signal of declining biological maintenance. In addition to aging, global loss of methylation occurs in response to some cancer-promoting exposures, including tobacco use. Reduced levels of global DNA methylation are associated with increased risk of several cancers, including lung. In lung tumors, global DNA hypomethylation is often associated with a more aggressive diseases and shorter survival time. Several studies have identified population-level differences in global methylation present at birth. Additionally, gender and ancestry influence DNA methylation age (DNAm) and may predispose some individuals to accelerated aging. We hypothesized that differences in global hypomethylation and accelerated aging may contribute to differences in lung tumor biology by genetic ancestry. Therefore, we investigated methylome differences between European Americans (EA) and African Americans (AA) from the NCI-Maryland Case Control Study, which is overrepresented with AA patients (~40%) from the Baltimore area. We assessed lung tumor and paired non-involved adjacent tissue (NAT) methylation (n = 77 EA, n = 39 AA) using the Illumina EPIC methylation array. We used the Repetitive Element Methylation Prediction (REMP) package in R to identify roughly 20,000 predicted LINE-1 CpG's. We observed significantly decreased LINE-1 methylation in tumor tissue compared with NAT in both AA and EA. Additionally, among tumor samples we observed significantly decreased LINE-1 methylation in AA LUSC samples compared to EA LUSC, with only modest differences between AA LUAD and EA LUAD. In addition to decreased levels, LINE-1 methylation in AA LUSC tumors also had the greatest heterogeneity within CpG's of the same sample and between other AA LUSC samples. We observed accelerated aging (increased DNAm relative to chronological age) in 57/67 EA NAT samples and 28/38 AA NAT samples with no significant differences in age acceleration between ancestry or histology. Our results show global hypomethylation of LINE-1 is a distinctive feature of LUSC in AA compared to EA, which is consistent with the enhanced genomic instability observed in AA LUSC relative to EA LUSC. We also observed accelerated aging in the vast majority of the NAT samples, which may implicate accelerated age with lung cancer risk. Future analysis will work towards completing a comprehensive analysis of the epigenetic landscape of lung cancer in AA and EA patients. We plan to study the relationship between global hypomethylation and genetic variants, smoking behaviors, and patient survival. Citation Format: Emily L. Rossi, Isaac Zhao, Rony F. Arauz, Adriana Zingone, Bríd M. Ryan. The effects of ancestry and histology on the lung tumor methylome [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1265.

The influence of obesity on folate status, DNA methylation and cancer-related gene expression in normal breast tissues from premenopausal women

ABSTRACT Epidemiological studies have established obesity as a critical risk factor for postmenopausal breast cancer (post-BC), whereas a reverse association holds prior to menopause. A significant scientific gap exists in understanding the mechanism(s) underpinning this epidemiological phenomenon, particularly the reverse association between obesity and premenopausal breast cancer (pre-BC). This study aimed to understand how folate metabolism and DNA methylation inform the association between obesity and pre-BC. Fifty normal breast tissue samples were collected from premenopausal women who underwent reduction mammoplasty. We modified the Lactobacillus Casei microbiological folate assay and measured folate levels in our breast tissue samples. The DNA methylation of LINE-1, a biomarker of genome-wide methylation, and the expression of a panel of breast cancer-related genes was measured by pyrosequencing and real-time PCR. We found that a high BMI is associated with an increase of folate levels in mammary tissue, with an increase of 2.65 ng/g of folate per every 5-unit increase of BMI (p < 0.05). LINE-1 DNA methylation was significantly associated with BMI (p < 0.05), and marginally associated with folate concentration (p = 0.087). A high expression of SFRP1 was observed in subjects with high BMI or high folate status (p < 0.05). This study demonstrated that, in premenopausal women, obesity is associated with increased mammary folate status, genome-wide DNA methylation and SFRP1 gene expression. Our findings indicated that the improved folate and epigenetic status represents a novel mechanism responsible for the reverse association between obesity and pre-BC.

An open-label, phase II multicohort study of an oral hypomethylating agent CC-486 and durvalumab in advanced solid tumors

PurposeTo evaluate whether administration of the oral DNA hypomethylating agent CC-486 enhances the poor response rate of immunologically ‘cold’ solid tumors to immune checkpoint inhibitor durvalumab.Experimental designPD-L1/PD-1 inhibitor naïve patients...

The Relationship Between Colorectal Cancer Risk Factors and LINE-1 DNA Methylation in Healthy Colon Tissue

Aim: LINE-1 DNA methylation is a modifiable epigenetic process linked to colorectal cancer (CRC). However, studies of methylation in the tissue of interest are limited. This research examines associations between CRC risk factors and LINE-1 DNA methylation in healthy colon tissue. Materials & methods: LINE-1 methylation was measured in colon tissue samples from 317 patients undergoing a screening colonoscopy. Associations were examined with established CRC risk factors including alcohol consumption, smoking, BMI, NSAIDs, physical activity and fruit and vegetable consumption. Results: All studied risk factors were not related to LINE-1 DNA methylation in this population. Conclusion: The observed results may reflect that the effect of this set of established risk factors is not mediated through LINE-1 DNA methylation in the healthy colon.

Tumor DNA hypomethylation of LINE-1 is associated with low tumor grade of breast cancer in Tunisian patients.

DNA hypomethylation of long interspersed repetitive DNA retrotransposon (LINE-1) and Alu repeats elements of short interspersed elements family (SINEs) is an early event in carcinogenesis that causes transcriptional activation and leads to chromosomal instability. In the current study, DNA methylation levels of LINE-1 and Alu repeats were analyzed in tumoral tissues of invasive breast cancer in a Tunisian cohort and its association with the clinicopathological features of patients was defined. DNA methylation of LINE-1 and Alu repeats were analyzed using pyrosequencing in 61 invasive breast cancers. Median values observed for DNA methylation of LINE-1 and Alu repeats were considered as the cut-off (59.81 and 18.49%, respectively). The results of the current study demonstrated a positive correlation between DNA methylation levels of LINE-1 and Alu repeats (rho=0.284; P<0.03). DNA hypomethylation of LINE-1 was also indicated to be associated with low grade (P=0.023). To the best of our knowledge, the current study is the first study regarding DNA methylation of LINE-1 and Alu repeats element in breast cancer of the Tunisian population. The results of the current study suggest that, since hypomethylation of LINE-1 is associated with low grade, it could be used as a biomarker for prognosis for patients with breast cancer.

LINE-1 hypomethylation is associated with poor risperidone response in a first episode of psychosis cohort.

Aim: We investigated the DNA methylation profile overLINE-1 in antipsychotic-naive, first-episode psychosis-patients (n=69) before and after 2 months of risperidone treatment and in healthy controls (n=62). Materials & methods: Patients were evaluated using standardized scales and classified as responders and nonresponders. DNA from blood was bisulfite converted and LINE-1 fragments were amplified and pyrosequencing was performed. Results: Lower LINE-1 methylation was observed in antipsychotic-naive first-episode psychosis patients than in healthy controls. Lower DNA methylation levels before treatment were associated with poor risperidone responses. A positive correlation was observed between LINE-1 methylation levels and positive symptoms response. Conclusion: Our study brings new insight regarding how epigenomic studies and clinical correlation studies can supplement psychosis treatment.