Applied nutritional investigationA higher degree of LINE-1 methylation in peripheral blood mononuclear cells, a one-carbon nutrient related epigenetic alteration, is associated with a lower risk of developing cervical intraepithelial neoplasia
Introduction
Biomarkers that are influenced by dietary factors may help explain the effects of those factors on cancer risk and assist in monitoring the effectiveness of dietary interventions. Aberrant DNA methylation, one of the most common molecular alterations in human cancer, has been shown to be associated with carcinogenic processes [1], but little is known about the relation between this epigenetic alteration and diet or other lifestyle factors.
The studies we conducted at the beginning of the US Folic Acid Fortification Program (1996–1998) demonstrated that higher circulating concentrations of folate can decrease the impact of high-risk (HR) human papillomaviruses (HPVs) on the risk of developing cervical intraepithelial neoplasia (CIN), the precursor of invasive cervical cancer [2], [3]. Our more recent studies, conducted a few years after the US Folic Acid Fortification Program had started (2004–2006), demonstrated that supraphysiologic concentrations of plasma folate are associated with significantly lower risk of CIN, especially when vitamin B12 is sufficient, demonstrating the importance of vitamin B12 in the high folate environment created by the US Folic Acid Fortification Program [4]. DNA methylation is a possible biomarker for the effect of folate and vitamin B12 on CIN risk. Evaluation of the influence of folate on DNA methylation is also important because concerns have been raised about population-wide exposure to higher levels of folic acid (synthetic form of folate) in the era after folic acid fortification, i.e., cognitive impairment, anemia, and immune function, decreasing the efficacy of antiepileptic drugs or antifolate chemotherapy or promoting the progression of initiated cancer cells [5], [6], [7], [8].
We chose to evaluate the degree of methylation in the LINE-1 promoter using pyrosequencing because this technique is preferable to COBRA, MsSNuPE, or MethyLight for the purpose of measuring changes in LINE methylation [9]. It has been hypothesized that DNA methylation evolved as a defense mechanism against DNA pathogens as a way to silence foreign DNA sequences [10], [11]. Thus, a lower degree of LINE-1 methylation may play a role in modifying the risk of HPV-associated cancer. In addition to changes in LINE-1 methylation in target cells (in our case, cervical epithelial cells), changes in LINE-1 methylation in peripheral blood mononuclear cells (PBMCs) may also alter cancer risk through an effect on immune response-related genes.
The main objectives of the present study were 1) to evaluate the association of LINE-1 methylation in cervical cells (CCs) and in PBMCs with CIN ≥2 and 2) to assess nutritional determinants of CC and PBMC LINE-1 methylation.
Section snippets
Patient population
The present analysis is based on women (n = 376) enrolled in an ongoing prospective follow-up study funded by the National Cancer Institute (R01 CA105448, Prognostic Significance of DNA and Histone Methylation). The study has been described in a previous publication [4]. All women were diagnosed with abnormal cervical cells in clinics of the health departments in Jefferson County and surrounding counties in Alabama and were referred to the University of Alabama at Birmingham for further
Results
All women were of premenopausal age, and all except three were younger than 45 y. Compared with the 273 non-cases, the 103 cases were significantly less likely to be African-American (P = 0.04) and more likely to be current smokers (P = 0.002). Parity was significantly higher in cases than in non-cases (P = 0.017), and non-cases were more frequently nulliparous than cases. Compared with the non-cases, fewer cases had sufficient plasma vitamin B12 concentrations (≥200.6 pg/mL, P = 0.032) and
Discussion
DNA methylation is a major epigenetic mechanism of controlling gene expression in mammalian cells [14], [15]. Although DNA methylation changes in human cancers are characterized by generalized genomic hypomethylation and hypermethylation of focal CpG islands and both events are able to alter gene expression, emphasis has been largely focused on functional significance of hypermethylation in CpG islands on promoters [16]. Because of this intense focus on hypermethylation events, the role of
References (37)
- et al.
Altered global methylation of DNA: an epigenetic difference in susceptibility for lung cancer is associated with its progression
Hum Pathol
(2001) - et al.
Lower red blood cell folate enhances the HPV-16–associated risk of cervical intraepithelial neoplasia
Nutrition
(2007) - et al.
Is folic acid good for everyone?
Am J Clin Nutr
(2008) - et al.
Folate and vitamin B12 status in relation to anemia, macrocytosis, and cognitive impairment among older Americans in the age of folic acid fortification
Am J Clin Nutr
(2007) - et al.
Unmetabolized folic acid in plasma is associated with reduced natural killer cell cytotoxicity among postmenopausal women
J Nutr
(2006) - et al.
Cytosine methylation and the ecology of intragenomic parasites
Trends Genet
(1997) - et al.
Local and systemic effects of cigarette smoking on folate and vitamin B12
Am J Clin Nutr
(1994) - et al.
The mammalian epigenome
Cell
(2007) - et al.
Methylation status in healthy subjects with normal and high serum folate concentration
Nutrition
(2008) - et al.
Utility of methylation markers in cervical cancer early detection: appraisal of the state-of-the-science
Gynecol Oncol
(2009)
Genomic methylation of leukocyte DNA in relation to colorectal adenoma among asymptomatic women
Gastroenterology
Beta-hydroxy-beta-methylbutyrate modifies human peripheral blood mononuclear cell proliferation and cytokine production in vitro
Nutrition
Dietary folate improves age related decrease in lymphocyte function
J Nutr Biochem
Folate is associated with the natural history of high-risk human papillomaviruses
Cancer Res
Lower risk of cervical intraepithelial neoplasia in women with high plasma folate and sufficient vitamin B12 in the post-folic acid fortification era
Cancer Prev Res
Folic acid fortification and supplementation—good for some but not so good for others
Nutr Rev
LINE-1 methylation in plasma DNA as a biomarker of activity of DNA methylation inhibitors in patients with solid tumors
Epigenetics
Functions for DNA methylation in vertebrates
Cold Spring Harb Symp Quant Biol
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This work was supported by grant R01 CA105448 from the National Cancer Institute.