Longitudinal Study of Leukocyte DNA Methylation and Biomarkers for Cancer Risk in Older Adults

Abstract

19Background: Changes in DNA methylation over the course of life may provide 20 an indicator of risk for cancer. We explored longitudinal changes in CpG 21 methylation from blood leukocytes, and likelihood of a future cancer diagnosis. 22Methods: Peripheral blood samples were obtained at baseline and at follow-up 23 visit from 20 participants in the Health, Aging and Body Composition prospective 24 cohort study. Genome-wide CpG methylation was assayed using the Illumina 25 Infinium Human MethylationEPIC (HM850K) microarray. Results: Global 26 patterns in DNA methylation from CpG-based analyses showed extensive 27 changes in cell composition over time in participants who developed cancer. By 28 visit year 6, the proportion of CD8+ T-cells decreased (p-value = 0.02), while 29 granulocytes cell levels increased (p-value = 0.04) among participants diagnosed 30 with cancer compared to those who remained cancer-free (cancer-free vs. 31 cancer-present: 0.03 ± 0.02 vs. 0.003 ± 0.005 for CD8+ T-cells; 0.52 ± 0.14 vs. 32 0.66 ± 0.09 for granulocytes). Epigenome-wide analysis identified three CpGs 33 with suggestive p-values ≤ 10 -5 for differential methylation between cancer-free 34 and cancer-present groups, including a CpG located in MTA3, a gene linked with 35 metastasis. At a lenient statistical threshold (p-value ≤ 3 x 10 -5 ), the top 10 36 cancer-associated CpGs included a site near RPTOR that is involved in the 37 mTOR pathway, and the candidate tumor suppressor genes REC8, KCNQ1, and 38 ZSWIM5. However, only the CpG in RPTOR (cg08129331) was replicated in an 39 independent data set. Analysis of within-individual change from baseline to Year 40 6 found significant correlations between the rates of change in methylation in 41 RPTOR, REC8 and ZSWIM5, and time to cancer diagnosis. Conclusion: The 42 results show that changes in cellular composition explains much of the cross-43 sectional and longitudinal variation in CpG methylation. Additionally, differential 44 methylation and longitudinal dynamics at specific CpGs could provide powerful 45 indicators of cancer development and/or progression. In particular, we highlight 46CpG methylation in the RPTOR gene as a potential biomarker of cancer that 47 awaits further validation. 48 DNA methylation plays a central role in cell differentiation and in defining cellular 60 phenotypes. Differences in DNA methylation have been associated with a 61 growing list of morbidities, ranging from metabolic disorders and age-related 62 decline in health, to developmental and neuropsychiatric conditions. The 63 standard approach in an epigenome-wide association study (EWAS), which 64 attempts to link DNA methylation to disease, involves collection of a single 65 biospecimen from each participant (typically peripheral blood or saliva) and 66 performing cross-sectional analyses to compare methylation patterns in cases 67 against matched healthy controls [1, 2]. While differences in CpG methylation 68 between cases and controls may be directly related to disease, these case-69 control diff...

DNA methyltransferase expression is associated with cell proliferation in salivary mucoepidermoid carcinoma

“…The increased expression of DNMTs 1, DNMT3A, and DNMT3B in cancer cells in comparison with adjacent normal tissue has been observed in a number of different organs, including the bladder, colon, kidney, pancreas, lung, and oropharynx 9,12,21,23 . As tumor cells increase their invasive properties, they display a tendency to modify the protein expression by epigenetics.…”

“…Methylation is one of the most important epigenetic modifications of the transcriptional inactivation of tumor suppressor genes in human cancer 9 . Methylation patterns are maintained through the action of DNA methyltransferases (DNMTs), a family of three enzymes: DNMT1, DNMT3A, and DNMT3B.…”

“…A number of studies have indicated that epigenetic regulation plays a crucial role in determining the properties of cancer cells, including self‐renewal and differentiation 9 . Aberrant DNMT activity facilitates malignant transformation through the site‐specific methylation of tumor suppressor genes.…”

Immunosenescence is both functional/adaptive and dysfunctional/maladaptive

“…There are documented changes in the main signaling pathways in T cells, including the TCR, costimulatory receptors, and cytokine receptors, which lead to the decrease of cytokine production, proliferation, cytotoxicity, and differentiation [153][154][155][156]. Moreover, the metabolism of these cells is also affected because of the changes in the mTOR pathway either favoring the autophagy or the anabolic effects of its stimulation [157]. The changes from OxPhos in the resting state to aerobic glycolysis characterizing activated T cells are delayed and less intense in aging T cells [158,159].…”

Long-term temporal stability of peripheral blood DNA methylation alterations in patients with inflammatory bowel disease

“…Nonetheless, the influence of ageing on genome-wide DNA methylation has been welldescribed in monozygotic twins 26,27 and unrelated healthy populations 28,29 , demonstrating a global decrease in methylation as individuals age, as well as site-specific increases in methylation in CpG-rich areas, both of which are thought to result from dynamic external and internal environmental changes [30][31][32] . As epigenetics and thus DNA methylation, is cell-type specific, observed differences found in heterogeneous populations such as PBL or tissue might reflect differences in the cellular composition [33][34][35] . Nonetheless, age-related differences were found in more homogeneous populations, such as purified T-cells and monocytes 15,36,37 Despite the strong effects of age on DNA methylation, a high correlation between baseline and followup methylation data in IBD pediatric mucosal tissue has been observed 20 .…”