Epigenetic research in cancer epidemiology: trends, opportunities, and challenges

Abstract

Epigenetics is emerging as an important field in cancer epidemiology that promises to provide insights into gene regulation and facilitate cancer control throughout the cancer care continuum. Increasingly, investigators are incorporating epigenetic analysis into the studies of etiology and outcomes. To understand current progress and trends in the inclusion of epigenetics in cancer epidemiology, we evaluated the published literature and the National Cancer Institute (NCI)-supported research grant awards in this field to identify trends in epigenetics research. We present a summary of the epidemiologic studies in NCI's grant portfolio (from January 2005 through December 2012) and in the scientific literature published during the same period, irrespective of support from the NCI. Blood cells and tumor tissue were the most commonly used biospecimens in these studies, although buccal cells, cervical cells, sputum, and stool samples were also used. DNA methylation profiling was the focus of the majority of studies, but several studies also measured microRNA profiles. We illustrate here the current status of epidemiologic studies that are evaluating epigenetic changes in large populations. The incorporation of epigenomic assessments in cancer epidemiology studies has and is likely to continue to provide important insights into the field of cancer research.

Figure 1

Number of NCI grants and PubMed indexed publications in cancer epigenetic epidemiology by exposure evaluated in the study. Different types of exposures are shown in the figure and discussed in the text.

Figure 2

Number of NCI grants and PubMed indexed publications in cancer epigenetic epidemiology by cancer site. Breast cancer site is the most studied cancer site in our grant portfolio whereas colorectal cancer site in publication analysis.

Figure 3

Number of NCI grants and PubMed indexed publications in cancer epigenetic epidemiology by biospecimen utilized in the study. For epidemiologic studies, the most frequently collected sample is tumor tissue followed by blood.

Figure 4

Number of NCI grants and PubMed indexed publications in cancer epigenetic epidemiology by study design. The most common study design was case-control study in publications and grants.

Figure 5

Number of NCI grants and PubMed indexed publications in cancer epigenetic epidemiology by method or technology utilized in the study. Abbreviations: AML, acute myelogenous leukemia; ALL, acute lymphoblastic leukemia; Chip-on-Chip, chromatin immunoprecipiation (Chip) on microarray Chip; CIMP, CpG island methylator phenotype; COBRA, combined bisulfate restriction analysis; DNMT assay, DNA methyl transferase assay; HPLC, high pressure liquid chromatography; LUMA assay, LUminometric methylation assay; MSI, microsatellite instability; qRT-PCR, quantitative reverse transcriptase polymerase chain reaction.