Abstract 3642: Profiles of DNA methylation in peripheral blood are associated with bladder cancer survival.
Authors: Koestler Devin C. , Murphy Megan A. , Houseman Eugene A. , Karagas Margaret R. , Kelsey Karl T. , Marsit Carmen J. 
Published: August 2014

Abstract
Bladder cancer is a common solid tumor, with greater than 71,000 cases diagnosed in the United States last year, and greater than 14,000 deaths attributable to this disease. In addition to this mortality, the morbidity of this disease can be great, as the non-invasive form of this disease, making up &gt;75% of the incidence, recurs frequently, and therefore requires frequent invasive monitoring through cystoscopy at a great cost to the health care system. There are critical gaps in our understanding of the predictors of its recurrence and survival, and identifying molecular alterations associated with these outcomes is essential for improving patient morbidity and the care of patients with this disease. We have shown that profiles of DNA methylation in peripheral blood are associated with human bladder cancer and have recently demonstrated that much, but not all, of the variation in DNA methylation is attributable to disease-associated changes in the underlying proportion of immune cells in the peripheral blood sample. We also have devised a novel statistical strategy that utilizes DNA methylation profiles to quantify the proportion of blood cell subtypes in archival DNA. This is able to disentangle the variability in DNA methylation profiles attributable to blood cell population differences from epigenetic variation arising within a cell population. We sought to determine if variation in DNA methylation identified in peripheral blood, reflective, in part, of altered white blood cell proportions, is associated with bladder cancer recurrence and survival in a population-based study of incident bladder cancers in New Hampshire, USA. Illumina Infinium 27K DNA methylation arrays were performed on whole peripheral blood derived DNA samples from 223 cases of bladder cancer, having a median follow-up time of approximately 13 years. Array data was subjected to quality control procedures and normalization using the ComBAT methodology to account for plate/BeadChip effects. Fitting a series of Cox proportional hazards models, stratified by histology (carcinoma in-situ, low-grade non-invasive, high-grade non-invasive, and invasive) and controlled for patient age and gender revealed 6,873 high-confidence (q &lt; 0.05) associations with bladder cancer specific death as the endpoint. In a principle components analysis, the first principal component, accounting for a striking 46% of the variability in methylation, was significantly associated with bladder cancer specific death. Ongoing analyses are examining how changes to underlying cell proportions mediate the relationship between DNA methylation and patient survival. These data suggest that peripheral blood DNA methylation profiles proximal to the time of diagnosis are strongly prospectively predictive of bladder cancer specific survival and suggest that these biomarkers may have important use as non-invasive prognostic tools worthy of continued study.
Citation Format: Devin C. Koestler, Megan A. Murphy, Eugene A. Houseman, Margaret R. Karagas, Karl T. Kelsey, Carmen J. Marsit. Profiles of DNA methylation in peripheral blood are associated with bladder cancer survival. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3642. doi:10.1158/1538-7445.AM2013-3642