Abstract 5012: DNA methylation profiles of endometrial cancer and benign endometrium suggest differences by mismatch repair status and possible early detection markers
Authors: Wentzensen Nicolas A. , Killian Keith , Adams Lisa , Luhn Patricia , Kloor Matthias , Guido Richard , Yang Hannah P. , Garcia-Closas Montserrat , Brinton Louise , d'Ambrosio Lori , Lissowska Jolanta , Hewitt Stephen , Meltzer Paul , Sherman Mark 
Published: August 2012

Abstract
Background: Increased risk for endometrial cancer, the most common gynecological malignancy in the United States, is related to obesity, nulliparity, and postmenopausal hormone use. Several molecular pathways and mechanisms are prominently involved in endometrial carcinogenesis including mismatch repair deficiency (MMR), abnormalities in the PTEN pathway and DNA methylation. We compared DNA methylation profiles in endometrial cancers to identify markers related to MMR deficiencies and contrasted results to normal endometrial tissue to identify potential biomarkers for early detection. Methods: We conducted methylation profiling on 148 paraffin embedded endometrial cancer tissues collected in the population-based Polish Endometrial Cancer Study and 23 normal tissues included within a study of benign endometrium at Magee Women's Hospital. 1.0 mm tissue cores removed from target-rich areas of tissue blocks were used for DNA extraction and bisulfite treatment. The Illumina Golden Gate platform was used to assess CpG methylation at 1505 sites. Microsatellite instability (MSI) testing using three markers (BAT25, BAT26, and CAT25) was performed to identify MMR deficient cases. We conducted unsupervised hierarchical clustering and class comparison analyses to evaluate DNA methylation by MMR status among cancers and class comparison and pathway analyses to identify differences in methylation markers between normal and tumor tissue. Results: Unsupervised hierarchical clustering of methylation profiles in cancers showed two major clusters with significantly different proportions of MSI cases (61.4% versus 10.6%, p&lt;0.0001). Class comparison by MSI status identified 52 differentially methylated genes with a p-value &lt;0.001, including MLH1. Further, we observed associations between age and BMI and methylation patterns in endometrial cancers. Unsupervised hierarchical clustering showed almost perfect separation of endometrial cancers from normal endometrial tissues, reflecting differential methylation of 332 genes at a p-value = 0.001. Higher methylation levels were found in cancers compared to normal tissues, with the most significant events in the PTEN pathway. Conclusions: Analyses of methylation profiles in endometrial cancer show differences by age, BMI and MMR status. Many genes show differences in DNA methylation in endometrial cancers as compared to benign endometrial tissues. These data suggest that methylation analyses may be important for understanding etiological heterogeneity in endometrial cancer and for identifying possible markers for early detection.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5012. doi:1538-7445.AM2012-5012