Abstract 3334: Epigenetic immune cell markers for CLL
Authors: Jung Janine , Werner Jeannette , Schildknecht Konstantin , Schulze Janika , Walter Steffi , Sachsenmaier Christoph , Phippard Deborah , Seliger Barbara , Wickenhauser Claudia , Olek Sven 
Published: June 2023

Abstract
CLL is a rare hematological cancer and is classified as low-malignancy non-Hodgkin lymphoma. While rare, it is the most frequent form of leukemia in Europe and US accounting for approximately a quarter of all leukemias. As it is a slowly growing tumor, its 5-year survival rate is high compared to faster developing B cell tumors and survival has further improved since introduction of Anti-CD20 Antibody therapies. However, overall the 5-year survival of rare cancers (49%) is significantly lower than for their common counterparts (63%), even though hematological cancers improved outcome over the last years. Due to the currently very late and often incidental diagnosis, some cases turn into aggressively progressing cancers prior to treatment and with concomitant poor outcome. Therefore, diagnosis of CLL and other B cell leukemias remains a challenge. To further improve outcome of CLL and other lymphatic leukemias earlier diagnosis is important. To this end, simple home testing could broaden access to diagnostic tools, but no current method would provide adequate remote initial screening of lymphatic leukemia in populations at risk, such as persons older than 65 years. Epigenetic qPCR has been shown to detect and quantify immune cell populations efficiently from liquid and dried blood samples (DBS). This system is based on specifically unmethylated regulatory elements in gene loci associated with certain cell types. These unique methylation patterns allow specific quantification of cells of interest via qPCR. Different epigenetic qPCR systems were developed for total B cells, naïve and memory B cells as well as IgM producing B cells. While these gene loci are fully unmethylated in the respective target cells, they are fully methylated in all relevant control cell types. The cell type specificity of these markers was shown using bisulfite specific sequencing using purified cells from healthy donors. Here, we investigated blood samples from healthy donors (n = 112) as well as patients at the time of their initial CLL diagnosis. The mean total B cell count of healthy donors at 5.7% was clearly lower than the 60.4% obtained for CLL patients. Similarly drastic differences were observed for naïve B (2.3% normal vs. 20.8% CLL) and IgM (3.3% vs. 49.5%) as well as memory B cells (1.6% vs. 32.6%). All differences were statistically significant. To investigate if these mean differences may also lead to differential (and potentially early) diagnosis, we designed receiver operator characteristics and contingency tables, both indicating near perfect segregation between CLL patients and healthy donors in Ig M, memory and all B cells. Our data indicate applicability of epigenetic immune cell counting as easy, potentially DBS- and home-based approach to test increase of immune cells in people potentially at risk of hematological cancers.
Citation Format: Janine Jung, Jeannette Werner, Konstantin Schildknecht, Janika Schulze, Steffi Walter, Christoph Sachsenmaier, Deborah Phippard, Barbara Seliger, Claudia Wickenhauser, Sven Olek. Epigenetic immune cell markers for CLL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3334.