Abstract B02: 5-Hydroxymethylcytosine profiles in circulating cell-free DNA are biomarkers of disease burden in children with neuroblastoma

Abstract

Abstract Background: 5-Hydroxymethylcytosine (5-hmC) is an epigenetic marker of open chromatin and active gene expression. The level of 5-hmC expression serves as a biomarker in adults with cancer, and we recently demonstrated the prognostic significance of tumor whole-genome 5-hmC profiling in children with neuroblastoma. Here, we used Nano-hmC-Seal technology to profile 5-hmC in circulating cell-free DNA (cfDNA) in blood samples from patients with neuroblastoma and age-matched healthy children. Methods: Plasma was collected from 32 children with neuroblastoma at various time points during therapy and 34 well children. 5-hmC sequencing was performed using 100ng of cfDNA extracted from plasma. Metastatic disease burden was classified as high, moderate, low, or none based on Curie MIBG scores, the percentage of tumor cells in bone marrow samples, and/or measurable disseminated soft tissue disease. Results: One hundred cfDNA 5-hmC profiles were generated from 27 high-risk, 3 intermediate-risk, and 2 low-risk patients and 34 well controls. Hierarchical clustering based on 5-hmC levels of 347 genes separated the samples into three main clusters corresponding to high, moderate, and low/no disease burden in the bone, bone marrow, and/or soft tissue. Using functional gene pathways, two subsets of patients within the low/no cluster were revealed that correlated with low tumor burden or no clinically detectable metastatic disease (sensitivity 70%, specificity 76.9%). 5-hmC profiles tracked closely with changes in disease status in 15 patients with serial samples. Samples from patients with a detectable tumor burden had genes with elevated 5-hmC in pathways of neuronal stem cell maintenance and the epigenetic regulatory complexes PRC2 and CTCF/cohesion. Conclusions: cfDNA 5-hmC profiles correlate with disease burden in children with neuroblastoma and may serve as sensitive biomarkers of treatment response. Analysis of transcriptional networks regulated by these epigenomic modifications may lead to a deeper understanding of the pathways that drive resistance to treatment. Citation Format: Mark A. Applebaum, Erin K. Barr, Jason Karpus, Meritxell Oliva, Alexandre Chlenski, Helen R. Salwen, Emma Wilkinson, Marija Dobratic, Elizabeth A. Sokol, Barbara E. Stranger, Chuan He, Susan L. Cohn. 5-Hydroxymethylcytosine profiles in circulating cell-free DNA are biomarkers of disease burden in children with neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B02.