chromatin Remodeling in Patient-Derived Colorectal Cancer Models

Purpose: Next-generation sequencing (NGS) has revolutionized systems-based analysis of cellular pathways. The goals of this study are to compare the epigenomes of different patient-derived models of colorectal cancer (PDO, PDX and PDOX) to the original patient tumor. Methods: The Omni-ATAC protocol was utilized for ATAC library preparations. The nulcei were extracted from samples (PT, PDO, PDX and PDOX). For each sample set, three biological replicates were included. The libraries were sequenced using Illumina HiSeq 4000 PE 150bp. Results: Using an optimized data analysis workflow, we achieved high quality ATAC-seq library. Data were mapped to hg19 with over 90% mapping rate, and relative low mitochondria fraction (<30%). We used Diffbind to assess the chromatin accessibility enrichment in each model with a strict threshold of p <0.05 and |logFC|>1. Conclusions: Our study represents the first detailed analysis of CRC PDMC epigenome. CRC cells from all three models share chromatin alterations when compared to PT cells, representing a PT-PDMC epigenetic axis. Chromatin alterations in CRC cells are more similar betweeen PDOX and PDX than between PDOX and PDO, indicating that the growth environment of the model exerts strong influence on chraomtin adaptation in tumor cells.