Abstract 3786: Genomic and transcriptomic characterization of peritoneal, lung and liver metastases of colorectal carcinoma reveals site-specific differences
Authors: Crnovrsanin Nerma , Lakbir Soufyan , Wit Renske d. , Ketelaars Steven L. , Kok Niels F. , Snaebjornsson Petur , Meijer Gerrit A. , Abeln Sanne , Fijneman Remond J. 
Published: March 2024

Abstract
Background: Metastasis in colorectal cancer (CRC) is a critical factor in patient outcomes, with 20% of patients affected at the time of diagnosis and up to 50% developing metachronous metastatic disease later on. Despite the growing importance of metastatic sites as independent predictors of overall survival (OS) and the ongoing development of new treatments, there has been limited effort to personalize systemic treatment based on specific metastatic locations. Aim: This study aims to compare the genomic landscape of different metastatic sites in CRC to detect novel diagnostic and therapeutic targets.
Methods: DNA whole-genome-sequencing and RNA gene expression data from metastatic CRC samples were retrieved from the Hartwig Medical Foundation (HMF). Single nucleotide variants (SNVs), somatic copy number aberrations (SCNAs) and structural variants (SVs) were reported by HMF with their pipelines. In addition, focal amplifications and deletions were identified using GISTIC2 (v6.15.30). We included 464 microsatellite stable samples derived from liver metastases (n=369), peritoneal metastases (n=58) and lung metastases (n=37). We compared DNA mutation frequencies between tumors from different metastatic sites (two-sided Mann-Whitney tests) and performed differential gene expression and pathway enrichment analysis.
Results: Liver metastases had the highest number of focal SCNAs per sample (median 33 vs 17 in peritoneum (p &lt; 0.001); vs 18 in lung (p &lt; 0.001)). Furthermore, we observed 39 site-specific SCNAs in liver, 9 in peritoneal and 15 in lung metastases. Of these, the most significant focal SCNAs were an amplification within 20q13.12 (79%) and deletion within 1p35.3 (64%) in peritoneal metastases and a deletion within 18q21.1 (84%) in lung metastases. Furthermore, peritoneal metastases displayed less genomic instability, featuring lower ploidy (median 2.65 vs 2.94 in liver (p=0.025); vs 3.15 in lung (p=0.025)) and lower aneuploidy scores (median 19 vs 26 in liver (p=0.016); vs 30 in lung (p=0.016)) while having no significant differences in tumor mutational burden or individual SNVs. Analysis of SVs revealed that peritoneal metastases exhibited fewer deletions (≥10kb; 1.3x fold change increase in liver and lung) and fewer duplications (≥1kb; 1.4x fold change increase in liver). Differential gene expression analysis uncovered higher expression of gene sets involved in the apical junction and the TGF-beta-signaling pathway in peritoneal metastases.
Conclusion: Specific focal SCNA and differences in genomic instability exhibit an association with preferential organotropism in CRC metastasis and could offer potential targets for the development of new diagnostic and therapeutic approaches.
Citation Format: Nerma Crnovrsanin, Soufyan Lakbir, Renske d. Wit, Steven L. Ketelaars, Niels F. Kok, Petur Snaebjornsson, Gerrit A. Meijer, Sanne Abeln, Remond J. Fijneman. Genomic and transcriptomic characterization of peritoneal, lung and liver metastases of colorectal carcinoma reveals site-specific differences [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3786.