Abstract 2169: New telomeres and chromosomal arm fusions in cancer genomes revealed by long-read genome sequencing

Abstract

Abstract Chromosomal rearrangements are widespread features of cancer genomes, and often lead to the generation of both larger and smaller chromosomes that are readily observed by cytogenetics analysis. The generation of these chromosomal alterations likely involves alterations in the structure and location of telomeres at chromosome ends, though these events have been difficult to assess due to the long and highly repetitive nature of telomeres. Here, we developed an analytic method (TeloFuse) to identify new telomeres and chromosomal arm fusions which are characterized by telomeric repeats at intra-chromosomal locations. We applied TeloFuse to identify telomere-containing fusions as well as novel sites of telomere addition using short-read genome sequencing data from 326 cancer cell lines followed by long-read genome sequencing and cytogenetic analysis of selected cell lines. We observed new telomeres at sites of terminal deletion in long read data (telomere length = 2-9 kb), and in 76/326 (23%) of cell line genomes with short read data. Telomere sequence-containing fusions at intra-chromosomal sites were detected in 75/326 (23%) of cancer cell lines and confirmed as chromosomal arm fusion events by long-read genome sequencing. Long-read genome sequencing further suggests that new telomeres have similar telomere length as telomeres found on normal chromosomal arms (median = 5kb). Conversely, telomeric repeats at sites of chromosomal arm fusions were found to be critically short (~200-500bp long). Extending our analysis to 97 lung adenocarcinoma patient samples from The Cancer Genome Atlas, we further found new telomeres in 17/97 (18%) and chromosomal arm fusions in 28/97 (29%) patients with short-read data. Notably, new telomeres and chromosomal arm fusion events were also found to disrupt protein-coding genes, suggesting that these events represent a poorly appreciated mode for gene inactivation in cancer. Our results suggest that the formation of new telomeres and chromosomal arm fusions are prevalent events during cancer genome evolution and are likely critical for the stabilization of new chromosomes in human cancers. More broadly, our findings also highlight the utility of long-read genome sequencing in delineating chromosomal-scale alterations that have been widely observed by cytogenetics analysis. Citation Format: Kar-Tong Tan, Michael K. Slevin, Max Garrity-Janger, Heng Li, Matthew Meyerson. New telomeres and chromosomal arm fusions in cancer genomes revealed by long-read genome sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2169.