Abstract 1986: The pan-cancer landscape of chromosome Y alterations.

Abstract Background: Despite the well-documented male bias in the incidence and mortality of most non-sex-specific cancers, the Y chromosome (chrY) remains as a genomic blind spot. Major pan-cancer genomic consortia, including The Cancer Genome Atlas (TCGA) and PCAWG, have historically excluded the chrY from somatic analyses due to computational challenges related to its haploid state, repetitive structure, and homology with the X chromosome. Consequently, the somatic landscape of chrY alterations, including complete loss of Y (LOY), structural variants (SVs), single-nucleotide variants (SNVs), and INDELs, remains largely uncharacterized. Methods: We implemented a pan-cancer computational framework utilizing deep whole-genome sequencing (WGS) data from a comprehensive re-analysis of 26 cancer types from the TCGA cohort. We developed and applied a novel bioinformatic pipeline to accurately call somatic LOY, complex SVs, SNVs, and INDELs. The pipeline was specifically designed to overcome analytical challenges of the chrY, including its repetitive structure and the correct handling of pseudoautosomal regions (PARs). Potential artifacts were flagged using variant-support metrics and by identifying breakpoints in problematic regions. Results: The analysis revealed a highly heterogeneous landscape of chrY alterations across tumor types. We found a high prevalence of somatic SVs in some tumor types, such as bladder (BLCA), head and neck (HSNC), stomach (STAD), and prostate (PRAD) cancers, while others, like thyroid (THCA) and renal clear cell carcinoma (KIRC), were rarely affected. In affected tumors, the SV landscape included numerous inter-chromosomal translocations, which often showed low variant allele frequency (VAF), suggesting a subclonal origin. In contrast, the clonality of chrY deletions varied across cancer types. The SNV/INDEL burden was substantial in certain cancers, for example, in glioblastoma (GBM) and PRAD, but was concentrated in non-coding regions, with protein-coding mutations being infrequent. Interestingly, we observed a chrY SNV spectrum enriched in CT and TC substitutions across several tumor types. Conclusion: We developed a computational framework to systematically analyze the Y chromosome across multiple cancer types, overcoming historical analytical challenges. Our results reveal a diverse spectrum of somatic alterations, including structural variants and point mutations. These findings provide the first comprehensive, pan-cancer map of the somatic chrY landscape. Citation Format: Luis Antonio Corchete Sanchez, Chunyang Bao, Saveliy Belkin, Andrew D. Cherniack, Brian P. Danysh, Zachary Everton, David I. Heiman, Ryul Kim, Antonia Kowalewski, Gang-Hee Lee, Won-Chul Lee, David Lehotzky, Xavi Loinaz, Vasuki Narasimha Swamy, Hansol Park, Ron Solan, Chip Stewart, Haruna Tomono, Samantha Van Seters, Gengchao Wang, Sam Wiseman, Young Seok Ju, Gad Getz, Esther Rheinbay. The pan-cancer landscape of chromosome Y alterations abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1986.