Human Y chromosome pan-organ mapping reveals progressive mosaic loss from normal to cancer

Loss of the Y chromosome (LOY) is a frequent event in male tumors and has been linked to cancer progression. However, the degree of mosaic LOY (mLOY) within normal tissues from men with or without cancer remains uncharacterized.

Here we used a FISH-based assay targeting X- and Y-chromosome centromeres to perform a pan-organ analysis of mLOY in 1,000 male tissue samples from 405 individuals representing 11 organs. Automated image processing generated a quantitative FISH-based mLOY score (YchrFISH) that we validated against a transcriptomic surrogate of Y-chromosome dosage from RNA-seq data.

mLOY burden varied by tumor type, with highest degree in colorectal carcinoma. Across tissue groups, YchrFISH scores declined progressively from normal tissues of cancer-free men to histologically normal tissues adjacent to cancer and carcinoma (P < 0.0001). Paired analyses confirmed consistently greater mLOY in malignant compared with tumor-adjacent histologically normal tissue in different organs. Spatially resolved RNA-seq maps of bladders removed for cancer demonstrated a transcriptional gradient of Y-chromosome loss from normal urothelium through intraepithelial neoplasia to invasive carcinoma.

mLOY gradients exist across histologically normal and malignant tissues, consistent with the concept of field cancerization. Our findings support epithelial mLOY as a biomarker of early malignant transformation and, to our knowledge, a previously unrecognized hallmark of male oncogenesis.

NIH grants R35CA294022, P01CA163227, and P50CA97186 (the Pacific Northwest Prostate Cancer SPORE) and the Institute for Prostate Cancer Research.