Chronic liver injury predisposes to cirrhosis and hepatocellular carcinoma, but how somatic mutations accumulate in liver disease is unexplored. We sequenced whole genomes of 400 microdissections of 100-500 hepatocytes from 5 normal and 6 cirrhotic livers. Compared to normal liver, cirrhotic liver had higher mutation burden, especially structural variants, including chromothripsis. Cirrhotic nodules were oligoclonal; sometimes entirely derived from a single, recent common ancestor. Clonal expansions millimeters in diameter occurred in cirrhosis in the absence of known driver mutations. Endogenous mutational processes predominated, although signatures of polycyclic aromatic hydrocarbon and aristolochic acid exposure occurred in some samples. Up to 10-fold within-patient variation in activity of exogenous signatures existed between adjacent cirrhotic nodules, with both clone-specific and microenvironmental forces shaping this heterogeneity. Synchronous hepatocellular carcinomas drew from the same repertoire of mutational signatures as background cirrhotic liver, but with higher ... (Show More)

Chronic liver injury predisposes to cirrhosis and hepatocellular carcinoma, but how somatic mutations accumulate in liver disease is unexplored. We sequenced whole genomes of 400 microdissections of 100-500 hepatocytes from 5 normal and 6 cirrhotic livers. Compared to normal liver, cirrhotic liver had higher mutation burden, especially structural variants, including chromothripsis. Cirrhotic nodules were oligoclonal; sometimes entirely derived from a single, recent common ancestor. Clonal expansions millimeters in diameter occurred in cirrhosis in the absence of known driver mutations. Endogenous mutational processes predominated, although signatures of polycyclic aromatic hydrocarbon and aristolochic acid exposure occurred in some samples. Up to 10-fold within-patient variation in activity of exogenous signatures existed between adjacent cirrhotic nodules, with both clone-specific and microenvironmental forces shaping this heterogeneity. Synchronous hepatocellular carcinomas drew from the same repertoire of mutational signatures as background cirrhotic liver, but with higher burden. Somatic mutations chronicle the exposures, toxicity, regeneration and clonal structure of liver tissue as it progresses from health to disease.

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