An even more pronounced effect was found when the same chemicals were tested on human liver cancer cells.

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In such cases, the pig liver is used as a bridge to transplantation, buying the patient time until a human liver can be found.

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In a human liver, this would be a marker of disease.

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But even more recently, chemist Vicky Colvin at Rice University showed that, while Fullerenes kill human liver and skin cells, they don't damage DNA and are non-carcinogenic.

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The possibility of liver damage has delayed human trials, but Smith is, as ever, impatient.

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Currently pig livers are sometimes considered for transplant when a patient is in liver failure and there is no human organ available.

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Caspase-blockers may limit collateral tissue damage from strokes, heart attacks or liver disease, and Vertex hopes to begin human trials of at least one compound next year.

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