ABCB4 and liver cancer: To directly test this hypothesis, we used a well-characterized model of liver cancer, in which the absence of ABCB4, a transporter for phosphatidylcholine expressed selectively in hepatocytes and encoded by the Mdr2 gene, results in defective emulsification of bile acids and their precipitation on the bile canalicular surface of hepatocytes, thus leading to membrane damage, cell death and chronic inflammation.