Effect of a xanthine analog on human hepatocellular carcinoma cells (Alexander) in culture and in xenografts in SCID mice.

ABSTRACT

Hepatocellular carcinoma (HCC) frequently overexpresses the MDR1 gene and is resistant to drugs transported by the multidrug-resistance efflux pump. A xanthine analog, 1-(11-dodecylamino-10-hydroxyundecyl)-3,7-dimethylxanthine (CT-2584,CTI), is cytotoxic to many tumors in culture and was four times more effective than verapamil in inhibiting Rhodamine 123 secretion in MDR1-overexpressing Chinese hamster ovary cells. However, studies using PRF/PLC/5 (Alexander) cells revealed that CT-2584 is cytotoxic by another mechanism not involving inhibition of MDR1 function. Alexander cells have integrated the hepatitis B surface antigen (HBsAg) gene and quantitatively secrete HBsAg. The parent cell line, Alex 0, has low MDR1 expression and is drug-sensitive, whereas a derived line, Alex 0.5, is drug-resistant and overexpresses MDR1 100 times. Both cell lines were similarly killed within 24 or 48 hours by CT-2584. Freshly isolated rat and human hepatocytes were considerably more resistant to killing by CT-2584. In vivo, CT-2584 significantly reduced tumor growth in SCID mice bearing Alex 0 or 0.5 xenografts as determined by serial measurements of HBsAg. Hepatic parenchyma was normal, whereas apoptosis and cellular loss were observed in xenografts. The xenograft model is useful for testing pharmacological therapy of HCC.