Gene expression profile of liver tissue in low-dose, repeated diethylnitrosamine (DEN)-treated rat treated with epigallocatechin gallate (EGCG)

Background: Hepatocellular carcinoma (HCC) is increasing in incidence and treatment is often unsuccessful. Thus, prevention in high-risk patients with established cirrhosis has been proposed as an alternative strategy. It has been suggested that the increased inflammation and fibrogenesis observed during cirrhosis predisposes the liver to future malignant transformation to HCC through a “field effect”. A growing body of evidence indicates that the green tea polyphenol, (-)-epigallocatechin gallate (EGCG), can reduce inflammation and fibrogenesis during chronic liver injury. Here, we test the hypothesis that EGCG administered in the setting of cirrhosis can prevent future HCC development. Methods: A rat model of diethylnitrosamine (DEN)-induced cirrhosis was used to examine the efficacy of EGCG for inhibition of HCC formation in these cirrhotic livers. DEN (50 mg/kg) was administered weekly throughout the study while 0.02% EGCG was given in drinking water beginning at the onset of cirrhosis. At the end of the study, rats were sacrificed, livers were sectioned and stained to analyze disease progression and tumor nodules were counted. Liver function tests were performed to determine liver injury and overall liver function. Finally, genome-wide gene expression profiling on the surrounding, non-tumoral liver tissue was used to monitor the “field effect” in response to EGCG. Results: EGCG significantly (p < 0.01) prevented the development of HCC tumor nodules from on average 18.8 in vehicle controls to on average 9.1 in EGCG-treated animals. EGCG also reduced liver injury and improved liver function as assessed by serum chemistry tests. Finally, a gene expression signature predictive of poor survival and HCC development in human cirrhosis patients was reversed in response to EGCG. Conclusions: Our data are consistent with the growing body of evidence suggesting that EGCG has protective effects in liver disease. Further, our results suggest that EGCG is a potentially effective HCC prevention strategy that can be monitored using gene expression signatures. Animals received humane care according to the criteria outlined in the “Guide for the Care and Use of Laboratory Animals” of the National Academy of Sciences. All animals were maintained in accordance with the institutional guidelines of the Massachusetts General Hospital Subcommittee on Research Animal Care. Male Wistar rats received weekly IP injections of diethylnitrosamine (DEN) at 50 mg/kg for 18 weeks. A subset of rats received either daily (5X a week) 0.02% EGCG in drinking water (n=3) or water (n=3) during weeks 13-18. Animals were sacrificed at 19 weeks after a one-week washout period to eliminate acute effects of DEN. At the time of sacrifice, the non-tumor liver tissues were collected in RNase-free tubes and snap-frozen in liquid nitrogen. Frozen tissues were stored at -80°C until RNA extraction.