Cancer caused by too much apoptosis--an intriguing contradiction?

Modeling human liver cancer heterogeneity: virally induced transgenic models and mouse genetic models of chronic liver inflammation

In addition to being the most common primary liver cancer, hepatocellular carcinoma (HCC) is the second most common cause of cancer-related death in humans. Treatment options are limited for this chemoresistant cancer, with liver transplantation and surgical intervention in early stages being the most successful treatments. Drug development over the past 15 years has focused on generating mouse models that mimic the human pathology for HCC. This has enabled the laboratory testing of potentially new human therapeutics. Described in this unit are the classification of HCC and an overview of hepatitis virus-related transgenic and genetically engineered mouse models (GEMMs) that are employed for elucidating the mechanism(s) responsible for the development of HCC, with particular emphasis on genetic, dietary, and environmental factors.

Inhibition of apoptosis in the management of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in the developed world. The pathogenesis of NAFLD is multifactorial, involving obesity, insulin resistance, inflammation and oxidative stress. Accordingly, several treatments targeting these pathways have been evaluated in patients with NAFLD but have either shown limited efficacy or an unfavorable safety profile. On the other hand, increased hepatocyte apoptosis also appears to be implicated in the development and progression of NAFLD and recent pilot studies suggest that inhibition of apoptosis might represent a useful approach in this disease. However, several issues pertaining both to the efficacy and safety of this new class of agents remain unresolved and larger studies are required to clarify the role of this therapeutic modality in the management of NAFLD.

A phase 2, randomized, double-blind, placebo-controlled study of GS-9450 in subjects with nonalcoholic steatohepatitis

In nonalcoholic steatohepatitis (NASH), the extent of hepatocyte apoptosis correlates with disease severity. Reducing hepatocyte apoptosis with the selective caspase inhibitor GS-9450 has a potential for altering the course of the liver disease. In this phase 2, double-blind study, 124 subjects with biopsy-proven NASH were randomized to once-daily placebo or 1, 5, 10, or 40 mg GS-9450 for 4 weeks. Absolute and percent changes from baseline in ALT levels, AST levels, and caspase-3-cleaved cytokeratin (CK)-18 fragments at week 4 were assessed by an analysis of covariance model with adjustment for baseline values. In the 40-mg group, mean (SD) ALT decreased by 47 (43) U/L from baseline to week 4 (P < 0.0001 versus placebo), and the proportion of subjects with normal ALT increased from 0% to 35% at week 4. In the 40-mg group, mean AST decreased by 13 U/L from baseline (not significant), and the proportion with normal AST increased from 20% at baseline to 48% at week 4. By week 4, mean CK-18 fragment levels had decreased to 393 (723) U/L in the GS-9450 10-mg group and 125 (212) U/L in the 40-mg group, but these reductions were not statistically significant. No serious adverse events were reported during treatment, and the percentage of subjects with at least one treatment-emergent grade 3 or 4 laboratory abnormality ranged from 11.5% to 17% across the GS-9450 treatment groups versus 35% in the placebo group.

CONCLUSION

GS-9450 treatment induced significant reductions in ALT levels in NASH patients. Reductions in CK-18 fragment levels also occurred, although they were not statistically significant. At appropriate therapeutic indices, selective caspase inhibitors may be a promising treatment option in patients with NASH.