Crucial role of JNK1 in non-alcoholic steatohepatitis-associated hepatocarcinogenesis

Background and Aim: Hepatocellular carcinoma (HCC), the second most fatal cancer worldwide, is increasingly recognized as a complication of non-alcoholic steatohepatitis (NASH) cirrhosis. We previously reported that the c-Jun NH2-terminal kinase (JNK) 1 is activated in a murine model of NASH in the context of obesity, hyperinsulinemia, and diabetes in foz/foz (Alms1 mutant) mice. We aimed to investigate the role of JNK1 in the pathogenesis of accelerated hepatocarcinogenesis in diethylnitrosamine (DEN)-injected foz/foz mice.

Methods: HCC incidence, intraperitoneal glucose tolerance test (ipGTT), indicators of metabolic health, and liver injury were evaluated in male, DEN-injected wild-type (Wt), foz/foz, Jnk1−/−, and Jnk1−/−.foz/foz C57Bl6 mice at 6 months of age. Immunoblotting using whole liver lysates and serum ELISA was performed.

Results: By 6 months, 57% of foz/foz and 25% of Wt mice developed HCC; all Jnk1−/− and Jnk1−/−.foz/foz mice remained tumor-free (0 with HCC). Fasting hyperinsulinemia was observed in obese foz/foz mice (7.59 ± 2.33 ng/mL), whereas this phenotype was rescued in both Jnk1−/− (0.38 ± 0.05 ng/mL) and Jnk1−/−.foz/foz (1.22 ± 0.15 ng/mL) mice. Glucose tolerance was impaired in foz/foz mice, which was evident by the area under the curve (AUC) calculated as a reflection of circulating levels of blood glucose during ipGTT (2444 mmol/L × 120 min × 103). Corresponding AUC in both Jnk1−/− (1419 mmol/L × 120 min × 103) and Jnk1−/−.foz/foz (1599 mmol/L × 120 min × 103) mice indicated normal glucose handling. Serum levels of alanine transaminase (ALT) (a liver injury marker) were increased in foz/foz versus Wt mice; JNK1 deletion prevented increase in ALT in Jnk1−/− and Jnk1−/−.foz/foz mice. While SOCS3 was clearly expressed in the livers of Wt and Jnk1−/− mice, it was barely detectable in foz/foz mice. Notably, SOCS3 expression was rescued in Jnk1−/−.foz/foz mice. To date, we have not detected changes in the hepatic SOCS3-associated signaling cascades (p-STAT3/STAT3, JAK2, IRS2, and TLR4). Proliferative (PCNA, Cdk2, Cyclin D1, and Cyclin E), apoptotic markers (p53, p21, PARP, and Bcl-xl), and PI3K/AKT/mTOR expression in normal and dysplastic liver surrounding HCC was similar between foz/foz, Jnk1−/−, Jnk1−/−.foz/foz, and Wt animals.

Conclusion: JNK1 appears to be critical in HCC development in NASH-affected livers. Although the precise molecular mechanisms of JNK1-dependent hepatocarcinogenesis remain to be elucidated, JNK1 may suppress SOCS3 expression, thereby removing a brake on cytokine signaling and/or other pathways that enhance hepatocarcinogenesis in fatty liver disease.