Tristetraprolin promotes hepatic inflammation and tumor initiation but restrains cancer progression to malignancy.

BACKGROUND & AIMS: Tristetraprolin (TTP) is a key post-transcriptional regulator of inflammatory and oncogenic transcripts. Accordingly, TTP was reported to act as a tumor suppressor in specific cancers. Herein, we investigated how TTP contributes to the development of liver inflammation and fibrosis, which are key drivers of hepatocarcinogenesis, as well as to the onset and progression of hepatocellular carcinoma (HCC).

METHODS: TTP expression was investigated in mouse/human models of hepatic metabolic diseases and cancer. The role of TTP in non-alcoholic steatohepatitis (NASH) and HCC development was further examined through in vivo/vitro approaches using liver-specific TTP knockout mice (LTTPKO mice) and a panel of hepatic cancer cells.

RESULTS: Our data demonstrate that TTP loss in vivo strongly restrains development of hepatic steatosis and inflammation/fibrosis in mice fed a methionine/choline-deficient diet, as well as HCC development induced by the carcinogen DEN. In contrast, low TTP expression fostered migration and invasion capacities of in vitro transformed hepatic cancer cells likely by unleashing expression of key oncogenes previously associated with these cancerous features. Consistent with these data, TTP was significantly downregulated in high-grade human HCC, a feature further correlating with poor clinical prognosis. Finally, we uncover HNF4α and EGR1, two key transcription factors lost with hepatocyte dedifferentiation, as a key regulators of TTP expression.

CONCLUSIONS: While TTP importantly contributes to hepatic inflammation and cancer initiation, its loss with hepatocyte dedifferentiation fosters cancer cells migration and invasion. Loss of TTP may represent a clinically relevant biomarker of high-grade HCC associated with poor prognosis.