The many ways to inhibit translation by Sorafenib in liver cancer cells

Sorafenib targets various tyrosine kinase receptors, inhibiting cell growth and proliferation, angiogenesis and metastasis in tumour cells. It is used to treat certain types of cancers including renal, thyroid and liver (hepatocellular carcinoma) cancers. Although Sorafenib is approved for advanced hepatocellular carcinoma, it only extends patient´s lives by a few months, highlighting the urgent need to better understand how it works and to develop more effective treatments. Sorafenib specifically inhibits translation initiation in hepatocellular carcinoma cells. Herein, we revealed that this inhibition results, at least, from the activation of PERK, triggering a stress response that leads to eIF2α phosphorylation, the inhibition of MNK1a-signalling-dependent eIF4E phosphorylation, and the aberrant assembly of the canonical eIF4F complex. Sorafenib also inhibits the ERK1/2 MAPK signalling in HepG2 cells. However, the mTORC1 pathway does appear to play a pivotal role in Sorafenib-dependent translation inhibition, as revealed by the phosphorylation levels of RPS6 and 4EBP1 proteins and the effects on translation of gene silencing 4EBP1/2 in Sorafenib-treated cells. Translation inhibition correlates with reduced production of cancer-promoting proteins like Cyclin D1 and c-Myc. Overexpression of the phosphomimetic eIF4E-S209D variant, which constitutively activates eIF4E, shows that inhibition of eIF4E phosphorylation directly causes Cyclin D1 down-regulation and cell-cycle delay in Sorafenib-treated cells. Taken together, our results confirm that Sorafenib induces translation reprogramming, whose understanding is crucial for improving its efficacy as a cancer therapy.