ABSTRACT: Sorafenib, an oral multikinase inhibitor, is the only approved agent for the treatment of advanced hepatocellular carcinoma (HCC). However, its benefits is modest, also because its mechanism of action remains elusive, therefore, a better understanding of its molecular action and molecular targets are needed. On the basis of our previous studies, here, we investigated the role of the nuclear protein 1 (NUPR1) in HCC and its role in the context of sorafenib treatment. NUPR1 is a stress-inducible protein over-expressed in different malignancies, however, its role in HCC is not yet fully understood. We found that NUPR1, is over-expressed in 53% of primary human HCC samples. Knockdown of NUPR1 significantly increased cell sensitivity to sorafenib and inhibits cell growth, migration and invasion of HCC cells in vitro and tumorigenicity in vivo. Moreover, NUPR1 silencing influenced expression of target genes RelB and IER3. Unsurprisingly, RelB and IER3 knockdown also inhibited HCC cells viability, growth and migration. By gene expression profiling of HCC cells following stable NUPR1 knockdown, we found that genes functionally involved in cell death and survival, cellular response to therapies, lipid metabolism, cell growth and proliferation, molecular transport and cellular movement were mostly suppressed. Network analysis of dynamic gene expression identified NF-κB and ERK as down-regulated gene nodes, and several genes known to be involved in hepatocarcinogenesis were also suppressed. In addition, we identified Runt-related transcription factor 2 (RUNX2) gene as a NUPR1 down-regulated gene. We also demonstrated that RUNX2 gene silencing inhibited HCC cells viability, growth, migration and increased cell sensitivity to sorafenib. Conclusion: We propose that NUPR1/RELB/IER3/RUNX2 pathway play pivotal role in hepatocarcinogenesis. The identification of NUPR1/RELB/IER3/RUNX2 pathway as a potential therapeutic target may contribute to the development of new treatment strategies for HCC management.
