Potential Therapeutic Applications of MDA-9/Syntenin-NF-κB-RKIP Loop in Human Liver Carcinoma

Background: Overexpression of MDA-9/Syntenin occurs in multiple human cancer cell lines and is associated with higher grade of tumor classification, invasiveness and metastasis. In some cases, its role in cancer biology depends on relationships between MDA-9/Syntenin and NF-κB. Objective: This study aims to analyze the presence of a regulation loop like that between MDA-9/Syntenin - NF-κB - RKIP in human liver carcinoma. Methods: Transient transfection was performed with siRNA anti-MDA-9/Syntenin. Expression of different factors was evaluated by Real time-PCR and Western blotting, while NF-κB activation by TransAM assay. Invasion capacity was analyzed by Matrigel Invasion Assay and the effects of agents on cell viability were examined by MTS assay. Results: We have examined basal expression of MDA-9/Syntenin in three cell lines of human liver carcinoma (HA22T/VGH, Hep3B and HepG2). In all cell lines there was an inverse relationship between MDA-9/Syntenin and RKIP expression levels, and a positive correlation between MDA-9/Syntenin expression and NF-κB activation levels. By silencing with a siRNA anti-MDA-9/Syntenin we observed in all cell lines a very strong increase of RKIP at mRNA level. Interestingly, in all cell lines, inhibition of MDA- 9/Syntenin expression induced NF-κB downregulation and contemporary a reduction in invasion ability MMP-2 dependent. Finally, we showed a good additive effect of MDA- 9/Syntenin siRNA when associated with Curcumin or Doxorubicin on cell growth inhibition. Conclusion: Our data confirm the key role of MDA-9/Syntenin in HCC biology. The presence of a regulation loop among MDA-9/Syntenin, NF-κB and RKIP provide new pharmacological approaches.