1674P - Identification of phosphorylated ribosomal protein s6 as a potential predictor of hepatocellular carcinoma response to sorafenib by pathway-based ph...
|Date||30 September 2012|
|Event||ESMO Congress 2012|
|Session||Poster presentation II|
|Topics|| Hepatobiliary Cancers
M. Masuda, K. Honda, T. Yamada
Sorafenib is a multi-kinase inhibitor that has been proved to be effective for the treatment of advanced hepatocellular carcinoma (HCC). However, only a small proportion of patients receiving sorafenib obtain the anticipated therapeutic benefits. It would therefore be desirable to clarify the precise molecular mechanisms that confer resistance to sorafenib and identify a predictive biomarker for unresponsiveness to sorafenib.Methods
We constructed reverse-phase protein microarrays (RPPAs) onto which whole lysates of 95 cell lines derived from various tumors, including 23 HCCs, were plotted and examined for phosphorylation expression of 183 proteins serving as nodes in 120 signaling pathways registered in the NCI-Nature curated pathway (NCI-Nature_Curated.bp2.owl 2011.12.19). The sensitivity (IC50 value) of the 23 HCC cell lines to sofafenib was quantified using the CellTiter-Glo Luminescent Cell Viability Assay kit.Results
Use of fluorescence dye significantly expanded the sensitivity and dynamic range of the RPPAs. We found that the relative level of phosphorylation of ribosomal protein S6 (p-rpS6) at the Ser235/236 residues showed the highest correlation with sensitivity to sorafenib among the 183 signaling nodes (P = 0.0044, Spearman correlation analysis), followed by phosphorylation of the same protein at the Ser240/244 residues (P = 0.0070). Immunoblot analysis confirmed that the sorafenib-resistant cell lines had the highest level of rpS6 phosphorylation. We found that in some HCC cell lines the mitogen-activated protein kinase (MAPK) pathway was activated downstream of RAF kinase and showed sensitivity to MEK (CI-1040) and RSK (SL0101) inhibitors.Conclusions
To achieve personalization of molecular therapies, precise mapping of activated signaling pathways in individual patients is essential. RPPA requires only a small amount of protein and is ideal for application to clinical settings. We are collecting tumor biopsy samples from HCC patients to verify the present findings, and plan to present the data at the meeting.Disclosure
All authors have declared no conflicts of interest.