MDM2 antagonists synergize with Trametinib in well-differentiated/dedifferentiated liposarcomas.
Session type: Poster / e-Poster / Silent Theatre session
Amplification of the MDM2 gene is a genetic hallmark of well-differentiated/dedifferentiated liposarcoma (WDLPS/DDLPS), one of the most frequent sarcoma sub-types. Antagonists of MDM2-p53 interaction are emerging anti-cancer drugs that are currently investigated in clinical trials for malignancies. p53 is reported to stimulate the mitogen-activated protein kinase (MAPK) pathway. In this study, we investigated the impact of MDM2 antagonists on the MAPK pathway in WDLPS/DDLPS and the potential anti-tumor activity of MAPK pathway inhibitors in this setting.
93T449 WDLPS and DDLPS cell lines (IB115 and IB111) were exposed to an increasing concentration of RG7388 (MDM2-TP53 interaction antagonist), SP141 (MDM2 inhibitor) and GSK1120212B (MEK inhibitor) alone or in combination for 72 hours and viability and colony forming ability were assessed by MTT and clonogenic assay respectively. Apoptosis using Annexin V/PI staining was studied by flow cytometry. Western blot analysis was performed to see expression of proteins of interest. shRNA mediated p53 silencing was performed in WDLPS/DDLPS cells to understand the importance of functional p53 for the activity of drugs.
Combinatorial treatment with RG7388, SP141 and GSK1120212B caused an increased anti-tumor activity than drug alone which was evident from MTT, clonogenic and apoptosis assay. Treatment of WDLPS and DDLPS cell lines with RG7388 and SP141 caused an increase in the phospho-ERK expression. MDM2 antagonists and MEK1/2 inhibitor treatment alone or in combination modulated the expression of several signaling proteins like p53, p21, phospho-ERK, phospho-MDM2 and MDM2. An increasing shift in the IC50 value was observed in shRNA mediated p53 silenced WDLPS/DDLPS cells on treatment with RG7388, SP141 and GSK1120212B.
Our results suggested that upregulation of the MAPK pathway is a mechanism of resistance to MDM2 antagonist in WDLPS/DLPS and combining MDM2 antagonist with MAPK inhibitors may represent a more efficient therapeutic strategy in this setting.