MEK inhibition induces apoptosis in osteosarcoma cells with constitutive ERK1/2 phosphorylation
Zuzanna Baranski1, Tijmen H. Booij1, Marieke L. Kuijjer3,4, Yvonne de Jong2, Anne-Marie Cleton-Jansen2, Leo S. Price1, Bob van de Water1, Judith V. M. G. Bovée2, Pancras C.W. Hogendoorn2 and Erik H.J. Danen1
1 Division of Toxicology, Leiden/Academic Center for Drug Research, Leiden University, Leiden, The Netherlands
2 Department of Pathology, Leiden University Medical Center, Leiden, The Netherlands
3 Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Boston, MA, USA
4 Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, USA
Correspondence:
Erik H.J. Danen, email:
Keywords: osteosarcoma, MEK, pharmacological inhibition, 3D culture, ERK phosphorylation
Received: October 31, 2015 Accepted: December 17, 2015 Published: December 21, 2015
Abstract
Conventional high-grade osteosarcoma is the most common primary bone cancer with relatively high incidence in young people. Recurrent and metastatic tumors are difficult to treat. We performed a kinase inhibitor screen in two osteosarcoma cell lines, which identified MEK1/2 inhibitors. These inhibitors were further validated in a panel of six osteosarcoma cell lines. Western blot analysis was performed to assess ERK activity and efficacy of MEK inhibition. A 3D culture system was used to validate results from 2D monolayer cultures. Gene expression analysis was performed to identify differentially expressed gene signatures in sensitive and resistant cell lines. Activation of the AKT signaling network was explored using Western blot and pharmacological inhibition. In the screen, Trametinib, AZD8330 and TAK-733 decreased cell viability by more than 50%. Validation in six osteosarcoma cell lines identified three cell lines as resistant and three as sensitive to the inhibitors. Western blot analysis of ERK activity revealed that sensitive lines had high constitutive ERK activity. Treatment with the three MEK inhibitors in a 3D culture system validated efficacy in inhibition of osteosarcoma viability. MEK1/2 inhibition represents a candidate treatment strategy for osteosarcomas displaying high MEK activity as determined by ERK phosphorylation status.
