Combined disruption of both the MEK/ERK and the IL-6R/STAT3 pathways is required to induce apoptosis of multiple myeloma cells in the presence of bone marrow stromal cells.
The interleukin-6 receptor (IL-6R)/signal transducer and activator of transcription 3 (STAT3) pathway contributes to the pathogenesis of multiple myeloma (MM) and protects MM cells from apoptosis. However, MM cells survive the IL-6R blockade if they are cocultured with bone marrow stromal cells (BMSCs), suggesting that the BM microenvironment stimulates IL-6-independent pathways that exert a pro-survival effect. The goal of this study was to investigate the underlying mechanism. Detailed pathway analysis revealed that BMSCs stimulate STAT3 via the IL-6R, and mitogen-activated protein (MAP) kinases via IL-6R-independent mechanisms. Abolition of MEK1,2 activity with PD98059, or ERK1,2 small interfering RNA knockdown, was insufficient to induce apoptosis. However, the combined disruption of the IL-6R/STAT3 and MEK1,2/ERK1,2 pathways led to strong induction of apoptosis even in the presence of BMSCs. This effect was observed with MM cell lines and with primary MM cells, suggesting that the BMSC-induced activation of MEK1,2/ERK1,2 renders MM cells IL-6R/STAT3 independent. Therefore, in the presence of cells from the BM micro-environment, combined targeting of different (and independently activated) pathways is required to efficiently induce apoptosis of MM cells. This might have direct implications for the development of future therapeutic strategies for MM.
Department of Hematology, Oncology, and Tumorimmunology, Robert Rössle Cancer Clinic and HELIOS-Clinics at the Max Delbrück Center for Molecular Medicine, Charité, Humboldt University, Campus Berlin-Buch, Lindenberger Weg 80, 13122 Berlin, Germany.
Manik
M
Chatterjee
Thorsten
T
Stühmer
Pia
P
Herrmann
Kurt
K
Bommert
Bernd
B
Dörken
Ralf C
RC
Bargou
D000368:Aged; D017209:Apoptosis; D001854:Bone Marrow Cells; D018920:Coculture Techniques; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005260:Female; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009101:Multiple Myeloma / Q000473:pathology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D019947:Receptors, Interleukin-6 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D017154:Stromal Cells / Q000166:cytology / Q000502:physiology*; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; D019947:Receptors, Interleukin-6; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1