Combinational Therapy Enhances the Effects of Anti-IGF-1R mAb Figitumumab to Target Small Cell Lung Cancer

BACKGROUND: Small cell lung cancer (SCLC) is a recalcitrant malignancy with distinct biologic properties. Antibody targeting therapy has been actively investigated as a new drug modality. METHODS: We tested the expression of IGF-1R and calculated the survival in 61 SCLC patients. We also evaluated the anti-tumor effects of anti-IGF-1R monoclonal antibody Figitumumab (CP) on SCLC, and tried two drug combinations to improve CP therapy. RESULTS: Our clinical data suggested that high IGF-1R expression was correlated with low SCLC patient survival. We then demonstrated the effect of CP was likely through IGF-1R blockage and down-regulation without IGF-1R auto-phosphorylation and PI3K/AKT activation. However, we observed elevated MEK/ERK activation upon CP treatment in SCLC cells, and this MEK/ERK activation was enhanced by ß-arrestin1 knockdown while attenuated by ß-arrestin2 knockdown. We found both MEK/ERK inhibitor and metformin could enhance CP treatment in SCLC cells. We further illustrated the additive effect of metformin was likely through promoting further IGF-1R down-regulation. CONCLUSION: Our results highlighted the potential of anti-IGF-1R therapy and the adjuvant therapy strategy with either MEK/ERK inhibitor or metformin to target SCLC, warranting further studies.