Fig. 6

Inhibition of growth and apoptosis of xenograft tumors by combination treatment of metformin and OSMI-1. A BALB/c nude female mice were inoculated subcutaneously with HCT116 cell administration vehicle (DMSO), metformin, OSMI-1 or a combination and tumor growth was monitored for 28 days. B Representative images of subcutaneous xenograft tumors in nude mice treated with metformin, OSMI-1, or a combination thereof (left). weight measurements at endpoints are presented as the mean ± SEM (right). Volumes of xenograft tumors in metformin, OSMI-1, and combination treatment groups at the indicated time points were measured and growth profiles were expressed as mean ± SEM (middle). The results of tumor weight measurements at endpoints are presented as mean ± SEM (right). Significance was determined by control and combination group Student’s t-test. *p < 0.05, ***p < 0.001. C Expression levels of proteins involved in autophagy (P-AMPK and p62) were determined by western blot analysis (left). The levels of proteins involved in apoptosis (CHOP, Bcl2, and cleaved caspase-3) were also determined by western blot, and β-actin was used as the loading control (right). D Proposed signaling pathways for the activity of metformin and OSMI-1. The activation pathways of metformin and OSMI-1 in HCT116 cells are shown in blue and red, respectively. Combination therapy induces apoptosis through caspase activation rather than cytoprotective autophagy. Arrows and bars indicate activation and inhibition, respectively