Increase in apoptosis by combination of metformin with silibinin in human colorectal cancer cells

Figure 1 Treatment with silibinin and metformin in combination or alone reduces the viability of COLO 205 cells. Reduced cell viability was observed following 24-h incubation with silibinin (0-200 μmol/L) and metformin (0-20 mmol/L) in combination or alone. The gray bars depict the results from COLO 205 cells, and the open bars correspond to the results from human colonic epithelial cells (HCoEpiC) (A). The time course (0-24 h) (B) and combination index (C) are shown in COLO 205 cells treated with silibinin (100 μmol/L) and metformin (10 mmol/L) in combination (M + S) or alone. The data are expressed as mean ± SE (n = 6 for each group). ^aP < 0.01 and ^bP < 0.001 vs Control COLO 205 cells; ^cP < 0.05 and ^dP < 0.01 vs Control HCoEpiC. M + S: Metformin and silibinin.

Figure 2 Combined metformin and silibinin treatment inhibits protein kinase B phosphorylation by enhancing phosphatase and tensin homolog expression. Proteins isolated from COLO 205 cells were probed using an antibody against phosphatase and tensin homolog (PTEN) (A) or phosphorylated protein kinase B (p-Akt) (B). The data are expressed as mean ± SE (n = 6 for each group). ^aP < 0.01 and ^bP < 0.001 vs Control. Con: Control; Veh: Vehicle; Sili: Silibinin; Met: Metformin; M + S: Metformin and silibinin.

Figure 3 Combined metformin and silibinin treatment enhances AMP-activated protein kinase phosphorylation. COLO 205 cells were treated with silibinin and metformin in combination or alone. The protein samples were then probed using an antibody against phosphorylated AMP-activated protein kinase (p-AMPK) (A) or phosphorylated mammol/Lalian target of rapamycin (p-mTOR) (B). The data are expressed as mean ± SE (n = 6 for each group). ^bP < 0.001 vs Control. Con: Control; Veh: Vehicle; Sili: silibinin; Met: Metformin; M + S: Metformin and silibinin.

Figure 4 Combined metformin and silibinin treatment induces COLO 205 cell apoptosis. COLO 205 cells were treated with silibinin and metformin in combination or alone. Apo-Glo assay showing apoptosis of COLO 205 cells treated with silibinin (100 μmol/L) and metformin (10 mmol/Lol/L) in combination (M + S) or alone (A); The protein samples were probed using an antibody against AIF (B) or activated caspase 3 (C). All data are expressed as mean ± SE (n = 6 for each group). ^bP < 0.001 vs Control. Con: Control; Veh: Vehicle; Sili: silibinin; Met: Metformin; M + S: Metformin and silibinin.