Acetyl-11-keto-β-boswellic acid inhibits proliferation and induces apoptosis of gastric cancer cells through the phosphatase and tensin homolog /Akt/ cyclooxygenase-2 signaling pathway

Figure 1 Molecular structure of acetyl-11-keto-β-boswellic acid.

Figure 2 Acetyl-11-keto-β-boswellic acid inhibits the proliferation and induces the apoptosis of gastric cancer cells. A and B: Dose- and time-dependent effects of acetyl-11-keto-β-boswellic acid (AKBA) on BGC823 and SGC7901 cell proliferation; C: Flow cytometry-based annexin V-FITC/PI labeling of apoptotic cells; D: Histogram showing apoptosis rates; E: Expression levels of proliferating cell nuclear antigen (PCNA), Bcl-2, and Bax in BGC823 and SGC7901 cells measured via Western blot analysis after AKBA treatment; F and G: Histograms showing the relative expression levels of PCNA, Bcl-2, and Bax compared with GAPDH in BGC823 and SGC7901 cells. Each data point represents the mean ± SD from three independent experiments. ^aP < 0.05, ^bP < 0.01 vs control (0 µM). ^cP < 0.05, ^dP < 0.01 vs control (24 h). AKBA: Acetyl-11-keto-β-boswellic acid; PCNA: Proliferating cell nuclear antigen; GAPDH: Glyceraldehyde-phosphate dehydrogenase.

Figure 3 Effects of acetyl-11-keto-β-boswellic acid on the expression of phosphatase and tensin homolog, cyclooxygenase-2, and p-Akt in gastric cancer cells. A: Expression levels of phosphatase and tensin homolog (PTEN), cyclooxygenase (COX)-2, and p-Akt in gastric cancer cells measured via Western blot analysis; B: Histograms showing the relative expression levels of PTEN and COX-2 compared with GAPDH, and p-Akt compared with Akt in gastric cancer cells. Each data point represents the mean ± SD from three independent experiments. ^aP < 0.05, ^bP < 0.01 vs control (0 µM). AKBA: Acetyl-11-keto-β-boswellic acid; PTEN: Phosphatase and tensin homolog; COX-2: Cyclooxygenase-2; GAPDH: Glyceraldehyde-phosphate dehydrogenase.

Figure 4 Effects of phosphatase and tensin homolog /Akt inhibitor on acetyl-11-keto-β-boswellic acid-induced down-regulation of cyclooxygenase-2 expression in gastric cancer cells. Gastric cells were pre-treated with the phosphatase and tensin homolog (PTEN) inhibitor bpv (HOpic, 17.4 ng/mL, A and B) or Akt inhibitor MK2206 (38.4 ng/mL, C and D) for 30 min and then treated with acetyl-11-keto-β-boswellic acid (40 µM) for 48 h. A: Expression of PTEN, cyclooxygenase (COX)-2, and total and phosphorylated forms of Akt in gastric cancer cells detected by Western blot analysis. B: Histograms showing the relative expression of PTEN and COX-2 compared with GAPDH, and phospho-Akt (p-Akt) compared with total Akt, respectively. Each data point represents the mean ± SD from three independent experiments. ^aP < 0.05, ^bP < 0.01 vs Control; ^cP < 0.05, ^dP < 0.01 vs AKBA. AKBA: Acetyl-11-keto-β-boswellic acid; PTEN: Phosphatase and tensin homolog; COX-2: Cyclooxygenase-2; GAPDH: Glyceraldehyde-phosphate dehydrogenase.

Figure 5 Acetyl-11-keto-β-boswellic acid inhibits the monolayer wound healing of gastric cancer cells. A and B: Phase micrographs of BGC823 and SGC7901 cells at various times after monolayer wounding (original magnification, × 100); C and D: Quantification of cell migration using monolayer wound-healing assay. The gastric cancer cells were treated without (control) or with 20 µM acetyl-11-keto-β-boswellic acid. Each data point represents the mean ± SD from three independent experiments. ^aP < 0.05, ^bP < 0.01 vs control (0 µM). AKBA: Acetyl-11-keto-β-boswellic acid.

Figure 6 Acetyl-11-keto-β-boswellic acid inhibits gastric cancer tumor growth in vivo. Twenty nude mice were subcutaneously injected with BGC823 and SGC7901 cells. When tumor size was approximately 0.1 cm³, the nude mice were randomly divided into different groups (n = 5) to receive different treatments. A: Acetyl-11-keto-β-boswellic acid (AKBA) inhibits gastric cancer xenograft tumor growth in vivo; B: Tumor volume was measured, and the tumor growth curves were plotted; C: Body weight change in the nude mice treated with saline or AKBA; D: Western blot analysis of cyclooxygenase (COX)-2 protein expression in gastric cancer tissues of control and AKBA treated nude mice (100 mg/kg/d); E: Histogram representing the relative expression of COX-2 compared with that of GAPDH. ^aP < 0.05, ^bP < 0.01 vs control (saline). AKBA: Acetyl-11-keto-β-boswellic acid.

Figure 7 Hypothetical model of acetyl-11-keto-β-boswellic acid’s inhibition of proliferation of gastric cancer cells and induction of apoptosis. AKBA: Acetyl-11-keto-β-boswellic acid; PTEN: Phosphatase and tensin homolog; COX-2: Cyclooxygenase-2; PCNA: Proliferating cell nuclear antigen.