Aim: To investigate the apoptosis of implanted primary gastric cancer cells in nude mice induced by resveratrol and the relation between this apoptosis and expression of bcl-2 and bax.
Methods: A transplanted tumor model was established by injecting human primary gastric cancer cells into subcutaneous tissue of nude mice. Resveratrol (500 mg/kg, 1,000 mg/kg and 1,500 mg/kg) was directly injected beside tumor body 6 times at an interval of 2 d. Then changes of tumor volume were measured continuously and tumor inhibition rate of each group was calculated. We observed the morphologic alterations by electron microscope, measured the apoptotic rate by TUNEL staining method, detected the expression of apoptosis-regulated genes bcl-2 and bax by immunohistochemical staining and PT-PCR.
Results: Resveratrol could significantly inhibit carcinoma growth when it was injected near the carcinoma. An inhibitory effect was observed in all therapeutic groups and the inhibition rate of resveratrol at the dose of 500 mg/kg, 1,000 mg/kg and 1,500 mg/kg was 10.58%, 29.68% and 39.14%, respectively. Resveratrol induced implanted tumor cells to undergo apoptosis with apoptotic characteristics, including morphological changes of chromatin condensation, chromatin crescent formation, nucleus fragmentation. The inhibition rate of 0.2 mL of normal saline solution, 1,500 mg/kg DMSO, 500 mg/kg resveratrol, 1 000 mg/kg resveratrol, and 1 500 mg/kg resveratrol was 13.68+/-0.37%, 13.8+/-0.43%, 48.7+/-1.07%, 56.44+/-1.39% and 67+/-0.96%, respectively. The positive rate of bcl-2 protein of each group was 29.48+/-0.51%, 27.56+/-1.40%, 11.86+/-0.97%, 5.7+/-0.84% and 3.92+/-0.85%, respectively by immunohistochemical staining. The positive rate of bax protein of each group was 19.34+/-0.35%, 20.88+/-0.91%, 40.02+/-1.20%, 45.72+/-0.88% and 52.3+/-1.54%, respectively by immunohistochemical staining. The density of bcl-2 mRNA in 0.2 mL normal saline solution, 1,500 mg/kg DMSO, 500 mg/kg resveratrol, 1,000 mg/kg resveratrol, and 1,500 mg/kg resveratrol decreased progressively and the density of bax mRNA in 0.2 mL normal saline solution, 1,500 mg/kg DMSO, 500 mg/kg resveratrol, 1,000 mg/kg resveratrol, and 1,500 mg/kg increased progressively with elongation of time by RT-PCR.
Conclusion: Resveratrol is able to induce apoptosis of transplanted tumor cells. This apoptosis may be mediated by down-regulating apoptosis-regulated gene bcl-2 and up-regulating the expression of apoptosis-regulated gene bax.