Anti-angiogenic effect of thymoquinone on breast cancer

AIM: To investigate the anti-angiogenic effect of thymoquinone on human breast cancer and the possible mechanism. METHODS: The activities of human umbilical vein endothelial cells (HUVECs) and human breast cancer MCF-7 cells were assessed by CCK-8 assay. The apoptotic rate was measured by flow cytometry. Furthermore, the assay of capillary tube formation was used to observe the effect of thymoquinone on the tube formation of HUVECs. The protein levels of cleaved caspase-3, p-ERK and p-AKT were detected by Western blot. MCF-7 cells were subcutaneously injected into nude mice to establish breast xenograft tumors. After 3 weeks of implantation, the mice were randomized into control group and thymoquinone group. After the mice were sacrificed, immunohistochemistry was used to detect the expression of CD31 in the tumors, and the TUNEL test kit was used to explore cell apoptosis in the tumor tissues. RESULTS: Thymoquinone at concentrations of 20~80 nmol/L exerted no growth inhibitiory effect on MCF-7 cells. However, the cell viability of HUVECs were (66.1±8.3)％, (53.7±3.4)％ and (41.6±4.9)％ when the concentrations of thymoquinone were 20, 40 and 80 nmol/L, respectively. The apoptotic ratio of MCF-7 cells were (2.6±0.3)％, (2.4±0.3)％ and (4.6±0.4)％ and the apoptotic ratio of HUVECs were (21.5±3.7)％, (23.8±2.9)％ and (27.8±3.1)％ when the concentrations of thymoquinone were 20, 40 and 80 nmol/L, respectively. HUVECs were more sensitive to thymoquinone-induced apoptosis and inhibition in the cell activity than MCF-7 cells. Incubation of HUVECs with diffe-rent concentrations of thymoquinone (20, 40 and 80 nmol/L) for 1 h decreased their tube formation capacity (P<0.05). The protein level of cleaved caspase-3 was up-regulated, but the phosphorylation of AKT and ERK were inhibited in a concentration-dependent manner. The immunohistochemical analysis of CD31 showed significant difference of the integral absorbance between control group and thymoquinone group, and the TUNEL-positive cells in thymoquinone group was significantly more than that in control group. CONCLUSION: Thymoquinone has the anti-angiogenic effect on breast cancer both in vitro and in vivo, which may be related to the decreases in p-ERK and p-AKT.