Objective: To examine the effect of the aqueous extract of Ligustrum robustum on tumor growth in vitro and in vivo and explore the possible molecular mechanisms.
Methods: In in vitro study, cell viabilities of human cervical carcinoma cells (HeLa), human breast cancer cells (MCF-7), human prostate cancer cells (PC-3), human hepatoma cells (7721) and human colon carcinoma cells (SW480) were evaluated with cell counting kit-8. For L. robustum-treated Hela cells, early or late apoptosis were evaluated by annexin V/PI staining. Mitochondrial membrane potential was measured by staining cells with JC-1. Apoptosis was monitored by nuclear morphology based on chromatin condensation and fragmentation by 4',6-diamidino-2-phenylinole (DAPI) staining. Caspase-3 and -8 activity levels were measured by a colorimetric assay. In vivo, to evaluate the possible mechanism of L. robustum-mediated antitumor effect, nude mouse xenograft study was also conducted.
Results: In in vitro study, L. robustum was found to be toxic to HeLa, MCF-7, PC-3, 7721, SW480, with an half maximal inhibitory concentration value of 2-5 mg/mL (P<0.05). Moreover, externalization of phosphatidylserine, loss of mitochondrial membrane potential, DNA fragmentation and activation of caspase-3 and -8 were detected in L. robustum-treated Hela cells. Using a nude mouse model bearing Hela xenografts, we found that L. robustum reduced tumor volume and tumor weight (P<0.05), but had no effect on body weight and histological damage of important organs. Intraperitoneal injection of L. robustum caused a significant reduction in serum aspartate transaminase and alanine transaminase levels (P<0.05). Furthermore, cleaved caspase-3-positive and terminal nucleotidyl transferase-mediated nick end labeling (TUNEL)-positive cells were observed in L. robustum-treated tumor tissues.
Conclusions: L. robustum inhibits tumor cell growth both in vitro and in vivo by inducing apoptosis in a caspase-dependent way without apparent hepatic toxicity and histological damage, which may offer partial scientific support for the ethnopharmacological claims of L. robustum as a herbal tea for its antitumor activity.
Keywords: Ku-Ding-Cha; Ligustrum robustum; antitumor effect; herbal tea.