Inhibitory effect and mechanism of curcumin on the growth of A549 cell line xenograft in nude mice

Objective To investigate the effect and mechanism of curcumin on the growth of A549 cell line xenograft in nude mice. Methods The human lung adenocarcinoma xenograft model in nude mice was established with A549 cells. Forty BALB/c-nu mice with lung cancer xenograft were randomly divided into control group and 10, 50, 100 mg/kg curcumin groups. Different treatments were given by peritoneal injection every other day for 8 times. The bodyweight of mice and the volume of tumor were measured every 4 days.In vitro the proliferation of A549 cell was determined by cell counting kit-8 (CCK-8) assay, and the apoptosis rate was measured by flow cytometry after Annexin V-fluoresceine isothiocyanate (FITC)/propidium iodide (PI) staining. The expression of B cell lymphoma/leukemia-2 associated X protein (bax) and B cell lymphoma/leukemia-2 (bcl-2) mRNA and protein was detected by real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) and Western blotting respectively. And Cysteinyl aspartate-specific protease-3 (Caspase-3) relative activity was measured by Caspase-3 assay kit. Results In vivo 10, 50, 100 mg/kg of curcumin effectively inhibited the growth of tumor in nude mice (P 0.05). In vitro 10, 50, 100 mmol/L of curcumin inhibited the proliferation of A549 cells, but induced the apoptosis of cells. The inhibition rate of A549 cells in 100 mmol/L curcumin group after 48 h treatment was (51.95±13.32)%, and the apoptosis rate was (30.89±6.27)%. The results of RT-qPCR and Western blotting showed that 100 mmol/L curcumin significantly up-regulated the bax expression and down-regulated the bcl-2 expression, leading to the maximum ratio of bax/bcl-2. In addition, Caspase-3 relative activity also reached the peak value (8.39±1.40) in 100 mmol/L curcumin group, with significant differences among groups (P<0.05). Conclusion Curcumin was able to inhibit the growth of A549 cell line xenograft tumor in nude mice. The potential mechanism was that curcumin inhibited the proliferation of and induced the apoptosis of A549 cells by increasing the expression of bax and reducing the expression of bcl-2, leading to the activation of down stream Caspase-3 signaling pathway. Key words: Curcumin; Lung adenocarcinoma; Xenograft; Apoptosis; Cysteinyl aspartate-specific protease-3