Statistical analysis
Data for continuous variables are presented as means ± standard deviations. All analyses were performed using SPSS 21.0 software (IBM, USA). All experiments were performed with three technical replicates, and at least three biological replicates were performed. Differences between groups were analyzed using unpaired Student’s t-test or one-way analysis of variance (ANOVA) with Tukey’s test. A P value of < 0.05 was considered to be statistically significant.