Statistical analyses were performed by using SPSS/PC+statistics 11.0 software (SPSS Inc., Chicago, IL). All data presented a normal distribution. Statistical significance was evaluated using standard unpaired Student's t test (two-tailed, 95% confidence intervals, P<0.05) with Welch's correction when appropriate. For multiple comparison analysis, one-way ANOVA with Dunnett's or Bonferroni correction post-test was applied when appropriate (P<0.05). Comparisons of groups with small sample size (n<6) were performed as follows: (i) Mann–Whitney test (two-sided, 95% confidence level; P<0.05) was used; (ii) Kruskal–Wallis test with Dunn's post-test (P<0.05) has been applied for multiple comparisons. All data are presented as mean±s.d. and represent a minimum of two independent experiments with at least two technical replicates.
