Statistics
Statistical analysis was performed with SPSS 18.0 software (SPSS, Chicago, IL, USA). Data derived from human tissue and animal studies are presented in dot plots with horizontal bars representing medians and error bars showing interquartile ranges unless specifically addressed. A Kruskal-Wallis H test was used to assess intergroup variability and a Mann-Whitney U test was used for between-group comparisons. The Spearman rank test was used for correlations. Chi-square test or Fisher’s exact test was applied to analyze differences in proportions between groups. Data from cell culture experiments are expressed as means ± SEMs and were analyzed by the paired Student’s t test. Significance was accepted at a P value of less than 0.05.