All data are presented as mean ± SEM. Statistical analysis was performed using two-tailed unpaired t test or Tukey-Kramer test. P value < 0.05 was considered significant. Overall survival was estimated according to Kaplan-Meier and Log-rank (Mantel-Cox) test. All statistics were performed with Prism 6, version 6.0 (GraphPad Software Inc., La Jolla, CA).