Grafted label-retaining cells are superior in tumor initiation and more resistant to MPA. (A) The macroscopic appearance of the tumors formed following secondary grafting of LRCs and non-LRCs, respectively. (B) Colony formation following grafting LRCs and non-LRCs harvested from xenograft tumor tissues (mean ± SEM, n = 19, ***P < 0.001). (C) Colony formation by LRCs and non-LRCs harvested from xenograft tumor tissues, when treated with MPA at a concentration of 10 μg/mL (mean ± SEM, n = 17, ***P < 0.001). NS, no signification.