传统的肿瘤干细胞理论主要是基于NOD/SCID mice的实验,就是把一定数量的肿瘤细胞打到这些免疫缺陷的老鼠里,看看长出了多少个独立的肿瘤,进而统计出有多少细胞能够致瘤,结论是能够致瘤的癌细胞数量占总细胞数的极少部分,进而支持了肿瘤干细胞理论。但NOD/SCID mice模型有个严重的缺点,就是残留的NK细胞活性,现在Sean Morrison整了新的“more severely immune-compromised mice, called NOD/SCID IL2Rγnull. These mice are missing the gene for a receptor protein required for immune cells known as natural killer cells to function properly. The team found that 250,000 times as many melanoma cells formed tumors in this modified assay as compared to the standard NOD/SCID mice. ”