For example, aggressive brain tumors called glioblastomas can have as many as six different subclones in a single patient.

例如，称为胶质母细胞瘤的侵袭性脑肿瘤在单个患者身上可以有多达六个不同的亚克隆。

Over time, distinct genetic mutations accumulate in cells in different parts of the tumor, giving rise to unique subclones.

随着时间的推移，不同的基因突变会在肿瘤不同部位的细胞中积累，从而产生独特的亚克隆。

This is called clonal heterogeneity, and it makes treatment difficult because a drug that works on one subclone may have no effect on another.

这称为克隆异质性，它使治疗变得困难，因为对一个亚克隆起作用的药物可能对另一个亚克隆无效。