Stem cells (SCs) govern tissue homeostasis and wound repair. They reside within niches, the special microenvironments within tissues that control SC lineage outputs. Upon injury or stress, new signals emanating from damaged tissue can divert nearby cells into adopting behaviours that are not part of their homeostatic repertoire. This behaviour, known as SC plasticity, typically resolves as wounds heal. However, in cancer, it can endure. Recent studies have yielded insights into the orchestrators of maintenance and lineage commitment for SCs belonging to three mammalian tissues: the haematopoietic system, the skin epithelium and the intestinal epithelium. We delineate the multifactorial determinants and general principles underlying the remarkable facets of SC plasticity, which lend promise for regenerative medicine and cancer therapeutics.

干细胞（SC）控制组织稳态和伤口修复。它们存在于生态位（niche）内，即组织内控制 SC 谱系输出的特殊微环境。在受伤或受到压力时，受损组织发出的新信号可以使附近的细胞采取不属于其稳态功能的行为。这种行为被称为 SC 可塑性，通常会随着伤口愈合而消失。然而，在癌症中，它可以忍受。最近的研究对属于三种哺乳动物组织（造血系统、皮肤上皮和肠上皮）的 SC 的维持和谱系承诺的协调者有了深入的了解。我们描述了 SC 可塑性非凡方面背后的多因素决定因素和一般原则，这为再生医学和癌症治疗带来了希望。