The protective blood–brain barrier has a major role in ensuring normal brain function by severely limiting and tightly controlling the ingress of substances into the brain from the circulation. In primary brain tumours, such as glioblastomas, as well as in brain metastases from cancers in other organs, including lung and breast cancers and melanoma, the blood–brain barrier is modified and is referred to as the blood–tumour barrier (BTB). Alterations in the BTB affect its permeability, and this structure participates in reciprocal regulatory pathways with tumour cells. Importantly, the BTB typically retains a heterogeneous capacity to restrict the penetration of many therapeutic agents into intracranial tumours, and overcoming this challenge is a key to improving the effectiveness of treatment and patient quality of life. Herein, current knowledge of BTB structure and function is reviewed from a cell and cancer biology standpoint, with a focus on findings derived from in vivo models and human tumour specimens. Additionally, how this knowledge can be translated into clinical advances for patients with cancer is discussed.

保护性血脑屏障通过严格限制和严格控制物质从循环进入大脑，在确保正常大脑功能方面发挥着重要作用。在原发性脑肿瘤（如胶质母细胞瘤）以及其他器官癌症的脑转移（包括肺癌、乳腺癌和黑色素瘤）中，血脑屏障发生了变化，被称为血肿瘤屏障 (BTB)。BTB 的改变会影响其通透性，并且该结构参与与肿瘤细胞的相互调节途径。重要的是，BTB 通常保留限制许多治疗剂渗透到颅内肿瘤的异质性能力，克服这一挑战是提高治疗效果和患者生活质量的关键。在此处，当前对 BTB 结构和功能的了解从细胞和癌症生物学的角度进行了回顾，重点是来自体内模型和人类肿瘤标本的发现。此外，还讨论了如何将这些知识转化为癌症患者的临床进展。