The role of the dura mater in cerebral metastases

OBJECTIVE The objective of this review was to describe the immunological changes that take place in the dura mater in response to metastatic disease that seeds the CNS. The authors hypothesized that the dura’s anatomy and resident immune cell population play a role in enabling metastasis to the brain and leptomeninges. METHODS An extensive literature search was conducted to identify evidence that supports the dura’s participation in metastasis to the CNS. The authors’ hypothesis was informed by a recent upsurge in studies that have investigated the dura’s role in metastatic development, CNS infections, and autoimmunity. They reviewed this literature as well as the use of immunotherapy in treating brain metastases and how these therapies change the meningeal immune landscape to overcome and reverse tumor-promoting immunosuppression. RESULTS Evidence suggests that the unique architecture and immune cell profile of the dura, compared with other immune compartments within the CNS, facilitate entry of metastatic tumor cells into the brain. Once these tumor cells penetrate the dural barrier, they propagate an immunosuppressive tumor microenvironment. Therefore, immunotherapy may serve to overcome this immunosuppressive environment and liberate proinflammatory immune cells in an effort to combat metastatic disease. CONCLUSIONS Within the next few years, the authors expect the addition of several more scientific studies into the literature that further underscore the dura as a chief participant and neuroanatomical barrier in neuro-oncology.