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![Advanced breast cancer metastasized in the brain: treatment standards and innovations](https://image.oaes.cc/57968829-418d-48d7-8d32-184a37c7afcc/5823.fig.3.jpg)
Figure 3. pSTAT3+ reactive astrocytes block CD8+ cytotoxic T cells from cancer cells and upregulate programmed cell death 1 (PDL-1) and vascular endothelial growth factor A (VEGF-A)[42]. Brain cancer cells also produce matrix metalloproteinases (MMPs) that degrade type IV collagen, the main vascular component of the basement membrane, thus enhancing the access points through the BBB[46]. The BBB is not disrupted in patients who have the HER2+ subtype. (Image created in BioRender.com)