Table 3.

Molecular characteristics which differentiate tumor cells metastasizing to the brain parenchyma and those with high affinity to the meninges.

Mediator of parenchymal metastasis formation	Tumor cell type/model used	Observation	References
TGF-β2	Melanoma cells/mouse allograft	Molecular determinant of parenchymal vs. leptomeningeal and ventricular metastases	228
Cytokines and cytokine receptors (lymphotoxin-β, CCL20, CCL2, PDGFR-β, CXCL1, GM-CSF, CXCL2, etc.)	Breast cancer cells/mouse allograft	Lymphotoxin-β: approximately 45-fold higher expression in parenchymal compared to dural cancer cell variants	161
NOD-like receptor signaling pathway	Breast cancer cells/mouse allograft	Pyrin: approximately 3-fold higher expression in parenchymal compared to dural cancer cell variants	161