TWIST1 and neoplasm: These effects are attributed to the release of soluble factors like heparanase, IL6, TNF, and IL1 by astrocytes, which stimulate metastatic determinants like endothelin-1 receptor expression, ERK phosphorylation, and induction of survival genes like BCL2L1 and TWIST1 in tumor cells.80,83–86 Astrocytes also regulate immune response within the brain during BrM progression.