CSF1 and cancer: Additionally, the PI3K/AKT pathway can upregulate immunosuppressive genes or promote the expression of genes associated with metastasis, such as PD-L1, cytotoxic T-lymphocyte-associated antigen-4, colony stimulating factor 1 (CSF1), and CSF1 receptor, in cancer cells or microglia within the brain metastasis microenvironment.