Another study has found that glioma stem cells (CD133 + GSCs) isolated from glioma cell lines and human glioma tissues, when activated by TLR-4 agonist LPS, significantly increase the expression of cytokines (e.g., MCP-1, MIP-1α, TNF-α, IL-1β, IL-6, IL-10), anti-apoptotic proteins (e.g., Bcl-2), cell cycle regulatory proteins (e.g., CDK4/6 and cyclin E), and transcription factors (e.g., NF-κB), leading to cancer progression [189]. Here, CDK4 is linked to central nervous system cancer.