What is more, Adrienne Boire’s study indicated upregulation of complement C3 in a model of meningeal metastasis of lung and breast cancer and found that cancer-derived C3 activated C3a receptors on choroid plexus epithelial cells to disrupt the blood–brain barrier, proving that C3 was necessary for cancer to grow in the meninges [32]. The gene discussed is C3; the disease is breast carcinoma.