SPP1 and central nervous system cancer: Specifically, the hyaluronic acid receptor CD44 can interact with microglial osteopontin (SPP1) and is related to glioma tumor growth36; IL-6 has been associated with myeloid cell polarization in posterior fossa ependymoma22; and IL-16 is a potent chemotactic cytokine that binds to the CD4 receptor37.