CXCR4 and neoplasm: CXCR4, an upstream molecule of the PI3 kinase/Akt pathway, has been shown to play critical roles in several aspects of tumor progression, such as angiogenesis, metastasis, and survival.33, 34, 35, 36, 37 An earlier study suggested that CD164 acted as a component of a CXCR4 complex and regulated the migration of CD133+ cells.