This EGFR-mediated increase of CXCR4 appears to be mediated by phosphatidylinositol 3-kinase/PTEN/AKT/mTOR signal transduction pathway, and by the activation of hypoxia inducible factor (HIF) 1α, a transcription factor that allows tumor to prosper under conditions of low oxygen tension. The gene discussed is CXCR4; the disease is neoplasm.