Hypoxic conditions, often present in brain tumors, lead to the enhanced expression of HIF-1α, what further stimulates CXCL12 expression in tumor cells, affects the spreading of tumor cells by CXCR4 receptor binding in endothelial cells [13], and upregulates the expression of VEGF, increasing angiogenesis. The gene discussed is CXCL12; the disease is brain neoplasm.