CXCR4 and neoplasm: CXCL12/CXCR4 axis plays a crucial role in determining the homing of metastatic tumor cells with poor prognosis, which the expression of CXCR4 and Bcl-2 and PI3K/Akt and ERK1/2 signaling are controlled and the level at which it is expressed mark the difference between normal and pathological events [37].