CXCR4 and cancer: However, despite the fact that each niche microenvironment uses specific factors to induce quiescence in cancer cells, the downstream intracellular signaling pathways commonly activated are the ERK signaling, C-X-C chemokine receptor type 4 (CXCR4) activated Src-dependent signaling, endoplasmic reticulum stress, VCAM1, Wnt and BMP-dependent signaling (19, 32, 33, 37, 39, 40).