CXCR4 and cancer: Interaction with cancer cells: Previous studies indicated that PDAC cells can induce adjacent quiescent fibroblasts to become CAFs by activating paracrine sonic hedgehog (SHH) signaling and CXCL12/CXCR4 signaling, and by secreting diverse inflammatory cytokines and growth factors, such as connective tissue growth factor (CTGF), TGF-β and IL-1 [74, 144, 145].