Majority of PaC cell lines (co)express CXCR4 and CXCR7, the receptors of CXCL12.[43] Beta-arrestin-2 and K-Ras dependent pathways coordinate the transduction of CXCL12 signals,[43] and the source of CXCL12 in PaC tissue is the PSC that acts in a paracrine way on cancer cells. This evidence concerns the gene KRAS and cancer.