CXCL8 and breast cancer: Interestingly, the differential analyses of these cytokines revealed that PAI-1 was significantly higher in breast cancer tissues compared with normal controls, while lower levels (CXCL5 and CXCL12) or no significant difference (IGF1R and CXCL8) of other cytokines were observed in breast cancer tissues versus normal tissues (Figure S1C).