CXCL8 and colonic neoplasm: 56 AI-2 could induce IL-8 expression in HCT-8 colon cancer cells.54 The autoinducing peptides (AIPs) synthesized by human microbiota were found to influence mammalian cells, promoting metastasis of cancer cells57,60 and penetrate the blood-brain barrier.57 Although the specific mechanism(s) through which AIs influence mammalian cells is unclear, modified immune responses by AIs unravel another circuit of how pathogens establish an infection.107