CXCR4 and breast cancer: MCF-7, MDA-MB-231 breast cancer and K562 leukemia cells were treated with SMRwt peptides for 60 min at 37° C, then treated with anti-CXCR4 antibody (to induce the complement cascade) in NHS or HIS for 60 min at 37° C. Culture supernatants were clarified at 2000 × g for 10 min to remove cell debris, and then EVs were isolated.