Interestingly, after implantation in the mammary fat pad, serum IL-8 levels are measurable only in animals bearing HPSE-High tumors, suggesting a role for HPSE in the access of tumor-derived cytokines to the circulation (HPSE-High: 15 ± 2 ng/mL; HPSE-Low: 3 ± 1 ng/mL (at the detection limit of the assay). This evidence concerns the gene CXCL8 and neoplasm.