CXCL8 and leukemia: For instance, 5-epi-ilimaquinone and its amine-based variants 2–4 are more active than 1 in the production of interleukin-8 (IL-8), a key cytokine in tumor progression and metastasis, but only 5-epi-smenospongine (4) raises the production of TNF-α in murine leukemia cells [14].