The “seed and soil” theory postulates that tumor cells produce several tumor-associated factors, including interleukins (IL-1β, IL-6, IL-8, IL-11, IL-17), macrophage inflammatory protein 1α, TNFα, parathyroid hormone-releasing protein (PTHrP), and prostaglandin E (PGE2). The gene discussed is IL17A; the disease is neoplasm.