To evaluate the stimulatory effect of IL-1 on tumor-induced osteoclastogenesis, IL-1 receptor antagonist (IL-1RA), an inhibitor for IL-1α and IL-1β or an antagonistic antibody for IL-1R1, a signaling receptor for both IL-1α and IL-1β, was applied to OPCs cultured with the culture supernatant of NEM-F. This evidence concerns the gene IL1A and neoplasm.