Studies by Howe et al (15) and Singh and Lucci (16) have shown that COX-2 regulates PG synthesis, that its overexpression increases PG production, stimulating cell proliferation and promoting tumor formation, and that PGE2 and PGF2α, among others, stimulate Balb/C3T3 fibroblast mitosis together with epidermal growth factor (EGF). The gene discussed is PTGS2; the disease is neoplasm.