We recently discovered the tumor-promoting potential of an immunoregulatory molecule, the p28 subunit of interleukin (IL)27, also known as IL30, which is expressed by activated macrophages and myeloid-derived suppressor cells6–9, but is also found as a membrane-anchored cytokine in the cytoplasmic membrane of cancer cells10–12. The gene discussed is IL27; the disease is neoplasm.