In a recent contribution to The Journal of Pathology, van der Weyden et al2 reported that mice deficient in any of the five NOX2 subunits Cyba, Cybb, Ncf1, Ncf2 or Ncf4 were markedly less prone to develop lung metastases following intravenous injection of several histiotypes of tumor cells. The gene discussed is NCF4; the disease is neoplasm.