Using the human colon carcinoma T84 cell line and the murine myeloid J774 cell line as in vitro model systems, we observed that both IFNγ-activated Jak-STAT and LPS/TNFα-activated NF-κB are essential for iNOS induction in both the tumor cells and the myeloid cells. The gene discussed is IFNG; the disease is colon carcinoma.