NU/NU nude female mice (6 weeks old; Charles River, Chicago, IL) were randomly divided into three groups of four each and inoculated in the right flank with KYSE450-shMock, KYSE450-shODC #2 or KYSE450-shODC #4 lentiviral-infected cells (3 × 106 cells permouse). Mice were maintained under “specific pathogen-free” conditions based on the guidelines established by the University of Minnesota Institutional Animal Care and Use Committee. Tumor volume and body weight were measured once a week. Tumor volume was calculated from measurements of three diameters of the individual tumor base using the following formula: tumor volume (mm3) = (length × width × height × 0.52). Mice were monitored until tumors reached 1000 mm3 total volume, at which time mice were euthanized and tumors extracted.