Treatment with the NO donor JS-K reduces MMP-2 and MMP-9 expression in primary tumors. WT mice were treated with saline (VC), IL-2, and/or α-CD40 in combination with either the NO donor JS-K or the non–NO-releasing analogue JS-43-126. On day 22, mice were euthanized and the primary tumor was dissected and homogenized in RIPA lysis buffer. (A) The expression of MMP2, MMP9, TIMP-1, and E-cadherin was determined by Western blot analysis. HPRT was used as a loading control. The results are representative of three separate experiments. (B) For each protein, the corresponding band intensity was determined by densitometric analysis. The results were then divided by the band intensity for the corresponding HPRT loading control. Graphs represent the mean and standard errors for the quantitated results obtained from all three experiments. *, P < 0.05; **, P < 0.005. The black bars indicate JS-43-126 control-treated mice and the white bars indicate JS-K–treated mice.