LLC tumor growth is restored in the footpad of plasminogen-deficient mice by genetic elimination of fibrinogen. (A) Weights of footpad tumors in cohorts of control •, Plg^– ○, Fib^– ▪, and Plg^–/Fib^– □ mice analyzed in parallel are shown 14 days after transplantation of LLC^GFP. The weight distribution of footpad tumors was significantly smaller in Plg^– mice than in control animals (P < .02), consistent with 2 other independent experiments. The elimination of fibrinogen relieved the impediment in tumor growth in Plg^– mice. Indeed, footpad tumors from Plg^–/Fib^– mice were larger than those derived from control mice, though this difference was not statistically significant (P = .1). Plasminogen was not a significant determinant of tumor mass in the absence of fibrinogen (P = .7). Horizontal lines indicate median values. (B) Serial tumor width measurements demonstrated similar tumor expansion in fibrinogen-deficient mice with (▪, n = 7) and without (□, n = 7) plasminogen (P > .1 at each time point). All P values were established using the Mann-Whitney U test. Error bars indicate standard deviation from the mean.