MX1 and neoplasm: Subsequent fluorescence microscopy analysis revealed that the homing of Gr-1+ granulocytes to metastatic B16F1 tumor cells was significantly lower in the lungs of pFN-deficient C57BL/6-Fn(fl/fl)Mx-Cre+ mice 1 h after tumor cell injection compared to pFN-competent C57BL/6-Fn(fl/fl)Mx-Cre− mice (Figure 2A,B).