Inhibition of Experimental Metastasis of Human Fibrosarcoma Cells by Anti‐recombinant 37‐kDa Laminin Binding Protein Antibody

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Abstract
The laminin binding protein of 37 kDa (37LBP) is regarded as a precursor protein of the high‐affinity 67‐kDa laminin receptor (67LR). Expression of 67LR/37LBP is well correlated with biological aggressiveness of cancer, particularly with invasive and metastatic potential. To investigate in detail the role of 37LBP in cancer cells, we synthesized recombinant 37LBP (r37LBP) as a fusion protein and generated an IgG‐type polyclonal antibody P4G against r37LBP. Western blot analysis with P4G showed a single band of 67LR under both nonreducing and reducing conditions using cell extract of human fibrosarcoma cells HT1080. It was shown that P4G inhibited cell attachment to immobilized laminin in a dose‐dependent manner. Further, the intravenous injection of HT1080 cells pretreated with P4G, compared with that of cells pretreated with normal rabbit serum, resulted in a reduced number of experimental metastases (3.3 ± 5.1 vs. 58.0 ± 38.0 nodules per mouse, respectively) (P < 0.005). These results suggest that P4G inhibits the colonization and growth of HT1080 cells in the lungs of mice, and that the blocking of r37LBP with the specific antibody P4G may offer a potential strategy for preventing cancer metastasis.