Comparison of autocrine mechanisms promoting motility in two metastatic cell lines: Human melanoma and ras‐transfected NIH3T3 cells

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Abstract
Tumor‐cell migration plays an essential role in invasion into surrounding tissues and the formation of metastatic colonies in distant organs. Metastatic human A2058 melanoma and ras‐ transfected NIH3T3 cells produce autocrine motility factors (AMFs) which stimulate their own motility, and the A2058 cell AMF (AMF/A2058) has been purified. In this study, we partially purified the AMF produced by N‐ras‐transfected NIH3T3 cells (AMF/NIH3T3) and compared it with AMF/A2058. The two AMFs differed in their gel filtration patterns and heat stability, although both elicited migration of N‐ras‐transfected NIH3T3 cells. The receptor for AMF/A2058 in A2058 cells is linked to pertussis‐toxin‐sensitive GTP‐binding protein. Pre‐treatment of N‐ras‐transfected NIH3T3 cells with pertussis toxin also specifically blocked the promotion of motility by AMF/A2058, but did not affect the activity of AMF/NIH3T3. Stimulation of N‐ras‐transfected NIH3T3 cells by both AMFs elicited an additive response. Thus, the autocrine mechanisms of these two metastatic tumor cell lines are different with regard to the AMF molecules, receptors, and signal transduction pathways.