Expression of a catalytically inactive H118Y mutant of nm23-H2 suppresses the metastatic potential of Line IVCl 1 human melanoma cells

Nm23-H1 and nm23-H2 are putative metastasis suppressor genes that encode nu cleoside diphosphate kinase (NDPK) A and B, NDPKs form oligomers distribute d between soluble and particulate fractions of cells and therefore may exer t their effects as either soluble or bound proteins. To determine whether m etastasis-related functions of NDPKs are mediated by their catalytic activi ty in membrane bound or soluble complexes, we have stably transfected highl y metastatic human melanoma Line IV CI I cells with wild-type and catalytic ally inactive (HI 18Y) nm23-H1 and nm23-H2 genes and assayed their metastat ic potential in nude mice. Transfection with wild-type nm23-H1 and nm23-H2 genes and catalytically inactive nm23-H1 did not significantly (all p > 0.1 0) alter the metastatic potential of Line IV CI cells while transfection wi th catalytically inactive nm23-H2 significantly (p < 0.01) reduced their me tastatic potential. The lack of effect of transfection with wild-type and c atalytically inactive nm23-H1 suggests that neither soluble nor membrane bo und NDPK A affect the metastatic potential of Line IV CI I cells. The metas tasis suppressive effect of catalytically inactive NDPK B overexpression su ggests that competition with bound complexes containing catalytically activ e NDPK B inhibits metastasis of Line IV CI I cells, These results imply tha t bound NDPK B promotes metastasis and suggest that inhibition of its funct ion or of its binding to critical sites may be a useful approach to limit t he development of metastases in human melanoma, Int. (C) 2000 Wiley-Liss, I nc.