KISS-1, A NOVEL HUMAN-MALIGNANT MELANOMA METASTASIS-SUPPRESSOR GENE

Background: Microcell-mediated transfer of chromosome 6 into human C81 61 and MelJuSo melanoma cells suppresses their ability to metastasize by at least 95% without affecting their tumorigenicity. This observati on demonstrates that the ability to metastasize is a phenotype distinc t from tumor formation and suggests that tumorigenic cells acquire met astatic capability only after accumulating additional genetic defects. These results also imply that mutations of genes on chromosome 6 are among those late genetic changes responsible for metastatic potential. They further suggest that a melanoma metastasis-suppressor gene(s) is encoded on chromosome 6 or is regulated by genes on chromosome 6. Pur pose: Our objective was to identify the gene(s) responsible for the su ppression of metastasis in chromosome 6/melanoma cell hybrids. Methods : A modified subtractive hybridization technique was used to compare t he expression of messenger RNAs (mRNAs), via an analysis of complement ary DNAs (cDNAs), in metastatic cells (C8161 or MelJuSo) and nonmetast atic hybrid clones (neo6/C8161 or neo6/MelJuSo). Results: A novel cDNA , designated KiSS-1, was isolated from malignant melanoma cells that h ad been suppressed for metastatic potential by the introduction of hum an chromosome 6. Northern blot analyses comparing mRNAs from a panel o f human melanoma cells revealed that KiSS-1 mRNA expression occurred o nly in nonmetastatic melanoma cells. Expression of this mRNA in normal heart, brain, liver, lung, and skeletal muscle was undetectable by no rthern blot analysis. Weak expression was found in the kidney and panc reas, but the highest expression was observed in the placenta. The KiS S-1 cDNA encodes a predominantly hydrophilic, 164 amino acid protein w ith a polyproline-rich domain indicative of an SH3 ligand (binds to th e homology 3 domain of the oncoprotein Src) and a putative protein-kin ase C-alpha phosphorylation site. Transfection of a full-length KiSS-1 cDNA into C8161 melanoma cells suppressed metastasis in an expression -dependent manner. Conclusions: These data strongly suggest that KiSS- 1 expression may suppress the metastatic potential of malignant melano ma cells, implications: KiSS-1 may be a useful marker for distinguishi ng metastatic melanomas from nonmetastatic melanomas.