Profiles of metastasis
DNA microarray analysis of metastatic cells reveals a new player, and an expression profile characteristic of reduced motility and invasive ability.
In the 3 August Nature Clark et al use DNA microarrays to find genes that are up- or down-regulated in metastatic (versus non-metastatic) melanoma cells (Nature 2000, 406:532-535). Variable results suggest that there is more than one way of becoming metastatic, but three genes — encoding fibronectin, thymosin beta4, and RhoC — come up in three independent samples from both human and mouse cells. Extracellular fibronectin probably lays down a permissive track for moving cells, and the actin-buffering thymosin beta4 probably aids cell movement. RhoC is more of a surprise: Clark et al show that overexpressing RhoC in non-metastatic cells is sufficient to make them metastatic, and a dominant inhibitory mutant inhibits metastasis. Bittner et al analyze patterns of gene expression in samples of melanoma cells and find that two distinct clusters robustly emerge from the analysis (Nature 2000, 406:536-540). Melanomas from the larger expression cluster show reduced motility and invasive ability, and initial patient data, although not yet statistically significant, suggest that the group may have better survival prospects.