Novel c-MYC target genes mediate differential effects on cell proliferation and migration.

The developmental and oncogenic roles of MYC proteins are well established, but the transcriptional targets mediating their functions remain elusive. Using small interfering RNA-mediated knockdown in breast and cervix carcinoma cell lines, which overexpress c-MYC, we show that c-MYC independently controls metabolism and cell proliferation, and can, depending on the cells, promote or inhibit migration. We identified new c-MYC target genes in these cell lines, and show that selective regulation of some targets correlates with the phenotypic responses of these different cell lines to c-MYC depletion. Notably, we show that a positive regulation of the WNT signalling pathway contributes to c-MYC pro-mitogenic effects in breast and cervix carcinoma cells. We also show that repression of CCL5/RANTES accounts for c-MYC anti-migratory effects in specific breast cancer cells. Our combined genomic and phenotypic analysis indicates that c-MYC functions are cellular-context-dependent and that selectively regulated genes are responsible for its differential properties.