PPARGC1A and neoplasm: In direct support of these observations, Kalluri and colleagues (81) observed that shRNA-mediated down-regulation of the key mitochondrial transcription factor, namely PGC-1α, significantly inhibited lung metastasis, in several independent cell lines (MDA-MB-231, 4T1 and B16F10 melanoma cells), but had little or no effect on tumor growth.