PPARGC1A and breast cancer: By contrast, and consistent with our prior studies in MDA-MB-231 breast cancer cells [14], expression of KIF17-NR selectively inhibited expression of ERR1 targets, including ERR1, PGC1A, and claudin-4, but had no significant effect on the mRNA levels of 14-3-3ζ, HIF1A, HIF2, and osteopontin.