To explore the mechanism by which FDXR regulates mitochondrial function in breast cancer cells, we performed liquid chromatography (LC) tandem mass spectrometry (MS/MS)-based metabolite profiling in FDXR-knockdown (KD) T47D human ER+ breast cancer cells (Supplementary Figure 1A; Supplementary Table 1). The gene discussed is ESR1; the disease is breast carcinoma.