SLC7A11 and breast cancer: Moreover, gain of function missense mutations of the TP53 gene (mut-p53), observed in about 30% of all breast cancer cases and in 80% of triple negative breast cancers (TNBC) [18], induce the downregulation of xCT by impairing the function of the nuclear factor erythroid 2-related factor (NRF2), the main activator of xCT transcription [19].