GLS and breast carcinoma: Differential glutamine dependency among these breast cancer cells does not correlate with the expression levels of known regulators in glutamine metabolism, such as glutaminase; instead, it was shown that the sensitivities of these cells to glutamine deprivation correlate with SLC7A11 expression levels and cystine consumption rates (i.e., compared to other breast cancer cell lines, basal and claudin-low TNBC cells express higher levels of SLC7A11, exhibit more cystine consumption, and are more sensitive to glutamine deprivation) (Timmerman et al., 2013).