However, as recently reviewed, the role of OCTN2 in breast cancer, either ER+ or ER-, is not straightforward when considering prognosis and patient survival after cancer treatment; upon a deep analysis of breast cancer data set, the existence of a threshold level of OCTN2 expression that may affect the different prognosis has been proposed (Juraszek and Nalecz, 2019). This evidence concerns the gene ESR1 and breast carcinoma.