(A) Negative and positive SLC7A5 protein expression and (B) negative and positive SLC3A2 protein expression in invasive breast cancer cores using IHC. Association of SLC7A5/SLC3A2 mRNA co-expression with proliferation associated-genes, including (C) CCNA2, (D) CCNB1, (E) TOP2A and (F) PCNA, using the METABRIC cohort. A one-way ANOVA with the post-hoc Tukey multiple comparison test was used, and p values of ≤ 0.05 were considered significant. (G) MCF-7 and (I) MDA-MB-175-VII cells were transfected with control siRNA or SLC7A5 and SLC3A2 siRNA (si-SLC7A5/SLC3A2) for 24 h. Cells were then seeded in duplicate in corresponding media, and on the indicated days, cells were trypsinized and stained with trypan-blue and counted. Results shown are mean ± SE of two independent experiments. Asterisks denote p-values as follows: * p < 0.05; ** p < 0.005; *** p < 0.001. The efficiency of SLC7A5 and SLC3A2 knockdown in (H) MCF7 and (J) MDA-MB-175-VII cells were confirmed by Western blotting.