van Geldermalsen et al. (2016) reported reduction of cell growth in HCC1806 basal-like breast cancer cells, but not in MCF-7 luminal cancer cells. ASCT2 knockdown also significantly reduced tumor size in HCC1806 xenografts. Hassanein et al. (2015) reported highly variable tumor size in A549 lung cancer cell xenografts, with very large tumors only occurring in cells containing ASCT2. When ASCT2 was deleted in A549 and LS174T colon cancer cells, in vitro, cell growth was reduced only in A549 cells, but xenograft tumor size of both cell lines was reduced (Cormerais et al., 2018). This evidence concerns the gene SLC1A5 and breast cancer.