By analysis of transcriptome data of breast cancer tissues and para-cancerous tissues obtained from TCGA database, we found that the expression of Slc6a8 gene was substantially upregulated in breast cancer tissues as compared to adjacent normal tissues (Fig. 2a), which was further confirmed by qRT-PCR in a cohort of 149 breast cancer patients (Fig. 2b). Here, SLC6A8 is linked to breast cancer.