Bioinformatic analysis of the role of solute carrier-glutamine transporters in breast cancer

BACKGROUND: Breast cancer (BC) is a highly heterogeneous disease. Solute carriers (SLCs) have been involved in the tumor progression of various cancer types. This study aimed to evaluate the role of these SLC-related glutamine transporters in the prognosis of BC patients by bioinformatics analysis. METHODS: This study examined the transcription and prognostic data for glutamine-related transporters in BC from Oncomine Database, which is currently the largest oncogene microarray database platform in the world. As well as Gene Expression Profiling Interactive Analysis (GEPIA), Kaplan-Meier (K-M), and cBioPortal online resources. The Tumor Immune Estimation Resource (TIMER) and GEPIA were also used to examine the relationship between SLCs and immune cell infiltration. RESULTS: The expression levels of SLC1A5, SLC3A2, SLC7A5, SLC7A8, and SLC38A1 were higher in BC tissues than normal breast tissues, but the expression level of SLC6A14 was lower. The expression levels of SLC7A5, SLC7A8, SLC6A14, and SLC38A2 were related to a later clinical tumor stage. In the K-M analyses, The K-M curves revealed that patients with high SLC1A5 expression had a poor prognosis (OS HR =1.28, 95% CI: 1.06–1.54; P=0.01). The high expression of SLC3A2 was significantly correlated with a poor prognosis (DMFS HR =1.19, 95% CI: 1.02–1.39; P=0.027). Increased SLC7A5 mRNA levels and decreased SLC7A8 mRNA levels were significantly associated with a poor prognosis in terms of OS, RFS, DMFS and PPS. The high expression of SLC6A14 was significantly correlated with a poor prognosis (PPS HR =1.35, 95% CI: 1.07–1.7; P=0.011). The high expression of SLC38A1 was correlated with a better prognosis than low expression of SLC38A1 (RFS HR =0.84, 95% CI: 0.76–0.93; P=0.00077; DMFS HR =0.78, 95% CI: 0.67–0.91; P=0.0013). The infiltration of immune cells and their marker genes were associated with SLC1A5, SLC3A2, SLC7A5, SLC7A8, SLC6A14, SLC38A1, and SLC38A2 expression. SLC7A5, SLC7A8, SLC38A1, and SLC38A2 have the potential to regulate polarization in tumor-associated macrophages. CONCLUSIONS: SLC7A5, SLC7A8, SLC38A1, and SLC38A2 may regulate the polarization of tumor-associated macrophages (TAMs). SLC1A5, SLC3A2, SLC7A5, and SLC6A14 may be promising biomarkers for the BC diagnosis and may represent potential therapeutic targets for these patients.