Increased SLC7A3 Expression Inhibits Tumor Cell Proliferation and Predicts a Favorable Prognosis in Breast Cancer.

Arginine plays significant and contrasting roles in breast cancer growth and survival. However, the factors governing arginine balance remain poorly characterized. We aimed to identify the molecule that governs arginine metabolism in breast cancer and to elucidate its significance. We analyzed the correlation between the expression of solute carrier family 7 member 3 (SLC7A3), the major arginine transporter, and breast cancer survival in various databases, including GEPIA, UALCAN, Metascape, String, Oncomine, KM-plotter, CBioPortal and PrognoScan databases. Additionally, we validated our findings through bioinformatic analyses and experimental investigations, including colony formation, wound healing, transwell, and mammosphere formation assays. Our analysis revealed a significant reduction in SLC7A3 expression in all breast cancer subtypes compared to adjacent breast tissues. Kaplan-Meier survival analyses demonstrated that high SLC7A3 expression was positively associated with decreased nodal metastasis (HR=0.70, 95% CI [0.55, 0.89]), ER positivity (HR=0.79, 95% CI [0.65, 0.95]), and HER2 negativity (HR=0.69, 95% CI [0.58, 0.82]), and increased recurrence-free survival. Moreover, low SLC7A3 expression predicted poor prognosis in breast cancer patients for overall survival. Additionally, the knockdown of SLC7A3 in MCF-7 and MDA-MB-231 cells resulted in increased cell proliferation and invasion in vitro. Our findings indicate a downregulation of SLC7A3 expression in breast cancer tissues compared to adjacent breast tissues. High SLC7A3 expression could serve as a prognostic indicator for favorable outcomes in breast cancer patients due to its inhibitory effects on breast cancer cell proliferation and invasion.