Objective   To investigate the relationship between fucosyltransferase 8(FUT8)and immune cell infiltration in breast cancer and its impact on prognosis.

  Methods   The expression of FUT8 in breast cancer as well as other types of cancer was retrieved and analyzed using the Tumor Immunoassay database (TIMER) and Oncomine database; survival curves was plotted by Kaplan-Meier Plotter database and the effects of FUT8 under different clinical characteristics on the prognosis of breast cancer patients were summarized; the association between FUT8 and immune cell infiltration in breast cancer was investigated by TIMER and TIMER2.0; TIMER2.0 and bc-GenExMiner database were used to derive the correlations between FUT8 and immune cell markers, immune checkpoints in breast cancer; finally, immunohistochemical staining was conducted to detect the expression of FUT8 in breast cancer.

  Results   FUT8 was expressed in 85% of breast cancer tissues, and high levels of FUT8 leaded to better survival and prognosis in most patients (HR < 1). In the basal subtype, the levels of FUT8 were positively correlated with infiltration of CD8⁺T cells, Treg cells, NK cells and macrophages; in the HER2 + subtype, the levels of FUT8 were positively correlated with infiltration of CD4⁺T cells and Treg cells; in basal and HER2 subtypes, FUT8 expression was positively correlated with most immune checkpoints and immune cell markers.

  Conclusion   FUT8 has important roles in evaluating the prognosis and the level of immune cell infiltration in breast cancer patients.