Objective: In our previous study, we showed that Bacillus Calmette-Guerin (BCG)-
activated macrophages have the ability to directly kill tumor cells. One of the main properties of
these macrophages is the high expression of tripartite motif family protein 59 (TRIM59). This study
was conducted to investigate the mechanism of BCG-induced TRIM59 expression on macrophages
and to identify the subcellular localization of TRIM59.
Methods: TRIM59 expression and TNF-α secretion were compared in RAW264.7 macrophage
cells that were stimulated using BCG with or without Toll-like receptor 2/4 (TLR2/4)-neutralizing
antibodies. Next, small interfering RNA (siRNA) was used to down-regulated interferon regulatory
factor 5 (IRF5) gene expression in RAW264.7 cells. Transfected cells were stimulated with BCG,
after which TRIM59 expression and TNF-α secretion were evaluated in cells pre-treated with
siRNA or scramble control. After treatments, supernatants were co-cultured with MCA207, and cell
viabilities were determined. Moreover, BCG-stimulated RAW264.7 cells were stained for TRIM59
and F4/80 expression.
Results: In this study, we showed that TRIM59 was expressed on the membrane of RAW264.7
cells. After blocking TLR2/4, treatment with BCG failed to induce the expression of TRIM59,
IRF5, and TNF-α on RAW264.7 cells. In addition, down-regulation of IRF5 inhibited TRIM59 and
Conclusion: Our study showed that TRIM59 is a membrane protein, and that BCG treatment upregulated
TRIM59 expression on macrophages via TLR2/4 and IRF5 pathways.