MGAT3 and breast cancer: Furthermore, Trim21 expression was increased in response to DOX treatment (Fig. 3H), while silencing Trim21 in DOX-exposed BC cells resulted in elevated levels of bisecting GlcNAc and MGAT3 (Fig. 3I, S4J), as well as reduced poly-ubiquitination on MGAT3 and increased resistance to chemotherapy (Fig. 3J, S4K-N).