Upregulation of GnT-IVa and Its Critical Roles in ATRA-Induced Differentiation of Acute Promyelocytic Leukemia Cells.

Glycosylation is essential for hematopoietic cell homeostasis and malignant transformation. Dysregulated expression of glycosylation genes in leukemia cells accelerates disease progression and fosters drug resistance. Therefore, targeting these genes offers a promising avenue for anti-leukemic therapy. In this study, we explore the roles of N-glycans in acute promyelocytic leukemia (APL) differentiation using the ATRA-induced wild-type NB4 (WT/ATRA) or HL-60 cell model. We found that expression of N-acetylglucosaminyltransferase IVa (GnT-IVa, encoded by the MGAT4A gene) and its product (β1,4-GlcNAc-branched N-glycan) increased significantly during differentiation, as evaluated by lectin blot, real-time PCR, and flow cytometry. Interestingly, analysis of the Gene Expression Omnibus (GEO) public data showed that MGAT4A expression is significantly lower in APL patients, and higher MGAT4A expression was associated with favorable survival in AML cohorts. To address the role of GnT-IVa in differentiation, we established MGAT4A- and MGAT4B-knockout (KO) NB4 cell lines using CRISPR/Cas9. Compared to WT/ATRA cells, MGAT4A KO, but not MGAT4B KO, markedly suppressed ATRA-induced differentiation, as evidenced by reduced expression of CD11b and CD11c. We found that CD11b is a major glycoprotein carrying β1,4-GlcNAc-branched N-glycans. This modification enhanced CD11b stability, as CD11b expression declined more rapidly in MGAT4A KO cells in the presence of cycloheximide. In addition, MGAT4A KO suppressed ERK/MAPK signaling, which contributed to differentiation. Our study highlights the critical role of GnT-IVa in regulating APL differentiation, which may provide a basis for developing new differentiation therapies for APL.