MGAT1 and cancer: To target β1,6-branching, we chose L-PHA (Phaseolus vulgaris, leukoagglutinin), a tetrameric plant lectin that requires β1,6-branching for binding, as targeted deletion of Mgat5 or earlier Golgi enzymes (e.g., Mgat1 and Mgat2) is also required for biosynthesis block binding.24,25,26 Flow cytometry with L-PHA confirmed high target density in a wide diversity of solid and liquid cancers, with binding up to ~25-fold higher than normal T cells (Figure S1A).