EIF4EBP1 and B-cell chronic lymphocytic leukemia: Of note, with our newly established SF3B1-mutant isogenic CLL cell lines (37), we confirmed that expression of SF3B1 mutation generates upregulated NFATC1 isoform 5 expression and increased MYC and the activation of the mTOR pathway by the detection of p-4E-BP1 and mTORC1 (Figure 4, L and M).