To test whether the HG3 cell line is a good model for endogenous NOTCH1 activity in CLL we made use of a recombinant human DLL4 Fc chimera protein to stimulate and the γ-secretase inhibitor nirogacestat (Niro) to inhibit NOTCH1 signaling. Here, NOTCH1 is linked to B-cell chronic lymphocytic leukemia.