MKI67 and plasma cell myeloma: While exposure to repetitive stimulations with BCMA-expressing human KMS-11 multiple myeloma cells (64) led to the expression of inhibitory receptors such as PD-1 and KLRG1 (Supplementary Figure 5), p16INK4a knockdown increased the fraction of Ki67+ cells and restricted the development of SA-β-Gal-expressing CAR T cells (Figures 7G, H).