Fig 2: CDK4/6 inhibitor-treated KSHV+ cells and EBV+ cells express increased ICAM-1 and B7-2 and induce increased T-cell activation. a, b Surface expression of ICAM-1 and B7-2 in BCBL-1 cells treated with 0.1 µM or 0.3 µM Abe (a) and Akata cells treated with 0.5 µM or 1 µM Abe (b) for 72 h. Cells were then harvested, and stained with PerCP/Cy5.5-conjugated IgG isotype control, anti-ICAM-1, or anti-B7-2 antibodies and analyzed using flow cytometry. Shown are fold changes in median fluorescent intensity (MFI) of one experiment of Abe-treated cells over untreated control cells. c–f T-cell activation in BCBL-1 (c and d) and Akata (e and f) cells in response to Abe treatment in the same experiment analyzed in panels a and b. Treated cells were washed with PBS to remove Abe and coincubated for 6 h with Jurkat cells expressing luciferase under the control of the IL-2 promoter at a 2:1 (BCBL-1) or 1:2 (Akata) target to effector ratio in the presence of anti-human CD3 antibody to measure Jurkat T-cell activation. Activation of the Jurkat T-cells are shown as relative light units (RLU) (c and e). Average fold changes in RLU from Jurkat cells coincubated with Abe-treated BCBL-1 and Akata cells over those coincubated with ethanol control (0 µM Abe) treated cells in the presence of 0.6 µg/mL anti CD3 antibody are shown in d and f. Error bars represent standard deviations from 3 independent experiments. Statistically significant differences (*p = 0.05, paired 2-tailed t-test) between control and Abe-treated cells are indicated

Fig 3: CDK4/6 inhibitors increase cell surface expression of ICAM-1, B7-2, and PD-L1 in KSHV- and EBV- uninfected and infected cells. BJAB, JSC-1, BCBL-1, BC-1, BC-2, Akata, Raji, and Daudi cells were treated with 1 µM Abe, 1 µM Pal, 5 µM Rib, or RPMI medium control for 72 h. HUVEC and HUVEC.BAC16 cells were treated with 0.5 µM Abe, 0.5 µM Pal, 2.5 µM Rib, or EGM-2 medium control for 4 days. Surface expression of ICAM-1, B7-2 and PD-L for the lymphoma cells (a–c) and endothelial cells (d–f) were analyzed by flow cytometry. Results shown are mean fold changes relative to untreated cells from 3 experiments. Statistics were done using unpaired two-tailed t-test. Asterisks indicate p values: *p < 0.05, **p < 0.01, ***p < 0.001

Fig 4: CDK4/6 inhibitors increase mRNA expression of MHC-I, ICAM-1, B7-2, and PD-L1 in KSHV+ cells and EBV+ cells. JSC-1 (a), BCBL-1 (b), Akata (c), and Raji (d) cells were treated with 1 µM abemaciclib, or with RPMI medium control for 24 h or 48 h. Total RNA was extracted and analyzed for mRNA expression of MHC-I, ICAM-1, B7-2 and PD-L1 using realtime qPCR. Results shown are mean fold changes relative to untreated cells from 3 experiments. Error bars represent standard deviations from the 3 experiments