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Background: Chemoresistant leukemia stem cells (LSCs) can cause relapse in leukemia. Doxorubicin (DXR) has been identified as an inhibitor of an immune checkpoint (IC) mechanism of resistance. The objective of this study was to determine the DXR doses that inhibit IC expression upregulation in vitro.
Methods: Kasumi and Jurkat cell lines were treated with low and high doses of DXR determined by previous kill curve experiments. Cells were collected at 12h timepoints over the course of 48h and analyzed for expression of CTLA-4, PD-1, PD-L1, TIGIT, and TIM-3 via flow cytometry. Statistical analysis was done using Tukey’s multiple comparisons test.
Results: 10 and 25 nM DXR treated Kasumi cells showed significantly lower CTLA-4, TIGIT, and TIM-3 expression at 36h (p < 0.0001) and 48h (p < 0.001) compared to 100 nM treated cells. PD-L1 showed lower expression at 48h (p < 0.0001). 10 and 25 nM DXR treated Jurkat cells showed significantly lower CTLA-4, TIGIT, and TIM-3 expression at 36h (p<0.01) and 48h (p<0.0001) compared to 100 nM treated cells. TIGIT and TIM-3 also showed lower expression at 24h (p<0.0001). PD-L1 showed lower expression at 48h (p < 0.0001).
Conclusions: Our results show that in mixed cell populations, low dose DXR prevents the upregulation of multiple ICs within the first two days of treatment. Overall, this presents a promising strategy for preventing a mechanism of resistance using an established chemotherapeutic agent.
Stockard, Bradley C.; Nemechek, Jacqelyn; Schroeder, Kealan; Pace, Jennifer; and Perry, John M., "Low Dose Doxorubicin Inhibits Immune Checkpoint Upregulation In Acute Leukemias" (2021). Research at Children's Mercy Month 2021. 32.