Thymocyte selection-associated high mobility box protein regulates T lymphocytes exhaustion in patients with myelodysplastic syndromes by inhibiting PI3K/AKT/mTOR pathway

Abstract

Myelodysplastic syndromes (MDS) patients often experience CD8⁺T lymphocytes exhaustion, which plays a crucial role in the development of MDS. However, the specific role of thymocyte selection-associated high mobility box protein (TOX) in the CD8⁺T lymphocytes exhaustion in MDS patients remains unclear. In this study, we investigated the role of TOX in CD8⁺T lymphocytes exhaustion in patients with MDS. The expression of TOX, inhibitory receptors (IRs), and functional molecules in peripheral blood T lymphocytes of MDS patients and normal controls were detected using flow cytometry. Lentiviral transduction was used to create stable TOX-knockdown CD8⁺T lymphocytes, and small interfering RNA (si-RNA) was used to knock down TOX in Jurkat cells. The expression of TOX was found to be significantly higher in CD8⁺T lymphocytes of MDS patients compared to normal controls. This was associated with upregulated IRs and reduced expression of functional molecules such as Granzyme and Perforin. Myelodysplastic syndromes patients with higher TOX expression had poor clinical indicators and shorter survival. Knockdown of TOX using sh-RNA partially reverses the exhausted phenotype and enhances the lethality of CD8⁺T lymphocytes. Moreover, the knockdown of TOX using si-RNA in Jurkat cells improved cell proliferation activity, down-regulated IRs and activated PI3K/AKT/mTOR signaling pathway. TOX promotes the exhaustion of CD8⁺T lymphocytes by inhibiting PI3K/AKT/mTOR pathway, and targeted inhibition of TOX could partially restore the effector functions and activity of CD8⁺T lymphocytes.