Thymocyte selection-associated high mobility group box protein (TOX) (TOX)

Thymocyte selection-associated high mobility group box protein (TOX) is a nuclear transcription factor and chromatin remodeler belonging to the HMG-box superfamily (UniProt Q96NM4). It plays a pivotal role in the development of T-cell lineages in the thymus, but its most prominent role in clinical research is as the master regulator of T-cell exhaustion (Nature 2019, 571:211-218). During chronic antigen exposure, such as in cancer or persistent viral infections, sustained TOX expression induces an epigenetic program that drives CD8+ T cells into an exhausted state, characterized by high expression of inhibitory receptors like PD-1 and loss of cytotoxic effector functions (Nature 2019, 571:205-210). This mechanism allows tumors to evade immune surveillance. Additionally, TOX is significantly overexpressed in cutaneous T-cell lymphomas (CTCL), such as Mycosis Fungoides and Sézary Syndrome, where it serves as both a diagnostic biomarker and a potential driver of malignancy (Journal of Investigative Dermatology 2014, 134:1428-1437). Therapeutic strategies targeting TOX mRNA or the protein itself aim to reinvigorate exhausted T cells and enhance the efficacy of existing checkpoint blockade therapies.

Other names

TOX1Thymocyte selection-associated HMG box protein

Inhibition of TOX expression (via mRNA degradation or transcriptional repression) or protein activity to prevent or reverse the epigenetic commitment to T-cell exhaustion, thereby enhancing the cytotoxic activity of CD8+ T cells against tumors or viral-infected cells (Nature 2019, 571:205-210).