Advances in T-Lymphokine-activated Killer Cell-originated Protein Kinase Research in Cancer Over the Past Thirty Years.

Nearly thirty years ago, T-lymphokine-activated killer (T-LAK) cell-originated protein kinase (TOPK), also known as PDZ-binding kinase, was first identified as a serine/threonine kinase with limited known functions. Over time, this molecule has gradually revealed a far more striking role in cancer biology. Initially detected mainly in proliferative tissues such as testes and activated lymphocytes, TOPK is now recognized as a protein that becomes aberrantly overexpressed in many human cancers, where it is consistently linked to aggressive tumor behavior and poor clinical outcomes. Research accumulated over the past three decades shows that TOPK governs a wide range of oncogenic processes, including proliferation, metastasis, cell cycle progression, DNA damage repair, resistance to apoptosis, autophagy regulation, inflammatory signaling, and immune modulation. Mechanistic studies reveal that TOPK communicates extensively with major signaling molecules such as extracellular signal-regulated kinase (ERK), β-catenin, the tyrosine-protein kinase Src/glycogen synthase kinase 3 beta/signal transducer and activator of transcription 3 (Src/GSK3β/STAT3), phosphoinositide 3-kinase/phosphatase and tensin homolog/protein kinase B (PI3K/PTEN/AKT), TGF-β/small mother against decapentaplegic (SMAD), NF-κB/Snail, and HIF-1α. Positive feedback interactions with ERK2, Src and other oncogenic regulators further intensify its tumor-promoting activity. TOPK also contributes to resistance to anti-cancer agents such as doxorubicin, gefitinib, oxaliplatin, and sorafenib through its influence on activator protein-1, phosphatase and tensin homolog, sirtuin 1 (SIRT1), p53, and additional downstream effectors. In the tumor immune microenvironment, TOPK enhances programmed cell death ligand 1 (PD-L1) expression and reduces CD8