Thymosin Alpha-1 Restores Chemotherapy-Induced Antitumor Immunity by Chaperoning a MicroRNA Ligand of TLR7 in Dendritic Cells.
This study investigated why chemotherapy often fails to generate robust anti-tumor immunity and how the endogenous peptide thymosin alpha-1 (Tα-1) might address this gap. The researchers first observed that circulating levels of Tα-1 were reduced after chemotherapy in both cancer patients (across multiple tumor types) and tumor-bearing mice. Mechanistically, the study found that chemotherapy-induced cancer cell death produces apoptotic bodies (ABs) that are poorly immunogenic. Tα-1 was shown to bind to these ABs and interact specifically with AB-associated microRNAs—particularly miR146a-5p—protecting them from degradation by lysosomal RNase A inside dendritic cells (DCs). This protection allowed miR146a-5p to activate Toll-like receptor 7 (TLR7), which in turn licensed DC maturation, migration to tumor-draining lymph nodes, and presentation of tumor antigens to CD8+ T cells. In mouse models, therapeutic Tα-1 supplementation synergized with chemotherapy to suppress established tumors in a TLR7-dependent and miR146a-5p-dependent manner. Limitations include that mechanistic and therapeutic efficacy data are primarily from mouse models, with human data limited to observational measurements of circulating Tα-1 levels.