Double-negative T cells: a promising avenue of adoptive cell therapy in transplant oncology.

Tumor recurrence is one of the major life-threatening complications after liver transplantation for liver cancer. In addition to the common mechanisms underlying tumor recurrence, another unavoidable problem is that the immunosuppressive therapeutic regimen after transplantation could promote tumor recurrence and metastasis. Transplant oncology is an emerging field that addresses oncological challenges in transplantation. In this context, a comprehensive therapeutic management approach is required to balance the anti-tumor treatment and immunosuppressive status of recipients. Double-negative T cells (DNTs) are a cluster of heterogeneous cells mainly consisting of two subsets stratified by T cell receptor (TCR) type. Among them, TCRαβ⁺ DNTs are considered to induce immune suppression in immune-mediated diseases, while TCRγδ⁺ DNTs are widely recognized as tumor killers. As a composite cell therapy, healthy donor-derived DNTs can be propagated to therapeutic numbers in vitro and applied for the treatment of several malignancies without impairing normal tissues or being rejected by the host. In this work, we summarized the biological characteristics and functions of DNTs in oncology, immunology, and transplantation. Based on the multiple roles of DNTs, we propose that a new balance could be achieved in liver transplant oncology using them as an off-the-shelf adoptive cell therapy (ACT).