Trabectedin reveals a strategy of immunomodulation in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is a B-cell neoplasia characterized by pro-tumor immune dysregulation involving non-malignant cells of the microenvironment, including T lymphocytes and tumor-associated myeloid cells. Although therapeutic agents have improved treatment options for CLL, many patients still fail to respond. Some patients also show immunosuppression. We have investigated trabectedin, a marine-derived compound with cytotoxic activity on macrophages in solid tumors. Here we demonstrate that trabectedin induces apoptosis of human primary leukemic cells and also selected myeloid and lymphoid immunosuppressive cells, mainly through the TRAIL/TNF pathway. Trabectedin modulates transcription and translation of IL-6, CCL2 and IFNα in myeloid cells and FOXP3 in regulatory T cells. Human memory CD8+ T cells downregulate PD-1 and, along with monocytes, exert in vivo antitumor function. In xenograft and immunocompetent CLL mouse models, trabectedin has anti-leukemic effects and antitumor impact on the myeloid and lymphoid cells compartment. It depletes myeloid- derived suppressor cells and tumor-associated macrophages and increases memory T cells. Trabectedin also blocks PD-1/PD-L1 axis by targeting PD-L1+ CLL cells, PD-L1+ monocytes/macrophages, and PD-1+ T cells. Thus trabectedin behaves as an immunomodulatory drug with potentially attractive therapeutic value in the subversion of the protumor microenvironment and in overcoming chemoimmune resistance.