Natural lung-tropic T9 cells: a sharp weapon for established lung metastases.

Background: Lung metastasis remains the primary cause of tumor-related mortality, with limited treatment options and unsatisfactory efficacy. In preclinical studies, T helper 9 (T9) cells have shown promise in treating solid tumors. However, it is unclear whether T9 cells can tackle more challenging situations, such as established lung metastases. Moreover, comprehensive exploration into the nuanced biological attributes of T9 cells is imperative to further unravel their therapeutic potential.

Methods: We adoptively transferred T1, T9, and T17 cells into subcutaneous, , and established lung metastases models of osteosarcoma and triple-negative breast cancer, respectively, comparing their therapeutic efficacy within each distinct model. We employed flow cytometry and an imaging system to evaluate the accumulation patterns of T1, T9, and T17 cells in the lungs after transfusion. We conducted bulk RNA sequencing on differentiated T9 cells to elucidate the chemokine receptor CXCR4, which governs their heightened pulmonary tropism relative to T1 and T17 cell counterparts. Using Cd4 Cxcr4 mice, we investigate the effects of CXCR4 on the lung tropism of T9 cells. We performed mass spectrometry to identify the E3 ligase responsible for CXCR4 ubiquitination and elucidated the mechanism governing CXCR4 expression within T9 cellular milieu. Ultimately, we analyzed the tumor immune composition after T9 cell transfusion and evaluated the therapeutic efficacy of adjunctive anti-programmed cell death protein-1 (PD-1) therapy in conjunction with T9 cells.

Results: In this study, we provide evidence that T9 cells exhibit higher lung tropism than T1 and T17 cells, thereby exhibiting exceptional efficacy in combating established lung metastases. CXCR4-CXCL12 axis is responsible for lung tropism of T9 cells as ablating CXCR4 in CD4 T cells reverses their lung accumulation. Mechanistically, tumor necrosis factor receptor-associated factor 6 (TRAF6)-driven hyperactivation of NF-κB signaling in T9 cells inhibited ITCH-mediated ubiquitination of CXCR4, resulting in increased CXCR4 accumulation and enhanced lung tropism of T9 cells. Besides, T9 cells' transfusion significantly improved the immunosuppressed microenvironment. T9 cells and anti-PD-1 exhibit synergistic effects in tumor control.

Conclusions: Our findings emphasized the innate lung tropism of T9 cells driven by the activation of TRAF6, which supports the potential of T9 cells as a promising therapy for established lung metastases.