选择性抑制eIF4A靶向肿瘤相关巨噬细胞以恢复淋巴瘤特异性免疫

Background: Silvestrol is an antineoplastic translation inhibitor targeting eukaryotic translation initiation factor 4 subunit A (eIF4A). Silvestrol's antineoplastic effects are well characterized, with our group reporting anti-tumor activity in Epstein-Barr Virus (EBV)-associated lymphoma. While the direct anti-tumor effect in EBV-associated lymphoma was modest, silvestrol mediated indirect tumor control by preserving CD8 + T-cell viability and cytotoxicity. However, silvestrol's impact on the myeloid compartment remains poorly understood. We hypothesize that silvestrol supports anti-tumor immune activity by suppressing tumor-associated macrophage (TAM) growth in the tumor microenvironment (TME). Methods: Co-cultures (co-cx) of EBV-transformed lymphoblastoid cell lines (LCL) and autologous peripheral blood mononuclear cells (PBMC) were used to model the lymphoma TME. LCLs were transformed by native virus in SCID mice before ex vivo culturing. Flow cytometry was used to profile immune population frequency and phenotype. Cell proliferation was monitored via MTS assay. Cytokine arrays and trans-well assays were used to explore soluble and contact-dependent features of the model. Magnet bead separation was used to deplete or enrich immune populations. Transcription was analyzed with AmpliSeq. Results: Depletion of CD8⁺ T-cells from co-cx led to LCL expansion, whereas CD14⁺ depletion improved LCL control. Cytokine arrays showed co-cx media (CM) was enriched for cytokines linked to recruitment, differentiation, and activity of immunosuppressive macrophages. Silvestrol-treated co-cx showed reduced CD14⁺ and CD206⁺ populations by flow and decreased CCL2, CCL8, CCL7, IL-8 by cytokine array. To assess silvestrol's direct effect on myeloid subsets, CD14⁺ cells were isolated and incubated in CM. CD14⁺ cells in CM showed increased proliferation and expression of TAM markers CD206 and CD163. CM-driven proliferation required LCL-PBMC contact and presence of T-cells in initial co-cx. CM-polarized CD14⁺ cells inhibited proliferation of activated T-cells. Silvestrol treatment of CM-cultured CD14⁺ cells reduced proliferation, CD206 and PD-L1 expression, and down regulated M2 and TAM transcriptional signatures. Conclusions: Our co-cx replicates features of a lymphoma TME, exhibiting monocyte polarization toward immunosuppressive TAMs. Silvestrol suppresses TAM proliferation and polarization in co-cx and in monocytes incubated in CM. Planned experiments include Ribo-seq to identify deferentially translated transcripts in silvestrol-treated monocytes, murine studies of silvestrol's effects on TAMs, and synergy studies with other immunotherapies. Overall, these findings, along with previously reported immune effector sparing qualities, support eIF4A inhibition as a therapeutic strategy to target immune escape mechanisms in the lymphoma TME.