Single-cell rna sequencing of neuroblastoma tumors reveals immunoregulatory interactions as novel targets for immunotherapy

Background Immunotherapy with CAR-T cells, as well as immune checkpoint blockade, show limited clinical efficacy in the pediatric solid cancer neuroblastoma, despite the success in various adult cancers. The lacking efficacy may be due to various immune evasion strategies employed by neuroblastoma tumors, leading to altered functionality of tumor-infiltrating immune cells. We aimed to provide a comprehensive overview of the composition and function of the neuroblastoma immune environment, as well as relevant immunoregulatory interactions (=), to identify novel targets for immunotherapy. Materials and Methods 25 tumor samples from 20 patients (17 with high-risk disease, 6 with MYCN amplification), were collected during diagnostic biopsy pre-treatment (n=10) or during resection surgery after induction chemotherapy (n=15). Samples were enzymatically digested, single-cell FACS sorted and sequenced by Cel-Seq2 protocol. Results Lymphoid cells in the TME consisted of αβ-, γδ-T cells, NK cells and B cells. Among αβ-T cells we identified CD8+ T cells, two functionally distinct clusters of CD4+ T cells, naive-like T cells and FOXP3+ regulatory T cells (Tregs). CD8+ T cells had reduced cytotoxic capacity compared to blood-derived T cells from a reference group. Tregs expressed high levels of PRDM1, LAYN and ICOS, suggesting an effector Treg profile, which is associated with increased inhibitory capacity. Although NK cells expressed the cytotoxic genes NKG7, KLRF1, GNLY, GZMB and PRF1, their expression was significantly lower than in blood-derived reference NK cells. Gene set enrichment analysis (GSEA) confirmed a reduced cytotoxic capacity of tumoral NK cells, which correlated with a decreased expression of activating receptors (r=0.41, p Conclusions Cytotoxic lymphocytes in the neuroblastoma TME show reduced cytotoxic capacity, likely due to highly immunosuppressive myeloid cells, Tregs and numerous immunoregulatory interactions, which may serve as novel targets for immunotherapy in neuroblastoma. Disclosure Information J. Wienke: None. W.M. Kholosy: None. L.L. Visser: None. K.M. Keller: None. P. Lijnzaad: None. T. Margaritis: None. K.P.S. Langenberg: None. R.R. De Krijger: None. F.C.P. Holstege: None. J.J. Molenaar: None.