biostudies-literatureWebb ERCancer Research UK104995https://www.ebi.ac.uk/biostudies/studies/S-EPMC9463572biostudies-literatureUnknown25(9)The outcome for children with high-risk neuroblastoma is poor despite intensive multi-modal treatment protocols. Toxicity from current treatments is significant, and novel approaches are needed to improve outcome. Cyclophosphamide (CPM) is a key component of current chemotherapy regimens and is known to have immunomodulatory effects. However, this has not been investigated in the context of tumor infiltrating lymphocytes in neuroblastoma. Using murine models of neuroblastoma, the immunomodulatory effects of low-dose CPM were investigated using detailed immunophenotyping. We demonstrated that CPM resulted in a specific depletion of intratumoral T regulatory cells by apoptosis, and when combined with anti-PD-1 antibody therapy, this resulted in improved therapeutic efficacy. CPM combined witiScienceCyclophosphamide depletes tumor infiltrating T regulatory cells and combined with anti-PD-1 therapy improves survival in murine neuroblastoma.PMC946357220537James SWebb ERGray JCLanati SWilliams ELMoreno-Vincente JEnglish VEaston ABeers SAPenfold CTaylor MfalseCyclophosphamide depletes tumor infiltrating T regulatory cells and combined with anti-PD-1 therapy improves survival in murine neuroblastoma.The outcome for children with high-risk neuroblastoma is poor despite intensive multi-modal treatment protocols. Toxicity from current treatments is significant, and novel approaches are needed to improve outcome. Cyclophosphamide (CPM) is a key component of current chemotherapy regimens and is known to have immunomodulatory effects. However, this has not been investigated in the context of tumor infiltrating lymphocytes in neuroblastoma. Using murine models of neuroblastoma, the immunomodulatory effects of low-dose CPM were investigated using detailed immunophenotyping. We demonstrated that CPM resulted in a specific depletion of intratumoral T regulatory cells by apoptosis, and when combined with anti-PD-1 antibody therapy, this resulted in improved therapeutic efficacy. CPM combined wit2022-01-01T00:00:00Z2022 Sep2026-05-28T03:18:24.279Z2025-04-07T08:29:22.91ZS-EPMC94635723609761810.1016/j.isci.2022.104995