Carbon ion irradiation plus CTLA4 blockade elicits therapeutic immune responses in a murine tumor model

ABSTRACT: Radiotherapy can act as in situ vaccine activating preventive tumor-specific immune responses in treated patients. While carbon ion radiotherapy holds superior biophysical properties over conventional photon irradiation, little is known about the immunological effects induced by this radiation type. Multiple strategies combining radiotherapy with immune checkpoint inhibition (radioimmunotherapy) to enhance anti-tumor immunity have been described, however, results on the immune cell composition in tumors following radioimmunotherapy with carbon ions are lacking. Here, we present a bilateral tumor model based on time-shifted transplantation of murine, Her2+ EO771 tumor cells onto the flanks of immune competent mice followed by selective irradiation of the primal tumor. αCTLA4- but not αPD-L1-based radioimmunotherapy induced complete tumor rejection and mediated eradication of even non-irradiated, distant tumors. Cured mice were protected against EO771 rechallenge indicative of long lasting, tumor-specific immunological memory. Single cell RNA-sequencing and flow cytometric analyses of irradiated tumors revealed activation of NK cells and distinct tumor-associated macrophage clusters with upregulated expression of TNF and IL1 responsive genes. Distant tumors of irradiated mice showed higher frequencies of naïve T cells, which were activated upon combination with CTLA4 blockade. Thus, radioimmunotherapy with carbon ions plus CTLA4 inhibition reshapes the tumor-infiltrating immune cell composition and can induce complete rejection even of non-irradiated tumors. Our data suggest to combine radiotherapy approaches with CTLA4 blockade to achieve durable anti-tumor immunity. Furthermore, evaluation of future radioimmunotherapy approaches should not be restricted to immunological impacts at the irradiation site, but should also consider systemic immunological effects on non-irradiated tumors.

ORGANISM(S): Mus musculus

PROVIDER: GSE214524 | GEO | 2022/09/30

REPOSITORIES: GEO