The effects of mIL-2/CD25 and anti-PD-1 mono- and combination therapies on the immune composition of the CT26 tumor microenvironment

ABSTRACT: Targeting IL-2 to CD8+ T cells expressing CD25 or PD-1 elicits optimal antitumor and antiviral CD8+ T cell responses. These effects are augmented when co-administered with PD-1/PD-L1 blockade. Here, we show that a mouse IL-2/CD25 fusion protein (mIL-2/CD25), which selectively targets CD25+ cells, promotes expansion of CD8+ T cells locally within CT26 tumors when administered at high doses (HD). However, tumor-associated CD25hi Tregs fail to expand and become unstable. Furthermore, in combination with PD-1 blockade, mIL-2/CD25 fusion protein-driven antitumor responses are enhanced and Treg migration is restricted to the tumor periphery. Single cell RNA sequencing (scRNA-seq) and TCR repertoire analysis show that hyperexpanded CD8+ T cells from mIL-2/CD25 fusion protein-treated mice exhibit high effector programming in a tumor antigen-specific manner. Expression of effector molecules was highest in CD8+ T cells generated by the combination of HD mIL-2/CD25 and anti-PD-1. Direct comparison of our scRNA-seq findings with that from an alternative approach, where IL-2 activity was targeted to PD-1+ CD8+ T cells using the PD1-IL2v fusion protein, reveals many similarities, but crucially, the combination of HD mIL-2/CD25 and anti-PD-1 is most effective at promoting effector function and “stem-like” CD8+ T cell subsets, suggesting this approach is superior. The differentiation of exhausted CD8+ T cells into highly functional cells and the potent antitumor responses by HD mIL-2/CD25 and anti-PD-1 raises the possibility that this combination approach may lead to greater response rates in patients than is achieved with either agent alone or with alternative IL-2 strategies.

ORGANISM(S): Mus musculus

PROVIDER: GSE299287 | GEO | 2026/09/30

REPOSITORIES: GEO