Short-term immune-checkpoint inhibition partially rescues perturbed bone marrow hematopoiesis in mismatch-repair deficient tumors

Abstract

Wide-spread cancer-related immunosuppression often curtails immune-mediated antitumoral responses. Immune-checkpoint inhibitors (ICIs) have become a state-of-the-art treatment modality for mismatch repair-deficient (dMMR) tumors. Still, the impact of ICI-treatment on bone marrow perturbations is largely unknown. Using anti-PD1 and anti-LAG-3 ICI treatments, we here investigated the effect of bone marrow hematopoiesis in tumor-bearing Msh2^{loxP/loxP;TgTg(Vil1-cre)} mice. The OS under anti-PD1 antibody treatment was 7.0 weeks (vs. 3.3 weeks and 5.0 weeks, control and isotype, respectively). In the anti-LAG-3 antibody group, OS was 13.3 weeks and thus even longer than in the anti-PD1 group (p = 0.13). Both ICIs induced a stable disease and reduced circulating and splenic regulatory T cells. In the bone marrow, a perturbed hematopoiesis was identified in tumor-bearing control mice, which was partially rescued by ICI treatment. In particular, B cell precursors and innate lymphoid progenitors were significantly increased upon anti-LAG-3 therapy to levels seen in tumor-free control mice. Additional normalizing effects of ICI treatment were observed for lin^-c-Kit⁺IRF8⁺ hematopoietic stem cells, which function as a "master" negative regulator of the formation of polymorphonuclear-myeloid-derived suppressor cell generation. Accompanying immunofluorescence on the TME revealed significantly reduced numbers of CD206⁺F4/80⁺ and CD163⁺ tumor-associated M2 macrophages and CD11b⁺Gr1⁺ myeloid-derived suppressor cells especially upon anti-LAG-3 treatment. This study confirms the perturbed hematopoiesis in solid cancer. Anti-LAG-3 treatment partially restores normal hematopoiesis. The interference of anti-LAG-3 with suppressor cell populations in otherwise inaccessible niches renders this ICI very promising for subsequent clinical application.

Keywords: Hematopoietic progenitor cell; hypermutated tumor; immunotherapy; tumor microenvironment.

Graphical abstract

Figure 1.

Workflow, ¹⁸F-FDG PET/CT imaging in vivo, and overall survival of Msh2^{loxP/loxP;TgTg(Vil1-cre)} mice treated with ICIs.

Figure 2.

Spectral flow cytometry of the peripheral blood.

Figure 3.

Spectral flow cytometry and gene expression analysis of spleens.

Figure 4.

Characterization of the TME using spectral flow cytometry and immunofluorescence.

Figure 5.

Gene expression analysis in residual tumors and IRF5 detection by tumor immunofluorescence.

Figure 6.

Altered murine haematopoiesis during tumor development.

Figure 7.

Impact of ICI treatment on murine haematopoiesis.