Inhibition of NFE2L1 Enables the Tumor-Associated Macrophage Polarization and Enhances Anti-PD1 Immunotherapy in Glioma.

Background And Objectives: A pivotal role of cancer (e.g., glioma) microenvironment is primarily executed by tumor-associated macrophages (TAMs) in facilitating cancer immune evasion and even resisting immunotherapies. However, the molecular base for governing such functionality of TAMs remains poorly understood. Thereby, we here explore the impact of such a key regulatory transcription factor NFE2L1 (also called Nrf1) on glioma-relevant TAMs.

Methods: A set of combining in vivo and in vitro experimental approaches, e.g., by utilizing CRISPR-Cas9 and overexpression plasmids to modulate NFE2L1 expression, and the resulting phenotypic changes in TAMs were evaluated. Besides, immunofluorescence, RT-qPCR and flow cytometry were conducted to assay the infiltration of various immune cells, such as CD8+ T cells and M1-type macrophages, in the glioma microenvironment, as well as their therapeutic response to anti-PD1 treatment.

Results: Deficiency of NFE2L1 causes a unique phenotypic switch in the TAMs from its pro-cancer M2-type to another anti-cancer M1-type, thereby inhibiting malignant progression of glioma. Such NFE2L1-deficiency leads to significantly increases of CD8+ T cells and M1 macrophages within tumor tissues of glioma and hence enhances its sensitivity to anti-PD1 therapy. Further experimental evidence has provided revealing a synergistic efficacy triggered by combined therapy of CD38 inhibitor with PD1 antibodies, significantly inhibited tumor growth, compared to that of their monotherapy. The mechanistic study unraveled that NFE2L1 enables for directly binding to those ARE sites within the promoter regions of both CD38 and PD-L1 genes in order to govern their transcriptional expression.

Conclusions: The aberrant role of NFE2L1 in the malignant progression of glioma was discovered in this study. It is of crucial significance to emphasize the potential of NFE2L1 inhibition as a strategic approach to enhance the efficacy of immunotherapeutic intervention. Overall, this discovery holds a substantial promise for advancement of innovative combination therapies, potentially enhancing treatment outcomes for individuals afflicted with glioma.