NRF2 activation in cancer cells suppresses immune infiltration into the tumor microenvironment.

Clinical observations have revealed that NRF2 hyperactivation in cancer cells is often associated with immune suppression in the tumor microenvironment. However, it remains unclear whether NRF2 hyperactivation directly reduces immune cell infiltration into tumors. To address this question, we established a syngeneic mouse model using the transplantation of 3LL lung cancer-derived cells with either NRF2 hyperactivation via Keap1 gene deletion or concomitant Keap1-Nrf2 gene deletion. A series of flow cytometry, histological analysis, and comprehensive gene expression profiling demonstrated that immune cell infiltration was significantly reduced in KEAP1-deleted tumors, with a marked decrease in CD45-positive cells, particularly myeloid and monocytic populations. In contrast, concomitant deletion of NRF2 restored immune cell infiltration in the KEAP1-deleted tumors. These findings provide convincing lines of evidence that NRF2 activation in cancer cells suppresses immune cell infiltration into tumors. Our study sheds light on the mechanistic basis by which NRF2 activation contributes to cancer malignancy.