Abstract 3450: The role of NRF2-HO-1 expressing macrophages in lung cancer progression
Authors: Ana Sofia Leal, Karen T. Liby
Journal: Cancer Research (2025)

Macrophages are a highly plastic cell, in the lung they have important physiological roles, such as removing reactive oxygen species (ROS). One of the main pathways that is used by macrophages to remove ROS is the NRF2-&amp;gt;HO-1, a detoxifying mechanism. KRAS mutated lung cancer, one of the most common diagnosed lung cancers, can deregulate the NRF2-&amp;gt;HO-1 pathway on macrophages within the lung microenvironment, promoting cancer progression. Bone marrow derived macrophages (BMDM) from both A/J WT and full body NRF2 KO mice were used. Monocytes were differentiated into macrophages using M-CSF for 5 days. On day 5, BMDM are further stimulated with conditioned media (CM) from murine lung cancer cells (VC1 and LL2). HO-1 and NRF2 (p&amp;lt;0.05) mRNA levels are higher in BMDM of WT mice compared with NRF2 KO mice. Assuming HO-1 is a “first” response mechanism, stimulation with CM from VC-1 and LL2 was extended to 48 hours. At 48 hours BMDM from WT mice compared with NRF2 KO mice have increased mRNA HO-1 expression in both VC-1 and LL2 stimulated (p&amp;lt;0.05). Moreover, other markers, such as CCL2 and IL6 are differently expressed between WT and NFF2 KO BMDM. CCL2 appears to be predominantly expressed in NRF2 KO BMDM. To determine the evolution of HO-1 expression in macrophages in the lung after tumorigenesis initiation with vinyl carbamate (VC), lung of A/J mice were collected at 1, 2, 4, and 8 weeks after VC injection. VC is a carcinogenic compound that induces KrasQ61L mutations and consequently lung adenocarcinomas 12 weeks after administration. CD11b cells were isolated from the lungs of mice after VC administration. CD11b cells show an increase in HO-1 mRNA at week 2 post VC, and in NRF2 one week after VC. IL6 and CD206 mRNA values do not significantly change over time. CCL2 mRNA levels increase 2-fold (p&amp;lt;0.001) at 4 weeks in CD11b positive cells when compared with mice receiving saline. Zinc (II) propoporphyrin IX (ZN-IX) is an HO-1 inhibitor, that has shown anti-tumor and immune modulatory effects. A/J WT mice 6 weeks after stimulation with VC, were treated with ZN-IX for 2 weeks, every 2 days at 50mg/Kg ip. Flow cytometry of lungs of mice treated with ZN-IX showed an increase in CD4 T cells (p=0.002) and increase in the activation of CD8 T cells (CD107, p=0.007). The number of macrophages infiltrating the lungs did not change between mice treated with control-DMSO or ZN-IX, however, significant reductions (p&amp;lt;0.05) in the macrophage tumor promoting marker CD206 were observed. Moreover, the same macrophage populations showed and increased expression of IA-IE (MHC-II, p&amp;lt;0.05), an anti-tumor marker in macrophages. Immune cell-cancer cell interactions and regulation are still not fully understood. Here we show that KRAS mutated lung cancer cells can hijack the natural detoxifying process in macrophages to promote cancer. Interrupting this process can unlock new therapeutic vulnerabilities for lung cancer prevention in high-risk populations. Citation Format: Ana Sofia Leal, Karen T. Liby. The role of NRF2-HO-1 expressing macrophages in lung cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3450.