High-dose irradiation promotes macrophage-mediated engulfment of triple-negative breast cancer through M1 polarization via the IKZF1-CCL5 axis.

Triple-negative breast cancer (TNBC) is an aggressive subtype characterized by high rates of locoregional and distant relapse. While radiotherapy remains a key component of local management, it also plays a critical palliative role in advanced disease, offering effective relief of symptoms. These clinical needs highlight the importance of optimizing radiation strategies for patients with TNBC. Macrophages within the tumor microenvironment (TME) are key regulators of TNBC progression, reprograming into pro-inflammatory M1 or anti-inflammatory M2 phenotypes in response to stimuli such as ionizing radiation (IR) and cytokines. We investigated how different IR doses (0.5 Gy vs. 8 Gy) influence macrophage polarization. High-dose IR promotes M1 polarization and inhibits M2 polarization. Transcriptomic and cytokine profiling revealed the suppression of the transcription factor IKAROS family zinc finger 1 (IKZF1) and its downstream target, C-C motif ligand 5 (CCL5), in macrophages after high-dose IR. Reduced CCL5 secretion contributes to decreased M2 polarization. In indirect co-cultures, conditioned medium (CM) from high-dose IR-treated macrophages suppressed TNBC cell migration and proliferation. Direct co-cultures further confirmed the enhanced phagocytic activity of macrophages in TNBC cells. Notably, addition of recombinant CCL5 reversed these effects. Our findings reveal a potential molecular mechanism by which high-dose IR promotes M1 macrophage polarization via the IKZF1-CCL5 axis and suppresses TNBC progression. This suggests that targeting macrophage polarization may enhance the efficacy of radiotherapy in TNBC.