AHR and breast cancer: Alternatively, it is possible that the increased AHR levels in macrophages within the PMN make them more susceptible to activation, and the ligand responsible for AHR activation may not necessarily originate from 4T1 cells, as endogenous AHR ligands have diverse sources.51,52 Nonetheless, our research highlights the critical role of AHR in shaping the immunosuppressive microenvironment that facilitates breast cancer metastasis to the lungs.