ALKAL1 and neoplasm: Using single-cell sequencing technology, multiple novel macrophage subpopulations can be identified, and they influence tumor progression through different signaling pathways; for example, aryl hydrocarbon receptor (AHR)-ALKAL1 signaling is a key regulator of the MerTK+ macrophage subpopulation,54 and in-depth studies of these novel macrophages may be able to identify new targets for tumor therapy.