Tumor cell-released kynurenine biases MEP differentiation into megakaryocytes in individuals with cancer by activating AhR–RUNX1

Tumor-derived factors are thought to regulate thrombocytosis and erythrocytopenia in individuals with cancer; however, such factors have not yet been identified. Here we show that tumor cell-released kynurenine (Kyn) biases megakaryocytic–erythroid progenitor cell (MEP) differentiation into megakaryocytes in individuals with cancer by activating the aryl hydrocarbon receptor–Runt-related transcription factor 1 (AhR–RUNX1) axis. During tumor growth, large amounts of Kyn from tumor cells are released into the periphery, where they are taken up by MEPs via the transporter SLC7A8. In the cytosol, Kyn binds to and activates AhR, leading to its translocation into the nucleus where AhR transactivates RUNX1, thus regulating MEP differentiation into megakaryocytes. In addition, activated AhR upregulates SLC7A8 in MEPs to induce positive feedback. Importantly, Kyn–AhR–RUNX1-regulated MEP differentiation was demonstrated in both humanized mice and individuals with cancer, providing potential strategies for the prevention of thrombocytosis and erythrocytopenia.