H&E staining of spleen sections, the most common site for leukemia metastasis 20, confirmed that the treatment with T140-KLA-EVs reduced the infiltration of leukemia cells in the spleen as evidenced by the lower number of leukemic cells (identified by the characteristic large nuclei and large nuclear-cytoplasmic ratio) (Figure 7F, S12B). The gene discussed is KL; the disease is leukemia.