We created PDX models for glucocorticoid-resistant primary human MLL-ALL by intravenously injecting CD34-CD38+ leukaemia-initiating cells (LICs) from five MLL-AF9 patients, CD34+ or CD34- LICs from three MLL-ENL patients, and CD34+38+ or CD34-38+ LICs from three MLL-AF4 patients into immunocompromised NSG newborns. Here, KMT2A is linked to acute lymphoblastic leukemia.