We tested this hypothesis by assessing in vitro drug responses in CRLF2-rearranged (CRLF2R) and -non-rearranged (CRLF2NR) cells from patient-derived xenografts of Ph-like ALL, and found that CRLF2R samples were uniformly less sensitive to GCs relative to many CRLF2NR samples. Here, CRLF2 is linked to acute lymphoblastic leukemia.