Characterization of episomal NUP214-ABL1 B-ALL and in vitro sensitivity of patient blasts to TKI. (Ai) May-Grunwald-Giemsa stain of blasts from a trephine roll. (ii-vi) Immunocytochemical stains of trephine sections stained with antibodies indicated above each panel. (Bi-v) Flow cytometric analysis of marrow blasts. (i) Cell populations in the blast cell gate (CD45⁺ and of the indicated side scatter (SSC) were studied further in subsequent panels. (ii-iv) Expression of the indicated cell surface and cytoplasmic (cyto) antigens was studied on blast cell populations. (Ci) FISH analysis of a blast cell with probes specific for ABL1 (green) and NUP214 (red). Two green and red signals indicate normal chromosomal ABL1 and NUP214. Yellow signals indicate location of fusion gene. (ii-iv) MPLA analysis shows deletion of IKZF1 exons 2-7 and CDKN2A exons 1-2. (D) Absolute cell counts of viable control BV173 (i) and patient primary blasts (ii) after 72 hours in culture with either no drug or the indicated concentration of imatinib (IM), dasatinib (DAS), nilotinib (NIL), or ponatanib (PON). (iii) FACS plots of aliquots of patient's cells after 72 hours of culture showing annexin V and 7-amino-actinomycin D (7-AAD) expression.