Effects of miR15a silencing and overexpression on tumorigenicity of B-ALL cells. (A) Left panel: volume of tumors grown in PBS- and hrIL-23–treated animals 14 days after intravenous injection of 697 cells transfected or not with anti-miR15a, irrelevant (irr) anti-miR, miR15a, or irrelevant pre-miR precursor (irr miR). Differences in tumors size were evaluated by the Mann-Whitney U test. Whisker lines represent highest and lowest values, horizontal lines represent median values. Right panel: relative quantification of miR15a expression in tumors explanted from PBS- or hrIL-23–treated animals injected with 697 cells transfected or not with anti-miR15a, irrelevant (irr) anti-miR, miR15a, or irrelevant pre-miR precursor. (B) Relative quantification of miR15a in wild-type and transfected Nalm-6 or 697 cells before injection. (C) Analysis of leukemic cell spreading in peripheral blood, spleen, and BM from hrIL-23– or PBS-treated mice injected intravenously with Nalm-6 cells transfected or not with pEP-has–-miR15a or pEP–miR-null (not shown). Analysis was performed 5 weeks after tumor cell inoculation. Nalm-6 cells were identified as human CD10⁺/CD19⁺ cells. One representative staining is shown.