miR-217 expression promotes mature B-cell lymphomas. (A-D) Thirty-four control and 40 miR-217^KI mice were monitored over 90 weeks for the appearance of B-cell lymphoma. (A) Representative pictures of (right) a nontumoral control spleen and (left) a miR-217^KI spleen with splenomegaly. (B) Quantification of B-cell lymphoma incidence in control mice and miR-217^KI mice. The proportions of FL (black), DLBCL (white), or other lymphomas (gray) are shown. Statistical significance was determined by 2-tailed Student t test (P = .028). (C) Representative hematoxilin and eosin (H&E) and immunohistochemical stainings for Pax5, CD3, and Bcl-6 in spleens from miR-217^KI mice with B-cell lymphomas. Scale bar is 50 μm. NT, nontumoral; SBL, small B-cell lymphoma. (D) PCR analysis of V(D)J rearrangements in tumor samples from miR-217^KI mice. DNA was isolated from total spleen and amplified using a V-degenerate primer in combination with an antisense primer downstream of J_H4. Sequencing results are shown in Table 2. Mouse IDs are shown. MW, molecular weight marker. (E) Quantification of B-cell lymphoma incidence in control (open bars) and miR-217^KI (filled bars) Ink4a/Arf^−/− and p53^−/− mice. Statistical significance was determined by 2-tailed Student t test (P = .03 in miR217^KI Ink4a/Arf^−/− vs control Ink4a/Arf^−/− and P = .33 in miR217^KI p53^−/− vs control p53^−/−). (F) miR-217 relative expression in human control samples (open circles, peripheral blood CD19⁺ B cells; open squares, tonsils; open triangles, lymph nodes), in BL samples (closed circles) and in DLBCL samples (closed triangles, GC B GCB-DLBCL; closed squares, activated B cell, ABC-DLBCL) as determined by qRT-PCR. Statistical significance was determined by 2-tailed Student t test (P = .05 for BL).