miR-28 expression suppresses established primary lymphomas. (A) Representative flow cytometry plots of lymph nodes from control and λ-MYC littermate mice. (B) Representative histochemistry images of control and λ-MYC littermate spleens. H&E, hematoxylin and eosin. (C) qRT-PCR analysis of miR-28 in naïve, GC, and lymphoma cells from λ-MYC mice. (D) Cells from enlarged spleen or lymph nodes from λ-MYC mice were injected subcutaneously into NSG mice. Two λ-MYC primary tumors were used as donors in 2 independent experiments to inject a total of 12 NSG recipient mice in both flanks. Once tumors were detectable (>200 mm³), each mouse was injected intratumorally with miR-28 mimic (blue) in 1 flank and control mimic (white bars, red circles) in the other (supplemental Figure 5E) in 3 injections. Tumor growth was monitored throughout the experiment (left graph; arrows indicate mimic injections, a representative experiment is shown) and at endpoint (central graph, data from 2 independent experiments, normalized to the average value; right, representative image). Each symbol represents an individual engrafted tumor. (E-F) Lymph node cells from control and λ-MYC littermate mice were injected IV into NSG recipients. (E) Spleen weights of NSG mice euthanized at the indicated posttransplant times. (F) Representative flow cytometry analysis of bone marrow or spleen from NSG mice 10 days after transplant with control or λ-MYC cells. Representative spleens are shown to the right. (G-I) Cells from enlarged λ-MYC spleen or lymph nodes were injected IV into NSG recipient mice; 10 days later, mice received intravenous injections of miR-28 or control mimics (supplemental Figure 5F). Two independent donor primary tumors were used in 2 independent experiments to inject a total of 10 recipient mice for control mimic treatment and 10 recipient mice for miR-28 mimic treatment. (G) Spleen weights of transplanted NGS mice (left) and images (right) after treatment with miR-28 or control mimics from 1 representative experiment. (H) Proportion of spleen B cells in transplanted NSG mice after treatment with miR-28 or control mimics (data from 2 independent experiments with 2 λ-MYC tumors normalized to the tumor with the maximum proportion of B cells). (I) Spleens from NSG mice transplanted with λ-MYC and treated with control or miR-28 mimic were stained with the indicated antibodies. Scale bar 100 µm for Pax5 and Ki67 and 25 µm for active caspase 3. Quantification of caspase 3 staining is shown on the right. *P < .05, **P < .01 unpaired Student t test.