Myc is overexpressed in gDLBCL and exhibits oncogenic properties in DLBCL cell lines in vitro. (A-B) Myc expression was analyzed by immunohistochemistry on a tissue microarray comprising 37 gDLBCL and 39 low-grade MALT lymphoma (MALT-L) cases. Representative micrographs are shown (A); the fraction of MALT lymphoma and gDLBCL cases with high, low and no Myc expression is indicated (B). (C-D) Myc expression as analyzed by immunohistochemistry of matched low-grade and high-grade lymphoma material from 3 patients. Representative micrographs are shown for case 1 (C); scores on a scale of 0-3 are shown for all cases (D). The scale bar indicates 50 μm. (E-F) Quantification of let-7a (E) and miR-34a (F) expression as determined by LNA real-time RT-PCR for the indicated cells lines (U2932, SUDHL4) 48 hours after electroporation with Myc-specific or scrambled (NC) siRNA. Expression values were normalized to U6 snRNA levels. (G-H) Proliferation as assessed by [³H] thymidine incorporation of U2932 (G) and SUDHL-4 (H) cells 72 hours after electroporation with Myc-specific or scrambled (NC) siRNA. (I-J) Proliferation as assessed by [³H] thymidine incorporation of U2932 (I) and SUDHL-4 (J) cells 72 hours after electroporation with the indicated pre-miRs or scrambled negative control (NC) oligonucleotide. (K-L) miR-34a promoter methylation as determined by methylation-specific PCR of 4 unrelated cases each of MALT lymphoma (K top) and gDLBCL (K bottom) as well as 3 matched low- and high-grade lymphoma samples from the same patients (cases 1-3, L). U indicates unmethylated; and M, methylated. The Myc staining in panels A and B was performed twice with similar results; the experiments shown in panels E through J were each reproduced 3-4 times. Error bars indicate SD. Pictures were taken at room temperature with a Leica Leitz DM RB microscope (20×/0.5 NA) equipped with a Leica DFC 420C camera. Images were acquired using the Leica Application Suite 3.3.0 software.