A Lin28b-regulated inflammatory pathway in vivo. (A) Expression of let-7a, let-7f, and let-7g (determined by TaqMan assays) in tumors from mice with PTCL compared with CD4⁺ WT splenocytes. Values shown are means ± SEM. All P values for the tumor samples were < .001 except 6297 for let-7a, which was P < .01. (B-C) Comparison as in panel A for Il6 (B) and Myc (C) mRNA. Values shown are means ± SEM. (D) Immunohistochemistry demonstrates nuclear NF-κB (p65) staining in the infiltrated livers of mice with PTCL: 6168 (i), 6226 (ii), 6297 (iii), and 6358 (iv). Scale bar indicates 100 μm. (E) Expression of the NF-κB target gene Ccl7 in PTCL tumors. Values shown are means ± SEM. For all RNA-expression experiments, the data were normalized to WT CD4⁺ splenocytes, which is set at 1. (F) Measurement of activated NF-κB in nuclear extracts from Lin28b tumors. Jurkat and LP-1³⁸  nuclear extracts were used as positive controls. The optical density 450 nm reflects binding of NF-κB p65 to the immobilized oligonucleotide (blue bars); the red bars reflect competition by a 5-fold excess of nonimmobilized oligonucleotide. TPA indicates 12-O-tetradecanoylphorbol 13-acetate; CI, calcium ionophore; and LN, lymph node. ***P < .001 compared with WT thymus. (G) Expression levels of Lin28a and Lin28b in tumors from transgenic Lin28b mice with PTCL. L-DNA ladder: mouse embryonic stem cell line (1); WT CD4⁺ splenocytes (2); 6222 (3); 6297 (4); 6316 (5); 6358 (6); 6502 (7); 6266 (8). w indicates water control; Tg, transgenic Lin28b; and Endo, endogenous Lin28b.