KLF4 is down-regulated in B-cell lymphomas. (A) KLF4 is not expressed in B-lymphoma cell lines. Expression of KLF4 in B-cell lymphoma and in LCL cell lines was analyzed by quantitative PCR. The results are represented as mean value plus or minus SD of target gene (KLF4) to reference gene (RPL13A) ratio. (B) Reactivation of KLF4 expression in cHL cell lines by treatment with 5-aza-dC. cHL cell lines were incubated with 2μM 5-aza-dC for 24 hours; then the medium was replaced. After an additional 96 hours of incubation, cells were harvested and used for mRNA extraction. Experiments were repeated at least twice with similar results (A-B). KLF4 expression was analyzed by quantitative PCR. (C) Differential expression of KLF4 in the tonsillar B-cell subsets. CD19⁺ cells (n = 9) and B-cell subsets: naive B cells, GC CD10⁺ B cells (GCC), centroblasts CD77⁺ (CB), centrocytes CD77⁻/CD10⁺ (CC), and memory B cells (n = 3 or 4) were isolated from human tonsils. Expression was determined by quantitative PCR and calculated in relation to internal control gene RPL13A by the comparative C_t method. Mean of CD19⁺ values was used as comparator. Data are represented as mean ± SD.