FIGURE 4. C/EBPβ mediates tumor induction of autophagy-related genes in skeletal muscle cells. (A) Potential C/EBPβ-binding cites are identified in autophagy-related genes. Data base search identified multiple potential biding sites of C/EBPβ in the 5’ promoter region of listed autophagy-related genes. (B) LC3b and Gabarapl1 are upregulated in skeletal muscle of LLC tumor-bearing mice in a C/EBPβ-dependent manner. Total RNA was extracted from the TA of wild type and C/EBPβ knockout mice implanted with LLC cells for 21 days, and analyzed for the mRNA of above identified autophagy-related genes by real-time PCR. (C) LC3b and Gabarapl1 are upregulated in LCM-treated myotubes in a C/EBPβ-dependent manner. Total RNA was extracted from C2C12 myotubes transfected with C/EBPβ-specific or control siRNA. The mRNA of C/EBPβ, LC3b and Gabarapl1 was determined by real-time PCR. Data from panel B and C were analyzed by one way ANOVA. * denotes a difference (p < 0.05). (D) LCM activates C/EBPβ binding to the LC3b and Gabarapl1 promoters in myotubes. C/EBPβ binding to the LC3b and Gabarapl1 promoters in C2C12 myotubes treated with LCM or the control NL20 cell-conditioned medium (NCM) was analyzed by the ChIP assay. Pre-immune IgG was used as control for C/EBPβ-specific antibody.