Fig. 4.

K-Ras-induced CD137 expression is mediated by IL-1α through NF-κB signaling. a IL1A mRNA in T-Rex/K-Ras cells measured by real-time PCR. The cells were incubated with 100 ng/mL doxycycline for 48 h. b CD137 mRNA expression in T-Rex/K-Ras cells incubated with various concentrations of IL-1α for 24 h. CD137 mRNA was measured by qTR-PCR. c CD137 mRNA expression in three human cancer cell lines incubated with 10 ng/mL IL-1α for 24 h. CD137 mRNA was measured by real-time PCR. d Impact of NF-κB on IL-1α-induced CD137 expression. T-Rex/K-Ras cells were first transfected with 100 nmol/L control siRNA (siCTL) or siRNA against p65 for 24 h, then incubated with 10 ng/mL IL-1α for 24 h. CD137 mRNA was measured by real-time PCR. e Impact of MAPK1 on IL-1α-induced CD137 expression. T-Rex/K-Ras cells were first transfected with 100 nmol/L control siRNA (siCTL) or siRNA against MAPK1 for 24 h, then incubated with 10 ng/mL IL-1α for 24 h. CD137 mRNA was measured by real-time PCR. f Relationship between CD137 and IL1A gene expression in 166 human pancreatic tumor samples recorded in the TCGA database. Data are presented as mean ± SEM of three repeated experiments. Statistical analysis: two-tailed unpaired t-test for a–e. Spearman’s rank correlation test for F. *P < 0.05; **P < 0.01; ***P < 0.001. CD137 tumor necrosis factor receptor superfamily member 9, IL1A/IL-1α interleukin-1 alpha, siCTL control siRNA, siMAPK1 siRNA against MAPK1, sip65 siRNA against p65, PCR polymerase chain reaction