Pdcd4 knockdown stimulates MAP4K1 expression and activates the JNK signaling pathway. (A) The mRNA level of map4k1 is up-regulated in Pdcd4 knockdown cells. The mRNA levels of map4k1 and GAPDH were determined by qPCR using total RNA isolated from GEO-shLacZ and GEO-shPdcd4 cells. The ratio of map4k1/GAPDH in GEO-shLacZ cells is designated as 100%. Three independent experiments were performed with triplicates for each sample. The data are shown and expressed as mean ± standard deviation (SD). The asterisk indicates a significant difference as determined by one-way ANOVA (P<0.01). (B) The protein level of MAP4K1 is increased and its downstream targets are activated in Pdcd4 knockdown cells. Western blot analysis was performed using antibodies against MAP4K1, phospho-JNK, phospho-c-Jun (ser73), JNK, c-Jun, and GAPDH.