ANPEP and neoplasm: In addition, we detected the expression of other signaling pathway proteins including NF-κB, IκBα, c-Jun, p38, and their phosphorylated forms; however, each showed inconsistent changes in tested cell lines (Supplementary Figure S6), thus indicating that they are not likely to be involved in fundamental molecular events in the modulation of the synergistic anti-tumor effects of TRAIL and CD13 inhibition.