These data show that the fusion proteins are produced, secreted and contain EGFR activation both IL-2 and IL-2Rα on the same molecule. We characterized the IL-2/PSAcs/IL-2Rα fusion proteins biochemically before and after cleavage with the protease PSA. Immunoblot analyses revealed that the fusion proteins could be cleaved by PSA and that there was an increase in intensity of the predicted low-molecular-weight cleavage product of approximately 20 000 MW reactive with an anti-IL-2 antibody (Fig. 2a). The degree

of cleavage was dependent upon the amount of PSA as well as the time of incubation (Fig. 2b,c). Interestingly, when we analysed the fusion protein before and after PSA treatment by ELISA, we found that the apparent amount of IL-2 was increased after PSA cleavage (Fig. 2d). In this experiment, there was an approximately twofold or fourfold increase in the amount of IL-2 detected using this sandwich ELISA depending on

the construct, suggesting that the detection antibody binding was partially hindered in the intact fusion protein. We also analysed aliquots Selumetinib supplier of the same samples shown in Fig. 2(a) after PSA treatment for functional IL-2 using the CTLL-2 cell line. As seen in Fig. 2(e,f) there is an increase in the amount of biologically active IL-2 after PSA cleavage. After protease treatment, the apparent amount of biologically available IL-2 increased approximately 3·5-fold for the fusion protein with the 2 × linker and ninefold for the fusion protein with the 4 × linker. Hence, the above data show that after PSA cleavage there is an increase in the predicted low-molecular-weight cleavage

fragment of approximately 20 000 MW that is reactive with an anti-IL-2 antibody, an increase in antibody accessibility, and most importantly, an increase in the amount of biologically active IL-2. Because the 4 × linker fusion protein had a larger fold increase in biologically active Metalloexopeptidase IL-2, this fusion protein was used in subsequent experiments. To examine the cleavage of the fusion protein in the context of prostate tissue that expresses a complex mixture of proteases, we took advantage of TG mice that express human PSA30 in prostate explants. Because conventional mice do not express PSA or any close homologue of human PSA, NTG mouse prostates served as a control for the expression of a variety of other proteases produced in the prostates that might cleave the fusion protein. The prostates were removed from TG mice and their NTG counterparts and placed into culture medium containing the IL-2/PSAcs/IL-2Rα fusion protein. At various times, samples were removed and analysed biochemically for cleavage and functionally for IL-2 activity.