Bioinformatic prediction and experimental validation of a PE38-based recombinant immunotoxin targeting the Fn14 receptor in cancer cells

AIM

AFn14R can serve as an ideal target for cancer immunotherapy. Here, a combined bioinformatic and experimental approach was applied to characterize an immunotoxin consisting of single-chain variable fragment antibody that targets Fn14 and a toxin fragment (PE38).

METHODS & RESULTS

Flow cytometry results showed that the rate of PE38-P4A8 binding to Fn14 was approximately 60 and 40% in HT-29 and A549 cells, respectively. Moreover, 1 ng/µl of immunotoxin was able to lyse approximately 53 and 41% of HT-29 and A549, respectively. PE38-P4A8 showed stability in mouse serum (∼90%) after 3-h incubation. Most importantly, using bioinformatics for determining the structure and function of fusion proteins can be very helpful in designing of experiments.

CONCLUSION

Coupled with bioinformatics, experimental approaches revealed that PE38-P4A8 could be used as a promising therapeutic agent for cancer cells expressing Fn14.

Binding specificity of the ectodomain of the parathyroid hormone receptor

The parathyroid hormone (PTH)1 receptor is a member of the class B G protein-coupled receptor (GPCR) family and regulates bone and mineral metabolism of vertebrates. A truncated highly active parathyroid hormone fragment PTH (1-34) exerts stimulatory effects on the receptor and is used for treatment of osteoporosis. To study the interacting amino acids of the natural peptide ligand PTH (1-84) with the ectodomain of its receptor we used peptide micro arrays on solid cellulose membranes. The amino acids Arg20 and Trp23 within the identified core binding stretch PTH (20-26) were found to be most important for affinity to the ectodomain of PTH1R. Isothermal titration calorimetry and NMR spectroscopy allowed peptide binding studies in solution and verified peptide positions required for high affinity. With this combination of biochemical and biophysical methods we extend former findings on this essential interaction and can now provide a strategy to screen for optimized therapeutic peptides.