T cell receptor-like recognition of tumor in vivo by synthetic antibody fragment.
A major difficulty in treating cancer is the inability to differentiate between normal and tumor cells. The immune system differentiates tumor from normal cells by T cell receptor (TCR) binding of tumor-associated peptides bound to Major Histocompatibility Complex (pMHC) molecules. The peptides, derived from the tumor-specific proteins, are presented by MHC proteins, which then serve as cancer markers. The TCR is a difficult protein to use as a recombinant protein because of production issues and has poor affinity for pMHC; therefore, it is not a good choice for use as a tumor identifier outside of the immune system. We constructed a synthetic antibody-fragment (Fab) library in the phage-display format and isolated antibody-fragments that bind pMHC with high affinity and specificity. One Fab, fE75, recognizes our model cancer marker, the Human Epidermal growth factor Receptor 2 (HER2/neu) peptide, E75, bound to the MHC called Human Leukocyte Antigen-A2 (HLA-A2), with nanomolar affinity. The fE75 bound selectively to E75/HLA-A2 positive cancer cell lines in vitro. The fE75 Fab conjugated with (64)Cu selectively accumulated in E75/HLA-A2 positive tumors and not in E75/HLA-A2 negative tumors in an HLA-A2 transgenic mouse as probed using positron emission tomography/computed tomography (PET/CT) imaging. Considering that hundreds to thousands of different peptides bound to HLA-A2 are present on the surface of each cell, the fact that fE75 arrives at the tumor at all shows extraordinary specificity. These antibody fragments have great potential for diagnosis and targeted drug delivery in cancer.
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA.
Keith R
KR
Miller
Akiko
A
Koide
Brenda
B
Leung
Jonathan
J
Fitzsimmons
Bryan
B
Yoder
Hong
H
Yuan
Michael
M
Jay
Sachdev S
SS
Sidhu
Shohei
S
Koide
Edward J
EJ
Collins
D000818:Animals; D016466:CHO Cells; D045744:Cell Line, Tumor; D006224:Cricetinae; D015789:HLA-A2 Antigen / Q000378:metabolism; D006801:Humans; D007128:Immunoglobulin Fragments / Q000276:immunology* / Q000378:metabolism*; D051379:Mice; D010455:Peptides; D011485:Protein Binding; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000276:immunology* / Q000378:metabolism*
D015789:HLA-A2 Antigen; D007128:Immunoglobulin Fragments; D010455:Peptides; D018719:Erb-b2 Receptor Tyrosine Kinases; D011948:Receptors, Antigen, T-Cell