title: SNAP-tag technology mediates site specific conjugation of antibody fragments with a photosensitizer and improves target specific phototoxicity in tumor cells.
abstract: Cancer cells can be killed by photosensitizing agents that induce toxic effects when exposed to nonhazardous light, but this also causes significant damage to surrounding healthy cells. The specificity of photodynamic therapy can be increased by conjugating photosensitizing agents to antibodies and antibody fragments that bind specifically to tumor cell antigens. However, standard conjugation reactions produce heterogeneous products whose targeting specificity and spectroscopic properties can be compromised. In this study, we used an antibody fragment (scFv-425) that binds to the epidermal growth factor receptor (EGFR) as a model to investigate the use of SNAP-tag fusions as an improved conjugation strategy. The scFv-425-SNAP-tag fusion protein allowed the specific conjugation of a chlorin e6 photosensitizer modified with O(6)-benzylguanine, generating a homogeneous product that was delivered specifically to EGFR(+) cancer cells and resulted in significant, tumor cell-specific cytotoxicity. The impact of our results on the development of photodynamic therapy is discussed.
authors: Department of Experimental Medicine and Immunotherapy, Institute of Applied Medical Engineering, Helmholtz-Institute for Biomedical Engineering, Germany.
authors: Ahmad Fawzi
authors: AF
authors: Hussain
authors: Florian
authors: F
authors: Kampmeier
authors: Verena
authors: V
authors: von Felbert
authors: Hans-F
authors: HF
authors: Merk
authors: Mehmet Kemal
authors: MK
authors: Tur
authors: Stefan
authors: S
authors: Barth
mesh_terms: D045744:Cell Line, Tumor; D002735:Chlorophyllides; D016503:Drug Delivery Systems; D066246:ErbB Receptors / Q000378:metabolism; D015870:Gene Expression; D006147:Guanine / Q000031:analogs & derivatives / Q000737:chemistry; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology; D011166:Porphyrins / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D057127:Single-Chain Antibodies / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D002735:Chlorophyllides; D017319:Photosensitizing Agents; D011166:Porphyrins; D011993:Recombinant Fusion Proteins; D057127:Single-Chain Antibodies; C114035:scFv 425; C064976:O(6)-benzylguanine; C062985:phytochlorin; D006147:Guanine; D066246:ErbB Receptors