EGF receptor and p185erbB-2-specific single-chain antibody toxins differ in their cell-killing activity on tumor cells expressing both receptor proteins.
Many human tumors over-express erbB-2 and EGF receptors. The membrane localization of these receptor tyrosine kinases make them appropriate targets for directed tumor therapy. We have used recombinant DNA technology to produce single-chain antibody exotoxin A (scFv-ETA) fusion proteins which specifically bind the erbB-2 and EGF receptors. The scFv portion is composed of the heavy- and light-chain variable domains of monoclonal antibodies which recognize the extracellular portion of each receptor. We have previously described the anti-tumor activity of the bacterially produced scFv(FRP5)-ETA directed to the erbB-2 receptor. In this paper we describe the characteristics of scFv(225)-ETA, a protein which binds the EGF receptor. The bacterially produced recombinant protein binds to the receptor with high affinity and inhibits the in vitro growth of the EGF receptor over-expressing tumor cell lines A431 and MDA-MB468. Combination treatment with scFv-(FRP5)-ETA and scFv(225)-ETA led to an additive inhibitory effect on the in vitro growth of A431 cells. SKBR3 cells expressing low levels of EGF receptor but high levels of p185erbB-2 were not affected by scFv(225)-ETA treatment but were sensitive to scFv(FRP5)-ETA. Stimulation of SKBR3 cells and HCII RI#11 mouse mammary epithelial cells expressing the human erbB-2 with EGF led to an increase in scFv(FRP5)-ETA activity, showing that the EGF-induced activation of erbB-2 can potentiate the action of the erbB-2-directed toxin. Treatment of athymic nude mice with scFv(FRP5)-ETA and the combination of both scFv-ETA proteins led to the transient arrest of growth of established A431 tumors. scFv(225)-ETA treatment alone was the most effective, leading to tumor shrinkage during the course of treatment, whereas treatment with the parental monoclonal antibody 225 led to retarded tumor growth.
Wels
W
W
Friedrich Miescher Institute, Basel, Switzerland.
Beerli
R
R
Hellmann
P
P
Schmidt
M
M
Marte
B M
BM
Kornilova
E S
ES
Hekele
A
A
Mendelsohn
J
J
Groner
B
B
Hynes
N E
NE
D036002:ADP Ribose Transferases; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D001427:Bacterial Toxins; D001483:Base Sequence; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000648:ultrastructure*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000648:ultrastructure*; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D066246:ErbB Receptors / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D005098:Exotoxins / Q000235:genetics / Q000633:toxicity*; D005260:Female; D006801:Humans; D000922:Immunotoxins / Q000633:toxicity*; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000633:toxicity; D012680:Sensitivity and Specificity; D037521:Virulence Factors; D014846:Vulvar Neoplasms / Q000188:drug therapy* / Q000648:ultrastructure*; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins; D066246:ErbB Receptors; D005098:Exotoxins; D000922:Immunotoxins; D009363:Neoplasm Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A