Pancreatic carcinoma is the fifth leading cause of
cancer-related deaths in North America and Europe. Major reasons for the high mortality rate include the inability to detect
pancreatic cancer at an early stage, extensive local invasion, and early formation of lymphatic and hematogenous
metastases. Consequently, novel and effective
therapies need to be developed urgently in order to improve the outcome of patients. Since overexpression of the
epidermal growth factor receptor (EGFR) in pancreatic
tumors correlates with advanced clinical staging, increased
tumor size and reduced patient survival, this receptor represents an appropriate target for
immunotherapy. We recently generated the recombinant
immunotoxin 425(scFv)-ETA' by genetically fusing the anti-EGFR
single chain variable fragment 425(scFv) to a truncated version of Pseudomonas aeroginosa
exotoxin A (ETA'). The
425(scFv)-ETA' fusion
protein was functionally expressed in the periplasmic space of Escherichia coli and was purified using a combination of
metal-ion affinity and
anion exchange chromatography. The
protein showed specific binding to and toxicity against the EGFR-positive, metastatic
pancreatic carcinoma cell line L3.6pl, but not to control cell systems. We report the anti-
tumor activity of this recombinant
immunotoxin in a disseminated human
pancreatic cancer nude mouse model. After intravenous (i.v.) injection of L3.6pl cells into immunodeficient nude mice, both single (20 microg on day 1 after challenge) and repeated (10 microg on days 1, 2, 3 and 4 after
tumor cell injection) i.v. administration of
425(scFv)-ETA' resulted in a significant reduction in the average number of lung
metastases from 56.25 per animal in the control groups to 0.875 per animal (single injection) and 0.286 per animal (repeated injection), respectively, in the experimental groups. In summary, this is the first report showing an in vivo anti-
tumor effect caused by the recombinant
immunotoxin 425(scFv)-ETA' against disseminated growing metastatic human
pancreatic carcinoma cells. Our data suggest that EGFR-specific antibody toxins could be suitable for further clinical investigation in the development of
therapies for
pancreatic carcinoma.