130. Targeting of Adenovirus Vectors to Mesothelin Via a Bispecific Antibody Reveals Enhanced Gene Transfer to Human Pancreatic Cancer Cells

Abstract

Pancreatic cancer is the 5th leading cause of cancer death in the Western world with no effective treatment yet. Adenoviral (Ad) 5 vectors have been studied for gene delivery into human pancreatic cancer, showing that wild type Ad5 has a limited transduction efficiency. Since the extracellular mesothelin protein is upregulated on primary human pancreatic cancer cells (Argani et al. (2001) Clin Canc Res 7, 3862), while no or limited expression is detected on normal pancreatic cells, we chose to target Ad5 to this surface antigen by using the bispecific antibody approach. We cloned the cDNA encoding for the single-chain and bispecific antibody that binds to mesothelin into an expression vector, and produced the bispecific antibody that binds both to adenovirus fiber knob and to mesothelin. Ad5 could indeed be targeted to mesothelin expressing OVCAR-3 control cells as shown by improved transduction with Ad5CMVGFP complexed with bispecific antibody compared to wt Ad5CMVGFP without bispecific antibody. Subsequently, two near primary and four established pancreatic cancer cells were infected with the AdCMVGFP-bispecific antibody complex, in the presence or in the absence of Ad5 fiber protein and single-chain antibody. It was shown that adenovirus complexed with bispecific antibody revealed a significant enhanced gene transfer to one established and two near primary CAR negative and mesothelin positive pancreatic carcinoma cells, compared to wt Ad5. This effect could be prevented by competitive pre-incubation of the cells with the single-chain antibody. We conclude that adenovirus vectors complexed with bispecific antibody directed to mesothelin can enter mesothelin expressing pancreatic tumor cells with a high efficiency and efficacy compared to wt Ad5, suggesting that mesothelin might be a promising antigen for targeted adenoviral gene therapy of pancreatic cancer.