abstract book - Clostridia

RECOMBINANT CLOSTRIDIUM ACETOBUTYLICUM EXPRESSING C.PERFRINGENS ENTEROTOXIN (CPE) FOR TREATMENT OFPANCREATIC CANCERS. König 1 , D. Meisohle 1 , G. Box 1 and P. Dürre 1 .1 Mikrobiologie und Biotechnologie, Universität Ulm, 89069 Ulm, Germany.Pancreatic cancer carries the most dismal prognosis of all solid tumours. Dueto the late clinical presentation, most patients only undergo palliativetreatment. Genetically modified clostridia open a new possibility of antitumourtreatment with enormous potential. Clostridial spores germinate onlyin the hypoxic regions of solid tumours and can deliver reactive agentsdirectly to their targets. CPE is one of the 15 toxins known from Clostridiumperfringens, is produced and released during the sporulation phase, andcauses food borne diarrhea. The toxin was shown to target claudin receptors,which are 1000fold overexpressed in many pancreatic carcinoma cell lines.The binding of CPE to these receptors results in the formation of pores thatultimately cause cell death. Clostridium acetobutylicum DSM 792 wastransformed with a vector carrying the gene for Clostridium perfringensenterotoxin, fused with a signal peptide sequence, and controlled by thebdhA promotor promoter. The modified strain produced and secreted 500ng/ml of the toxin into the surrounding medium. This production isindependent of sporulation and starts in the early exponential growth phase.The levels of production were sufficient to cause cell death in cytotoxicitytests with a pancreatic carcinoma cell line, but proved to be too low fortherapy in an in vivo mouse model. Current work focuses on improvedexpression.