Cytotoxic activities of a fusion protein comprised of TGFα and Pseudomonas exotoxin

Abstract

A cDNA encoding transforming growth factor type alpha (TGFα) was fused to the 5' end of a gene encoding a modified form of Pseudomonas exotoxin A (PE), which is devoid of the cell recognition domain (domain Ia). The chimeric molecule, termed TGFα-PE40, was expressed in Escherichia coli and isolated from the periplasm or inclusion bodies depending on the construction expressed. TGFα-PE40 was found to be extremely cytotoxic to cells displaying epidermal growth factor (EGF) receptors. Comparison with a similar molecule in which TGFa was placed at the carboxyl end of PE40 demonstrated the importance of the position of the cell recognition element; TGFα-PE40 was found to be about 30-fold more cytotoxic to cells bearing EGF receptors than PE40-TGFα. In addition, TGFα-PE40 was shown to be extremely cytotoxic to a variety of cancer cell lines including liver, ovarian, and colon cancer cell lines, indicating high levels of EGF receptor expression in these cells.—Siegall, C. B.; Xu, Y.-H.; Chaudhary, V. K.; Adhya, S.; FitzGerald, D.; Pastan, I. Cytotoxic activities of a fusion protein comprised of TGFα and Pseudomonas exotoxin. FASEB J. 3: 2647-2652; 1989.