Hapten-directed targeting to single-chain antibody receptors

Tian Lu Cheng, Kuang-Wen Liao, Shey-Cherng Tzou, Chiu Min Cheng, Bing Mae Chen, Steve R. Roffler*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Artificial recombinant receptors may be useful for selectively targeting imaging and therapeutic agents to sites of gene expression. To evaluate this approach, we developed transgenes to express highly on cells a single-chain antibody (scFv) against the hapten 4-ethoxymethylene-2-phenyl-2-oxazoline-5-one (phOx). A phOx enzyme conjugate was created by covalently attaching phOx molecules to polyethylene glycol (PEG)-modified β-glucuronidase. Cells expressing phOx scFv but not control scFv receptors were selectively killed after exposure to β-glucuronidase derivatized with phOx and PEG (phOx-βG-PEG) and a glucuronide prodrug (p-hydroxy aniline mustard β-D-glucuronide, HAMG) of p-hydroxyaniline mustard. Targeted activation of HAMG produced bystander killing of receptor-negative cells in mixed populations containing as few as 10% phOx-receptor-positive cells. Functional phOx scFv receptors were stably expressed on B16-F1 melanoma tumors in vivo. Treatment of mice bearing established phOx-receptor-positive tumors with phOx-βG-PEG and HAMG significantly (P≤.0005) suppressed tumor growth as compared with treatment with βG-PEG and HAMG or prodrug alone. phOx was unstable in the serum, suggesting alternative haptens may be more suitable for in vivo applications. Our results show that therapeutic agents can be targeted to artificial hapten receptors in vitro and in vivo. The expression of artificial receptors on target cells may allow preferential delivery of therapeutic or imaging molecules to sites of transgene expression.

Original languageEnglish
Pages (from-to)380-388
Number of pages9
JournalCancer Gene Therapy
Issue number5
StatePublished - May 2004


  • Bystander killing
  • Chimeric protein
  • Hapten
  • Prodrug
  • Single-chain antibody
  • phOx


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