Role for the double-stranded RNA-activated protein kinase PKR in Ad-TNF-alpha gene therapy in esophageal cancer.

Abstract

BACKGROUND:

Tumor necrosis factor alpha (TNF-alpha) is a cytokine with direct antitumor activity. Clinical trials with TNF-alpha have been limited because of the severe side effects of systemic administration. Gene therapy with an adenoviral vector allows delivery of high local doses of TNF-alpha. Activation of protein kinase R (PKR) has been implicated as a general transducer of apoptosis in response to a variety of different stimuli including TNF-alpha. We, therefore, evaluated the role of PKR in Ad-TNF-alpha-induced apoptosis in esophageal cancer cells.

METHODS:

A tetracycline-responsive adenoviral vector was used to transfect the TNF-alpha gene (Ad-TNF-alpha) into human esophageal cancer cell lines Bic1, Seg1 and TT, as well as in transformed PKR(+/+) and PKR(-/-) early-passage mouse embryo fibroblasts. Ad-luciferase, Ad-Bak, and mock infection with phosphate buffered saline solution were used as controls. Gene expression was determined by Western blot analysis. Apoptosis was detected by propidium iodide staining and fluorescence-activated cell sorter analysis.

RESULTS:

Overexpression of TNF-alpha in the lysate was evident in all cell lines treated with Ad-TNF-alpha. Treatment with Ad-TNF-alpha was associated with PKR upregulation and induction of apoptosis. Inhibition of TNF-alpha expression by tetracycline resulted in downregulation of PKR and decreased apoptosis. Transduction of PKR(+/+) and PKR(-/-) mouse embryo fibroblasts with Ad-TNF-alpha demonstrated that Ad-TNF-alpha-induced apoptosis was mediated in part through a PKR-dependent process.

CONCLUSIONS:

These results suggest that Ad-TNF-alpha-mediated apoptosis in esophageal cancer cell lines is dependent in part on PKR upregulation. Strategies to enhance PKR upregulation may allow increased Ad-TNF-alpha antitumoral activity in the treatment of esophageal cancer.

• Authors: Urs von Holzen, Dora Bocangel, Abujiang Pataer, Stephan A Vorburger, Yanna Liu, Xialolin Lu, Kelly K Hunt, Stephen G Swisher
• Journal: Surgery (Surgery) Vol. 138 Issue 2 Pg. 261-8 (Aug 2005) ISSN: 0039-6060 [Print] United States
• PMID: 16153435 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Culture Media, Conditioned
• RNA, Double-Stranded
• Tetracyclines
• Tumor Necrosis Factor-alpha
• eIF-2 Kinase

Topics

• Adenocarcinoma (therapy)
• Adenoviridae (genetics)
• Apoptosis
• Cell Line, Tumor
• Culture Media, Conditioned
• Esophageal Neoplasms (therapy)
• Gene Expression Regulation, Neoplastic (drug effects)
• Genetic Therapy (methods)
• Humans
• Phosphorylation
• RNA, Double-Stranded (metabolism)
• Tetracyclines (pharmacology)
• Tumor Necrosis Factor-alpha (genetics)
• Up-Regulation
• eIF-2 Kinase (metabolism)