Abstract
The interferon-induced, double-stranded RNA-dependent protein kinase (PKR) can play critical roles in inhibiting virus replication and inducing apoptosis. To develop new agents that may inhibit viral replication or induce apoptosis in cancer cells via the PKR signaling pathway, we screened a chemical library for compounds that have differential cytotoxic effects on wild-type [mouse embryonic fibroblast (MEF)/PKR(+/+)] and PKR-knockout [MEF/PKR(-/-)] mouse embryonic fibroblast cells. We identified a synthetic compound, BEPP [1H-benzimidazole1-ethanol,2,3-dihydro-2-imino-a-(phenoxymethyl)-3-(phenylmethyl)-,monohydrochloride], that induces a cytotoxic effect more effectively in MEF/PKR(+/+) cells than in MEF/PKR(-/-) cells. BEPP also relatively effectively inhibited the growth of a human lung cancer cell line overexpressing PKR, compared with other cancer cell lines. In sensitive cells, BEPP induced apoptosis with activation of caspase-3. Treatment with BEPP led to increased phosphorylation of PKR and eIF2α, increased expression of BAX, and decreased expression of Bcl-2. BEPP-induced apoptosis was PKR dependent and was blocked by the adenovector expressing the dominant-negative PKR. Furthermore, pretreatment of HeLa cells at a noncytotoxic dose of BEPP effectively inhibited Vaccinia virus replication. Together, our results suggest that BEPP and its analogs may induce PKR-dependent apoptosis and inhibition of viral replication and that they can be a potential anticancer or anti-virus agent.
Footnotes
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This work was supported in part by the National Institutes of Health National Cancer Institute [Grant 5R01-CA092487-05, 5P50CA070907-100007 Lung SPORE Developmental Award]; the National Institutes of Health [Grant 3P30-CA016672-32S3]; Lockton grant-matching funds; the Homer Flower Gene Therapy Research Fund; the Charles Rogers Gene Therapy Fund; the Flora and Stuart Mason Lung Cancer Research Fund; the Charles B. Swank Memorial Fund for Esophageal Cancer Research; the George O. Sweeney Fund for Esophageal Cancer Research; the Phalan Thoracic Gene Therapy Fund; and the M.W. Elkins Endowed Fund for Thoracic Surgical Oncology.
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doi:10.1124/jpet.108.141754.
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ABBREVIATIONS: dsRNA, double-stranded RNA; PKR, double-stranded RNA-dependent protein kinase; MEF, mouse embryonic fibroblast; BEPP, 1H-benzimidazole-1-ethanol,2,3-dihydro-2-imino-a-(phenoxymethyl)-3-(phenylmethyl)-,monohydrochloride; HBE, human bronchial epithelial; BECC, 1H-benzimidazole-1-ethanol,α-[(4-chlorophenoxy)methyl]-3-[(4-chlorophenyl)methyl]-2,3-dihydro-2-imino-,monohydrochloride; DMSO, dimethyl sulfoxide; JNK, c-Jun NH2-terminal kinase; SRB, sulforhodamine B; PBS, phosphate-buffered saline; TCID50, median tissue culture infective dose; MOI, multiplicity of infection; Akt, protein kinase B; PACT, a protein activator of double-stranded RNA-dependent protein kinase.
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The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material. - Received June 3, 2008.
- Accepted December 8, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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Double-Stranded RNA-Dependent Protein Kinase-Dependent Apoptosis Induction by a Novel Small Compound
