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Molecular and Cellular Biology, November 1998, p. 6493-6504, Vol. 18, No. 11
Department of Microbiology & Immunoogy,1
Greenebaum Cancer
Center,2
Molecular and Cellular
Biology Program,4 and
Program in
Oncology,
Received 12 March 1998/Returned for modification 5 May
1998/Accepted 3 August 1998
Interferons (IFNs) and retinoids are potent biological response
modifiers. By using JAK-STAT pathways, IFNs regulate the expression of
genes involved in antiviral, antitumor, and immunomodulatory actions.
Retinoids exert their cell growth-regulatory effects via nuclear
receptors, which also function as transcription factors. Although these
ligands act through distinct mechanisms, several studies have shown
that the combination of IFNs and retinoids synergistically inhibits
cell growth. We have previously reported that
IFN-
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Thioredoxin Reductase Mediates Cell Death Effects
of the Combination of Beta Interferon and Retinoic Acid
-all-trans-retinoic acid (RA) combination is a more potent growth suppressor of human tumor xenografts in vivo than either
agent alone. Furthermore, the IFN-RA combination causes cell death in
several tumor cell lines in vitro. However, the molecular basis for
these growth-suppressive actions is unknown. It has been suggested that
certain gene products, which mediate the antiviral actions of IFNs, are
also responsible for the antitumor actions of the IFN-RA combination.
However, we did not find a correlation between their activities and
cell death. Therefore, we have used an antisense knockout approach to
directly identify the gene products that mediate cell death and have
isolated several genes associated with retinoid-IFN-induced mortality
(GRIM). In this investigation, we characterized one of the GRIM cDNAs,
GRIM-12. Sequence analysis suggests that the GRIM-12 product is
identical to human thioredoxin reductase (TR). TR is
posttranscriptionally induced by the IFN-RA combination in human breast
carcinoma cells. Overexpression of GRIM-12 causes a small amount of
cell death and further enhances the susceptibility of cells to
IFN-RA-induced death. Dominant negative inhibitors directed against TR
inhibit its cell death-inducing functions. Interference with TR
enzymatic activity led to growth promotion in the presence of the
IFN-RA combination. Thus, these studies identify a novel function for TR in cell growth regulation.
*
Corresponding author. Mailing address: Department of
Microbiology & Immunology, Greenebaum Cancer Center, University
of Maryland School of Medicine, Baltimore, MD 21201. Phone:
(410) 328-1396. Fax: (410) 328-1397. E-mail:
dkalvako{at}umaryland.edu.
Molecular and Cellular Biology, November 1998, p. 6493-6504, Vol. 18, No. 11
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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