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Interferon regulatory factor-1 mediates interferon-gamma-induced apoptosis in ovarian carcinoma cells
Eun-Joo Kim1, Joon-Mo Lee, Sung-Eun Namkoong
1Department of Medical Bioscience, Graduate School, Catholic University, Seoul, Korea.
Abstract:
Interferon-gamma (IFN-gamma), as one of interferon family that regulates antiviral, antiproliferative, and immunomodulatory responses, has been implicated for the growth regulation of ovarian cancer cells. However, the molecular mechanisms are not yet fully defined. To analyze detailed mechanisms, the ovarian cancer cell lines (2774, PA-1, OVCAR-3, and SKOV-3) were treated with IFN-gamma. The growth of 2774 was most effectively suppressed than that of other cells in both time-course and dose-dependent experiments. The order of sensitivity in other cells was PA-1 >> OVCAR-3 > SKOV-3 (not responded at all). The DNA fragmentation and DAPI staining assays suggested that the IFN-gamma-mediated cytotoxicity could be triggered by apoptosis. The treatment induced IFN regulatory factor-1 (IRF-1) in two IFN-gamma-sensitive cells (2774, PA-1), whereas IRF-1 was not induced in two IFN-gamma-resistant cells (OVCAR-3, SKOV-3). The levels of p53 and p21WAF1 were not strikingly changed in all four cells. Interestingly, the expression of interleukin-converting enzyme (ICE, or caspase-1) was increased by the treatment in a kinetically consistent manner to the induction of IRF-1. However, CD95 (Fas/APO-1) was not changed. Apoptosis was greatly induced, when IRF-1 was transiently expressed in PA-1 without the treatment of IFN-gamma. However, it was repressed when IRF-1 together with IRF-2, an antagonist of IRF-1, were coexpressed. In addition, the effect of IFN-gamma was reduced in the 2774 and PA-1 cells stably expressing either IRF-1 antisense or IRF-2 sense, as shown by the cytotoxicity and FACS analysis. Furthermore, the IFN-gamma-induced apoptosis was greatly reduced, when inhibitors of ICE were treated into PA-1 cells. Taken together, these results suggest that IRF-1 directly mediates the IFN-gamma-induced apoptosis via the activation of caspase-1 gene expression in IFN-gamma-sensitive ovarian cancer cells.
Insights
Interferon-gamma (IFN-gamma) triggers apoptosis in sensitive ovarian cancer cells by activating Interferon Regulatory Factor-1 (IRF-1) and caspase-1. This research clarifies the molecular pathway of IFN-gamma
Area of Science:
- Immunology
- Molecular Biology
- Oncology
Background:
- Interferon-gamma (IFN-gamma) regulates cellular responses and impacts ovarian cancer growth.
- The precise molecular mechanisms of IFN-gamma's effect on ovarian cancer remain incompletely understood.
Purpose of the Study:
- To elucidate the molecular mechanisms by which IFN-gamma influences ovarian cancer cell growth and survival.
- To investigate the role of key regulatory factors and apoptotic pathways in IFN-gamma's anti-cancer effects.
Main Methods:
- Ovarian cancer cell lines were treated with IFN-gamma.
- Assays included DNA fragmentation, DAPI staining, Western blotting (for IRF-1, p53, p21WAF1, ICE, CD95), transient and stable gene expression, and caspase inhibition.
- Flow cytometry (FACS) was used to analyze apoptosis.
Main Results:
- IFN-gamma effectively suppressed the growth of specific ovarian cancer cell lines (2774, PA-1) but not others (OVCAR-3, SKOV-3).
- Sensitivity correlated with the induction of Interferon Regulatory Factor-1 (IRF-1) and caspase-1 (ICE), suggesting apoptosis induction.
- IRF-1 expression alone induced apoptosis, while coexpression with IRF-2 repressed it. Caspase-1 inhibition reduced IFN-gamma-induced apoptosis.
Conclusions:
- IFN-gamma induces apoptosis in sensitive ovarian cancer cells through the IRF-1 pathway.
- Activation of caspase-1 gene expression is a critical downstream event mediated by IRF-1.
- These findings highlight IRF-1 as a key mediator in IFN-gamma's anti-ovarian cancer activity.