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Enhanced in vitro macrophage cytotoxicity against interferon-treated B16 melanoma cells
C M Fleischmann1, W R Fleischmann
1Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, USA.
Abstract:
Resistance to the in vitro antiproliferative effects of INF-alpha rapidly develops in mouse B16 melanoma cells that are maintained in vitro in IFN-alpha (B16 alpha res cells). B16 alpha res cells, however, are significantly more sensitive to the antitumor effects of IFN-alpha when they are injected into mice. This enhanced sensitivity appears to be due, at least in part, to activated macrophages. To investigate enhanced macrophage sensitivity of B16 alpha res cells, macrophage-mediated cytotoxicity assays have been performed using both B16 and B16 alpha res cell targets. Thioglycollate-elicited peritoneal macrophages activated in vitro with IFN-gamma exhibited dose-dependent cytotoxicity against both B16 and B16 alpha res cells, but significantly higher levels of cytotoxicity occurred with B16 alpha res targets. Kinetics experiment results showed that the cytolytic effects against B16 alpha res cells occurred at a very much faster rate than the cytolytic effects against B16 cells (50% cytotoxicity with 2 h of incubation versus 40% cytotoxicity by 24 h, respectively). Finally, peritoneal macrophages from B16-inoculated mice also were significantly more cytotoxic against B16 alpha res cells than against B16 cells. Macrophages from B16 alpha res-inoculated mice were significantly more cytotoxic against B16 alpha res cells than were macrophages from B16-inoculated mice. Taken together, these observations provide in vitro evidence to support the suggestion that peritoneal macrophages are important mediators of the enhanced host-mediated antitumor effects against B16 alpha res cells.
Insights
Mouse melanoma cells resistant to interferon-alpha (IFN-alpha) in vitro show enhanced sensitivity to its antitumor effects in vivo. This heightened response is mediated by activated macrophages, crucial for host- antitumor activity.
Area of Science:
- Immunology
- Cancer Biology
- Cell Biology
Background:
- Mouse B16 melanoma cells develop resistance to interferon-alpha (IFN-alpha) in vitro.
- These resistant cells (B16 alpha res) exhibit increased sensitivity to IFN-alpha's antitumor effects when grown in vivo.
- Activated macrophages are implicated as a key factor in this enhanced host-mediated antitumor response.
Purpose of the Study:
- To investigate the role of macrophages in the enhanced sensitivity of B16 alpha res cells to IFN-alpha.
- To compare the cytotoxic effects of activated macrophages on both B16 and B16 alpha res melanoma cells.
Main Methods:
- Macrophage-mediated cytotoxicity assays were performed using B16 and B16 alpha res cells as targets.
- Thioglycollate-elicited peritoneal macrophages were activated in vitro with IFN-gamma.
- Peritoneal macrophages were also isolated from B16- and B16 alpha res-inoculated mice.
Main Results:
- IFN-gamma-activated macrophages exhibited dose-dependent cytotoxicity against both cell types, with significantly higher efficacy against B16 alpha res cells.
- Cytolytic effects against B16 alpha res cells occurred at a faster rate compared to B16 cells.
- Macrophages from B16- and B16 alpha res-inoculated mice showed greater cytotoxicity against B16 alpha res cells, with macrophages from B16 alpha res-inoculated mice being more potent.
Conclusions:
- These in vitro findings support the role of peritoneal macrophages as important mediators of enhanced host-mediated antitumor effects against IFN-alpha-resistant melanoma cells.
- Activated macrophages contribute significantly to the improved therapeutic outcomes observed with IFN-alpha in vivo despite in vitro resistance.