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Induction of tumor necrosis factor expression and resistance in a human breast tumor cell line
Abstract:
Tumor necrosis factor (TNF) is a polypeptide cytokine that is cytotoxic to some but not all tumor cells. The basis for resistance to the cytotoxic effects of this agent remains unclear. We have studied the development of TNF resistance in human ZR-75-1 breast carcinoma cells. ZR-75-1 cells have undetectable levels of TNF RNA and protein. However, TNF transcripts are transiently induced in these cells by exposure to recombinant human TNF. This induction of TNF RNA is associated with production of TNF-like protein in cell lysates and culture supernatants. Stable resistance to TNF-induced cytotoxicity develops when ZR-75-1 cells are exposed to increased concentrations of TNF. The TNF-resistant cells, designated ZR-75-1R, continuously express TNF transcripts and a TNF-like protein. Furthermore, ZR-75-1R cell supernatants contain cytotoxic activity that is abrogated by polyclonal antibody against TNF. The ZR-75-1R cells also possess TNF receptors that are occupied or down-regulated by the TNF-like protein. These findings thus suggest that (i) TNF induces TNF transcripts and production of a TNF-like protein in ZR-75-1 cells and (ii) resistance to TNF-induced cytotoxicity is associated with stable TNF expression.
Insights
Tumor necrosis factor (TNF) resistance develops in breast cancer cells when they stably express TNF. This stable expression leads to the production of TNF-like proteins, causing resistance to TNF cytotoxicity.
Area of Science:
- Cancer Biology
- Immunology
- Cellular Signaling
Background:
- Tumor necrosis factor (TNF) is a cytokine with cytotoxic effects on some tumor cells.
- The mechanisms underlying resistance to TNF cytotoxicity are not fully understood.
- ZR-75-1 breast carcinoma cells exhibit variable sensitivity to TNF.
Purpose of the Study:
- To investigate the development of resistance to TNF-induced cytotoxicity in ZR-75-1 breast carcinoma cells.
- To elucidate the molecular mechanisms associated with TNF resistance.
- To characterize the properties of TNF-resistant ZR-75-1 cells.
Main Methods:
- Exposure of ZR-75-1 cells to increasing concentrations of recombinant human TNF.
- Analysis of TNF RNA and protein expression in sensitive and resistant cells.
- Assessment of cytotoxic activity in cell supernatants using antibody neutralization.
- Evaluation of TNF receptor status in resistant cells.
Main Results:
- ZR-75-1 cells, initially sensitive to TNF, develop stable resistance (ZR-75-1R) upon prolonged TNF exposure.
- ZR-75-1R cells exhibit continuous expression of TNF transcripts and a TNF-like protein.
- Supernatants from ZR-75-1R cells contain TNF-like cytotoxic activity neutralized by anti-TNF antibody.
- Resistant cells show occupied or down-regulated TNF receptors due to endogenous TNF-like protein.
Conclusions:
- Tumor necrosis factor (TNF) can induce its own transcripts and protein production in sensitive breast cancer cells.
- Stable expression of TNF and associated TNF-like proteins is linked to acquired resistance to TNF-induced cytotoxicity.
- The findings suggest an autocrine mechanism contributing to TNF resistance in cancer cells.