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Tumor-bearing animals contain suppressed antitumor effectors the function of which can be unmasked by IL-2
S Salvadori1, F M Rosenthal, K Cronin
1Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029.
Abstract:
CMS5 fibrosarcoma cells were infected with retroviral constructs containing interleukin-2 (IL-2) cDNA and selected in G418. Parental tumor cells and those that produced IL-2 were injected in vivo. Whereas injection of parental tumor cells resulted in progressive tumor growth, those secreting high levels of IL-2 were rejected. Furthermore, the immunosuppression associated with inoculation of parental tumor cells was not seen. To understand the failure of mice to reject non-IL-2-secreting tumor cells, functional responses of spleen cells from immune and tumor-bearing mice were studied in vitro. As expected, immune spleen cells proliferated under a variety of conditions but were inhibited in the presence of parental tumor cells. Even spleen cells from tumor-bearing animals responded well in the absence of parental tumor cells or in the presence of parental tumor cells, if supplied with adequate levels of IL-2. These results suggest that both tumor-bearing and immune mice generate antitumor effectors but that the cells might be functionally suppressed because of their inability to secrete IL-2 after contact with parental tumor cells.
Insights
Tumor cells engineered to secrete interleukin-2 (IL-2) were rejected by mice, unlike parental cells. This suggests IL-2 is crucial for overcoming tumor-induced immune suppression and enabling anti-tumor responses.
Area of Science:
- Immunology
- Cancer Biology
- Molecular Biology
Background:
- Tumor cells can evade immune detection and rejection.
- Interleukin-2 (IL-2) is a critical cytokine for immune cell function.
- Understanding immune suppression in cancer is vital for developing effective therapies.
Purpose of the Study:
- To investigate the role of IL-2 secretion in tumor rejection.
- To determine if IL-2 can overcome tumor-induced immunosuppression.
- To analyze the functional responses of immune cells in the context of tumor growth.
Main Methods:
- Retroviral transduction of CMS5 fibrosarcoma cells with IL-2 cDNA.
- In vivo injection of parental and IL-2-secreting tumor cells into mice.
- In vitro assessment of spleen cell proliferation and function from immune and tumor-bearing mice.
Main Results:
- IL-2 secreting tumor cells were rejected, while parental cells caused progressive tumor growth.
- Immunosuppression observed with parental tumor cells was absent in IL-2 secreting tumors.
- Spleen cells from tumor-bearing mice showed restored function with exogenous IL-2.
- Immune spleen cells were inhibited by parental tumor cells but not by IL-2 secreting cells.
Conclusions:
- Tumor cells secreting IL-2 can elicit an anti-tumor immune response and prevent tumor growth.
- IL-2 is essential for overcoming tumor-induced immune suppression.
- The generation of anti-tumor effector cells is possible in tumor-bearing hosts, but their function is dependent on IL-2 availability.