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Published on: May 10, 2017
Interleukin (IL)-12 and IL-12 gene transfer up-regulate Fas expression in human osteosarcoma and breast cancer cells
E A Lafleur1, S F Jia, L L Worth
1Department of Cancer Biology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA.
Abstract:
Expression of Fas (CD95, APO-1), a cell surface receptor capable of inducing ligand-mediated apoptosis, is involved in tissue homeostasis and elimination of targeted cells by natural killer and T cells. Corruption of this pathway, such as reduced Fas expression, can allow tumor cells to escape elimination and promote metastatic potential. In this study, the status of Fas expression has been examined in the parental SAOS human osteosarcoma cells that do not metastasize and in selected variants that cause lung metastases in 16 weeks (LM2) or 8 weeks (LM6) after i.v. injection into nude mice. Fas expression correlated with the metastatic potentials of the three cell lines. Northern and fluorescence-activated cell-sorting analyses indicated that LM6 cells expressed Fas at a lower level than seen in the parental cells. Infection of the LM6 cells with an adenoviral vector containing the murine interleukin (IL)-12 gene (AD:mIL-12) or treatment with recombinant murine IL-12 resulted in a dose-dependent up-regulation of FAS: The up-regulation of Fas by IL-12 was also demonstrated in human etoposide-resistant MDA-MB-231 breast cancer cells. [(3)H]Thymidine growth inhibition studies indicated that the cell surface Fas induced after IL-12 exposure was functional and able to mediate cell death on cross-linking with anti-FAS: We also demonstrate that this effect is independent of IFN-gamma. Whereas these cell lines are sensitive to IFN-gamma, incubation with IFN-gamma does not increase susceptibility to Fas-mediated cell death, nor do these cells produce IFN-gamma with or without IL-12 treatment. We hypothesize that expression of Fas may play a role in the elimination of metastatic tumor cells in the lung, an organ in which Fas ligand is expressed. The antitumor activity of IL-12 may be secondary in part to its ability to up-regulate Fas expression on tumor cells, which subsequently increases immune-mediated destruction of osteosarcoma cells.
Insights
Reduced Fas expression in osteosarcoma cells promotes metastasis. Interleukin-12 (IL-12) treatment up-regulates Fas, enhancing immune-mediated tumor cell death.
Area of Science:
- Immunology
- Cancer Biology
- Molecular Biology
Background:
- Fas receptor (CD95, APO-1) mediates apoptosis crucial for tissue homeostasis and immune surveillance.
- Reduced Fas expression can enable tumor cells to evade immune elimination and enhance metastatic potential.
Purpose of the Study:
- To investigate the correlation between Fas expression and metastatic potential in human osteosarcoma cells.
- To determine the effect of interleukin-12 (IL-12) on Fas expression and function in metastatic cancer cells.
Main Methods:
- Analysis of Fas expression in parental and metastatic osteosarcoma cell lines (SAOS, LM2, LM6) using Northern and fluorescence-activated cell-sorting (FACS).
- Treatment of metastatic cells with adenoviral vector carrying murine IL-12 (AD:mIL-12) or recombinant murine IL-12.
- Assessment of Fas-mediated cell death via [(3)H]thymidine growth inhibition assays and cross-linking with anti-FAS antibodies.
- Evaluation of the role of interferon-gamma (IFN-γ) in IL-12-induced Fas-mediated apoptosis.
Main Results:
- Fas expression inversely correlated with the metastatic potential of osteosarcoma cell lines, with LM6 cells showing lower Fas levels.
- IL-12 treatment dose-dependently up-regulated Fas expression on LM6 osteosarcoma and MDA-MB-231 breast cancer cells.
- Induced cell surface Fas was functional, mediating cell death upon anti-FAS cross-linking, independent of IFN-γ.
- IFN-γ did not enhance susceptibility to Fas-mediated cell death or induce its production in these cell lines.
Conclusions:
- IL-12 up-regulates functional Fas expression on metastatic osteosarcoma and breast cancer cells.
- This IL-12-induced Fas up-regulation may contribute to the antitumor activity by increasing immune-mediated destruction of tumor cells.
- Fas expression likely plays a role in eliminating metastatic tumor cells, particularly in organs like the lung where Fas ligand is present.
