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Local Fas/APO-1 (CD95) ligand-mediated tumor cell killing in vivo
A Rensing-Ehl1, K Frei, R Flury
1Department of Internal Medicine, University Hospital, Zürich, Switzerland.
Abstract:
Fas/APO-1 (CD95) is a cell surface receptor which mediates apoptosis when ligated by specific antibodies or by its recently cloned natural ligand, FasL. We have studied the cytotoxic potential of FasL in vivo using Fas/APO-1-expressing Yac-1 cells as targets. Supernatant harvested from Neuro-2a cells transfected with the murine FasL cDNA contains FasL and transduces a potent apoptotic signal to Yac-1 cells in vitro. Specificity of FasL-mediated cytotoxicity was confirmed by competition assays using soluble Fas or anti-Fas/APO-1 F(ab')2 fragments which specifically interfere with FasL-Fas/APO-1 interactions. Intraperitoneal injection of FasL-containing supernatant efficiently killed Yac-1 target cells which had been implanted in capsules into the peritoneal cavity of mice. Analysis of the target cells revealed DNA fragmentation and nuclear changes typical of apoptosis. As previously shown, intraperitoneal injection of anti-Fas/APO-1 antibodies caused liver failure (Ogasawara, J., Watanabe, F.R., Adachi, M., Matsuzawa, A., Kasugai, T., Kitamura, Y., Itoh, N., Suda, T. and Nagata, S., Nature 1993. 364:806) and was observed at doses which did not reduce Yac-1 cell viability. In contrast, FasL did not induce histopathology in the liver when applied intraperitoneally at doses cytotoxic for Yac-1 cells. However, intravenous administration of FasL induced lethal liver hemorrhages and hepatocyte apoptosis. Thus, locally applied FasL kills tumor cells very efficiently without systemic toxicity and may therefore represent a candidate for local tumor treatment.
Insights
Locally administered FasL (Fas ligand) effectively kills tumor cells via apoptosis without causing systemic toxicity. This makes FasL a promising candidate for local tumor treatment strategies.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Fas/APO-1 (CD95) is a cell surface receptor that triggers apoptosis upon binding its ligand, FasL.
- FasL has been identified as the natural ligand for Fas/APO-1, mediating programmed cell death.
Purpose of the Study:
- To investigate the in vivo cytotoxic potential of FasL against Fas/APO-1 expressing target cells.
- To evaluate the safety and efficacy of FasL as a potential agent for local tumor treatment.
Main Methods:
- Utilized Neuro-2a cells transfected with murine FasL cDNA to generate FasL-containing supernatant.
- Assessed FasL-mediated cytotoxicity in vitro using Yac-1 cells and in vivo via intraperitoneal injection into mice with encapsulated Yac-1 cells.
- Confirmed specificity using soluble Fas and anti-Fas/APO-1 F(ab')2 fragments in competition assays.
- Analyzed target cells for DNA fragmentation and nuclear changes indicative of apoptosis.
Main Results:
- FasL-containing supernatant induced potent apoptosis in Yac-1 cells in vitro.
- Intraperitoneal injection of FasL efficiently killed encapsulated Yac-1 target cells in vivo, with observed DNA fragmentation and nuclear apoptosis.
- Unlike anti-Fas/APO-1 antibodies, local FasL administration did not cause liver histopathology at cytotoxic doses for Yac-1 cells.
- Intravenous FasL administration, however, resulted in lethal liver hemorrhages and hepatocyte apoptosis.
Conclusions:
- Locally applied FasL demonstrates efficient tumor cell killing through apoptosis with minimal systemic toxicity.
- FasL represents a potential therapeutic candidate for localized tumor treatment.
- Systemic administration of FasL carries risks, including liver damage, highlighting the importance of targeted delivery.