Sensitization of human colon cancer cells to TRAIL-mediated apoptosis
A Hernandez1, Q D Wang, S A Schwartz
1Department of Surgery, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0536, USA.
Abstract:
TNF-related apoptosis-inducing ligand (TRAIL), a novel member of the tumor necrosis factor (TNF) family, is thought to induce apoptosis preferentially in cancer cells; however, increasing evidence suggests that a number of cancers are resistant to TRAIL treatment. FLICE-like inhibitory protein (FLIP), which structurally resembles caspase-8, can act as an inhibitor of apoptosis when expressed at high levels in certain cancer cells. The purpose of our present study was to determine whether human colon cancer cells are sensitive to TRAIL treatment and, if not, to identify potential mechanisms of resistance. Colon cancer cells of different metastatic potential (KM12C, KML4A, and KM20) were found to be resistant to the effects of TRAIL when used as a single agent. FLIP expression levels were increased in all three KM cell lines. Treatment with either actinomycin D (Act D;10 :g/ml) or cycloheximide (CHX; 10 :g/ml) decreased FLIP expression levels in all three cell lines. The decrease in cellular levels of FLIP was associated with sensitization to TRAIL-mediated apoptosis, as demonstrated by enhanced cell death and caspase-3 activity compared with either Act D or CHX alone. Our findings suggest that reduction of FLIP levels by Act D or CHX renders TRAIL-resistant human colon cancer cells sensitive to TRAIL-mediated apoptosis. The combination of TRAIL along with agents such as Act D or CHX, which target proteins that prevent cell death, may provide a more effective and less toxic regimen for treatment of resistant colon cancers.
Insights
Human colon cancer cells resistant to TRAIL therapy can be sensitized by reducing FLICE-like inhibitory protein (FLIP) levels. Combining TRAIL with actinomycin D or cycloheximide enhances apoptosis in resistant cancer cells.
Area of Science:
- Oncology
- Molecular Biology
- Cell Death Research
Background:
- Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptosis in cancer cells.
- Cancer cells can develop resistance to TRAIL therapy.
- FLICE-like inhibitory protein (FLIP) inhibits apoptosis and is upregulated in some cancers.
Purpose of the Study:
- To investigate TRAIL sensitivity in human colon cancer cells.
- To identify mechanisms of TRAIL resistance in colon cancer.
- To explore strategies to overcome TRAIL resistance.
Main Methods:
- Assessed TRAIL sensitivity in KM12C, KML4A, and KM20 colon cancer cell lines.
- Measured FLIP expression levels in colon cancer cells.
- Treated cells with actinomycin D (Act D) or cycloheximide (CHX) to reduce FLIP levels.
- Evaluated TRAIL-mediated apoptosis and caspase-3 activity following combined treatments.
Main Results:
- Colon cancer cell lines (KM12C, KML4A, KM20) were resistant to TRAIL as a single agent.
- Elevated FLIP expression was observed in all tested colon cancer cell lines.
- Actinomycin D and cycloheximide treatment reduced FLIP levels.
- Reduced FLIP levels sensitized colon cancer cells to TRAIL-induced apoptosis, increasing cell death and caspase-3 activity.
Conclusions:
- FLIP upregulation contributes to TRAIL resistance in human colon cancer.
- Reducing FLIP levels via Act D or CHX resensitizes TRAIL-resistant colon cancer cells.
- Combination therapy of TRAIL with FLIP-reducing agents may offer a novel treatment strategy for resistant colon cancers.
