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TRAIL-induced apoptosis of thyroid cancer cells: potential for therapeutic intervention
1Department of Biological and Medical Research, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
Abstract:
To determine whether the apoptotic machinery of thyroid cancer cells is functional and could be activated for tumoricidal purposes, we examined the apoptosis induced by the cytokines TNF-alpha, Fas and TRAIL in thyroid cancer cell lines, NPA and SW579. Interestingly, out of these cytokines, only TRAIL was able to trigger significant apoptosis. The tumoricidal effect of TRAIL was further enhanced by CHX, suggesting the presence of CHX-sensitive inhibitor(s) of apoptosis in these thyroid cancer cell lines. The anti-apoptotic proteins like FLAME-1, Bcl-2 and Bcl-xL are believed to be such CHX-sensitive inhibitors in various types of cancer cells. We, however, provide the evidence using NPA and SW579 cell lines that these proteins were not affected by the CHX treatment in thyroid cancer cells. The apoptosis of thyroid cancer cells was mediated by the classical activation of caspases that in turn activated the DNA Fragmentation Factor (DFF-45). To elucidate the role of individual caspases in TRAIL-mediated apoptosis, the inhibitory effects of several general and specific tetrapeptide caspase inhibitors were studied. The inhibitors of caspase-1, -6, -8, and -9 as well as general upstream inhibitors of apoptosis could dramatically inhibit TRAIL-induced apoptosis in thyroid cancer cells. Caspase-2 and -3 inhibitors, on the other hand, had no significant effect. When the cells were treated with either agonistic Fas antibody (CH11) or TNF-alpha, no apoptotic changes were observed. The apoptosis induced by agonistic Fas Ab could be seen only after a prolonged exposure (24 h) to CHX, whereas TNF-alpha had no effect even in the presence of CHX. The efficacy of TRAIL was also tested on other types of thyroid cancer cells like ARO, FRO (anaplastic carcinoma) and TPC-1 (papillary carcinoma) and compared to that triggered by other death inducing cytokines FasL and TNF-alpha. Again TRAIL was more potent in triggering apoptosis than Fas and TNF-alpha. Since TRAIL is effective in selectively killing thyroid tumor cells without affecting normal thyrocytes and also does not cause organ toxicity and inflammation in vivo, its potential for the treatment of thyroid cancer seems very promising.
Insights
Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) effectively induces apoptosis in thyroid cancer cells, offering a promising therapeutic avenue. This targeted cell death mechanism bypasses common inhibitors and shows potential for selective cancer treatment.
Area of Science:
- Oncology
- Molecular Biology
- Cell Death Research
Background:
- Thyroid cancer cell lines NPA and SW579 were investigated to assess their apoptotic machinery's functionality.
- The study aimed to determine if apoptosis could be therapeutically activated for tumoricidal effects in thyroid cancer.
Purpose of the Study:
- To evaluate the efficacy of Tumor Necrosis Factor-alpha (TNF-alpha), Fas, and TRAIL in inducing apoptosis in thyroid cancer cells.
- To identify potential inhibitors of apoptosis in thyroid cancer and elucidate the role of caspases in TRAIL-mediated cell death.
Main Methods:
- Thyroid cancer cell lines (NPA, SW579, ARO, FRO, TPC-1) were treated with TNF-alpha, Fas, and TRAIL.
- Cycloheximide (CHX) was used to identify CHX-sensitive apoptosis inhibitors.
- Caspase inhibitors (general and specific) were employed to dissect the apoptotic pathway.
- Western blotting or similar techniques were likely used to assess protein levels (e.g., Bcl-2, Bcl-xL, FLAME-1), though not explicitly stated.
Main Results:
- TRAIL significantly induced apoptosis in thyroid cancer cells, an effect enhanced by CHX, suggesting the presence of inhibitors.
- Unlike other cancers, CHX did not affect levels of Bcl-2, Bcl-xL, or FLAME-1 in these thyroid cancer cells.
- TRAIL-induced apoptosis involved caspase activation, specifically caspases-1, -6, -8, and -9, but not caspases-2 or -3.
- TNF-alpha and Fas agonists induced minimal apoptosis, requiring prolonged CHX treatment for Fas to show an effect.
Conclusions:
- TRAIL is a potent inducer of apoptosis in various thyroid cancer cell types, superior to TNF-alpha and Fas.
- TRAIL selectively targets thyroid tumor cells without harming normal thyrocytes and shows no significant in vivo organ toxicity.
- TRAIL represents a highly promising therapeutic agent for thyroid cancer treatment due to its efficacy and selectivity.