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p53 re-expression inhibits proliferation and restores differentiation of human thyroid anaplastic carcinoma cells
F Moretti1, A Farsetti, S Soddu
1Molecular Oncogenesis Laboratory, Regina Elena Cancer Institute, Rome, Italy.
Abstract:
Alterations of the tumor suppressor gene p53 are uncommon in differentiated thyroid neoplasia but are detected at high frequency in anaplastic thyroid carcinoma suggesting that impaired p53 function may contribute to the undifferentiated and highly aggressive phenotype of these tumors. Effects of wild type p53 (wt-p53) re-expression were investigated in a human anaplastic thyroid carcinoma cell line (ARO) expressing a mutated p53. ARO cells were stably transfected with the temperature-sensitive p53 Val135 gene (ts-p53) which exhibits wild type-like activity at 32 degrees C. Exogenous wt-p53 function in ARO-tsp53 clones was assessed by evaluating its transcriptional activity on a CAT reporter vector containing p53 binding sites. At 32 degrees C, a significant reduction in the proliferation rate (approximately or equal to 50%) was observed, with accumulation of cells in the G0/G1 phase of the cell cycle. This effect was accompanied by induction of the expression of the growth inhibitor p21/Waf1 gene. At 32 degrees C, ARO-tsp53 clones also showed a marked impairment of their tumorigenic potential. Furthermore, transfected clones re-acquired the ability to respond to thyrotropin (TSH) stimulation showing an increased expression of thyroid-specific genes (thyroglobulin, thyroperoxidase and TSH receptor). In conclusion, re-expression of wt-p53 activity in ARO cells, inhibits cell proliferation and restores responsiveness to physiological stimuli.
Insights
Restoring wild-type p53 (wt-p53) function in anaplastic thyroid carcinoma cells significantly inhibits proliferation and tumor growth. This intervention also restores cellular responsiveness to thyroid-stimulating hormone (TSH).
Area of Science:
- Oncology
- Molecular Biology
- Endocrinology
Background:
- Alterations in the p53 tumor suppressor gene are rare in differentiated thyroid cancers but frequent in aggressive anaplastic thyroid carcinoma.
- Impaired p53 function is implicated in the aggressive, undifferentiated phenotype of anaplastic thyroid tumors.
Purpose of the Study:
- To investigate the effects of re-expressing wild-type p53 (wt-p53) in a human anaplastic thyroid carcinoma cell line (ARO) that harbors mutated p53.
- To assess the impact of wt-p53 re-expression on cell proliferation, cell cycle, gene expression, tumorigenic potential, and responsiveness to thyroid-specific stimuli.
Main Methods:
- Stable transfection of ARO cells with a temperature-sensitive p53 Val135 gene (ts-p53), which functions as wt-p53 at 32°C.
- Evaluation of wt-p53 transcriptional activity using a CAT reporter vector.
- Assessment of cell proliferation, cell cycle distribution (G0/G1 phase), p21/Waf1 gene expression, and tumorigenic potential at permissive (32°C) and non-permissive temperatures.
- Measurement of thyroid-specific gene expression (thyroglobulin, thyroperoxidase, TSH receptor) in response to thyrotropin (TSH) stimulation.
Main Results:
- At 32°C, re-expression of wt-p53 significantly reduced ARO cell proliferation by approximately 50% and caused cell cycle arrest in the G0/G1 phase.
- wt-p53 re-expression induced the expression of the growth inhibitor p21/Waf1.
- Tumorigenic potential was markedly impaired in ARO cells expressing functional wt-p53.
- Transfected cells regained responsiveness to TSH, exhibiting increased expression of thyroid-specific genes.
Conclusions:
- Re-expression of wild-type p53 activity in anaplastic thyroid carcinoma cells effectively inhibits cell proliferation and impairs tumorigenicity.
- Restoring wt-p53 function can re-establish responsiveness to physiological stimuli like TSH, potentially offering a therapeutic strategy for anaplastic thyroid carcinoma.