Recent studies have suggested that p53 plays a role along thyroid differentiation pathway. In a previous report, we showed that p53 re-expression in a human thyroid anaplastic carcinoma cell line (ARO), inhibits growth and tumorigenicity while inducing partial restoration of thyroid differentiated properties. Particularly, recovery of wt-p53 function was able to restore ARO cell responsiveness to TSH stimulus with an increased expression of thyroid specific markers Tg, TPO and TSH-R. With the aim to investigate molecular basis underlying this phenomenon, we evaluated the expression of the specific thyroid transcription factors TTF-1 and PAX-8. RT-PCR analysis of mRNA isolated from ARO cells and ARO p53-transfected clones (ARO-tsp53), cultured either in absence or presence of TSH (10mU/ml), was performed. No expression of these thyroid transcription factors was observed both in ARO parental and ARO-tsp53 clones. This finding indicates that partial re-expression in ARO-tsp53 clones of thyroid specific markers Tg, TPO and TSH-R, following TSH treatment, is not mediated by modulation of their specific transcriptional activators. Since activation of TSH receptor transduction pathway leads to increased intracellular cAMP levels and since phosphorilation of CREB protein is known to be a major target of cAMP activation, CREB activity was analyzed in ARO cells. Transient transfection assays using CAT reporter gene driven by a CREB-responsive promoter was performed. A strong reduction of CREB activity was detected in ARO-tsp53 clones as compared to ARO parental cells. Moreover, upon TSH stimulation, re-induction of CREB activity was observed only in ARO-tsp53 clones, suggesting that recovery of p53 activity may interfere with transduction pathways leading to modulation of CREB activity. Further experiments are in progress to analyze mechanism underlying p53 effects in thyroid differentiation on the TSH receptor transduction pathway.
Modulation of thyroid differentiation following p53 re-expression in human anaplastic carcinoma cells"
FMoretti;
1997
Abstract
Recent studies have suggested that p53 plays a role along thyroid differentiation pathway. In a previous report, we showed that p53 re-expression in a human thyroid anaplastic carcinoma cell line (ARO), inhibits growth and tumorigenicity while inducing partial restoration of thyroid differentiated properties. Particularly, recovery of wt-p53 function was able to restore ARO cell responsiveness to TSH stimulus with an increased expression of thyroid specific markers Tg, TPO and TSH-R. With the aim to investigate molecular basis underlying this phenomenon, we evaluated the expression of the specific thyroid transcription factors TTF-1 and PAX-8. RT-PCR analysis of mRNA isolated from ARO cells and ARO p53-transfected clones (ARO-tsp53), cultured either in absence or presence of TSH (10mU/ml), was performed. No expression of these thyroid transcription factors was observed both in ARO parental and ARO-tsp53 clones. This finding indicates that partial re-expression in ARO-tsp53 clones of thyroid specific markers Tg, TPO and TSH-R, following TSH treatment, is not mediated by modulation of their specific transcriptional activators. Since activation of TSH receptor transduction pathway leads to increased intracellular cAMP levels and since phosphorilation of CREB protein is known to be a major target of cAMP activation, CREB activity was analyzed in ARO cells. Transient transfection assays using CAT reporter gene driven by a CREB-responsive promoter was performed. A strong reduction of CREB activity was detected in ARO-tsp53 clones as compared to ARO parental cells. Moreover, upon TSH stimulation, re-induction of CREB activity was observed only in ARO-tsp53 clones, suggesting that recovery of p53 activity may interfere with transduction pathways leading to modulation of CREB activity. Further experiments are in progress to analyze mechanism underlying p53 effects in thyroid differentiation on the TSH receptor transduction pathway.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
