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Ret gene silencing is associated with Raf-1-induced medullary thyroid carcinoma cell differentiation
E B Carson1, M McMahon, S B Baylin
1Program in Human Genetics and Molecular Biology, Johns Hopkins University School of Medicine, Balimore, Maryland 21231, USA.
Abstract:
Mutations in the ret proto-oncogene constitute the germ line defect in patients with inherited forms of medullary thyroid carcinoma (MTC) and are also present in tumor DNA from a subset of patients with sporadic forms of MTC. We now show that the TT cell line of human MTC can be induced within 48 h to resemble mature C cell differentiation by activation of the raf-1 signal transduction pathway. Within this time period, expression of both the mutant and wild-type ret gene alleles, present in these cells, are silenced at the mRNA and protein levels. This definition of a signal transduction pathway that can regulate ret gene expression, and of the position of ret gene expression in endocrine differentiation, should help clarify the precise role of this gene in normal neuroendocrine development and in the formation of MTC.
Insights
Activating the raf-1 pathway in medullary thyroid carcinoma (MTC) cells triggers differentiation and silences the ret proto-oncogene. This finding clarifies the ret gene's role in neuroendocrine development and MTC formation.
Area of Science:
- Oncology
- Molecular Biology
- Cell Signaling
Background:
- Mutations in the ret proto-oncogene are linked to inherited and sporadic medullary thyroid carcinoma (MTC).
- The precise role of the ret gene in MTC development and endocrine differentiation requires further elucidation.
Purpose of the Study:
- To investigate the effect of activating the raf-1 signal transduction pathway on MTC cell differentiation.
- To determine the impact of raf-1 pathway activation on ret gene expression in MTC cells.
Main Methods:
- Utilized the TT cell line, a human MTC cell line.
- Activated the raf-1 signal transduction pathway.
- Analyzed ret gene expression at mRNA and protein levels post-activation.
Main Results:
- Activation of the raf-1 pathway induced MTC cell differentiation within 48 hours.
- Both mutant and wild-type ret gene alleles were silenced at mRNA and protein levels.
- This demonstrates a signal transduction pathway that regulates ret gene expression.
Conclusions:
- The raf-1 pathway can regulate ret gene expression in MTC.
- Ret gene expression is positioned within the endocrine differentiation process.
- This research clarifies the ret gene's role in normal neuroendocrine development and MTC pathogenesis.