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Status and expression of the p16INK4 gene in human thyroid tumors and thyroid-tumor cell lines
V Calabrò1, M Strazzullo, G La Mantia
1Dipartimento di Genetica, Biologia Generale e Molecolare, Università Federico II, Naples, Italy.
Abstract:
The p16INK4 tumor-suppressor gene (also known as CDKN2, CDK41 and MTS1) encodes a negative regulator of the cell cycle. This gene, located in 9p21, is mutated or homozygously deleted in a high percentage of tumor cell lines and specific types of primary tumors. We have examined the status of the p16INK4 gene in 31 thyroid tumors and 7 thyroid cell lines. No DNA abnormalities were found in primary tumors. Conversely, p16INK4 gene structural alterations, deletions and point mutations were found in 4 thyroid cell lines. The expression of the 2 different p16INK4 mRNAs, the p16alpha and p16beta transcripts, was determined by RNA-PCR experiments. All the primary thyroid tumors expressed the beta transcript, while the p16alpha was barely detectable. The thyroid cell lines always expressed the p16beta transcript, while the alpha transcript was absent or, whenever present, coded for a mutated form of the p16INK4 gene product. Taken together, our results suggest that loss of p16INK4 function is not directly involved in the process of thyroid-tumor development, but it probably gives cells in tissue culture a selective growth advantage.
Insights
The p16INK4 tumor-suppressor gene (CDKN2) mutations were not found in primary thyroid tumors. However, alterations in thyroid cell lines suggest p16INK4 loss provides a selective growth advantage in culture.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- The p16INK4 (CDKN2) gene is a crucial cell cycle regulator and tumor suppressor.
- Alterations in p16INK4 are common in various cancer cell lines and primary tumors.
- Thyroid cancer development involves complex genetic alterations.
Purpose of the Study:
- To investigate the status of the p16INK4 gene in thyroid tumors and cell lines.
- To determine the role of p16INK4 gene alterations and expression in thyroid tumorigenesis.
Main Methods:
- Analysis of p16INK4 gene structure (DNA abnormalities, deletions, point mutations) in 31 thyroid tumors and 7 cell lines.
- RNA-PCR experiments to assess the expression of p16INK4alpha and p16INK4beta transcripts.
Main Results:
- No DNA abnormalities of the p16INK4 gene were detected in the 31 primary thyroid tumors.
- Structural alterations, deletions, and point mutations in the p16INK4 gene were identified in 4 out of 7 thyroid cell lines.
- All primary thyroid tumors expressed the p16INK4beta transcript, with minimal p16INK4alpha transcript detection.
- Thyroid cell lines consistently expressed p16INK4beta, while p16INK4alpha was absent or mutated.
Conclusions:
- Loss of p16INK4 gene function is unlikely to be a primary driver in thyroid tumor development.
- The absence or mutation of p16INK4 may confer a selective growth advantage to thyroid cells in vitro.
- Further research is needed to elucidate the precise role of p16INK4 in thyroid cancer progression.