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Cooperative alterations of Rb pathway regulators in mouse primary T cell lymphomas
I P Pérez de Castro1, M Malumbres, J Santos
1Department of Pathology and Kaplan Comprehensive Cancer Center, New York University Medical Center, 550 First Avenue, New York, NY 10016, USA. perezi01@popmail.med.nyu.edu
Abstract:
Alterations in the Rb pathway have been described in many different tumors. In order to study this cell cycle regulatory mechanism in murine T cell lymphomas, we have analyzed the RNA and protein expression of the cyclin D1, cdk4 and retinoblastoma genes in primary tumor samples. We have detected overexpression of the cyclin D1 gene and deficient expression of the retinoblastoma gene in 42 and 28% of these tumors, respectively. The immunohistochemical analysis showed that these RT-PCR results are correlated with a significant increase in the number of positive cells for cyclin D1 and a moderate decrease in the expression of Rb protein, respectively. The analysis of cyclin D1, Rb, p15(INK4b) and p16(INK4a) showed that 75% of lymphomas had alterations in these genes and indicates that the Rb pathway is frequently altered in mouse primary T cell lymphomas. Moreover, 31% of lymphomas presented simultaneous alterations in at least two of these genes, suggesting the importance of concurrent alteration of different Rb pathway regulators. In addition, we have characterized these samples for mutational status of the N-ras and K-ras genes. We have only detected mutations in codon 12 of K-ras in six of 49 lymphomas (12%). Interestingly, five of these lymphomas also showed alterations in at least one of the Rb pathway regulators analyzed here. Taken together, these data suggest that deregulation of the Rb pathway regulators and/or oncogenic activation of K-ras may represent a common important clue in progression of murine T cell lymphomas.
Insights
Alterations in the Retinoblastoma (Rb) pathway are common in mouse T cell lymphomas. Overexpression of cyclin D1 and deficient Rb protein were observed, suggesting Rb pathway deregulation contributes to lymphoma progression.
Area of Science:
- Oncology
- Molecular Biology
- Cell Cycle Regulation
Background:
- The Retinoblastoma (Rb) pathway is a critical regulator of the cell cycle.
- Alterations in the Rb pathway are implicated in various cancers.
- Understanding these alterations in T cell lymphomas is crucial for identifying therapeutic targets.
Purpose of the Study:
- To investigate alterations in Rb pathway regulators (cyclin D1, cdk4, Rb, p15INK4b, p16INK4a) in murine T cell lymphomas.
- To correlate RNA and protein expression of these genes.
- To examine the role of K-ras and N-ras mutations in conjunction with Rb pathway alterations.
Main Methods:
- Analysis of RNA and protein expression using RT-PCR and immunohistochemistry.
- Assessment of gene alterations in cyclin D1, Rb, p15INK4b, and p16INK4a.
- Mutation analysis of K-ras and N-ras genes.
Main Results:
- Overexpression of cyclin D1 (42%) and deficient Rb expression (28%) were detected.
- 75% of lymphomas showed alterations in Rb pathway genes, with 31% having simultaneous alterations.
- K-ras mutations (12%) were found, often co-occurring with Rb pathway alterations.
Conclusions:
- The Rb pathway is frequently altered in murine T cell lymphomas.
- Concurrent alterations in Rb pathway regulators are common.
- Rb pathway deregulation and/or K-ras activation may drive lymphoma progression.