Rac2 expression and mutation in human brain tumors
S-L Hwang1, A-S Lieu, J-H Chang
1Division of Neurosurgery, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
Background:
Rac1 and Rac2 are interchangeable in NADPH oxidase activation. Rac1 plays an important role in regulating nuclear signalling and in the activation of transcriptional factors that regulate gene expression and cell growth. Our previous study observed mutation in effector region of Rac1 gene in brain tumors. Little is known about the expression and mutation of Rac2 in human brain tumors.
Method:
We examined the expression of Rac2 by using reverse transcriptase-polymerase chain reaction (RT-PCR) and northern blot analysis and the mutation of Rac2 gene by using DNA sequence analysis.
Findings:
The decreased expression of Rac2 was found in 15 cases (57.7%) including 8 of 10 astrocytomas, 2 of 8 meningiomas, and 5 of 8 pituitary adenomas. Two of 13 cases with decreased expression of Rac2 had gene mutation. Only two of 26 cases had Rac2 overexpression in which no Rac2 gene mutation was found. Four of 8 cases with normal Rac2 expression had Rac2 gene mutation. The site of Rac2 gene mutation had no hot spots and was not concentrated in the effector region.
Conclusions:
Our results showed a low frequency of mutation and no hot spots of mutation in Rac2 gene in brain tumors, suggesting a decreased possibility of Rac2 in the brain tumorigenesis. The role of high frequency of decreased Rac2 expression in brain tumors, particularly in malignant astrocytomas, needs further investigations to be elucidated.
Insights
Rac2 gene mutations are infrequent in brain tumors, indicating a minor role in their development. However, decreased Rac2 expression is common, especially in astrocytomas, warranting further research into its specific function.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Rac1 and Rac2 proteins are crucial for NADPH oxidase activation.
- Rac1 influences nuclear signaling, gene expression, and cell growth.
- Rac1 gene mutations were previously found in brain tumors, but Rac2's role is less understood.
Purpose of the Study:
- To investigate the expression and mutation status of the Rac2 gene in human brain tumors.
- To determine the potential involvement of Rac2 in brain tumorigenesis.
Main Methods:
- Reverse transcriptase-polymerase chain reaction (RT-PCR) and northern blot analysis were used to assess Rac2 expression.
- DNA sequencing was employed to analyze Rac2 gene mutations.
Main Results:
- Decreased Rac2 expression was observed in 57.7% of brain tumor cases, notably in astrocytomas, meningiomas, and pituitary adenomas.
- Rac2 gene mutations were rare (2/13 cases with decreased expression) and lacked specific mutation hotspots.
- Rac2 overexpression occurred in a small number of cases (2/26) without associated gene mutations.
Conclusions:
- The low frequency of Rac2 mutations suggests it plays a limited role in brain tumor development.
- The high prevalence of decreased Rac2 expression, particularly in malignant astrocytomas, requires further investigation to clarify its significance in tumorigenesis.
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