Rac2 expression and mutation in human brain tumors

Abstract

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. 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. 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. 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.