Mutation status of genes encoding RhoA, Rac1, and Cdc42 GTPases in a panelof invasive human colorectal and breast tumors

Purpose: The constitutive activation of Ras proteins by point mutation is t he most frequently observed oncogene activation in human malignancies. The goal of this study was to investigate whether the constitutive activation o f RhoA, Rac1, and Cdc42 proteins by point mutations, which can lead to expe rimental transformation of cultured cells, actually occurred in a panel of invasive colorectal and breast tumors. Methods: We performed denaturing gra dient gel electrophoresis and sequencing of transcripts amplified by revers e transcription and PCR for RhoA; we used direct sequencing of PCR-amplifie d genomic DNA to search for mutations in coding exons of the Rac1 and Cdc42 genes. Results: Although mutations of the Kras4B and the p53 genes were de tected using these methods, no mutation was found in the coding sequences o f RhoA, Rac1, and Cdc42 genes, in primary as well as in associated metastas is. Conclusions: Point mutations in the coding sequences of genes encoding RhoA, Rac1, and Cdc42 GTPases do not occur at high frequency in invasive br east and colorectal tumors.