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Preferential and novel activation of H-ras in human bladder carcinomas
K V Visvanathan1, R D Pocock, I C Summerhayes
1Department of Cell and Molecular Biology, Institute of Cancer Research, Chester Beatty Laboratories, London, UK.
Abstract:
In a survey of primary human bladder carcinomas from 24 patients, using the NIH/3T3 transfection nude mouse tumor assay, we have detected an activated c-H-ras-1 gene in four cases. Two of these scored negative in primary transfections using a NIH/3T3 focus assay. Oligonucleotide analysis of genomic and enzymatically amplified DNA revealed substitution of valine at codon 12 in DNA from three transfectants and their parental carcinomas, which was absent from the DNA of normal tissue of each of these patients. The fourth activation was identified as a cysteine substitution at codon 13, a novel activation of c-H-ras-1 in a solid tumor sample. Thus, all seven activated ras genes reported in human urothelial tumors (Fujita et al., Proc. Natl. Acad. Sci. USA 82, 3849-3853, 1985) have been c-H-ras-1 genes, strongly suggesting that this member of the ras gene family is preferentially activated in cells of transitional origin.
Insights
Activated c-H-ras-1 genes were found in human bladder carcinomas using a mouse tumor assay. Specific mutations at codons 12 and 13 were identified, suggesting c-H-ras-1
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Ras genes are critical regulators of cell signaling.
- Aberrant ras gene activation is implicated in various cancers.
- Specific ras gene family members may play distinct roles in different tumor types.
Purpose of the Study:
- To investigate the presence and nature of activated ras genes in primary human bladder carcinomas.
- To identify specific mutations within the c-H-ras-1 gene in bladder tumor samples.
- To determine if c-H-ras-1 is preferentially activated in urothelial tumors.
Main Methods:
- Utilized the NIH/3T3 transfection nude mouse tumor assay for detecting activated oncogenes.
- Employed NIH/3T3 focus assay for primary transfection screening.
- Conducted oligonucleotide analysis of genomic and amplified DNA to identify specific mutations.
Main Results:
- Detected activated c-H-ras-1 gene in four out of 24 primary human bladder carcinomas.
- Identified valine substitution at codon 12 in three cases and cysteine substitution at codon 13 in one case.
- Confirmed that all seven reported activated ras genes in human urothelial tumors are c-H-ras-1.
Conclusions:
- The c-H-ras-1 gene is activated in a subset of human bladder carcinomas.
- Specific point mutations in c-H-ras-1, particularly at codon 12 and 13, are associated with bladder tumorigenesis.
- Evidence suggests a preferential activation of c-H-ras-1 in transitional cell origin tumors.