Missense mutations but not allelic variants alter the function of ATM by dominant interference in patients with breast cancer.
The human genetic disorder ataxia-telangiectasia (A-T) is characterized by hypersensitivity to ionizing radiation and an elevated risk of malignancy. Epidemiological data support an increased risk for breast and other cancers in A-T heterozygotes. However, screening breast cancer cases for truncating mutations in the ATM (A-T mutated) gene has failed largely to reveal an increased incidence in these patients. It has been hypothesized that ATM missense mutations are implicated in breast cancer, and there is some evidence to support this. The presence of a large variety of rare missense variants in addition to common polymorphisms in ATM makes it difficult to establish such a relationship by association studies. To investigate the functional significance of these changes we have introduced missense substitutions, identified in either A-T or breast cancer patients, into ATM cDNA before establishing stable cell lines to determine their effect on ATM function. Pathogenic missense mutations and neutral missense variants were distinguished initially by their capacity to correct the radiosensitive phenotype in A-T cells. Furthermore missense mutations abolished the radiation-induced kinase activity of ATM in normal control cells, caused chromosome instability, and reduced cell viability in irradiated control cells, whereas neutral variants failed to do so. Mutant ATM was expressed at the same level as endogenous protein, and interference with normal ATM function seemed to be by multimerization. This approach represents a means of identifying genuine ATM mutations and addressing the significance of missense changes in the ATM gene in a variety of cancers including breast cancer.
Scott
Shaun P
SP
Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Herston, Brisbane 4029, Australia.
Bendix
Regina
R
Chen
Philip
P
Clark
Raymond
R
Dork
Thilo
T
Lavin
Martin F
MF
D000483:Alleles; D001260:Ataxia Telangiectasia / Q000235:genetics; D064007:Ataxia Telangiectasia Mutated Proteins; D001943:Breast Neoplasms / Q000235:genetics* / Q000503:physiopathology; D018797:Cell Cycle Proteins; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics; D004268:DNA-Binding Proteins; D005260:Female; D005799:Genes, Dominant; D014644:Genetic Variation; D006579:Heterozygote; D006801:Humans; D066298:In Vitro Techniques; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000502:physiology*; D014162:Transfection; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases