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[What do we know about ATM protein expression in breast tissue?]
1Groupe de réparation de l'ADN, Centre international de recherche sur le cancer, 150, Cours Albert-Thomas, 69372 Lyon Cedex 08.
Abstract:
The great majority of breast cancer cases are not associated with a mutated gene of high penetrance such as BRCA1, BRCA2 and TP53. Genes of low penetrance, frequently mutated in the general population, might play an important role in breast cancer development. The ATM gene, which encodes the ATM protein, mutated in the disorder ataxia telangiectasia (AT) could be such a susceptibility gene. Indeed, 1% of the general population is estimated to be AT heterozygote and females have an increased risk of developing breast cancer. The ATM protein is involved in the signalling pathway of DNA double-strand breaks. Studies on its expression in normal breast tissues have shown that ATM is expressed in the epithelial cells of breast ducts, but not in the myoepithelial cells. In sclerosing adenosis, a benign lesion of the breast, the ATM protein is expressed in both cell types whereas its expression is absent or reduced in tumour epithelial cells in about 30-50% of invasive carcinomas. Moreover, the study of the p53 status in some of these tumours has revealed that the ATM/p53 signalling pathway is frequently altered either by a very low ATM expression or by the presence of a mutated p53. It remains to be determined whether alterations in the expression of other proteins also involved in this DNA damage signalling cascade are specifically associated with breast cancer development and/or a radiosensitive phenotype seen in some breast cancer patients after radiotherapy.
Insights
The ATM gene, a low-penetrance breast cancer susceptibility gene, shows altered expression in about half of invasive carcinomas. This suggests a role for ATM in DNA damage signaling and breast cancer development.
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- Most breast cancer cases lack high-penetrance mutations (e.g., BRCA1, BRCA2, TP53).
- Low-penetrance genes, common in the general population, may contribute to breast cancer risk.
- The ATM gene, implicated in ataxia telangiectasia, is a potential low-penetrance breast cancer susceptibility gene.
Purpose of the Study:
- To investigate the role of the ATM gene and its protein in breast cancer development.
- To examine ATM protein expression in normal breast tissue, benign lesions, and invasive carcinomas.
- To explore the interplay between ATM and p53 signaling pathways in breast tumors.
Main Methods:
- Immunohistochemical analysis of ATM protein expression in breast tissue samples.
- Evaluation of ATM protein expression in normal ducts, sclerosing adenosis, and invasive carcinomas.
- Assessment of p53 status in conjunction with ATM expression in tumors.
Main Results:
- ATM protein is expressed in epithelial cells of normal breast ducts but not myoepithelial cells.
- In sclerosing adenosis, ATM is expressed in both cell types.
- ATM expression is absent or reduced in 30-50% of invasive breast carcinomas.
- The ATM/p53 signaling pathway is frequently altered in tumors due to low ATM expression or mutated p53.
Conclusions:
- Alterations in ATM gene expression are common in invasive breast carcinomas.
- The ATM/p53 signaling pathway is frequently disrupted in breast cancer.
- Further research is needed to determine if ATM alterations correlate with breast cancer development or radiosensitivity.
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