Two New Breast Cancer Genes Identified in Black Women
A first-of-its-kind study has identified two genetic variants linked to breast cancer in black South African women.
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A genome-wide association study (GWAS) conducted by researchers at the Sydney Brenner Institute for Molecular Bioscience (SBIMB) has revealed two genetic variants linked to breast cancer in black South African women.
This study, published in Nature Communications, is the first GWAS of breast cancer performed on African women living in Africa.
Novel genes linked to breast cancer risk
For this study, the researchers analyzed DNA from black South African women with breast cancer enrolled in the Johannesburg Cancer Study and compared the findings to those from women without cancer participating in the Africa Wits-INDEPTH Partnership for Genomic Research (AWI-Gen) study.
Genome-wide association study (GWAS)
A research method that examines the DNA of many individuals to find genetic variations linked to specific diseases or traits. It scans the whole genome to detect patterns that differ between people with and without a condition.
Following this approach, the researchers identified genetic signals near two genes: RAB27A, part of the RAS oncogene family, and USP22, which is highly active in breast cancer cells and linked to poor prognosis. These genes have not been previously associated with breast cancer, marking an important advance in understanding the disease’s genetic basis in African ancestry populations.
Limitations of existing cancer risk tools for African populations
GWAS has also played a role in developing the polygenic risk score (PRS) system. PRSs are a way to estimate an individual's genetic predisposition to a specific disease, compared to other with a different genetic composition.
Existing PRSs have been shown to perform poorly in distinguishing non-European demographics of women with breast cancer from those without.
“This is because most PRSs were developed in European populations, and their inaccuracy in African populations highlights the urgent need for ancestry-specific tools in cancer risk prediction,” says lead Dr Jean-Tristan Brandenburg, of the SBIMB.
Breast cancer is the second most common cancer in South Africa and the most common cancer in women globally, with genetic factors contributing to about 30% of cases.
“Our study makes a compelling case for investing in genomic research rooted in African contexts,” said Dr Mahtaab Hayat, the lead author of the study.
Implications for precision medicine
If further research confirms the role of USP22 and RAB27A in breast cancer, these genes could become targets for new drug development.
Additionally, genes associated with poorer survival could serve as biomarkers to identify more aggressive cancers, potentially guiding treatment intensity and patient monitoring.
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“We could potentially target harmful cancer cells while sparing healthy tissue, which is ideally what we want when administering cancer treatment,” said Chris Mathew, Distinguished Professor at the SBIMB and a lead project investigator.
Importance of African genomic diversity
African populations have the highest genetic diversity worldwide but remain underrepresented in genomic research.
“The study reveals that more people can benefit from genetic discoveries. It proves that new risk factors are still out there, waiting to be found,” emphasized Hayat.
The underrepresentation of African and other non-European populations in genomics research limits the global understanding of disease risks and the development of effective tools and treatments. The current study illustrates the potential for new genetic discoveries that can benefit a broader range of populations.
Reference: Hayat M, Chen WC, Babb De Villiers C, et al. Genome-wide association study identifies common variants associated with breast cancer in South African Black women. Nat Commun. 2025;16(1):3542. doi: 10.1038/s41467-025-58789-0
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