What you carry at this position in your DNA and what research says about it.
Breast Cancer Risk: 8/10 evidence, 18 publications.
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Sample genotype (not yours): A/A
Higher Breast and Ovarian Cancer Risk
Two copies of the A allele are associated with a slightly increased risk of developing breast and ovarian cancers. Conversely, this profile is linked to a lower risk of respiratory cancers.
What this genotype means: Slightly higher risk of breast cancer; Slightly higher risk of ovarian cancer; Lower risk of respiratory cancers.
Sample genotype (not yours): A/G
Typical Breast and Ovarian Cancer Risk
One copy of each allele provides a balanced genetic profile with typical risks for breast, ovarian, and respiratory cancers. This intermediate state does not significantly skew cancer susceptibility in either direction.
What this genotype means: Typical risk of breast and ovarian cancers; Typical risk of respiratory cancers.
Sample genotype (not yours): G/G
Lower Breast and Ovarian Cancer Risk
Two copies of the G allele are associated with a reduced risk of breast and ovarian cancers. However, this profile is linked to a slightly higher risk of respiratory cancers.
What this genotype means: Lower risk of breast cancer; Lower risk of ovarian cancer; Slightly higher risk of respiratory cancers.
Gene function and biological role
Gene Function: The TERT gene encodes telomerase reverse transcriptase, the essential catalytic subunit of the telomerase enzyme [1]. Telomerase maintains the length of telomeres, which are protective caps at the ends of chromosomes that prevent cellular aging and genomic instability [1]. In most adult cells, telomerase is turned off, leading to gradual telomere shortening over time [2]. However, cancer cells frequently reactivate TERT to achieve cellular immortality and uncontrolled division [2]. Genetic variations in the TERT promoter region can alter how this gene is regulated and transcribed [3].
Variant Impact: Located in the promoter region of the TERT gene, rs2853669 is a single nucleotide change. This change disrupts a binding site for the E2F1 and Ets2 transcription factors, which normally help regulate TERT expression [3]. By altering transcription factor binding, the variant can influence telomerase activity and telomere maintenance [3]. These changes in telomere biology can affect cellular lifespan and susceptibility to various cancers [2]. Clinically, this variant has been extensively studied for its role in modifying cancer risk and prognosis [4].
Key Insight: This variant acts as a genetic double-edged sword, where the allele that increases breast cancer risk actually decreases the risk of respiratory cancers.
Location: TERT. Chromosome 5 · 5p15.33 · 1.3 Mb
Estimated prevalence by population
Global 56.6%; European 48.2%; African 76.8%; East Asian 40.1%; South Asian 22.2%; Americas 58.4%; Ashkenazi 41.2%; Finnish 59.8%; Middle Eastern 40.1%; Amish 41.9%.
Estimated AA genotype frequency.
Global 36.1%; European 42.5%; African 21.7%; East Asian 46.5%; South Asian 49.8%; Americas 36.1%; Ashkenazi 46.0%; Finnish 35.0%; Middle Eastern 46.4%; Amish 45.6%.
Estimated AG genotype frequency.
Global 7.4%; European 9.4%; African 1.5%; East Asian 13.5%; South Asian 28.0%; Americas 5.6%; Ashkenazi 12.8%; Finnish 5.1%; Middle Eastern 13.4%; Amish 12.4%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Cancer & Oncology
Breast Cancer
Breast Cancer. Evidence: 8/10. Source: PMID 29059683. Increased Risk.
Gynecological Cancers
Ovarian Cancer. Evidence: 6/10. Source: PMID 38723632. ~1.09x Increased Risk.
Lung Cancer
Respiratory Cancer. Evidence: 6/10. Source: PMID 39024449. Decreased Risk.
Gastrointestinal Cancers
Gastric Cancer. Evidence: 4/10. Source: PMID 33002439. Direction unresolved.
Organ Systems
Respiratory Health
Pulmonary Fibrosis. Evidence: 7/10. Typical Risk.
Showing effects for A/G genotype
Breast Cancer. Evidence: 8/10. Source: PMID 29059683. Typical Risk.
Ovarian Cancer. Evidence: 6/10. Source: PMID 38723632. Typical Risk.
Respiratory Cancer. Evidence: 6/10. Source: PMID 39024449. Typical Risk.
Showing effects for G/G genotype
Breast Cancer. Evidence: 8/10. Source: PMID 29059683. Decreased Risk.
Ovarian Cancer. Evidence: 6/10. Source: PMID 38723632. Decreased Risk.
Respiratory Cancer. Evidence: 6/10. Source: PMID 39024449. Increased Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Presence of two copies of the common A allele in the TERT promoter is linked to specific cancer susceptibilities. Large-scale genome-wide association studies have consistently linked the A allele to an elevated susceptibility to breast cancer [1]. Additionally, research indicates a modest increase in the risk of ovarian cancer for individuals with this genetic profile [2]. The biological mechanism is thought to involve altered transcription factor binding, which influences telomerase expression and telomere length maintenance [3]. Interestingly, while this genotype increases the risk for certain hormone-related cancers, it appears to offer a protective effect against respiratory cancers [4]. ClinVar database submissions confirm that this variant is benign regarding rare, severe telomere syndromes like idiopathic pulmonary fibrosis.
Slightly higher risk of breast cancer; Slightly higher risk of ovarian cancer; Lower risk of respiratory cancers.
Sample genotype: AG (Heterozygous)
A heterozygous profile represents a genetic middle ground for telomerase regulation. Individuals with this profile generally exhibit average risks for breast and ovarian cancers, as they carry only one copy of the risk-associated A allele [1]. Similarly, the risk for respiratory cancers remains at baseline because only one copy of the G allele is present [2]. The presence of both alleles means transcription factor binding at the TERT promoter is moderately modified but not fully disrupted [3]. This intermediate state typically results in standard telomerase regulation and telomere maintenance [3]. Clinical databases like ClinVar classify this common variation as entirely harmless for severe degenerative disorders such as pulmonary fibrosis.
Typical risk of breast and ovarian cancers; Typical risk of respiratory cancers.
Sample genotype: GG (Homozygous)
Inheriting two copies of the minor G allele in the TERT promoter alters transcription factor binding. Having two copies of the G allele is associated with a lower risk of developing breast cancer compared to the more common A/A genotype [1]. Research also suggests a protective effect against ovarian cancer [2]. The G allele disrupts a specific transcription factor binding site, which can lower TERT expression and telomerase activity in certain tissues [3]. However, this same mechanism is associated with an increased susceptibility to respiratory cancers [4]. Despite these complex cancer associations, ClinVar evaluations confirm that this variant does not cause severe telomere-shortening diseases like dyskeratosis congenita.
Lower risk of breast cancer; Lower risk of ovarian cancer; Slightly higher risk of respiratory cancers.
Variants with shared genetic architecture
rs2242652 · TERT Gene · Chr 5 · Cancer Risk Trade-offs
rs2735940 · TERT Gene · Chr 5 · Colorectal Cancer Risk
rs2853677 · TERT Gene · Chr 5 · Cancer Susceptibility
Functional dissection of breast cancer risk-associated TERT promoter variants.
Association analysis identifies 65 new breast cancer risk loci.
Diversity and scale: Genetic architecture of 2068 traits in the VA Million Veteran Program.
Content updated August 2026.
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