TOX3 rs3803662: What Your Genotype Means
The rs3803662 variant is a single nucleotide polymorphism located near the TOX3 gene. It is widely recognized in genetic research for its statistical association with an increased risk of developing estrogen receptor-positive breast cancer.
What each genotype means
Baseline breast cancer risk
This genotype represents the common state at this location in the TOX3 gene. Research indicates that individuals with this genotype do not carry the specific allele associated with increased susceptibility to estrogen receptor-positive breast cancer observed in some populations.
This is the most common genotype in many populations, including those of European ancestry.
Slightly elevated risk profile
Carrying one copy of the G allele is associated with a statistically higher risk of developing estrogen receptor-positive breast cancer compared to those without it. This variant is thought to influence TOX3 enhancer activity, though the overall impact on individual health remains a subject of ongoing research.
This genotype is found in a significant portion of the population, with the minor allele frequency typically ranging between 0.25 and 0.30 in European ancestry cohorts.
Increased breast cancer risk
Carrying two copies of the G allele is associated with a higher statistical risk of developing estrogen receptor-positive breast cancer compared to individuals with the AA genotype. While this variant is linked to altered TOX3 gene expression, it is only one of many factors that contribute to breast cancer risk, and it does not determine a clinical diagnosis.
This genotype is less common than the heterozygous state, appearing in roughly 1 in 10 to 1 in 15 individuals of European ancestry.
Understanding the rs3803662 Variant
The rs3803662 variant is a specific change in the DNA sequence located approximately 8 kilobases upstream of the TOX3 gene. In genetics, a single nucleotide polymorphism (SNP) like this represents a variation at a single position in the genome. Because this variant is located in a non-coding region, it does not change the protein sequence of the TOX3 gene itself. Instead, researchers believe it functions as a regulatory element, potentially acting as an enhancer that influences how much TOX3 protein is produced in breast tissue. By altering the activity of these regulatory regions, the variant may influence cellular processes that contribute to breast cancer development. It is important to note that this variant is just one of many genetic factors that contribute to complex disease risk, and its presence does not determine a clinical outcome.
The Role of the TOX3 Gene
The TOX3 gene, also known as TNRC9, encodes a protein that is thought to play a role in chromatin remodeling and transcriptional regulation. Research indicates that TOX3 is highly expressed in luminal subtype breast tumors compared to normal breast tissue. Because of its involvement in gene expression, scientists have investigated whether TOX3 influences estrogen-dependent signaling pathways, which are critical in the development of many breast cancers. Studies have shown that the rs3803662 variant is associated with altered TOX3 expression levels in tumor samples. While the exact mechanism remains a subject of ongoing study, the link between this gene and estrogen receptor-positive tumors suggests that TOX3 may be involved in the biological pathways that drive tumor growth or influence how tumors respond to hormonal signals.
Research and Evidence Strength
The association between rs3803662 and breast cancer risk has been identified through numerous genome-wide association studies (GWAS) across diverse populations, including European, Asian, and South American cohorts. The evidence for this association is considered robust in terms of statistical correlation, though the individual risk conferred by this variant is relatively low. Research has shown that the risk allele is associated with an increased likelihood of developing breast cancer, particularly the estrogen receptor-positive subtype. Some studies have also explored whether this variant influences tumor prognosis or survival, with mixed results that suggest the biological impact may be subtype-specific. Because this is a low-penetrance variant, it does not act like a high-risk mutation (such as those in BRCA1 or BRCA2); rather, it contributes a small, incremental increase to overall risk when considered alongside other genetic and environmental factors.
Population Frequency
The frequency of the rs3803662 variant varies across different ancestral groups. In European ancestry cohorts, the minor allele frequency is typically reported between 0.25 and 0.30. Research has confirmed that the variant is present and associated with breast cancer risk in other populations as well, including Korean and Chilean cohorts. Because allele frequencies can differ significantly based on genetic background, the specific risk profile associated with this SNP may not be identical across all global populations. Large-scale databases like gnomAD continue to refine these frequency estimates, providing a clearer picture of how common this variant is worldwide. Understanding these population-specific differences is a key area of focus for researchers aiming to improve the accuracy of genetic risk models for diverse groups of people.
Interpreting Your Genetic Information
If you have information about your rs3803662 genotype, it is important to view it in the context of your overall health and family history. This variant is a common genetic marker associated with a small, statistical increase in breast cancer risk, not a diagnostic test for cancer. It cannot predict whether an individual will develop the disease, nor can it be used to rule out risk. Genetic predisposition is complex, involving the interplay of many different genes, lifestyle factors, and environmental exposures. If you are concerned about your breast cancer risk, the most effective approach is to consult with a healthcare provider or a genetic counselor. They can help you interpret your family history and determine if you meet the criteria for clinical screening or further genetic testing. Never use genetic data to make medical decisions without professional guidance.
How common is this variant?
The minor allele frequency for rs3803662 is approximately 0.25 to 0.30 in European ancestry cohorts, with varying frequencies observed across other global populations.
Frequently asked questions
Does having the rs3803662 risk allele mean I will get breast cancer?
No. This variant is a common genetic marker associated with a small, statistical increase in risk. It is not a diagnostic test, and most people who carry the risk allele will never develop breast cancer.
How does rs3803662 affect the TOX3 gene?
Research suggests that rs3803662 acts as a regulatory element that influences the expression levels of the TOX3 gene. It may function as an enhancer, potentially altering how much TOX3 protein is produced in breast tissue.
Should I get tested for this variant?
Genetic testing for common, low-risk variants like rs3803662 is generally not recommended for clinical decision-making. If you have concerns about your breast cancer risk, speak with a doctor or genetic counselor about your family history and appropriate screening options.
Is this variant related to BRCA1 or BRCA2?
While both are associated with breast cancer, they are very different. BRCA1 and BRCA2 mutations are rare and confer a high risk of cancer, whereas rs3803662 is a common variant that confers a very small, incremental increase in risk.
Sources & further reading
Educational information only, last refreshed 10/14/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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This locus variant in TOX3 confers a moderately increased risk of estrogen receptor-positive breast cancer.
A common intergenic risk allele at the 16q12/TOX3 locus strongly associated with estrogen receptor-positive breast cancer susceptibility.
Variant in a non-coding regulatory element modulating FOXA1 binding and chromatin affinity, significantly influencing TOX3 expression and predisposition to breast cancer.