What you carry at this position in your DNA and what research says about it.
Breast Cancer Risk: 10/10 evidence, 26 publications.
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Sample genotype (not yours): C/C
Typical Breast Cancer Risk
Carrying two copies of the C allele is associated with baseline breast cancer risk and typical blood pressure regulation.
What this genotype means: Typical breast cancer risk; Typical blood pressure regulation.
Sample genotype (not yours): C/T
Slightly Elevated Breast Cancer Risk
Carrying one copy of the T allele is associated with a minor increase in breast cancer risk and slightly higher blood pressure susceptibility.
What this genotype means: Slightly increased breast cancer risk; Slightly higher blood pressure susceptibility.
Sample genotype (not yours): T/T
Elevated Breast Cancer Risk
Carrying two copies of the T allele is associated with a modest increase in breast cancer risk and higher blood pressure susceptibility.
What this genotype means: Modestly increased breast cancer risk; Higher blood pressure susceptibility.
Gene function and biological role
Gene Function: The SLC4A7 gene encodes a sodium bicarbonate cotransporter protein, often referred to as NBCn1, which plays a vital role in maintaining intracellular pH by transporting sodium and bicarbonate ions into cells [1]. This regulation of cellular acidity is critical for normal physiological processes, including sensory transmission in the eyes and ears [1]. In vascular smooth muscle cells, SLC4A7 activity helps regulate arterial tone and has been linked to the control of blood pressure [1]. Furthermore, this transporter is frequently upregulated in breast cancer cells, where it promotes an alkaline intracellular environment that supports tumor growth and survival [2]. Consequently, genetic variations in this gene can influence both cardiovascular health and cancer susceptibility [1] [2].
Variant Impact: The rs4973768 variant is a single nucleotide polymorphism located in the 3 prime untranslated region of the SLC4A7 gene [1]. This genetic change is thought to alter the binding affinity of microRNAs, thereby modifying the stability and translation of the SLC4A7 mRNA [1]. Specifically, the T allele is associated with increased expression of the sodium bicarbonate cotransporter, leading to enhanced acid extrusion from cells [1]. This upregulation can alter intracellular pH regulation in both vascular smooth muscle and breast tissues [1]. As a result, this variant has been identified as a low-penetrance susceptibility locus that influences breast cancer risk across multiple populations [3].
Key Insight: The same genetic variant that slightly increases breast cancer risk is also involved in cellular pH regulation and has been linked to blood pressure levels.
Location: SLC4A7. Chromosome 3 · 3p24.1 · 27.4 Mb
Estimated prevalence by population
Global 32.0%; European 27.4%; African 41.3%; East Asian 65.3%; South Asian 31.2%; Americas 21.5%; Ashkenazi 19.1%; Finnish 30.6%; Middle Eastern 18.1%; Amish 22.8%.
Estimated CC genotype frequency.
Global 48.1%; European 49.9%; African 46.0%; East Asian 31.0%; South Asian 49.3%; Americas 49.7%; Ashkenazi 49.2%; Finnish 49.4%; Middle Eastern 48.9%; Amish 49.9%.
Estimated CT genotype frequency.
Global 19.9%; European 22.7%; African 12.8%; East Asian 3.7%; South Asian 19.4%; Americas 28.8%; Ashkenazi 31.7%; Finnish 20.0%; Middle Eastern 33.0%; Amish 27.4%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Cancer & Oncology
Breast Cancer
Breast Cancer. Evidence: 10/10. Source: PMID 23535729. Typical Risk.
Mammographic Density. Evidence: 10/10. Source: PMID 25881232. Typical.
Cardiovascular & Metabolic
Hypertension
Blood Pressure. Evidence: 3/10. Source: PMID 23117855. Typical.
Showing effects for C/T genotype
Breast Cancer. Evidence: 10/10. Source: PMID 23535729. ~1.1x Risk.
Blood Pressure. Evidence: 3/10. Source: PMID 23117855. Slightly Higher.
Showing effects for T/T genotype
Breast Cancer. Evidence: 10/10. Source: PMID 23535729. ~1.2x Risk.
Mammographic Density. Evidence: 10/10. Source: PMID 25881232. Altered Density.
Blood Pressure. Evidence: 3/10. Source: PMID 23117855. Higher.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Inheriting two copies of the C allele represents the baseline genetic profile for this locus. Large-scale genome-wide association studies show that this genotype is associated with typical breast cancer susceptibility [1]. Because the C allele does not cause the upregulation of the SLC4A7 sodium bicarbonate cotransporter, cellular pH regulation in breast and vascular tissues remains at typical levels [2]. This baseline expression supports normal arterial tone and typical blood pressure regulation [2]. Additionally, studies in pre-menopausal women suggest this genotype is linked to typical mammographic breast density [3]. Overall, this profile represents a standard baseline with no elevated genetic risks for the associated conditions.
Typical breast cancer risk; Typical blood pressure regulation.
Sample genotype: CT (Heterozygous)
Inheriting one copy of the T allele is linked to a minor increase in breast cancer susceptibility, with an odds ratio of approximately 1.1 per risk allele [1]. This genetic variant, located in the 3 prime untranslated region of the SLC4A7 gene, is associated with increased expression of the sodium bicarbonate cotransporter [2]. Higher levels of this transporter enhance cellular acid extrusion, which can support the survival and proliferation of breast cancer cells [3]. In vascular smooth muscle, this increased expression can also influence intracellular pH, potentially contributing to slightly higher blood pressure levels [2]. The overall impact of this low-penetrance variant is modest and is heavily influenced by other lifestyle and genetic factors.
Slightly increased breast cancer risk; Slightly higher blood pressure susceptibility.
Sample genotype: TT (Homozygous)
Inheriting two copies of the T allele is associated with a modest increase in breast cancer susceptibility, with studies indicating a 1.1-fold to 1.2-fold higher risk compared to the baseline genotype [1]. This variant leads to increased expression of the SLC4A7 sodium bicarbonate cotransporter, which regulates intracellular pH [2]. In breast tissue, enhanced acid extrusion creates an alkaline intracellular environment that can facilitate tumor development and progression [3]. In the cardiovascular system, this altered pH regulation in vascular smooth muscle cells is associated with higher blood pressure levels [2]. Additionally, some research in pre-menopausal women has linked this genotype to variations in mammographic breast density [4]. While this variant increases susceptibility, it is considered a low-penetrance factor, meaning overall risk is determined by a combination of genetics and lifestyle.
Modestly increased breast cancer risk; Higher blood pressure susceptibility.
Variants with shared genetic architecture
rs12710696 · MIR4757 Gene · Chr 2 · Breast Cancer Risk
rs1432679 · EBF1 Gene · Chr 5 · Breast Cancer Risk
rs4784227 · CASC16 Gene · Chr 16 · Breast Cancer Risk
Large-scale genotyping identifies 41 new loci associated with breast cancer risk.
Content updated August 2026.
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