What you carry at this position in your DNA and what research says about it.
Breast Cancer Risk: 8/10 evidence, 51 publications.
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Sample genotype (not yours): C/C
Slightly Higher Breast Cancer Risk
Carrying two copies of the C allele is linked to a very small increase in breast cancer risk, but also a slightly lower risk of pancreatic cancer.
What this genotype means: Slightly increased risk of breast cancer; Slightly decreased risk of pancreatic cancer; Potentially altered response to specific chemotherapies.
Sample genotype (not yours): A/A
Typical Breast and Pancreatic Cancer Risk
Carrying two copies of the A allele represents the baseline genetic profile for breast and pancreatic cancer risk at this locus.
What this genotype means: Typical baseline risk of breast cancer; Typical baseline risk of pancreatic cancer; Standard response to specific chemotherapies.
Sample genotype (not yours): C/A
Carrying one copy of the C allele is associated with a very small increase in breast cancer risk, alongside a slightly lower risk of pancreatic cancer.
Gene function and biological role
Gene Function: The MAP3K1 gene encodes a mitogen-activated protein kinase kinase kinase that plays a pivotal role in controlling cell growth, survival, and programmed cell death [1]. It acts as a molecular switch, integrating signals from various pathways to regulate cellular responses to stress and growth factors [1]. In normal tissue, this protein helps maintain cellular stability and prevents uncontrolled division [1]. However, alterations in its signaling cascade can contribute to tumor development and influence how cancer cells migrate [1]. Because of its central role in cellular regulation, variations near this gene are frequently studied for their impact on cancer susceptibility and treatment outcomes [2].
Variant Impact: The rs889312 variant is an intergenic single nucleotide polymorphism located near the MAP3K1 gene on chromosome 5 [2]. This genetic change is thought to influence the expression levels of the nearby MAP3K1 gene, thereby subtly altering downstream signaling pathways [2]. Large-scale genomic studies have identified this specific change as a key low-penetrance marker for breast cancer susceptibility [3]. While it does not directly disable the gene, the subtle regulatory shift it causes is enough to alter long-term disease risk [3].
Key Insight: While the C allele slightly increases the risk of developing breast cancer, it has been linked to a slightly lower risk of developing pancreatic cancer, representing a rare genetic trade-off.
Location: MAP3K1. Chromosome 5 · 5q11.2 · 56.7 Mb
Estimated prevalence by population
Global 10.5%; European 8.0%; African 11.2%; East Asian 30.2%; South Asian 15.0%; Americas 15.2%; Ashkenazi 10.1%; Finnish 5.4%; Middle Eastern 11.3%; Amish 10.7%.
Estimated CC genotype frequency.
Global 42.7%; European 40.6%; African 44.5%; East Asian 49.5%; South Asian 47.5%; Americas 47.6%; Ashkenazi 43.3%; Finnish 35.7%; Middle Eastern 44.7%; Amish 44.1%.
Estimated CA genotype frequency.
Global 46.8%; European 51.4%; African 44.2%; East Asian 20.3%; South Asian 37.5%; Americas 37.2%; Ashkenazi 46.6%; Finnish 58.8%; Middle Eastern 44.0%; Amish 45.2%.
Estimated AA genotype frequency.
Showing effects for C/C genotype
Cancer & Oncology
Breast Cancer
Breast Cancer. Evidence: 8/10. Source: PMID 17529967. ~1.13x Higher Risk.
Gastrointestinal Cancers
Pancreatic Cancer. Evidence: 3/10. Source: PMID 19843670. ~15% Lower Risk.
Cancer Prognosis & Treatment Outcome
Gastric Cancer Prognosis. Evidence: 3/10. Source: PMID 24759887. Poorer Prognosis.
Showing effects for A/A genotype
Breast Cancer. Evidence: 8/10. Source: PMID 17529967. Typical Risk.
Pancreatic Cancer. Evidence: 3/10. Source: PMID 19843670. Typical Risk.
Gastric Cancer Prognosis. Evidence: 3/10. Source: PMID 24759887. Typical Prognosis.
Showing effects for C/A genotype
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
A large meta-analysis involving tens of thousands of subjects confirmed that the C allele acts as a low-penetrance risk factor for breast cancer [1]. For individuals with this genotype, the relative risk of developing breast cancer is increased by approximately 13% to 22% compared to those with the typical genotype [1]. Interestingly, this same genetic variant has been associated with a protective effect against pancreatic cancer, reducing the risk by about 15% [2]. In the context of cancer treatment, clinical observations suggest that patients with this genotype undergoing certain chemotherapies for gastric cancer may experience shorter overall survival [3]. The overall impact of this variant is highly dependent on family history and other lifestyle factors.
Slightly increased risk of breast cancer; Slightly decreased risk of pancreatic cancer; Potentially altered response to specific chemotherapies.
Sample genotype: AA (Homozygous)
This genotype is considered the normal or baseline genetic profile at this chromosomal location [1]. Individuals with this genotype do not carry the low-penetrance risk allele for breast cancer, meaning they have a typical baseline risk for the disease [1]. However, they also do not benefit from the minor protective effect against pancreatic cancer associated with the alternative allele [2]. In clinical studies of gastric cancer patients receiving chemotherapy, those with this genotype demonstrated a more favorable overall survival rate compared to carriers of the C allele [3]. Overall, this profile represents the standard genetic baseline for these conditions.
Typical baseline risk of breast cancer; Typical baseline risk of pancreatic cancer; Standard response to specific chemotherapies.
Sample genotype: CA (Heterozygous)
Genomic data indicates that carrying a single C allele elevates the relative risk of breast cancer by a small margin, similar to carrying two copies [1]. This low-penetrance variant is common in many populations and is particularly relevant for estrogen receptor-positive breast cancer [2]. Conversely, research has shown that the C allele correlates with a modest reduction in pancreatic cancer susceptibility, particularly among non-smokers [3]. In terms of prognosis, some studies have noted that carriers of this genotype who are treated with platinum-based chemotherapies for gastric cancer may have a less favorable survival profile compared to those with the typical genotype [4]. These subtle genetic influences are best understood as small pieces of a much larger health puzzle.
Variants with shared genetic architecture
rs80359365 · BRCA2 Gene · Chr 13 · Hereditary Cancer Risk
rs80358163 · BRCA1 Gene · Chr 17 · Breast and Ovarian Cancer
rs118203998 · PALB2 Gene · Chr 16 · Hereditary Cancer Risk
Low-penetrance susceptibility variants and postmenopausal oestrogen receptor positive breast cancer.
Genome-wide association study identifies novel breast cancer susceptibility loci.
Association of breast cancer susceptibility variants with risk of pancreatic cancer.
A MAP3k1 SNP predicts survival of gastric cancer in a Chinese population.
Content updated August 2026.
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