What you carry at this position in your DNA and what research says about it.
Chemotherapy Neuropathy Risk: 6/10 evidence, 10 publications.
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Sample genotype (not yours): A/A
Typical Neuropathy Risk and Higher Colorectal Cancer Risk
This genotype is associated with standard sensitivity to chemotherapy-induced nerve damage but carries an elevated risk of colorectal cancer in older non-smokers.
What this genotype means: Standard risk of chemotherapy-induced nerve damage; Elevated risk of colorectal cancer in older non-smokers; Typical cholesterol response to atenolol.
Sample genotype (not yours): A/G
Lower Neuropathy Risk with Variable Medication Responses
This genotype offers protection against nerve damage during chemotherapy but is linked to higher cholesterol when taking certain blood pressure drugs.
What this genotype means: Reduced risk of chemotherapy-induced nerve damage; Increased risk of high cholesterol when taking atenolol; May respond less strongly to methadone.
Sample genotype (not yours): G/G
Lowest Neuropathy Risk with Variable Medication Responses
This genotype provides strong protection against chemotherapy-induced nerve damage but increases the risk of high cholesterol during beta-blocker therapy.
What this genotype means: Strong protection against chemotherapy-induced nerve damage; Increased risk of high cholesterol when taking atenolol; May respond less strongly to methadone.
Gene function and biological role
Gene Function: The ABCB1 gene encodes P-glycoprotein, a vital cellular pump that expels toxins, foreign compounds, and medications from cells [1]. This pump is highly active in protective barriers like the blood-brain barrier, intestines, and kidneys, where it limits the accumulation of potentially harmful substances [2]. In tumor cells, overactivity of this protein can lead to multidrug resistance by pumping chemotherapy drugs out before they can work [1]. Genetic variations in this gene can alter how much of the protein is produced or how effectively it functions [2]. Consequently, these variants influence how individuals process various medications, including chemotherapy agents, beta-blockers, and pain relievers [3].
Variant Impact: The rs3213619 variant is located in the promoter region of the ABCB1 gene, which controls how much P-glycoprotein is manufactured [1]. The change from an A to a G allele alters the transcriptional activity of this promoter, leading to differences in pump expression [4]. This altered expression directly impacts the cellular clearance of several common prescription medications [5]. Because P-glycoprotein is a major transporter of chemotherapy drugs, this single nucleotide change plays a significant role in determining susceptibility to treatment-related toxicities [1].
Key Insight: This variant acts as a genetic shield against nerve damage during breast cancer chemotherapy, yet the same genetic change is associated with higher cholesterol levels when taking certain blood pressure medications.
Location: ABCB1. Chromosome 7 · 7q21.12 · 87.6 Mb
Estimated prevalence by population
Global 90.1%; European 92.1%; African 83.7%; East Asian 90.2%; South Asian 93.3%; Americas 93.4%; Ashkenazi 95.7%; Finnish 93.3%; Middle Eastern 90.1%; Amish 98.5%.
Estimated AA genotype frequency.
Global 9.6%; European 7.7%; African 15.6%; East Asian 9.6%; South Asian 6.6%; Americas 6.5%; Ashkenazi 4.3%; Finnish 6.6%; Middle Eastern 9.7%; Amish 1.5%.
Estimated AG genotype frequency.
Global 0.3%; European 0.2%; African 0.7%; East Asian 0.3%; South Asian 0.1%; Americas 0.1%; Ashkenazi < 0.1%; Finnish 0.1%; Middle Eastern 0.3%; Amish < 0.1%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Pharmacogenomics
Chemotherapy Response
Chemotherapy Neuropathy. Evidence: 6/10. Source: PMID 24599932. Typical Risk.
Cardiovascular Drug Response
Atenolol Cholesterol Effect. Evidence: 5/10. Source: PMID 24116192. Typical.
Pain Medication Response
Methadone Dosage. Evidence: 3/10. Source: PMID 18424454. Typical Response.
Cancer & Oncology
Colorectal Cancer
Colorectal Cancer. Evidence: 3/10. Source: PMID 17146660. Increased Risk.
Showing effects for A/G genotype
Chemotherapy Neuropathy. Evidence: 6/10. Source: PMID 24599932. Lower Risk.
Atenolol Cholesterol Effect. Evidence: 5/10. Source: PMID 24116192. Increased Risk.
Methadone Dosage. Evidence: 3/10. Source: PMID 18424454. Higher Tolerance.
Colorectal Cancer. Evidence: 3/10. Source: PMID 17146660. Typical Risk.
Showing effects for G/G genotype
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Carrying two copies of the common A allele means P-glycoprotein expression levels are typical, resulting in standard clearance of chemotherapy drugs like paclitaxel [1]. While this ensures normal drug processing, it does not provide the protective effect against sensory neuropathy seen in G allele carriers [2]. Additionally, clinical research indicates that this genotype is linked to a higher risk of developing colorectal cancer, particularly among older individuals who have never smoked [3]. On the positive side, those with this genotype maintain a typical cholesterol response when treated with the blood pressure medication atenolol [4].
Standard risk of chemotherapy-induced nerve damage; Elevated risk of colorectal cancer in older non-smokers; Typical cholesterol response to atenolol.
Sample genotype: AG (Heterozygous)
Possessing one copy of the G allele alters P-glycoprotein pump activity, which significantly reduces the risk of developing painful sensory neuropathy during paclitaxel chemotherapy [1]. This protective effect is highly valuable for patients undergoing cancer treatments [2]. However, this same alteration in transport activity is associated with an increased risk of high cholesterol when taking the beta-blocker atenolol [3]. Furthermore, individuals with this genotype may respond less strongly to methadone, because of altered drug transport across the blood-brain barrier [4].
Reduced risk of chemotherapy-induced nerve damage; Increased risk of high cholesterol when taking atenolol; May respond less strongly to methadone.
Sample genotype: GG (Homozygous)
Carrying two copies of the rare G allele leads to modified P-glycoprotein expression, offering robust protection against severe sensory neuropathy during chemotherapy regimens involving paclitaxel, epirubicin, or cyclophosphamide [1]. This genetic profile is highly beneficial for minimizing nerve pain and numbness during cancer care [2]. Conversely, this genotype is associated with an increased risk of hypercholesterolemia when using the common blood pressure medication atenolol [3]. Additionally, because P-glycoprotein actively pumps opioids out of the central nervous system, individuals with this genotype may respond less strongly to methadone [4].
Strong protection against chemotherapy-induced nerve damage; Increased risk of high cholesterol when taking atenolol; May respond less strongly to methadone.
Variants with shared genetic architecture
rs1045642 · ABCB1 Gene · Chr 7 · Medication Response
rs2032582 · ABCB1 Gene · Chr 7 · Lung Cancer Risk
rs1128503 · ABCB1 Gene · Chr 7 · Medication Response
Novel and functional ABCB1 gene variant in sporadic Parkinson's disease.
Association of MDR1 genotypes with susceptibility to colorectal cancer in older non-smokers.
Content updated August 2026.
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