What you carry at this position in your DNA and what research says about it.
Cancer Risk: 6/10 evidence, 55 publications.
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Sample genotype (not yours): G/G
Typical Cancer Risk and Standard Drug Response
Standard DNA repair capacity maintains baseline susceptibility to environmental carcinogens. Chemotherapy drugs are processed at typical clinical rates.
What this genotype means: Typical baseline oral cancer risk; Standard response to platinum-based chemotherapy; Lower risk of chemotherapy-induced bone marrow suppression.
Sample genotype (not yours): A/A
Lower Skin Cancer Risk but Higher Oral Cancer Risk
A protective effect against squamous cell skin cancer is offset by a higher risk of oral cancer. Chemotherapy response is improved but carries higher toxicity risks.
What this genotype means: Lower risk of squamous cell skin cancer; Increased risk of oral cancer in Asian populations; Enhanced response to platinum-based chemotherapy with higher toxicity risk.
Sample genotype (not yours): G/A
Mixed Cancer Susceptibility and Enhanced Drug Sensitivity
Slightly higher risk for oral cancer is paired with a better response to certain chemotherapy drugs. There is also a higher chance of chemotherapy side effects.
What this genotype means: Slightly increased risk of oral cancer in Asian populations; Better response to platinum-based chemotherapy; Higher risk of chemotherapy-induced bone marrow suppression.
Gene function and biological role
Gene Function: The XRCC1 gene encodes a critical scaffolding protein involved in the base excision repair pathway, which mends single-strand DNA breaks caused by radiation and reactive oxygen species [1]. By coordinating with DNA ligase III and polymerase beta, this protein ensures genomic stability and prevents the accumulation of mutagenic lesions [2]. Variations in this gene can alter DNA repair efficiency, affecting how the body handles cellular damage [3]. Consequently, these changes influence susceptibility to various malignancies and modulate how tumor cells respond to DNA-damaging chemotherapeutic agents [4].
Variant Impact: This missense variant, also known as Arg194Trp, alters the amino acid at codon 194 from arginine to tryptophan, which resides in a highly conserved linker region of the XRCC1 protein [5]. This structural change is thought to reduce the overall DNA repair capacity of the base excision pathway [6]. Because the variant protein is less efficient at fixing DNA damage, it can lead to different health outcomes depending on environmental exposures [7]. Interestingly, this reduced repair capacity can also make cancer cells more vulnerable to certain chemotherapy drugs [8].
Key Insight: While this variant slightly increases the risk of certain cancers, it simultaneously makes tumor cells more sensitive to platinum-based chemotherapy, potentially improving treatment survival rates.
Location: XRCC1. Chromosome 19 · 19q13.31 · 43.6 Mb
Estimated prevalence by population
Global 86.1%; European 88.1%; African 87.9%; East Asian 50.1%; South Asian 80.5%; Americas 80.8%; Ashkenazi 88.5%; Finnish 92.7%; Middle Eastern 84.3%; Amish 94.8%.
Estimated GG genotype frequency.
Global 13.2%; European 11.6%; African 11.7%; East Asian 41.4%; South Asian 18.5%; Americas 18.2%; Ashkenazi 11.1%; Finnish 7.1%; Middle Eastern 15.0%; Amish 5.1%.
Estimated GA genotype frequency.
Global 0.7%; European 0.4%; African 0.4%; East Asian 8.5%; South Asian 1.1%; Americas 1.0%; Ashkenazi 0.3%; Finnish 0.1%; Middle Eastern 0.7%; Amish 0.1%.
Estimated AA genotype frequency.
Showing effects for G/G genotype
Cancer & Oncology
Head, Neck & Oral Cancers
Oral Cancer. Evidence: 4/10. Source: PMID 19713684. Typical Risk.
Skin Cancer
Skin Cancer. Evidence: 3/10. Source: PMID 22687647. Typical Risk.
Pharmacogenomics
Chemotherapy Response
Chemotherapy Response. Evidence: 6/10. Source: PMID 28743242. Poorer Response.
Chemotherapy Toxicity. Evidence: 5/10. Source: PMID 28844589. Typical Risk.
Showing effects for A/A genotype
Oral Cancer. Evidence: 4/10. Source: PMID 19713684. ~1.4x Increased Risk.
Skin Cancer. Evidence: 3/10. Source: PMID 22687647. Lower Risk.
Chemotherapy Response. Evidence: 6/10. Source: PMID 28743242. Stronger Response.
Chemotherapy Toxicity. Evidence: 5/10. Source: PMID 28844589. Increased Risk.
Showing effects for G/A genotype
Oral Cancer. Evidence: 4/10. Source: PMID 19713684. ~1.3x Increased Risk.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Carrying two copies of the common G allele results in a fully functional XRCC1 protein that performs standard base excision repair [1]. This baseline repair efficiency keeps the risk of oral cancer at typical population levels [2]. However, because the DNA repair machinery is highly efficient, cancer cells in these individuals may also repair themselves more quickly during chemotherapy, which is associated with a poorer response to platinum-based treatments like cisplatin [3]. On the positive side, this standard repair capacity helps protect healthy tissues, resulting in a lower risk of severe bone marrow suppression during chemotherapy regimens [4].
Typical baseline oral cancer risk; Standard response to platinum-based chemotherapy; Lower risk of chemotherapy-induced bone marrow suppression.
Sample genotype: AA (Homozygous)
Carrying two copies of the variant A allele significantly alters the XRCC1 protein, leading to a more pronounced reduction in DNA repair efficiency [1]. This altered state appears to offer a protective effect against squamous cell skin cancer, lowering susceptibility to UV-induced skin malignancies [2]. However, the compromised repair pathway simultaneously elevates the risk of oral cancer, particularly in Asian populations, by about 1.4-fold [3]. In a clinical oncology setting, this genotype is highly sensitive to platinum-based chemotherapy, which translates to a higher likelihood of survival but also a significantly increased risk of severe bone marrow suppression [4].
Lower risk of squamous cell skin cancer; Increased risk of oral cancer in Asian populations; Enhanced response to platinum-based chemotherapy with higher toxicity risk.
Sample genotype: GA (Heterozygous)
Possessing one copy of the variant A allele slightly reduces the overall efficiency of the base excision repair pathway [1]. In Asian populations, this intermediate repair capacity is associated with an approximate 1.3-fold increase in oral cancer risk [2]. Conversely, when treating existing cancers, this reduced repair ability prevents tumor cells from fixing the damage caused by platinum-based chemotherapy, leading to better treatment response and improved survival outcomes [3]. This same vulnerability, however, means healthy cells are more susceptible to chemotherapy-induced toxicity, increasing the likelihood of experiencing bone marrow suppression during treatment [4].
Slightly increased risk of oral cancer in Asian populations; Better response to platinum-based chemotherapy; Higher risk of chemotherapy-induced bone marrow suppression.
Variants with shared genetic architecture
rs25487 · XRCC1 Gene · Chr 19 · Skin Cancer Risk
rs25489 · XRCC1 Gene · Chr 19 · DNA Repair and Cancer Risk
rs11615 · ERCC1 Gene · Chr 19 · DNA Repair and Cancer Risk
Variants of Base Excision Repair Genes MUTYH , PARP1 and XRCC1 in Alzheimer's Disease Risk.
XRCC1 genetic polymorphism acts a potential biomarker for lung cancer.
Content updated August 2026.
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