What you carry at this position in your DNA and what research says about it.
Cancer Risk Trade-Off: 8/10 evidence, 52 publications.
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Sample genotype (not yours): C/C
Higher Lung and Skin Cancer Risk, Lower Melanoma Risk
An increased risk of lung, bladder, and basal cell skin cancers is associated with this genetic profile, alongside protection against pancreatic cancer and melanoma.
What this genotype means: Slightly higher risk of lung, bladder, and basal cell cancers; Slightly lower risk of melanoma and pancreatic cancer.
Sample genotype (not yours): C/T
Balanced Cancer Risk Trade-Off
A balanced risk profile occurs with one copy of each allele, presenting intermediate risks and protective effects across several cancer types.
What this genotype means: Intermediate risk for lung, bladder, and basal cell cancers; Intermediate risk for melanoma and pancreatic cancer.
Sample genotype (not yours): T/T
Higher Melanoma and Pancreatic Risk, Lower Lung Risk
A slightly higher risk of melanoma and pancreatic cancer is paired with a protective effect against lung, bladder, and basal cell skin cancers.
What this genotype means: Slightly higher risk of melanoma and pancreatic cancer; Slightly lower risk of lung, bladder, and basal cell cancers.
Gene function and biological role
Gene Function: The CLPTM1L gene encodes a protein that is overexpressed in many cancers and is located in a critical genomic region on chromosome 5 next to the TERT gene [1]. This region is highly involved in telomere maintenance and cell survival [2]. Variations in this gene can influence how cells regulate telomerase, an enzyme that maintains the protective caps on the ends of chromosomes [2]. Consequently, this gene plays a pivotal role in determining susceptibility to multiple distinct types of cancer [1].
Variant Impact: A single-nucleotide change in the CLPTM1L gene acts as a genetic pivot point, altering susceptibility to different cancers in opposite directions [1]. Specifically, the C allele increases the risk of lung, bladder, and basal cell skin cancers while lowering the risk of melanoma and pancreatic cancer [1]. Conversely, the T allele reverses this pattern, increasing melanoma and pancreatic cancer risk while protecting against the others [1].
Key Insight: This variant acts as a genetic double-edged sword, where the allele that increases skin and lung cancer risk actually protects against melanoma and pancreatic cancer.
Location: CLPTM1L. Chromosome 5 · 5p15.33 · 1.3 Mb
Estimated prevalence by population
Global 28.6%; European 31.9%; African 16.6%; East Asian 46.4%; South Asian 61.9%; Americas 32.1%; Ashkenazi 30.4%; Finnish 25.6%; Middle Eastern 30.4%; Amish 27.7%.
Estimated CC genotype frequency.
Global 48.3%; European 49.2%; African 48.3%; East Asian 43.5%; South Asian 33.5%; Americas 49.1%; Ashkenazi 49.5%; Finnish 50.0%; Middle Eastern 49.5%; Amish 49.9%.
Estimated CT genotype frequency.
Global 23.1%; European 19.0%; African 35.2%; East Asian 10.2%; South Asian 4.5%; Americas 18.8%; Ashkenazi 20.2%; Finnish 24.4%; Middle Eastern 20.2%; Amish 22.4%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Cancer & Oncology
Lung Cancer
Lung Cancer. Evidence: 6/10. Source: PMID 18978787. ~1.16x Increased Risk.
Skin Cancer
Basal Cell Carcinoma. Evidence: 8/10. Source: PMID 19151717. ~1.24x Increased Risk.
Melanoma. Evidence: 8/10. Source: PMID 21983787. Typical Risk.
Gastrointestinal Cancers
Pancreatic Cancer. Evidence: 7/10. Source: PMID 20101243. Typical Risk.
Urologic Cancers
Bladder Cancer. Evidence: 6/10. Source: PMID 20972438. ~1.12x Increased Risk.
Showing effects for C/T genotype
Lung Cancer. Evidence: 6/10. Source: PMID 18978787. Slightly Increased.
Basal Cell Carcinoma. Evidence: 8/10. Source: PMID 19151717. Slightly Increased.
Melanoma. Evidence: 8/10. Source: PMID 21983787. Slightly Increased.
Pancreatic Cancer. Evidence: 7/10. Source: PMID 20101243. Slightly Increased.
Bladder Cancer. Evidence: 6/10. Source: PMID 20972438. Slightly Increased.
Showing effects for T/T genotype
Lung Cancer. Evidence: 6/10. Source: PMID 18978787. Typical Risk.
Basal Cell Carcinoma. Evidence: 8/10. Source: PMID 19151717. Typical Risk.
Melanoma. Evidence: 8/10. Source: PMID 21983787. ~1.2x Increased Risk.
Pancreatic Cancer. Evidence: 7/10. Source: PMID 20101243. ~1.19x Increased Risk.
Bladder Cancer. Evidence: 6/10. Source: PMID 20972438. Typical Risk.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Two copies of the C allele are linked to an increased risk of several epithelial cancers, including lung cancer, bladder cancer, and basal cell carcinoma [1] [2]. Large-scale genetic studies show a modest increase in risk, typically around 1.15 to 1.25 times the baseline [1] [3]. Interestingly, this same genetic profile appears to offer a protective benefit against other malignancies [1]. Individuals with this genotype have a lower risk of developing cutaneous melanoma and pancreatic cancer [1] [4]. This biological trade-off is thought to be related to how the variant influences telomere biology and cell longevity [1]. While it increases susceptibility to some environmental carcinogens, it reduces it for others [1]. Understanding this balance helps paint a complete picture of personal genetic risk.
Slightly higher risk of lung, bladder, and basal cell cancers; Slightly lower risk of melanoma and pancreatic cancer.
Sample genotype: CT (Heterozygous)
The heterozygous CT genotype represents a middle ground in this genetic trade-off [1]. Studies suggest that carriers of one C allele and one T allele experience a blend of the risks and protective factors associated with both variants [1]. There is a slightly elevated risk for lung, bladder, and basal cell skin cancers compared to the TT genotype, but it is generally lower than or similar to the CC genotype [1] [2]. At the same time, the presence of the T allele slightly increases the risk of melanoma and pancreatic cancer compared to CC, while the C allele offers some protection [1] [3]. This dual nature highlights how a single genetic change can have opposing effects depending on the tissue type [1]. It underscores the complexity of genetic risk, where a single variant is rarely entirely harmful or entirely beneficial [1]. Environmental factors like sun exposure and smoking remain highly influential alongside these genetic markers.
Intermediate risk for lung, bladder, and basal cell cancers; Intermediate risk for melanoma and pancreatic cancer.
Sample genotype: TT (Homozygous)
Two copies of the T allele reverse the typical risk profile of this variant [1]. Lower risks of developing lung cancer, bladder cancer, and basal cell skin cancer are observed with this genotype [1] [2]. However, this protective effect is accompanied by an increased susceptibility to other serious conditions [1]. Specifically, the T allele is associated with a higher risk of cutaneous melanoma and pancreatic cancer [1] [3]. Research indicates that the T allele may be linked to longer telomeres, which can promote cell survival in some tissues but also allow certain cancers like melanoma to develop [1]. This genotype demonstrates that genetic risk is often a complex balance rather than a simple good or bad outcome [1]. Proactive health habits like sun protection and regular skin checks are particularly relevant for this profile.
Slightly higher risk of melanoma and pancreatic cancer; Slightly lower risk of lung, bladder, and basal cell cancers.
Variants with shared genetic architecture
rs4635969 · CLPTM1L Gene · Chr 5 · Cancer Risk Trade-offs
rs31489 · CLPTM1L Gene · Chr 5 · Lung Cancer Risk
rs402710 · CLPTM1L Gene · Chr 5 · Lung Cancer Risk
Sequence variants at the TERT-CLPTM1L locus associate with many cancer types.
Common 5p15.33 and 6p21.33 variants influence lung cancer risk.
Genome-wide association study identifies three new melanoma susceptibility loci.
Content updated August 2026.
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