Some genes that raise prostate cancer risk became common in certain populations not because they helped with cancer, but because they were stuck next to genes that helped people adapt to sunlight—like lighter skin in Europe.
Scientific Claim
Genetic hitchhiking—where prostate cancer risk alleles increased in frequency because they were linked to genes under positive selection for traits like skin pigmentation—likely explains elevated risk in some populations, such as the protective allele at 2q37 rising in Europeans due to selection on MLPH.
Original Statement
“A protective allele at 2q37 appears to have risen to high frequency in Europe due to selection acting on pigmentation... rs7584330 is a CaP SNP that is located at 2q37... signatures of positive selection at 2q37 are consistent with previous studies that suggest variation at pigmentation genes is adaptive in non-African populations.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The study infers hitchhiking from correlated selection signals and linkage, not direct experimental proof. The use of 'appears to have risen' and 'consistent with' appropriately reflects the inferential nature of the evidence.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.
Prospective Cohort StudyLevel 2aWhether individuals carrying the 2q37 risk allele (rs7584330) have higher prostate cancer incidence only if they also carry specific pigmentation-associated haplotypes.
Whether individuals carrying the 2q37 risk allele (rs7584330) have higher prostate cancer incidence only if they also carry specific pigmentation-associated haplotypes.
What This Would Prove
Whether individuals carrying the 2q37 risk allele (rs7584330) have higher prostate cancer incidence only if they also carry specific pigmentation-associated haplotypes.
Ideal Study Design
A cohort of 15,000 men of European descent genotyped for rs7584330 and SNPs in MLPH/PRLH, followed for 20 years, with prostate cancer incidence analyzed by haplotype combinations, adjusting for skin pigmentation phenotype and UV exposure.
Limitation: Cannot prove the ancestral selection event occurred; relies on modern linkage patterns.
Case-Control StudyLevel 3aWhether the 2q37 risk allele is in strong linkage disequilibrium with pigmentation alleles in European populations but not in African populations.
Whether the 2q37 risk allele is in strong linkage disequilibrium with pigmentation alleles in European populations but not in African populations.
What This Would Prove
Whether the 2q37 risk allele is in strong linkage disequilibrium with pigmentation alleles in European populations but not in African populations.
Ideal Study Design
A case-control study of 3,000 European men with prostate cancer and 3,000 controls, and 3,000 West African men with and without cancer, performing phased haplotype analysis across 2q37 to test if the risk allele is co-inherited with pigmentation variants only in Europeans.
Limitation: Cannot determine timing of selection or whether selection acted on pigmentation or another trait.
Transgenic Animal ModelLevel 4Whether selection for lighter pigmentation in mice leads to increased frequency of a linked prostate cancer risk allele in subsequent generations.
Whether selection for lighter pigmentation in mice leads to increased frequency of a linked prostate cancer risk allele in subsequent generations.
What This Would Prove
Whether selection for lighter pigmentation in mice leads to increased frequency of a linked prostate cancer risk allele in subsequent generations.
Ideal Study Design
A mouse breeding experiment where a transgenic risk allele (rs7584330) is inserted near a pigmentation gene (e.g., Mc1r), and mice are selected over 10 generations for light vs. dark coat color; frequency of the linked risk allele is tracked.
Limitation: Mouse pigmentation and prostate biology differ from humans; cannot replicate human population history.
Systematic Review & Meta-AnalysisLevel 1aWhether the 2q37 region shows consistent signatures of selection across diverse populations and whether those signatures correlate with pigmentation traits.
Whether the 2q37 region shows consistent signatures of selection across diverse populations and whether those signatures correlate with pigmentation traits.
What This Would Prove
Whether the 2q37 region shows consistent signatures of selection across diverse populations and whether those signatures correlate with pigmentation traits.
Ideal Study Design
A meta-analysis of 20+ genome-wide selection scans (CMS, iHS, FST) across global populations, testing for correlation between selection scores at 2q37 and skin reflectance measurements from 100+ populations.
Limitation: Correlation does not prove causation; pigmentation may be a proxy for another selected trait.
Functional Genomics AssayLevel 5Whether the rs7584330 variant or linked SNPs directly alter gene expression in prostate tissue or melanocytes.
Whether the rs7584330 variant or linked SNPs directly alter gene expression in prostate tissue or melanocytes.
What This Would Prove
Whether the rs7584330 variant or linked SNPs directly alter gene expression in prostate tissue or melanocytes.
Ideal Study Design
CRISPR-based editing of rs7584330 in human prostate epithelial cells and melanocytes, measuring changes in MLPH, PRLH, and nearby oncogene expression via RNA-seq and ChIP-seq under UV exposure conditions.
Limitation: Cannot replicate population-level evolutionary dynamics or tissue-tissue interactions.
Evidence from Studies
Supporting (1)
Genetic Hitchhiking and Population Bottlenecks Contribute to Prostate Cancer Disparities in Men of African Descent.
The study found that a gene variant that lowers prostate cancer risk became common in Europeans because it was accidentally carried along with another gene that helped people adapt to sun exposure — exactly what the claim says.