rs6983267 — 8q24

8q24 rs6983267 — A Distal Enhancer Wiring MYC for Cancer

Chromosome 8q24 is the most frequently implicated region in cancer genome-wide association studies, yet it contains no protein-coding genes for hundreds of kilobases. The variant rs6983267 sits in an intergenic desert roughly 335 kilobases upstream of MYC¹¹ MYC
MYC is one of the most potent human oncogenes; its protein product drives cell proliferation, and it is overexpressed in the majority of human cancers, one of the most important oncogenes in human biology. Despite its distance from any gene, this single nucleotide change has a direct and well-characterized mechanism linking it to cancer risk.

The Mechanism

The region surrounding rs6983267 functions as a transcriptional enhancer — a stretch of DNA that boosts the expression of distant genes through physical looping of the chromosome. Pomerantz et al.²² Pomerantz et al.
Pomerantz MM et al. The 8q24 cancer risk variant rs6983267 shows long-range interaction with MYC in colorectal cancer. Nat Genet, 2009 used chromosome conformation capture (3C) to demonstrate that this enhancer physically contacts the MYC promoter across 335 kb of intervening DNA. The G risk allele creates a stronger binding site for TCF7L2³³ TCF7L2
Also known as TCF4; a transcription factor in the Wnt signaling pathway that, when activated, drives expression of growth-promoting genes including MYC, a key transcription factor in the Wnt signaling pathway⁴⁴ Wnt signaling pathway
The Wnt pathway controls cell proliferation, polarity, and fate during development; its aberrant activation is a hallmark of colorectal cancer.

Tuupanen et al.⁵⁵ Tuupanen et al.
Tuupanen S et al. The common colorectal cancer predisposition SNP rs6983267 at chromosome 8q24 confers potential to enhanced Wnt signaling. Nat Genet, 2009 confirmed this mechanism using reporter assays and chromatin immunoprecipitation: the G allele binds TCF7L2 more strongly both in vitro and in vivo, effectively amplifying Wnt-driven MYC expression. In the most striking functional validation, Sur et al.⁶⁶ Sur et al.
Sur IK et al. Mice lacking a Myc enhancer that includes human SNP rs6983267 are resistant to intestinal tumors. Science, 2012 deleted this enhancer region in mice and found they were markedly resistant to intestinal tumors driven by APC mutations — the same pathway responsible for most human colorectal cancers.

The Evidence

rs6983267 is one of the most replicated cancer GWAS findings in the literature. The initial identification came from two independent 2007 studies: Tomlinson et al.⁷⁷ Tomlinson et al.
Tomlinson I et al. A genome-wide association scan of tag SNPs identifies a susceptibility variant for colorectal cancer at 8q24.21. Nat Genet, 2007 found the G allele increased colorectal cancer risk with an OR of 1.27 for heterozygotes and 1.47 for GG homozygotes in a large British cohort. Simultaneously, Haiman et al.⁸⁸ Haiman et al.
Haiman CA et al. A common genetic risk factor for colorectal and prostate cancer. Nat Genet, 2007 showed the same variant conferred risk for both colorectal and prostate cancer with an OR of 1.22 per allele.

A comprehensive meta-analysis of 78 studies⁹⁹ comprehensive meta-analysis of 78 studies
Zhu M et al. Association between 8q24 rs6983267 polymorphism and cancer susceptibility: a meta-analysis involving 170,737 subjects. Oncotarget, 2017 pooling 73,996 cancer cases and 96,741 controls confirmed statistically robust associations across multiple cancer types. The GG genotype conferred an OR of 1.31 compared to TT, while per-allele risk was 1.14. The association was strongest for colorectal cancer in Caucasians and prostate cancer in both Caucasians and Asians.

A critical point: this is a very common variant with a small per-allele effect. The G allele is actually the major allele in most populations (frequency ~50-58%), meaning the majority of people carry at least one copy. The absolute risk increase per individual is modest — this is not a rare, high-penetrance mutation like BRCA1. Its public health significance comes from its extreme prevalence.

Practical Implications

The actionability of rs6983267 centers on cancer screening adherence rather than lifestyle interventions. Because the Wnt/MYC mechanism directly promotes colorectal neoplasia through adenoma formation, colonoscopy screening is the most evidence-based response — it detects and removes the precancerous adenomas that this variant promotes. For prostate cancer, the variant contributes to a genetic risk profile that informs PSA screening discussions.

An intriguing pharmacogenomic interaction exists with aspirin: Nan et al.¹⁰¹⁰ Nan et al.
Nan H et al. Aspirin use, 8q24 single nucleotide polymorphism rs6983267, and colorectal cancer according to CTNNB1 alterations. JNCI, 2013 found that aspirin's colorectal cancer protection was confined to individuals carrying the protective T allele, while those homozygous for the risk G allele derived less benefit. This may relate to the G allele's stronger Wnt activation partially overriding aspirin's anti-Wnt effects.

Interactions

rs6983267 resides in the same cancer risk region as other 8q24 variants that influence different cancer types through distinct mechanisms. Its colorectal cancer association intersects with the mismatch repair pathway: individuals who carry both the rs6983267 GG genotype and variants in mismatch repair genes such as MLH1 (rs1800734) or APC pathway components (rs1801155/APC I1307K) may face compounded colorectal cancer susceptibility. The Wnt pathway activation from rs6983267 combined with impaired DNA repair from mismatch repair variants would create a dual vulnerability — both increased cell proliferation and reduced error correction. This interaction is biologically plausible given that APC mutations and MYC overexpression are sequential events in the adenoma-carcinoma progression model.