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Colorectal Cancer Risk Is Not Associated with Increased Levels of Homozygosity in a Population from the United Kingdom

¹ The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom and ² Section of Cancer Genetics, Institute of Cancer, Sutton, Surrey, United Kingdom

Requests for reprints: Ian Tomlinson, The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom. Phone: 44-0-1865-287832/287501; Fax: 44-0-1865-287832/287501; E-mail: iant{at}well.ox.ac.uk.

Key Words: Autozygosity • Colorectal cancer • Homozygosity

Genome-wide association studies have identified several common single nucleotide polymorphisms (SNP) associated with an increased risk of colorectal cancer (CRC), although they have failed to identify any recessively acting alleles that contribute to disease risk. However, two recent studies have suggested that inbreeding and runs of homozygosity (ROH) increase the risk of developing cancer, perhaps by exposing recessive alleles as a result of autozygosity. To examine these results in a relatively large case-control series, we analyzed samples from a cohort in the United Kingdom comprising 921 colorectal tumor cases and 929 controls. Individuals were genotyped using a 550,000 tagging SNP panel. Additionally, we identified from these SNPs a set of 30,000 SNPs in low pairwise linkage disequilibrium. To determine whether homozygosity was associated with CRC, we performed multiple tests to assess homozygosity at individual SNPs and ROHs in cases and controls. No association was found between CRC and (i) homozygosity at any individual SNP, (ii) overall homozygosity or level of inbreeding, (iii) total length or number of ROHs per individual, or (iv) a ROH at any particular genomic location. In conclusion, our results from a large case-control series do not replicate those of previous studies and suggest that homozygosity/autozygosity is not a major risk factor for CRC in an outbred population. [Cancer Res 2009;69(18):7422–9]