FURIN and cancer: The lack of colocalising signal and estimated protective effect of serum furin on cancer risk in genetic analyses may be attributable to our ability to reliably instrument (proxy) serum furin with a single cis SNP (rs6227), a reduced signal in the furin locus in the GWAS of proteins measured using the SomaScan platform,44 or potential genetic pleiotropy of the variant (this SNP has also been found to influence expression of FES proto-oncogene, tyrosine kinase). 49