Similarly, it can be difficult to interpret colocalization between a protein and cancer risk where a cognate gene sits in a genomic region with irregular haplotype structure, such as C4A associations with lung cancer on chromosome six, or when two genes that lie immediately adjacent to each other, both share similar associations with cancer risk, such as PTPN9 and SNUPN with breast cancer risk in our analyses. This evidence concerns the gene PTPN9 and lung cancer.