We found evidence to support the presence of a shared causal variant, using colocalization analysis (posterior probability for shared variant > 0.8) for the associations between MIF and overall breast cancer, IL-1ra and endometrioid endometrial cancer, IL-18 and lung adenocarcinoma, CTACK and lung cancer (in never smokers) and RANTES in relation to serous ovarian cancer (Additional file 2: Table S10). The gene discussed is IL18; the disease is ovarian serous adenocarcinoma.