GDNF and colorectal carcinoma: The Bonferroni correction showed that higher circulating levels of GDNF (IVW; OR = 1.11; 95% CI: 1.06–1.17; P = 6.19 × 10-5) and TRAIL (WM; OR = 0.91; 95% CI: 0.87–0.96; P = 1.81 × 10-4) stayed significantly related to an increased and decreased CRC risk, respectively.